[{"id":"cambrian-explosion","emoji":"🐚","title":"The Cambrian explosion","explanation":"Beginning about 538.8 million years ago and lasting roughly 13 to 25 million years, the fossil record shows the first appearances of practically every animal phylum, a complex ocean of predators and prey. Rising oxygen and an evolutionary arms race between predators and prey are among the ideas for what drove it.","year":-538800000,"yearEnd":-521000000,"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Cambrian explosion","url":"https://en.wikipedia.org/wiki/Cambrian_explosion"},{"label":"Sperling et al. 2013, Oxygen, ecology, and the Cambrian radiation of animals (PNAS)","url":"https://doi.org/10.1073/pnas.1312778110"}],"minAge":7},{"id":"greening-of-land","emoji":"🌿","title":"Plants conquer the land","explanation":"The first land plants appear about 470 million years ago. Many early ones had no true roots, but by the late Devonian (about 370 million years ago) some, like Archaeopteris, formed forests of tall trees. The greening of the continents acted as a carbon sink, so CO2 may have dropped, and land plants increased the rate at which oxygen built up in the air.","year":-470000000,"yearEnd":-370000000,"links":["vegetation","co2","oxygen"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Evolutionary history of plants","url":"https://en.wikipedia.org/wiki/Evolutionary_history_of_plants"},{"label":"Wikipedia — Devonian","url":"https://en.wikipedia.org/wiki/Devonian"}],"minAge":4},{"id":"ordovician-ice","emoji":"🧊","title":"A sudden ice age strikes","explanation":"A short, sharp glaciation locked water into ice sheets over Gondwana, dropping sea level and draining the shallow seas, which wiped out the homes of many species. That habitat loss is blamed for the first pulse of the first of the \"big five\" mass extinctions.","year":-445000000,"yearEnd":-443000000,"links":["ice-cover","sea-level","biodiversity"],"edge":"triggered","weight":0.82,"sources":[{"label":"Wikipedia — Late Ordovician mass extinction","url":"https://en.wikipedia.org/wiki/Late_Ordovician_mass_extinction"},{"label":"Finnegan et al. 2011, The magnitude and duration of Late Ordovician-Early Silurian glaciation (Science)","url":"https://doi.org/10.1126/science.1200803"}],"minAge":7},{"id":"carboniferous-coal","emoji":"🌲","title":"Forests that became coal","explanation":"The Carboniferous is named for the many coal beds that formed then, as vast amounts of plant debris piled up in peat mires across low-lying, humid equatorial wetlands. Why so much coal formed is debated: one idea is that fungi able to break down wood fibre (lignin) evolved late; another points to the period's unique geography and climate, with low, waterlogged, slowly sinking basins. Increased burial of organic matter, along with the weathering of growing mountains, lowered CO2 and cooled the climate, while oxygen rose from low levels to highs of 25-30%.","year":-358860000,"yearEnd":-298900000,"links":["vegetation","co2","oxygen"],"edge":"caused","weight":0.86,"sources":[{"label":"Wikipedia — Carboniferous","url":"https://en.wikipedia.org/wiki/Carboniferous"}],"minAge":4},{"id":"giant-insects","emoji":"🦗","title":"Giant insects rule the skies","explanation":"In the late Carboniferous, oxygen rose to highs of 25-30%, and giant arthropods lived then: Meganeura, a dragonfly-like insect with a wingspan around 65-75 cm, and the millipede Arthropleura, at least 2 metres long. A famous idea is that the extra oxygen let them grow so big, but the evidence is mixed: giant relatives of Meganeura still lived in the Late Permian after oxygen levels had dropped, Arthropleura was already giant when oxygen was only about 23%, and a 2026 study concluded that probably no link can be made between how insects take in oxygen and a large body size.","year":-323000000,"yearEnd":-299000000,"links":["oxygen"],"edge":"enabled","weight":0.95,"sources":[{"label":"Wikipedia — Carboniferous","url":"https://en.wikipedia.org/wiki/Carboniferous"},{"label":"Wikipedia — Meganeura","url":"https://en.wikipedia.org/wiki/Meganeura"},{"label":"Wikipedia — Arthropleura","url":"https://en.wikipedia.org/wiki/Arthropleura"}],"minAge":4},{"id":"great-dying","emoji":"🌋","title":"The Great Dying","explanation":"The end-Permian extinction - the Great Dying - is Earth's most severe known extinction event, wiping out about 81% of marine species and 70% of land vertebrate species. The scientific consensus is that Siberian Traps eruptions released CO₂ and sulfur dioxide, warming the planet, acidifying the oceans and leaving them starved of oxygen.","year":-252500000,"yearEnd":-251000000,"links":["temperature","co2","oxygen","ocean-ph"],"edge":"triggered","weight":0.97,"sources":[{"label":"Wikipedia — Permian–Triassic extinction event","url":"https://en.wikipedia.org/wiki/Permian–Triassic_extinction_event"},{"label":"Burgess et al. 2014, High-precision timeline for Earth's most severe extinction (PNAS)","url":"https://doi.org/10.1073/pnas.1317692111"}],"minAge":7},{"id":"end-triassic","emoji":"🌋","title":"Volcanoes clear the way for dinosaurs","explanation":"The end-Triassic extinction is generally thought to have been caused by huge eruptions of the Central Atlantic Magmatic Province, which released large amounts of CO₂ and caused profound global warming and ocean acidification. Afterwards dinosaurs, pterosaurs, crocodylomorphs and mammals were left largely untouched and became the dominant land animals.","year":-201500000,"yearEnd":-200000000,"links":["co2","temperature","biodiversity"],"edge":"triggered","weight":0.83,"sources":[{"label":"Blackburn et al. 2013, Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province (Science)","url":"https://doi.org/10.1126/science.1234204"},{"label":"Wikipedia — Triassic–Jurassic extinction","url":"https://en.wikipedia.org/wiki/Triassic–Jurassic_extinction"}],"minAge":7},{"id":"cretaceous-flood","emoji":"🌊","title":"Continents underwater","explanation":"The warm Cretaceous world was largely ice-free, and sea level stood roughly 100 to 170 metres higher than today. Shallow seas flooded the continents, and at the peak one-third of Earth's present land area was submerged.","year":-120000000,"yearEnd":-80000000,"links":["sea-level","temperature","ice-cover"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Cretaceous","url":"https://en.wikipedia.org/wiki/Cretaceous"},{"label":"Wikipedia — Mid-ocean ridge","url":"https://en.wikipedia.org/wiki/Mid-ocean_ridge"}],"minAge":4},{"id":"kpg-asteroid","emoji":"☄️","title":"The day the dinosaurs died","explanation":"A roughly 10 km asteroid struck Chicxulub in Mexico, and darkness and cooling followed. About three-quarters of all species, including every non-avian dinosaur, died out.","year":-66500000,"yearEnd":-65500000,"place":{"lat":21.3,"lon":-89.5,"label":"Chicxulub crater, Yucatán"},"links":["temperature","biodiversity"],"edge":"triggered","weight":0.98,"sources":[{"label":"Schulte et al. 2010, The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary (Science)","url":"https://doi.org/10.1126/science.1177265"},{"label":"Wikipedia — Cretaceous–Paleogene extinction event","url":"https://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event"}],"minAge":7},{"id":"petm-hyperthermal","emoji":"🔥","title":"A carbon spike warms the world","explanation":"About 56 million years ago, the Paleocene-Eocene Thermal Maximum released thousands of petagrams of carbon and warmed the planet by 5-8°C. The carbon release is thought to have lasted under 20,000 years and the whole event about 200,000 years, which makes it arguably our best past analogue for today's warming. The oceans acidified, and many modern mammal orders appear on land.","year":-56000000,"yearEnd":-55800000,"links":["temperature","co2","ocean-ph"],"edge":"caused","weight":0.86,"sources":[{"label":"McInerney & Wing 2011, The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future (Annu. Rev. Earth Planet. Sci.)","url":"https://doi.org/10.1146/annurev-earth-040610-133431"},{"label":"Wikipedia — Paleocene–Eocene thermal maximum","url":"https://en.wikipedia.org/wiki/Paleocene–Eocene_thermal_maximum"}],"minAge":4},{"id":"antarctic-glaciation","emoji":"❄️","title":"Antarctica freezes over","explanation":"Carbon dioxide slowly declined through the Middle and Late Eocene. Around 34 million years ago the cooling crossed a threshold and a large permanent ice sheet formed over East Antarctica in two steps - the start of the Late Cenozoic Ice Age; in the first step CO2 fell from about 885 to about 560 ppm. A climate model found falling CO2 mattered more than the opening of Southern Ocean gateways, which played a secondary role. A major fall in sea level has also been suggested.","year":-34100000,"yearEnd":-33550000,"links":["co2","ice-cover","sea-level"],"edge":"caused","weight":0.83,"sources":[{"label":"DeConto & Pollard 2003, Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2 (Nature)","url":"https://doi.org/10.1038/nature01290"},{"label":"Wikipedia — Eocene–Oligocene extinction event","url":"https://en.wikipedia.org/wiki/Eocene–Oligocene_extinction_event"}],"minAge":4},{"id":"ice-ages-begin","emoji":"🧊","title":"The ice ages begin","explanation":"Great ice sheets began advancing and retreating in cycles - about 41,000 years long at first, then about 100,000 years after roughly a million years ago. At the coldest times the ice on land made sea level about 120 m lower than today. The cycles have not ended: Earth is now in a warm interglacial, the Holocene, which began 11,700 years ago.","year":-2580000,"yearEnd":-11700,"links":["temperature","sea-level","ice-cover"],"edge":"caused","weight":0.9,"sources":[{"label":"Lisiecki & Raymo 2005, A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records (Paleoceanography)","url":"https://doi.org/10.1029/2004pa001071"},{"label":"Wikipedia — Quaternary glaciation","url":"https://en.wikipedia.org/wiki/Quaternary_glaciation"}],"minAge":4},{"id":"toba-bottleneck","emoji":"🌋","title":"A supervolcano and a human bottleneck","explanation":"About 74,000 years ago the largest known explosive eruption of the Quaternary period blanketed the Indian subcontinent in ash and may have caused a volcanic winter. One theory says it squeezed early human populations through a genetic bottleneck, but some evidence disputes this and some scientists consider the theory disproven.","year":-75000,"yearEnd":-70000,"place":{"lat":2.6,"lon":98.8,"label":"Lake Toba, Sumatra"},"links":["temperature","population"],"edge":"constrained","weight":0.84,"sources":[{"label":"Wikipedia — Youngest Toba eruption","url":"https://en.wikipedia.org/wiki/Youngest_Toba_eruption"}],"minAge":7},{"id":"out-of-africa","emoji":"🚶","title":"Out of Africa","explanation":"Modern humans spread from Africa across Eurasia and beyond, in more than one wave: early groups reached Arabia by about 130,000 to 115,000 years ago, but people outside Africa today descend mainly from an expansion about 70,000 to 50,000 years ago. Ice-age low sea level helped shape the routes: it narrowed the Red Sea crossing and opened a land bridge between Siberia and Alaska.","year":-130000,"yearEnd":-16000,"place":{"lat":9,"lon":40,"label":"East Africa"},"links":["population","sea-level"],"edge":"enabled","weight":0.88,"sources":[{"label":"Bae, Douka & Petraglia 2017, On the origin of modern humans: Asian perspectives (Science)","url":"https://doi.org/10.1126/science.aai9067"},{"label":"Wikipedia — Recent African origin of modern humans","url":"https://en.wikipedia.org/wiki/Recent_African_origin_of_modern_humans"},{"label":"Wikipedia — Beringia","url":"https://en.wikipedia.org/wiki/Beringia"}],"minAge":4},{"id":"farming-revolution","emoji":"🌾","title":"Farming changes everything","explanation":"After the last ice age ended, people in several parts of the world began to farm, a change some researchers link to the steadier climate that followed. More food let populations grow and settle in villages, though early farmers' diets were poorer and their life expectancy lower than foragers'.","year":-10000,"yearEnd":-4000,"links":["population","life-expectancy"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Neolithic Revolution","url":"https://en.wikipedia.org/wiki/Neolithic_Revolution"},{"label":"Bocquet-Appel 2011, When the world's population took off: the springboard of the Neolithic Demographic Transition (Science)","url":"https://doi.org/10.1126/science.1208880"}],"minAge":4},{"id":"black-death","emoji":"🐀","title":"The Black Death","explanation":"Plague swept across Europe between 1346 and 1353 and killed around 30% to 60% of its people. With so many dead, wages soared in response to the labour shortage, and the pandemic is said to have restructured religion and political forces in a feudal society.","year":1346,"yearEnd":1353,"place":{"lat":48,"lon":12,"label":"Europe"},"links":["population","life-expectancy"],"edge":"triggered","weight":0.92,"sources":[{"label":"Wikipedia — Black Death","url":"https://en.wikipedia.org/wiki/Black_Death"}],"minAge":10},{"id":"columbian-exchange","emoji":"⛵","title":"Two worlds collide","explanation":"1492 began a widespread transfer of plants, animals and diseases between the Americas and Afro-Eurasia. Diseases of Old World origin killed an estimated 80 to 95 percent of the Indigenous population of the Americas within the first 100 to 150 years, while American crops such as maize and potatoes became important crops around the world and supported increases in food production and population in the Old World.","year":1492,"yearEnd":1642,"place":{"lat":19,"lon":-70,"label":"The Americas"},"links":["population","biodiversity"],"edge":"caused","weight":0.88,"sources":[{"label":"Wikipedia — Columbian exchange","url":"https://en.wikipedia.org/wiki/Columbian_exchange"}],"minAge":10},{"id":"tambora-1816","emoji":"🌋","title":"The year without a summer","explanation":"Tambora’s 1815 eruption - the largest observed eruption in recorded history - sent a veil of sulfate aerosols into the stratosphere, dimming the sun. In 1816 summer snow fell in places, and crop failures brought food shortages across the Northern Hemisphere.","year":1816,"place":{"lat":-8.25,"lon":118,"label":"Mount Tambora, Indonesia"},"links":["temperature"],"edge":"triggered","weight":0.95,"sources":[{"label":"Wikipedia — Year Without a Summer","url":"https://en.wikipedia.org/wiki/Year_Without_a_Summer"},{"label":"Wikipedia — 1815 eruption of Mount Tambora","url":"https://en.wikipedia.org/wiki/1815_eruption_of_Mount_Tambora"}],"minAge":10},{"id":"industrial-warming","emoji":"🏭","title":"The Industrial Revolution warms the world","explanation":"Since the Industrial Revolution, burning fossil fuels such as coal has pushed CO₂ in the atmosphere up from about 280 ppm. That has strengthened the greenhouse effect, and each of the last four decades has been warmer than any decade before it since 1850.","year":1850,"yearEnd":2024,"links":["temperature","co2"],"edge":"caused","weight":0.9,"sources":[{"label":"IPCC AR6 WG1 (2021), Summary for Policymakers","url":"https://www.ipcc.ch/report/ar6/wg1/chapter/summary-for-policymakers/"},{"label":"Wikipedia — Carbon dioxide in the atmosphere of Earth","url":"https://en.wikipedia.org/wiki/Carbon_dioxide_in_the_atmosphere_of_Earth"}],"minAge":4},{"id":"ocean-acidification","emoji":"🧪","title":"The oceans turn acidic","explanation":"The ocean absorbs CO₂ from the air, forming carbonic acid. From 1850 to 2022 it took up 26% of all human carbon emissions, and human CO₂ is the primary cause of ocean acidification: between 1950 and 2020 average surface pH fell from about 8.15 to 8.05, about a 26% rise in hydrogen ions, making it harder for shell-building sea life to build shells and skeletons.","year":1850,"yearEnd":2024,"links":["co2","ocean-ph"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Ocean acidification","url":"https://en.wikipedia.org/wiki/Ocean_acidification"},{"label":"IPCC AR6 WG1 (2021), Summary for Policymakers","url":"https://www.ipcc.ch/report/ar6/wg1/chapter/summary-for-policymakers/"}],"minAge":4},{"id":"modern-deforestation","emoji":"🪓","title":"Clearing the forests","explanation":"Farms, pasture and cities have cleared forests: forest cover is about one-third less than before agriculture expanded, and half of that loss came in the last century. Clearing forests reduces the carbon dioxide they take up and destroys habitat, which leads to biodiversity loss.","year":1900,"yearEnd":2024,"links":["vegetation","co2","biodiversity"],"edge":"caused","weight":0.87,"sources":[{"label":"Wikipedia — Deforestation","url":"https://en.wikipedia.org/wiki/Deforestation"}],"minAge":7},{"id":"new-world-crops","emoji":"🥔","title":"The potato feeds the world","explanation":"American crops such as maize and potatoes became important crops around the world. One study finds that the potato, brought to the Old World from the Americas, was responsible for a significant portion of the increase in Old World population and urbanization in the 18th and 19th centuries, about one-quarter of the growth between 1700 and 1900 by its most conservative estimate.","year":1700,"yearEnd":1900,"links":["population"],"edge":"caused","weight":0.8,"sources":[{"label":"Nunn & Qian 2011, The Potato's Contribution to Population and Urbanization: Evidence From A Historical Experiment (Q. J. Econ.)","url":"https://doi.org/10.1093/qje/qjr009"},{"label":"Wikipedia — Columbian exchange","url":"https://en.wikipedia.org/wiki/Columbian_exchange"}],"minAge":4},{"id":"germ-theory-sanitation","emoji":"🦠","title":"Germs revealed, lives saved","explanation":"Learning that germs can spread disease changed medicine. John Snow’s 1854 cholera study influenced public health and the building of sanitation, Louis Pasteur’s work from the late 1850s began the shift to germ theory, and Lister’s antiseptics made surgery safer. Public health measures are credited with much of the later rise in life expectancy: in the 20th century, average lifespan in the United States rose by more than 30 years, 25 of them attributed to advances in public health.","year":1854,"yearEnd":2000,"links":["life-expectancy"],"edge":"caused","weight":0.86,"sources":[{"label":"Wikipedia — 1854 Broad Street cholera outbreak","url":"https://en.wikipedia.org/wiki/1854_Broad_Street_cholera_outbreak"},{"label":"Wikipedia — Joseph Lister","url":"https://en.wikipedia.org/wiki/Joseph_Lister"},{"label":"Our World in Data — Life Expectancy","url":"https://ourworldindata.org/life-expectancy"},{"label":"Wikipedia — Germ theory of disease","url":"https://en.wikipedia.org/wiki/Germ_theory_of_disease"},{"label":"Wikipedia — Life expectancy","url":"https://en.wikipedia.org/wiki/Life_expectancy"}],"minAge":7},{"id":"world-war-one-toll","emoji":"🎖️","title":"The Great War","explanation":"One of the deadliest conflicts in history, the war killed an estimated 15 to 22 million people, and four ruling dynasties fell: the Romanovs, Hohenzollerns, Habsburgs and Ottomans. It also helped spread the Spanish flu pandemic.","year":1914,"yearEnd":1918,"links":["population"],"edge":"triggered","weight":0.86,"sources":[{"label":"Wikipedia — World War I","url":"https://en.wikipedia.org/wiki/World_War_I"}],"minAge":10},{"id":"flu-1918","emoji":"😷","title":"The 1918 pandemic","explanation":"As WWI ended, an influenza pandemic infected nearly a third of the world’s people and killed an estimated 17 to 50 million, possibly as many as 100 million: between 1 and 6 percent of humanity. India's population fell between its 1911 and 1921 censuses, mostly because of the pandemic, and in the United States it caused a brief drop in average lifespan.","year":1918,"yearEnd":1920,"links":["population","life-expectancy"],"edge":"triggered","weight":0.88,"sources":[{"label":"Wikipedia — Spanish flu","url":"https://en.wikipedia.org/wiki/Spanish_flu"},{"label":"Wikipedia — Life expectancy","url":"https://en.wikipedia.org/wiki/Life_expectancy"}],"minAge":10},{"id":"antibiotics-era","emoji":"💊","title":"Antibiotics and vaccines","explanation":"Penicillin, discovered by Alexander Fleming in 1928, opened the era of antibiotics that revolutionised medicine in the 20th century; in the Second World War it saved an estimated 12-15% of lives among Allied soldiers with infected wounds. Smallpox killed an estimated 250-500 million people in the 20th century, until vaccination campaigns ended it: the WHO certified its global eradication in 1980.","year":1928,"yearEnd":1980,"links":["life-expectancy"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Penicillin","url":"https://en.wikipedia.org/wiki/Penicillin"},{"label":"Wikipedia — Antibiotic","url":"https://en.wikipedia.org/wiki/Antibiotic"},{"label":"Wikipedia — Smallpox","url":"https://en.wikipedia.org/wiki/Smallpox"}],"minAge":7},{"id":"haber-bosch","emoji":"🌱","title":"Bread from thin air","explanation":"The Haber-Bosch process turns nitrogen from the air into ammonia, the basis of nitrogen fertiliser. First made at industrial scale in 1913, it has been called the \"detonator of the population explosion\", letting world population rise from 1.6 billion in 1900 to 7.7 billion by 2018.","year":1913,"yearEnd":2024,"links":["population"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Haber process","url":"https://en.wikipedia.org/wiki/Haber_process"},{"label":"Wikipedia — Nitrogen fixation","url":"https://en.wikipedia.org/wiki/Nitrogen_fixation"}],"minAge":4},{"id":"wwii-toll","emoji":"☢️","title":"The deadliest war","explanation":"The Second World War was the deadliest conflict in history, with an estimated 60 to 75 million deaths - about 3% of the world’s 2.3 billion people in 1940.","year":1939,"yearEnd":1945,"links":["population"],"edge":"triggered","weight":0.9,"sources":[{"label":"Wikipedia — World War II","url":"https://en.wikipedia.org/wiki/World_War_II"},{"label":"Wikipedia — World War II casualties","url":"https://en.wikipedia.org/wiki/World_War_II_casualties"}],"minAge":10},{"id":"green-revolution","emoji":"🌾","title":"The Green Revolution","explanation":"New high-yielding cereal varieties, expanded irrigation and synthetic fertiliser brought a significant increase in crop yields, with early work in Mexico and India. Between 1950 and 1984, as the Green Revolution spread around the globe, world grain production rose by 160%. Its leading scientist, Norman Borlaug, is credited with saving over a billion people from starvation.","year":1950,"yearEnd":1984,"links":["population"],"edge":"caused","weight":0.83,"sources":[{"label":"Wikipedia — Green Revolution","url":"https://en.wikipedia.org/wiki/Green_Revolution"}],"minAge":4},{"id":"great-ordovician-biodiversification","emoji":"🪸","title":"The great Ordovician diversification","explanation":"Over about 30 million years, from the late Cambrian into the Middle Ordovician, the number of marine orders doubled and families tripled, one of the most potent bursts of new species in the Phanerozoic. Possible causes include more oxygen in the sea, changes in geography or tectonics, a modified nutrient supply, or global cooling.","year":-497000000,"yearEnd":-467000000,"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.85,"sources":[{"label":"Wikipedia — Great Ordovician Biodiversification Event","url":"https://en.wikipedia.org/wiki/Great_Ordovician_Biodiversification_Event"}],"minAge":4},{"id":"carboniferous-rainforest-collapse","emoji":"🍂","title":"The rainforests collapse","explanation":"The climate turned cooler and drier, and the Carboniferous coal forests shrank into isolated patches. Many amphibians died out, while the ancestors of reptiles and mammals, whose eggs hold water, spread into more species - a minor extinction event on land.","year":-307000000,"yearEnd":-304000000,"links":["vegetation","biodiversity"],"edge":"triggered","weight":0.84,"sources":[{"label":"Wikipedia — Carboniferous rainforest collapse","url":"https://en.wikipedia.org/wiki/Carboniferous_rainforest_collapse"}],"minAge":7},{"id":"azolla-event","emoji":"🍃","title":"The Azolla event","explanation":"Around 49 million years ago, blooms of the freshwater fern Azolla are thought to have grown across the Arctic Ocean for about 800,000 years, sinking to its stagnant sea floor and being buried. The carbon dioxide this drew down has been speculated to have helped tip the planet from its Eocene hothouse toward an icehouse world.","year":-50000000,"yearEnd":-48000000,"place":{"lat":85,"lon":0,"label":"Arctic Ocean"},"links":["co2","temperature"],"edge":"enabled","weight":0.82,"sources":[{"label":"Brinkhuis et al. 2006, Episodic fresh surface waters in the Eocene Arctic Ocean (Nature)","url":"https://doi.org/10.1038/nature04692"},{"label":"Speelman et al. 2009, The Eocene Arctic Azolla bloom: environmental conditions, productivity and carbon drawdown (Geobiology)","url":"https://doi.org/10.1111/j.1472-4669.2009.00195.x"},{"label":"Wikipedia — Azolla event","url":"https://en.wikipedia.org/wiki/Azolla_event"}],"minAge":4},{"id":"messinian-salinity-crisis","emoji":"🧂","title":"The Mediterranean dries up","explanation":"When the Mediterranean was cut off from the Atlantic, apparently by mainly tectonic movements, the sea dried up in cycles of partial or nearly complete desiccation, leaving a deep dry basin 3 to 5 km below normal sea level. The crisis ended when the Atlantic rapidly refilled it.","year":-6000000,"yearEnd":-5300000,"place":{"lat":35,"lon":18,"label":"Mediterranean basin"},"links":["sea-level"],"edge":"triggered","weight":0.83,"sources":[{"label":"Krijgsman et al. 1999, Chronology, causes and progression of the Messinian salinity crisis (Nature)","url":"https://www.nature.com/articles/23231"},{"label":"Wikipedia — Messinian salinity crisis","url":"https://en.wikipedia.org/wiki/Messinian_salinity_crisis"}],"minAge":4},{"id":"little-ice-age","emoji":"🥶","title":"The Little Ice Age","explanation":"Some experts date the Little Ice Age from about 1300 to about 1850, a period of regional cooling that was strongest in the North Atlantic. Canals and rivers in Great Britain and the Netherlands often froze, and in the mid-17th century glaciers destroyed farms and villages in the Swiss Alps. The historian Brian Fagan describes the plight of European peasants from 1300 to 1850 as famine, cold and bread riots, and the 17th-century 'General Crisis' of crop failure, hardship and high death rates is linked to the cold.","year":1300,"yearEnd":1850,"place":{"lat":50,"lon":8,"label":"Northern Hemisphere"},"links":["temperature","population"],"edge":"caused","weight":0.82,"sources":[{"label":"Wikipedia — Little Ice Age","url":"https://en.wikipedia.org/wiki/Little_Ice_Age"},{"label":"Mann et al. 2009, Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly (Science)","url":"https://doi.org/10.1126/science.1177303"}],"minAge":10},{"id":"dust-bowl","emoji":"🏜️","title":"The Dust Bowl","explanation":"From the summer of 1930 an unusually dry era struck the Great Plains, with drought in waves in 1934, 1936 and 1939-1940. Deep plowing had displaced the native deep-rooted grasses that trapped soil, so the unanchored soil turned to dust that winds blew away in huge clouds that sometimes blackened the sky, forcing tens of thousands of families to abandon their farms - many migrated to California and other states.","year":1930,"yearEnd":1940,"place":{"lat":36.5,"lon":-100,"label":"US Southern Plains"},"links":["vegetation"],"edge":"caused","weight":0.8,"sources":[{"label":"Wikipedia — Dust Bowl","url":"https://en.wikipedia.org/wiki/Dust_Bowl"}],"minAge":7},{"id":"demographic-transition","emoji":"👶","title":"The demographic transition","explanation":"As food supply, sanitation and public health improved, death rates dropped quickly, and birth rates fell later. In between, population grew at an unprecedented pace, before growth slowed in every region.","year":1900,"yearEnd":2024,"links":["population","life-expectancy"],"edge":"caused","weight":0.84,"sources":[{"label":"Wikipedia — Demographic transition","url":"https://en.wikipedia.org/wiki/Demographic_transition"}],"minAge":4},{"id":"great-enrichment","emoji":"📈","title":"The great enrichment","explanation":"Since 1800 real income per person has risen by about 3,000 percent, beginning in northwestern Europe and spreading across much of the world - a leap the economist Deirdre McCloskey calls the Great Enrichment. With the Industrial Revolution, average income and population began to show unprecedented sustained growth, though some historians argue living standards for most did not improve much until the late 19th century.","year":1800,"yearEnd":2024,"links":["gdp","population"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — The Bourgeois Era","url":"https://en.wikipedia.org/wiki/The_Bourgeois_Era"},{"label":"Wikipedia — Industrial Revolution","url":"https://en.wikipedia.org/wiki/Industrial_Revolution"}],"minAge":4},{"id":"great-acceleration","emoji":"🚀","title":"The Great Acceleration","explanation":"Graphs of human activity and Earth-system trends since 1750 show a sharp acceleration after 1950, called the Great Acceleration. Economic activity keeps growing at a rapid rate, most population growth since 1950 has been outside the wealthy OECD countries, and burning coal, oil and gas has driven up the carbon dioxide in the air. Only after the mid-20th century is there clear evidence of human-driven shifts in the Earth system beyond anything in the Holocene, so the scientists behind the graphs argue the Great Acceleration is the most convincing start for the Anthropocene.","year":1950,"yearEnd":2024,"links":["population","gdp","co2","emissions"],"edge":"caused","weight":0.88,"sources":[{"label":"Steffen et al. 2015, The trajectory of the Anthropocene: The Great Acceleration (The Anthropocene Review)","url":"https://doi.org/10.1177/2053019614564785"},{"label":"Wikipedia — Anthropocene","url":"https://en.wikipedia.org/wiki/Anthropocene"}],"minAge":4},{"id":"devonian-nekton","emoji":"🦴","title":"The age of jawed fish","explanation":"Fish, especially jawed fish, reached such diversity in the Devonian that it is called the Age of Fishes, and armoured placoderms came to dominate almost every known aquatic environment. Many researchers call the spread of swimming animals into open water the \"Devonian Nekton Revolution\", but a 2018 study questioned it: it found that swimmers were well established before the Devonian and that their colonization of open water was more gradual than had been thought.","year":-419620000,"yearEnd":-358860000,"links":["biodiversity"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Devonian","url":"https://en.wikipedia.org/wiki/Devonian"},{"label":"2018, The Palaeozoic colonization of the water column and the rise of global nekton (Proc. R. Soc. B)","url":"https://doi.org/10.1098/rspb.2018.0883"}],"minAge":7},{"id":"mammal-radiation","emoji":"🐾","title":"Mammals inherit the Earth","explanation":"With the non-avian dinosaurs gone, the surviving mammals - generally small, about the size of rats - evolved to fill the empty niches. Fossil statistics show mammals grew rapidly in size and diversity in the early Paleocene: within about 700,000 years some reached 50 kg, a 100-fold increase. Whether new groups burst out explosively is still debated; some research finds that mammal diversification stalled across the boundary.","year":-66000000,"yearEnd":-56000000,"links":["biodiversity"],"edge":"enabled","weight":0.85,"sources":[{"label":"Halliday, Upchurch & Goswami 2017, Resolving the relationships of Paleocene placental mammals (Biological Reviews)","url":"https://doi.org/10.1111/brv.12242"},{"label":"Wikipedia — Evolution of mammals","url":"https://en.wikipedia.org/wiki/Evolution_of_mammals"},{"label":"Wikipedia — Cretaceous–Paleogene extinction event","url":"https://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event"}],"minAge":4},{"id":"pleistocene-megafauna","emoji":"🦣","title":"The great beasts vanish","explanation":"Between about 50,000 and 10,000 years ago around 65% of the world's large animal species (those weighing 45 kg or more) died out, including woolly mammoths: in Australia from around 50,000 years ago, in the Americas about 13,000 years ago, and in northern Eurasia in stages. The losses came as modern humans spread; most scholars think humans played at least a part alongside a changing climate, but how much each mattered is still debated.","year":-50000,"yearEnd":-10000,"place":{"lat":55,"lon":-110,"label":"Northern continents"},"links":["biodiversity","population"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Late Pleistocene extinctions","url":"https://en.wikipedia.org/wiki/Late_Pleistocene_extinctions"},{"label":"Barnosky et al. 2004, Assessing the causes of late Pleistocene extinctions on the continents (Science)","url":"https://doi.org/10.1126/science.1101476"}],"minAge":7},{"id":"antonine-plague","emoji":"🤒","title":"The Antonine Plague","explanation":"A pandemic, generally believed to be smallpox and possibly spread by soldiers returning from a campaign in the Near East, struck the Roman Empire from AD 165 to 180, in the last years of the Pax Romana. Estimates put the deaths at 5-10 million, roughly 10% of the empire's people, and it decimated the army. Historians still disagree about how much it mattered.","year":165,"yearEnd":180,"place":{"lat":42,"lon":13,"label":"Roman Empire"},"links":["population","life-expectancy"],"edge":"triggered","weight":0.82,"sources":[{"label":"Wikipedia — Antonine Plague","url":"https://en.wikipedia.org/wiki/Antonine_Plague"}],"minAge":10},{"id":"justinian-plague","emoji":"🦠","title":"The Plague of Justinian","explanation":"The first recorded plague pandemic struck the Byzantine Empire in AD 541-549, with waves that continued for two centuries. Some estimates say up to a quarter of the Eastern Mediterranean's people died, though other historians think the toll was much smaller. It hit just as Justinian's armies had nearly retaken Italy, but how much it changed history is still debated.","year":541,"yearEnd":549,"place":{"lat":41,"lon":29,"label":"Eastern Mediterranean"},"links":["population","life-expectancy"],"edge":"triggered","weight":0.86,"sources":[{"label":"Wikipedia — Plague of Justinian","url":"https://en.wikipedia.org/wiki/Plague_of_Justinian"},{"label":"Mordechai et al. 2019, The Justinianic Plague: An inconsequential pandemic? (PNAS)","url":"https://doi.org/10.1073/pnas.1903797116"}],"minAge":10},{"id":"atlantic-slave-trade","emoji":"⛓️","title":"The Atlantic slave trade","explanation":"Between the 16th and 19th centuries about 12 million enslaved Africans entered the Atlantic trade, and about 10.5 million arrived in the Americas to work on plantations and in mines. The raids, wars and forced marches that fed the trade killed more: one estimate is that 4 million died inside Africa after capture. Its effect on Africa's population is hotly debated: one estimate puts sub-Saharan Africa at about 18% of the world's population in 1600 but only 6% in 1900, though historians argue over why.","year":1500,"yearEnd":1867,"place":{"lat":6,"lon":3,"label":"West Africa"},"links":["population"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Atlantic slave trade","url":"https://en.wikipedia.org/wiki/Atlantic_slave_trade"}],"minAge":13},{"id":"printing-press-literacy","emoji":"📚","title":"Printing spreads reading","explanation":"Johannes Gutenberg invented the movable-type printing press around 1440. The cost of printed texts declined and their availability increased, which helped raise adult literacy rates across Europe, and printing spread new ideas that contributed to the Reformation and the Scientific Revolution.","year":1440,"yearEnd":1700,"place":{"lat":50,"lon":8.27,"label":"Mainz, Germany"},"links":["literacy"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Printing press","url":"https://en.wikipedia.org/wiki/Printing_press"}],"minAge":4},{"id":"steam-engine-industrialisation","emoji":"⚙️","title":"The steam engine powers industry","explanation":"James Watt's steam engine, patented in 1769 and sold from 1776, was a driving force of the Industrial Revolution, using half as much coal as earlier designs to produce the same power. From 1781, with rotary motion, it could replace water wheels, so power sources could be placed anywhere instead of needing a suitable water source. By about 1840 the Industrial Revolution had spread from Britain to continental Europe and the United States, and output greatly increased.","year":1769,"yearEnd":1840,"place":{"lat":52.5,"lon":-2,"label":"Britain"},"links":["gdp"],"edge":"caused","weight":0.87,"sources":[{"label":"Wikipedia — Watt steam engine","url":"https://en.wikipedia.org/wiki/Watt_steam_engine"},{"label":"Wikipedia — Industrial Revolution","url":"https://en.wikipedia.org/wiki/Industrial_Revolution"}],"minAge":4},{"id":"vaccination-life-expectancy","emoji":"💉","title":"Vaccines push back death","explanation":"From Jenner’s smallpox vaccine in 1796 onward, vaccination has saved millions of lives. A WHO-funded study estimated that vaccination prevented 154 million deaths in the 50 years from 1974, 146 million of them children under five, and accounted for 40% of the fall in infant deaths worldwide. Life expectancy at birth is very sensitive to deaths in the first years of life, so saving children raises it.","year":1796,"yearEnd":2024,"place":{"lat":51.69,"lon":-2.46,"label":"Berkeley, England"},"links":["life-expectancy"],"edge":"caused","weight":0.86,"sources":[{"label":"Wikipedia — Smallpox vaccine","url":"https://en.wikipedia.org/wiki/Smallpox_vaccine"},{"label":"Wikipedia — Vaccination","url":"https://en.wikipedia.org/wiki/Vaccination"},{"label":"Shattock et al. 2024, Contribution of vaccination to improved survival and health: modelling 50 years of the Expanded Programme on Immunization (The Lancet)","url":"https://doi.org/10.1016/S0140-6736(24)00850-X"},{"label":"Wikipedia — Life expectancy","url":"https://en.wikipedia.org/wiki/Life_expectancy"}],"minAge":7},{"id":"mass-schooling-literacy","emoji":"🏫","title":"Schools for everyone","explanation":"Compulsory school attendance on the Prussian model gradually spread to other countries, and the spread of literacy has been closely linked to the expansion of education. In 1870 only about one in four people in the world attended school and one in five could read; today both figures are above 80%. Only about one in ten people could read and write in 1820; today only about one in ten cannot.","year":1820,"yearEnd":2015,"links":["literacy"],"edge":"caused","weight":0.84,"sources":[{"label":"Wikipedia — Compulsory education","url":"https://en.wikipedia.org/wiki/Compulsory_education"},{"label":"Wikipedia — Literacy","url":"https://en.wikipedia.org/wiki/Literacy"},{"label":"Our World in Data — Literacy","url":"https://ourworldindata.org/literacy"}],"minAge":4},{"id":"new-world-silver","emoji":"🪙","title":"The silver that circled the globe","explanation":"Silver from the New World, including Mexico, Peru and Bolivia, was minted into the Spanish dollar, or \"piece of eight\", which became the first world currency by the 16th century. Starting in the 1540s a growing amount of silver was shipped to Europe, and the large influx of gold and silver from the Spanish treasure fleet is generally thought to have caused the Price Revolution, a rise in prices of roughly sixfold across Western Europe over 150 years. Chinese goods such as silk, tea and ceramics were in great demand in Europe, so silver also flowed to China.","year":1540,"yearEnd":1640,"place":{"lat":-19.59,"lon":-65.75,"label":"Potosí, Bolivia"},"links":["gdp"],"edge":"caused","weight":0.8,"sources":[{"label":"Wikipedia — Spanish dollar","url":"https://en.wikipedia.org/wiki/Spanish_dollar"},{"label":"Wikipedia — Price revolution","url":"https://en.wikipedia.org/wiki/Price_revolution"},{"label":"Wikipedia — Great Divergence","url":"https://en.wikipedia.org/wiki/Great_Divergence"}],"minAge":4},{"id":"sugar-plantation-complex","emoji":"🍬","title":"Sugar, slavery and the plantation","explanation":"The Portuguese set up sugar plantations off Brazil in the 1550s. From the 1640s Barbados, using a sugar mill bought in Dutch Brazil, became the sugar capital of the Caribbean and for about 100 years its richest European colony. Imperial powers forcibly displaced West Africans to work the cane: before 1650 more than three-quarters of the islands' people were of European descent, but sugar dramatically raised the ratio of enslaved to free people, and by 1832 the median Jamaican plantation held about 150 enslaved people. The plantations produced 80 to 90 percent of the sugar consumed in Western Europe.","year":1640,"yearEnd":1832,"place":{"lat":13.1,"lon":-59.5,"label":"Barbados / Caribbean"},"links":["gdp","population"],"edge":"caused","weight":0.78,"sources":[{"label":"Wikipedia — Sugar plantations in the Caribbean","url":"https://en.wikipedia.org/wiki/Sugar_plantations_in_the_Caribbean"}],"minAge":10},{"id":"trading-companies","emoji":"⚓","title":"Early global corporations","explanation":"Chartered joint-stock companies, the English East India Company (1600) and the Dutch East India Company or VOC (1602), traded in Asia and had their own armed forces or quasi-governmental powers. Shares in the VOC could be bought and sold in open-air secondary markets, one of which became the Amsterdam Stock Exchange, and the VOC is sometimes considered the world's first multinational corporation.","year":1600,"yearEnd":1800,"place":{"lat":6,"lon":80,"label":"Indian Ocean trade"},"links":["gdp"],"edge":"enabled","weight":0.78,"sources":[{"label":"Wikipedia — Dutch East India Company","url":"https://en.wikipedia.org/wiki/Dutch_East_India_Company"},{"label":"Wikipedia — East India Company","url":"https://en.wikipedia.org/wiki/East_India_Company"}],"minAge":10},{"id":"latin-american-independence","emoji":"🌎","title":"Latin America breaks free","explanation":"Between 1808 and 1826 most of Spain’s American empire broke apart into new republics, with leaders such as Bolívar and San Martín. Independence brought sovereignty, but investment, regional markets, credit and transport systems were disrupted, so economic expansion did not follow straight away.","year":1808,"yearEnd":1826,"place":{"lat":6.4,"lon":-66.6,"label":"Gran Colombia / South America"},"links":["gdp"],"edge":"caused","weight":0.75,"sources":[{"label":"Wikipedia — Spanish American wars of independence","url":"https://en.wikipedia.org/wiki/Spanish_American_wars_of_independence"},{"label":"Wikipedia — Economic history of Latin America","url":"https://en.wikipedia.org/wiki/Economic_history_of_Latin_America"}],"minAge":10},{"id":"scramble-for-africa","emoji":"🗺️","title":"The Scramble for Africa","explanation":"The Berlin Conference of 1884-85 regulated European colonisation and trade in Africa and became the emblem of the 'scramble', though the only borders it set were in the Congo region and most of Africa's borders took their final form more than two decades later. By 1914 European powers held almost all of Africa except Ethiopia and Liberia. The colonial borders ignored many ethnic, linguistic and cultural divides, and the new states inherited lasting consequences, including economic instability and political and inter-ethnic conflict.","year":1884,"yearEnd":1914,"place":{"lat":52.52,"lon":13.4,"label":"Berlin Conference"},"links":["gdp"],"edge":"caused","weight":0.8,"sources":[{"label":"Wikipedia — Scramble for Africa","url":"https://en.wikipedia.org/wiki/Scramble_for_Africa"},{"label":"Wikipedia — Berlin Conference","url":"https://en.wikipedia.org/wiki/Berlin_Conference"}],"minAge":10},{"id":"colonial-divergence","emoji":"📉","title":"The great divergence","explanation":"Scholars have proposed many theories for the Great Divergence, in which Western Europe and its settler colonies pulled ahead of other civilizations, and a variety of them point to Europe's relationship with the New World as a major cause. Early European colonization was sustained by selling New World goods to Asia, especially silver to China, and profits from the colonies and the slave trade were high. Historians still disagree about when the divergence began.","year":1500,"yearEnd":1900,"links":["gdp"],"edge":"enabled","weight":0.78,"sources":[{"label":"Wikipedia — Great Divergence","url":"https://en.wikipedia.org/wiki/Great_Divergence"}],"minAge":10},{"id":"theia-moon-formation","emoji":"🌑","title":"A world-shattering birth of the Moon","explanation":"Not long after Earth formed, a Mars-sized planet called Theia is thought to have slammed into it, and the debris blasted into orbit clumped together to make the Moon. The impact is thought to have heated Earth into a global ocean of molten rock.","year":-4500000000,"links":["day-length","temperature","sea-level"],"edge":"triggered","weight":0.96,"sources":[{"label":"Wikipedia — Giant-impact hypothesis","url":"https://en.wikipedia.org/wiki/Giant-impact_hypothesis"}],"minAge":4},{"id":"hadean-short-day-tides","emoji":"🌊","title":"A six-hour day and stronger tides","explanation":"The newborn Moon settled into a much closer orbit than today, so its tidal effects were stronger. Earth also spun faster: the length of a day at Earth's formation is estimated at about 6 hours.","year":-4400000000,"links":["day-length","sea-level"],"edge":"caused","weight":0.88,"sources":[{"label":"Wikipedia — Moon","url":"https://en.wikipedia.org/wiki/Moon"},{"label":"Wikipedia — Day","url":"https://en.wikipedia.org/wiki/Day"}],"minAge":4},{"id":"faint-young-sun-greenhouse","emoji":"☀️","title":"A dim Sun, a warm Earth","explanation":"The young Sun shone at only about 70 percent of today's intensity, so early Earth should have been completely frozen — yet it seems to have had liquid water. Greenhouse gases, mainly carbon dioxide and perhaps methane from microbes, are thought to have kept it warm: the \"faint young Sun paradox.\"","year":-4400000000,"yearEnd":-2500000000,"links":["solar-luminosity","co2","methane","temperature"],"edge":"caused","weight":0.9,"sources":[{"label":"Wikipedia — Faint young Sun paradox","url":"https://en.wikipedia.org/wiki/Faint_young_Sun_paradox"},{"label":"Catling & Zahnle 2020, The Archean atmosphere (Science Advances)","url":"https://doi.org/10.1126/sciadv.aax1420"}],"minAge":4},{"id":"hadean-ocean-condensation","emoji":"🌧️","title":"The first oceans form","explanation":"As Earth's surface cooled, the water vapour in its atmosphere condensed into liquid water and eventually formed a global ocean. Studies of tiny zircon crystals suggest liquid water may have existed as early as about 4.4 billion years ago.","year":-4400000000,"links":["temperature","sea-level"],"edge":"caused","weight":0.9,"sources":[{"label":"Wikipedia — Hadean","url":"https://en.wikipedia.org/wiki/Hadean"},{"label":"Wikipedia — Origin of water on Earth","url":"https://en.wikipedia.org/wiki/Origin_of_water_on_Earth"}],"minAge":4},{"id":"hadean-water-delivery","emoji":"☄️","title":"Where Earth's water came from","explanation":"Some of Earth's water may come from hydrogen inside the planet itself, but several geochemical studies conclude that asteroids are most likely the main source of its oceans. Comets probably supplied less than 10%.","year":-4300000000,"links":["sea-level"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Origin of water on Earth","url":"https://en.wikipedia.org/wiki/Origin_of_water_on_Earth"}],"minAge":4},{"id":"late-heavy-bombardment","emoji":"💥","title":"The Late Heavy Bombardment","explanation":"Around 4.1 to 3.8 billion years ago, a disproportionately large number of asteroids and comets may have crashed into the inner planets, including Earth and the Moon. Whether this was a single spike is still debated, and some researchers think the bombardment was spread over a longer time.","year":-4100000000,"yearEnd":-3800000000,"links":["temperature","sea-level","biodiversity"],"edge":"triggered","weight":0.85,"sources":[{"label":"Wikipedia — Late Heavy Bombardment","url":"https://en.wikipedia.org/wiki/Late_Heavy_Bombardment"}],"minAge":7},{"id":"hydrothermal-vent-first-life","emoji":"🦠","title":"Life may have begun at deep-sea vents","explanation":"Hydrothermal vents — seafloor springs of mineral-rich water — are hypothesised to be where life began, and microbes around vents live on chemicals instead of sunlight. Putative fossil microbes in vent rocks in Quebec may be as old as 4.28 billion years, though some scientists think non-living processes explain them.","year":-4280000000,"place":{"lat":56.5,"lon":-76.7,"label":"Nuvvuagittuq greenstone belt, Quebec, Canada"},"links":["biodiversity"],"edge":"enabled","weight":0.95,"sources":[{"label":"Wikipedia — Hydrothermal vent","url":"https://en.wikipedia.org/wiki/Hydrothermal_vent"},{"label":"Wikipedia — Earliest known life forms","url":"https://en.wikipedia.org/wiki/Earliest_known_life_forms"}],"minAge":4},{"id":"archean-anoxic-ocean","emoji":"⛔","title":"A world without breathable air","explanation":"From about 3.85 to 2.45 billion years ago the atmosphere held little or no free oxygen, and the oceans were mostly without it too, apart from possible small oxygen oases in shallow water. Most life then was made of anaerobic microbes that did not need oxygen.","year":-3800000000,"yearEnd":-2500000000,"links":["oxygen","biodiversity"],"edge":"constrained","weight":0.86,"sources":[{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"},{"label":"Holland 2006, The oxygenation of the atmosphere and oceans (Philosophical Transactions of the Royal Society B)","url":"https://doi.org/10.1098/rstb.2006.1838"}],"minAge":4},{"id":"archean-first-continents","emoji":"🏔️","title":"The first continents rise","explanation":"Cratons, the old, stable cores of today's continents, mostly formed in the Archean, between 4 and 2.5 billion years ago. There is little evidence of continental crust before 3.5 billion years ago, and about 60% of its present volume formed between 3.0 and 2.5 billion years ago.","year":-3500000000,"links":["sea-level"],"edge":"enabled","weight":0.84,"sources":[{"label":"Wikipedia — Craton","url":"https://en.wikipedia.org/wiki/Craton"},{"label":"Wikipedia — Continental crust","url":"https://en.wikipedia.org/wiki/Continental_crust"}],"minAge":4},{"id":"archean-stromatolites","emoji":"🪨","title":"Living reefs of microbes","explanation":"Microbes in shallow Archean seas formed mats that trapped sediment grains, layer upon layer, building rocks called stromatolites. The 3,430-million-year-old Strelley Pool Chert in Western Australia holds stromatolites of probable biological origin, though the biogenicity of such ancient fossils is still debated.","year":-3430000000,"place":{"lat":-20.9,"lon":119.1,"label":"Strelley Pool, Pilbara, Western Australia"},"links":["biodiversity"],"edge":"enabled","weight":0.87,"sources":[{"label":"Allwood et al. 2006, Stromatolite reef from the Early Archaean era of Australia (Nature)","url":"https://doi.org/10.1038/nature04764"},{"label":"Wikipedia — Stromatolite","url":"https://en.wikipedia.org/wiki/Stromatolite"}],"minAge":4},{"id":"banded-iron-formations","emoji":"🟥","title":"The oceans rust away","explanation":"Banded iron formations are theorised to have formed when oxygen made by photosynthetic cyanobacteria combined with iron dissolved in the oceans, making iron oxides that sank in thin layers to the seafloor. Today they hold more than 60% of the world's iron reserves and supply most of the iron ore mined.","year":-3000000000,"yearEnd":-2500000000,"place":{"lat":-22.3,"lon":117.8,"label":"Hamersley Basin, Pilbara, Western Australia"},"links":["oxygen","ocean-ph"],"edge":"caused","weight":0.88,"sources":[{"label":"Wikipedia — Banded iron formation","url":"https://en.wikipedia.org/wiki/Banded_iron_formation"}],"minAge":4},{"id":"archean-methane-haze","emoji":"🌫️","title":"A methane haze in the sky","explanation":"Before oxygen rose, Earth's air may have held an organic haze like the one on Titan. Rocks 2.65 to 2.5 billion years old suggest the air was at times rich in methane from microbes, and that it flipped between hazy and haze-free. Methane is a greenhouse gas that may also have helped keep early Earth warm.","year":-2650000000,"links":["methane","temperature"],"edge":"caused","weight":0.83,"sources":[{"label":"Zerkle et al. 2012, A bistable organic-rich atmosphere on the Neoarchaean Earth (Nature Geoscience)","url":"https://doi.org/10.1038/ngeo1425"},{"label":"Pavlov et al. 2000, Greenhouse warming by CH4 in the atmosphere of early Earth (Journal of Geophysical Research: Planets)","url":"https://doi.org/10.1029/1999JE001134"}],"minAge":4},{"id":"cyanobacteria-first-oxygen","emoji":"🫧","title":"Cyanobacteria start making oxygen","explanation":"Tiny blue-green cyanobacteria split water molecules using sunlight and release oxygen as a by-product; they are the first organisms known to have done so. Evidence suggests they were doing it by about 2.7 billion years ago, long before oxygen built up in the air around 2.4 billion years ago.","year":-2700000000,"links":["oxygen","co2"],"edge":"caused","weight":0.97,"sources":[{"label":"Wikipedia — Cyanobacteria","url":"https://en.wikipedia.org/wiki/Cyanobacteria"},{"label":"Buick 2008, When did oxygenic photosynthesis evolve? (Philosophical Transactions of the Royal Society B)","url":"https://doi.org/10.1098/rstb.2008.0041"}],"minAge":4},{"id":"goe-great-oxidation-event","emoji":"💨","title":"Oxygen fills the sky","explanation":"Around 2.4 billion years ago free oxygen began to build up in the air for the first time, an upheaval scientists call the Great Oxidation Event. We can date it because sulfur signatures in rocks that form only when oxygen is scarce disappear after about 2.45 billion years ago.","year":-2400000000,"yearEnd":-2000000000,"links":["oxygen"],"edge":"triggered","weight":0.97,"sources":[{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"},{"label":"Farquhar, Bao & Thiemens 2000, Atmospheric influence of Earth's earliest sulfur cycle (Science)","url":"https://doi.org/10.1126/science.289.5480.756"},{"label":"Bekker et al. 2004, Dating the rise of atmospheric oxygen (Nature)","url":"https://doi.org/10.1038/nature02260"}],"minAge":4},{"id":"goe-oxygen-catastrophe-anaerobes","emoji":"☠️","title":"The oxygen poisoning","explanation":"For the mostly anaerobic microbes of the young Earth, free oxygen was toxic. It may have wiped out many early organisms, and the event is inferred to have been a mass extinction, even though it is not usually counted among the \"great extinctions.\"","year":-2400000000,"yearEnd":-2100000000,"links":["oxygen","biodiversity"],"edge":"triggered","weight":0.9,"sources":[{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"}],"minAge":7},{"id":"goe-methane-greenhouse-collapse","emoji":"🔥","title":"Oxygen eats the warm blanket","explanation":"Before oxygen rose, methane may have helped keep Earth warm. Oxygen reacted with the methane to form carbon dioxide and water, both much weaker greenhouse gases, which greatly cut the greenhouse effect and may have helped trigger the first widespread glaciation.","year":-2400000000,"yearEnd":-2300000000,"links":["oxygen","methane","temperature"],"edge":"caused","weight":0.93,"sources":[{"label":"Wikipedia — Huronian glaciation","url":"https://en.wikipedia.org/wiki/Huronian_glaciation"},{"label":"Pavlov et al. 2000, Greenhouse warming by CH4 in the atmosphere of early Earth (Journal of Geophysical Research: Planets)","url":"https://doi.org/10.1029/1999JE001134"},{"label":"Kopp et al. 2005, The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis (PNAS)","url":"https://doi.org/10.1073/pnas.0504878102"}],"minAge":4},{"id":"goe-huronian-snowball-earth","emoji":"❄️","title":"The great freeze","explanation":"As oxygen built up in the air it destroyed much of the methane that kept early Earth warm, and with the Sun possibly fainter too, the planet cooled into an icehouse. Rocks north of Lake Huron record at least three ice ages, laid down from about 2.4 to 2.1 billion years ago. Whether any of them was a global \"Snowball Earth\" is contested: one study dates all three before a global freeze recorded in South Africa about 2.3 to 2.2 billion years ago.","year":-2400000000,"yearEnd":-2100000000,"place":{"lat":46.4,"lon":-82.6,"label":"Huronian Supergroup, Ontario, Canada"},"links":["temperature","ice-cover","methane"],"edge":"triggered","weight":0.95,"sources":[{"label":"Wikipedia — Huronian glaciation","url":"https://en.wikipedia.org/wiki/Huronian_glaciation"},{"label":"Kopp et al. 2005, The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis (PNAS)","url":"https://doi.org/10.1073/pnas.0504878102"},{"label":"Gumsley et al. 2017, Timing and tempo of the Great Oxidation Event (PNAS)","url":"https://doi.org/10.1073/pnas.1608824114"}],"minAge":4},{"id":"goe-ozone-shield-begins","emoji":"🛡️","title":"A sunscreen for the planet","explanation":"As oxygen began to accumulate in the air, sunlight turned some of it into ozone, which absorbs harmful ultraviolet light. The disappearance of a sulfur signature in rocks suggests an ozone shield began to form then, although the ozone layer as we know it formed about 500 million years ago.","year":-2400000000,"yearEnd":-2000000000,"links":["oxygen","biodiversity"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"},{"label":"Wikipedia — Ozone layer","url":"https://en.wikipedia.org/wiki/Ozone_layer"}],"minAge":4},{"id":"goe-continental-red-beds","emoji":"🟥","title":"The land turns red","explanation":"Red beds are sandstones coated with the iron mineral hematite, which forms when iron is oxidised, so they show there was enough oxygen to rust iron. Continental red beds begin to appear in the rock record at about the time of the Great Oxidation Event, a sign the air had gained oxygen.","year":-2300000000,"yearEnd":-2000000000,"links":["oxygen"],"edge":"caused","weight":0.81,"sources":[{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"},{"label":"Kopp et al. 2005, The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis (PNAS)","url":"https://doi.org/10.1073/pnas.0504878102"}],"minAge":4},{"id":"goe-lomagundi-carbon-excursion","emoji":"📈","title":"The great carbon spike","explanation":"As oxygen rose, Earth's rocks recorded the largest and longest-lasting swing in carbon chemistry ever found in ancient seabed carbonate rocks, the Lomagundi-Jatuli event. It is thought to reflect a huge amount of carbon being buried by living things, which may have released extra oxygen before levels dropped back. It hints that the newborn oxygen world was unstable.","year":-2220000000,"yearEnd":-2060000000,"place":{"lat":-17,"lon":30.2,"label":"Lomagundi, Zimbabwe"},"links":["oxygen","co2"],"edge":"enabled","weight":0.85,"sources":[{"label":"Wikipedia — Lomagundi-Jatuli Carbon Isotope Excursion","url":"https://en.wikipedia.org/wiki/Lomagundi-Jatuli_Carbon_Isotope_Excursion"},{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"}],"minAge":4},{"id":"goe-aerobic-respiration-energy","emoji":"⚡","title":"Breathing unlocks power","explanation":"Using oxygen to release energy from food can yield up to 15 times as much as living without it. Mitochondria, the tiny energy-makers inside complex cells, are thought to descend from oxygen-using bacteria that came to live inside another cell; this partnership probably developed 1.7 to 2 billion years ago, after the Great Oxidation Event. Researchers argue that the power of mitochondria was a prerequisite for complex life and the key step on the way to many-celled creatures.","year":-2000000000,"yearEnd":-1700000000,"links":["oxygen","biodiversity"],"edge":"enabled","weight":0.84,"sources":[{"label":"Wikipedia — Cellular respiration","url":"https://en.wikipedia.org/wiki/Cellular_respiration"},{"label":"Lane & Martin 2010, The energetics of genome complexity (Nature)","url":"https://doi.org/10.1038/nature09486"},{"label":"Wikipedia — Mitochondria","url":"https://en.wikipedia.org/wiki/Mitochondria"},{"label":"Wikipedia — Great Oxidation Event","url":"https://en.wikipedia.org/wiki/Great_Oxidation_Event"}],"minAge":4},{"id":"goe-eukaryote-endosymbiosis","emoji":"🧬","title":"The first complex cells","explanation":"A leading idea is that after oxygen rose, one microbe took in another that could use oxygen, and the two became partners instead of one digesting the other. That partnership, called endosymbiosis, produced the mitochondria inside complex cells, including yours. When it happened is hard to pin down: coiled fossils from Michigan, first dated to 2.1 billion years ago and since redated to about 1.87 billion, may be early algae, and fossils from China about 1.8 to 1.6 billion years old may be the oldest known eukaryotes - the group that includes all animals, plants and fungi.","year":-2100000000,"yearEnd":-1600000000,"place":{"lat":46.5,"lon":-87.6,"label":"Negaunee Iron Formation, Michigan"},"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.94,"sources":[{"label":"Wikipedia — Symbiogenesis","url":"https://en.wikipedia.org/wiki/Symbiogenesis"},{"label":"Wikipedia — Eukaryote","url":"https://en.wikipedia.org/wiki/Eukaryote"},{"label":"Han & Runnegar 1992, Megascopic Eukaryotic Algae from the 2.1-Billion-Year-Old Negaunee Iron-Formation, Michigan (Science)","url":"https://doi.org/10.1126/science.1631544"},{"label":"Wikipedia — Grypania","url":"https://en.wikipedia.org/wiki/Grypania"}],"minAge":4},{"id":"boring-billion-oxygen-ceiling","emoji":"🫧","title":"The billion-year lull","explanation":"For roughly a billion years the air and seas held little oxygen, thought to be perhaps 0.1% to 10% of today's level, with only minor ups and downs. That low ceiling is often blamed for why complex life evolved so slowly, which is why this age is nicknamed the 'Boring Billion'. Yet it was also when early complex cells developed new adaptations, important precursors to the bigger life that followed.","year":-1800000000,"yearEnd":-800000000,"links":["oxygen","biodiversity","temperature"],"edge":"constrained","weight":0.93,"sources":[{"label":"Wikipedia — Boring Billion","url":"https://en.wikipedia.org/wiki/Boring_Billion"},{"label":"Holland 2006, The oxygenation of the atmosphere and oceans (Philosophical Transactions of the Royal Society B)","url":"https://doi.org/10.1098/rstb.2006.1838"}],"minAge":4},{"id":"boring-billion-canfield-ocean","emoji":"🟡","title":"The sulfur seas","explanation":"Below a thin, moderately oxygen-rich surface, the deeper ocean was probably laced with poisonous hydrogen sulfide instead of oxygen. Under those conditions trace metals that microbes need, like molybdenum, would have been scarce, potentially restricting how nitrogen was supplied to life. That chemical bottleneck may help explain why evolution moved so slowly.","year":-1800000000,"yearEnd":-800000000,"links":["oxygen","ocean-ph","biodiversity"],"edge":"constrained","weight":0.89,"sources":[{"label":"Wikipedia — Boring Billion","url":"https://en.wikipedia.org/wiki/Boring_Billion"},{"label":"Wikipedia — Canfield ocean","url":"https://en.wikipedia.org/wiki/Canfield_ocean"},{"label":"Anbar & Knoll 2002, Proterozoic Ocean Chemistry and Evolution: A Bioinorganic Bridge? (Science)","url":"https://doi.org/10.1126/science.1069651"}],"minAge":4},{"id":"proterozoic-phosphorus-famine","emoji":"🍽️","title":"A world on a diet","explanation":"Phosphorus is a key nutrient for ocean life, and the rocks suggest it was scarce for a very long time: ocean phosphate was probably only about 10-25% of today's level in the early Proterozoic, and low burial points to phosphorus shortage until about 800 to 700 million years ago. Too little of it should have slowed photosynthesis, which helped keep oxygen low, one proposed explanation for the long low-oxygen stretch.","year":-1800000000,"yearEnd":-800000000,"links":["oxygen","biodiversity"],"edge":"constrained","weight":0.84,"sources":[{"label":"Reinhard et al. 2017, Evolution of the global phosphorus cycle (Nature)","url":"https://doi.org/10.1038/nature20772"},{"label":"Bjerrum & Canfield 2002, Ocean productivity before about 1.9 Gyr ago limited by phosphorus adsorption onto iron oxides (Nature)","url":"https://doi.org/10.1038/417159a"}],"minAge":4},{"id":"boring-billion-climate-stasis","emoji":"🌡️","title":"A billion years without ice ages","explanation":"Between roughly 1.8 and 0.8 billion years ago the geological record shows no evidence of long-lasting glaciers, a very long stretch without the ice ages seen at other times. Carbon chemistry, continents and climate all appear to have been unusually stable. Against that quiet backdrop, early complex cells took their slow first steps.","year":-1800000000,"yearEnd":-800000000,"links":["temperature","ice-cover"],"edge":"constrained","weight":0.85,"sources":[{"label":"Wikipedia — Boring Billion","url":"https://en.wikipedia.org/wiki/Boring_Billion"},{"label":"Brasier & Lindsay 1998, A billion years of environmental stability and the emergence of eukaryotes: New data from northern Australia (Geology)","url":"https://doi.org/10.1130/0091-7613(1998)026<0555:abyoes>2.3.co;2"}],"minAge":4},{"id":"proterozoic-faint-sun-methane","emoji":"🌫️","title":"A warm world under a dim Sun","explanation":"During the Boring Billion the Sun was 5-18% less luminous than today, yet there is no evidence that Earth's climate was significantly cooler. Greenhouse gases other than carbon dioxide, such as methane and probably nitrous oxide, may have made up the difference. Scientists are still working out the exact balance.","year":-1800000000,"yearEnd":-800000000,"links":["solar-luminosity","methane","temperature"],"edge":"enabled","weight":0.86,"sources":[{"label":"Wikipedia — Boring Billion","url":"https://en.wikipedia.org/wiki/Boring_Billion"}],"minAge":4},{"id":"rodinia-assembly-grenville","emoji":"🏔️","title":"A supercontinent comes together","explanation":"Between about 1.26 and 0.90 billion years ago, continents collided and assembled into the supercontinent Rodinia, building mountain belts such as the Grenville orogeny, whose record spans much of North America from Labrador to Mexico, and reaches Scotland. The extreme cooling of the Cryogenian, around 717 to 635 million years ago, is thought to have been triggered by Rodinia's later break-up or by a slowing of tectonic processes.","year":-1260000000,"yearEnd":-900000000,"place":{"lat":45,"lon":-75,"label":"Grenville mountain belt (eastern North America)"},"links":["temperature","ice-cover"],"edge":"caused","weight":0.88,"sources":[{"label":"Wikipedia — Rodinia","url":"https://en.wikipedia.org/wiki/Rodinia"},{"label":"Wikipedia — Grenville orogeny","url":"https://en.wikipedia.org/wiki/Grenville_orogeny"}],"minAge":4},{"id":"bangiomorpha-first-sex","emoji":"🌹","title":"The first known sex","explanation":"On what is now Somerset Island in Canada, a tiny red alga called Bangiomorpha left the oldest evidence of sexual reproduction. Sex increased genetic variation, which led to a faster rate of evolution and the diversification of complex cells. This alga, about 1,047 million years old, is where that story begins in the fossil record.","year":-1047000000,"place":{"lat":73.7,"lon":-93.5,"label":"Somerset Island, Arctic Canada"},"links":["biodiversity"],"edge":"enabled","weight":0.95,"sources":[{"label":"Wikipedia — Bangiomorpha","url":"https://en.wikipedia.org/wiki/Bangiomorpha"}],"minAge":4},{"id":"proterocladus-green-seaweeds","emoji":"🌿","title":"An ancient green seaweed","explanation":"In what is now China, delicate branching green algae named Proterocladus grew about a billion years ago. These millimetre-sized, many-celled fossils show that green algae became large and multicellular nearly a billion years ago, much earlier than previously thought. They belong to the chlorophytes, a branch of the green-plant family tree that probably dominated ocean productivity and helped ecosystems become more complex, before diatoms and other plankton diversified in the Mesozoic.","year":-1000000000,"place":{"lat":40.5,"lon":123.7,"label":"North China (Nanfen Formation)"},"links":["biodiversity"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Proterocladus","url":"https://en.wikipedia.org/wiki/Proterocladus"},{"label":"Tang et al. 2020, A one-billion-year-old multicellular chlorophyte (Nature Ecology & Evolution)","url":"https://doi.org/10.1038/s41559-020-1122-9"}],"minAge":4},{"id":"tonian-eukaryote-radiation","emoji":"🦠","title":"Complex cells wake up","explanation":"As the Boring Billion drew to a close, the fossil record shows algae and other complex cells diversifying: the Tonian saw the first large radiation of acritarchs and some of the earliest known macroalgae, and the middle to late Tonian holds the first putative animal fossils. Oxygen began to rise in the Neoproterozoic Oxygenation Event, and very early many-celled organisms may have evolved and diversified in oxygen 'oases' in the deep ocean.","year":-1000000000,"yearEnd":-720000000,"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.87,"sources":[{"label":"Wikipedia — Tonian","url":"https://en.wikipedia.org/wiki/Tonian"},{"label":"Wikipedia — Boring Billion","url":"https://en.wikipedia.org/wiki/Boring_Billion"},{"label":"Wikipedia — Neoproterozoic oxygenation event","url":"https://en.wikipedia.org/wiki/Neoproterozoic_oxygenation_event"}],"minAge":4},{"id":"rodinia-breakup-weathering-cooldown","emoji":"🌋","title":"Rifting rock cools the planet","explanation":"Starting around 825 million years ago Rodinia began to break apart, which exposed huge volcanic basalt fields to warm, moist conditions. Weathering of that rock draws carbon dioxide out of the air and locks it into rock. This drawdown of greenhouse gas is believed to have contributed to the start of the Sturtian glaciation, the first of the deep freezes.","year":-825000000,"yearEnd":-720000000,"links":["co2","temperature","sea-level"],"edge":"caused","weight":0.92,"sources":[{"label":"Wikipedia — Rodinia","url":"https://en.wikipedia.org/wiki/Rodinia"},{"label":"Wikipedia — Snowball Earth","url":"https://en.wikipedia.org/wiki/Snowball_Earth"}],"minAge":4},{"id":"cryo-rodinia-weathering-freeze","emoji":"🌋","title":"A shattering supercontinent invites the ice","explanation":"As the supercontinent Rodinia reached the equator and rifted apart, the huge Franklin eruptions about 719 million years ago laid down vast fresh basalts in Arctic Canada. Weathering of that new rock pulled carbon dioxide out of the air, and the thinning greenhouse is proposed to have pushed the planet into the Sturtian glaciation, which began just 0.9 to 1.6 million years later and lasted until about 660 million years ago.","year":-717000000,"yearEnd":-660000000,"place":{"lat":72,"lon":-100,"label":"Franklin igneous province, Arctic Canada"},"links":["co2","temperature","ice-cover"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Franklin Large Igneous Province","url":"https://en.wikipedia.org/wiki/Franklin_Large_Igneous_Province"},{"label":"Wikipedia — Rodinia","url":"https://en.wikipedia.org/wiki/Rodinia"},{"label":"Macdonald et al. 2010, Calibrating the Cryogenian (Science)","url":"https://doi.org/10.1126/science.1183325"}],"minAge":4},{"id":"cryo-albedo-runaway-snowball","emoji":"❄️","title":"Snowball Earth","explanation":"Models show that once ice spread to within about 25 to 30 degrees of the equator, a runaway loop began: bright white ice reflected sunlight back to space, cooling things further and growing yet more ice. With the young Sun also about 6 percent fainter than today, the Sturtian glaciation lasted about 57 million years and is thought to have been a global freeze, with ice at sea level near the equator, though scientists still debate whether it was a full 'snowball' or a 'slushball'.","year":-717000000,"yearEnd":-660000000,"place":{"lat":0,"lon":0,"label":"Tropical oceans, frozen over"},"links":["ice-cover","temperature","solar-luminosity"],"edge":"triggered","weight":0.95,"sources":[{"label":"Wikipedia — Snowball Earth","url":"https://en.wikipedia.org/wiki/Snowball_Earth"},{"label":"Macdonald et al. 2010, Calibrating the Cryogenian (Science)","url":"https://doi.org/10.1126/science.1183325"}],"minAge":4},{"id":"cryo-co2-supergreenhouse-thaw","emoji":"🔥","title":"The volcanoes that melted the ice","explanation":"With the oceans capped by ice, weathering could no longer pull carbon dioxide out of the air, so the CO2 that volcanoes kept releasing built up. One estimate is that about 350 times today's level was needed to thaw the ice, though in a later climate model the planet stayed frozen even at 550 times. Once melting began, it could finish in as little as a thousand years.","year":-660000000,"links":["co2","temperature","ice-cover"],"edge":"enabled","weight":0.93,"sources":[{"label":"Wikipedia — Snowball Earth","url":"https://en.wikipedia.org/wiki/Snowball_Earth"},{"label":"Hoffman et al. 1998, A Neoproterozoic Snowball Earth (Science)","url":"https://doi.org/10.1126/science.281.5381.1342"},{"label":"Pierrehumbert 2004, High levels of atmospheric carbon dioxide necessary for the termination of global glaciation (Nature)","url":"https://doi.org/10.1038/nature02640"}],"minAge":4},{"id":"cryo-marinoan-second-freeze","emoji":"🧊","title":"The world freezes a second time","explanation":"After a relatively warm interglacial period, Earth entered a second worldwide glaciation, the Marinoan. Its timing is poorly constrained: it is often given as roughly 650 to 635 million years ago, though a 2025 study dates it to between 639 and 635 million years ago. The Ediacaran Period is defined at the base of a cap carbonate laid down just above its glacial rocks in South Australia's Flinders Ranges, and it marks the first widespread appearance of complex multicellular life; the most recent snowball episode may have triggered the evolution of multicellularity.","year":-650000000,"yearEnd":-635000000,"place":{"lat":-31.3,"lon":138.6,"label":"Elatina glacials, Flinders Ranges, Australia"},"links":["ice-cover","temperature"],"edge":"enabled","weight":0.88,"sources":[{"label":"Wikipedia — Marinoan glaciation","url":"https://en.wikipedia.org/wiki/Marinoan_glaciation"},{"label":"Wikipedia — Ediacaran","url":"https://en.wikipedia.org/wiki/Ediacaran"},{"label":"Wikipedia — Snowball Earth","url":"https://en.wikipedia.org/wiki/Snowball_Earth"}],"minAge":4},{"id":"cryo-cap-carbonate-aftermath","emoji":"🪨","title":"A blanket of rock over the ice","explanation":"When the snowball ended, the atmosphere held huge amounts of CO2 and the planet warmed to extreme greenhouse conditions. One leading explanation is that CO2 moving into the ocean, along with weathering that washed in calcium, rapidly formed a layer of carbonate rock, typically 3 to 30 metres thick, that still sits directly on the glacial deposits on most continents. It is a rock signature of a planet lurching from deep freeze to hothouse.","year":-635000000,"place":{"lat":-19.5,"lon":17,"label":"Otavi cap carbonates, Namibia"},"links":["co2","ocean-ph","temperature"],"edge":"enabled","weight":0.87,"sources":[{"label":"Wikipedia — Cap carbonate","url":"https://en.wikipedia.org/wiki/Cap_carbonate"},{"label":"Wikipedia — Snowball Earth","url":"https://en.wikipedia.org/wiki/Snowball_Earth"},{"label":"Hoffman et al. 1998, A Neoproterozoic Snowball Earth (Science)","url":"https://doi.org/10.1126/science.281.5381.1342"}],"minAge":4},{"id":"ediacaran-phosphorus-oxygen-pulse","emoji":"🫧","title":"Meltwater feeds a breath of oxygen","explanation":"As the snowballs melted, more phosphorus is thought to have reached the seas, and one study found unusually high dissolved phosphate in the aftermath of the snowball glaciations. That extra nutrient would have driven high rates of life and of carbon burial, shifting the ocean and air toward more oxygen. Rocks from about 635 to 630 million years ago in South China record a widely oxygenated ocean, part of the Neoproterozoic Oxygenation Event, an oxygen rise proposed as a driver of early animal diversification.","year":-635000000,"yearEnd":-630000000,"place":{"lat":-19.5,"lon":17,"label":"Post-Marinoan seas, southern Africa"},"links":["oxygen","co2","biodiversity"],"edge":"caused","weight":0.9,"sources":[{"label":"Planavsky et al. 2010, The evolution of the marine phosphate reservoir (Nature)","url":"https://doi.org/10.1038/nature09485"},{"label":"Sahoo et al. 2012, Ocean oxygenation in the wake of the Marinoan glaciation (Nature)","url":"https://doi.org/10.1038/nature11445"},{"label":"Wikipedia — Neoproterozoic oxygenation event","url":"https://en.wikipedia.org/wiki/Neoproterozoic_oxygenation_event"}],"minAge":4},{"id":"ediacaran-oxygen-enables-big-life","emoji":"🌱","title":"Enough oxygen to grow big","explanation":"Over the Ediacaran the oceans gradually became better oxygenated, with marine oxygen rising markedly after the short Gaskiers glaciation about 580 million years ago. Some scientists credit that oxygen with letting the oxygen-using, many-celled Ediacaran organisms spread and become widespread, though the oldest of their large fossils come about 9 million years after the ice.","year":-580000000,"links":["oxygen","biodiversity"],"edge":"enabled","weight":0.89,"sources":[{"label":"Wikipedia — Neoproterozoic oxygenation event","url":"https://en.wikipedia.org/wiki/Neoproterozoic_oxygenation_event"},{"label":"Sperling et al. 2013, Oxygen, ecology, and the Cambrian radiation of animals (PNAS)","url":"https://doi.org/10.1073/pnas.1312778110"},{"label":"Wikipedia — Gaskiers glaciation","url":"https://en.wikipedia.org/wiki/Gaskiers_glaciation"}],"minAge":4},{"id":"ediacaran-avalon-first-giants","emoji":"🪸","title":"The first giants of the deep","explanation":"On the deep, dark seafloor around 575 million years ago, strange fern-like fronds called rangeomorphs lived with no sign of a mouth or gut; one idea is that they absorbed nutrients straight from the water, though some researchers argue for filter feeding instead. Preserved under fine volcanic ash at Mistaken Point in Newfoundland, this Avalon assemblage is the oldest place with a large number of Ediacaran fossils, records of the oldest known complex life on Earth.","year":-575000000,"yearEnd":-560000000,"place":{"lat":46.63,"lon":-53.18,"label":"Mistaken Point, Newfoundland"},"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Rangeomorph","url":"https://en.wikipedia.org/wiki/Rangeomorph"},{"label":"Wikipedia — Avalon explosion","url":"https://en.wikipedia.org/wiki/Avalon_explosion"},{"label":"Wikipedia — Mistaken Point Formation","url":"https://en.wikipedia.org/wiki/Mistaken_Point_Formation"},{"label":"Wikipedia — Ediacaran biota","url":"https://en.wikipedia.org/wiki/Ediacaran_biota"}],"minAge":4},{"id":"ediacaran-dickinsonia-first-animal","emoji":"🧬","title":"Fat molecules reveal early animals","explanation":"Dickinsonia, a flat ribbed oval up to about 1.4 metres long, puzzled scientists for decades. In 2018 researchers reported cholesterol-like molecules (cholesteroids), a hallmark of animals, in Russian specimens, and concluded that Dickinsonia and its relatives were the oldest confirmed large animals in the rock record. Other scientists consider the link between the molecules and the fossils not definitive, and Dickinsonia's place in the tree of life is still debated.","year":-560000000,"place":{"lat":65.5,"lon":40,"label":"White Sea coast, Russia"},"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.86,"sources":[{"label":"Bobrovskiy et al. 2018, Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals (Science)","url":"https://doi.org/10.1126/science.aat7228"},{"label":"Wikipedia — Dickinsonia","url":"https://en.wikipedia.org/wiki/Dickinsonia"},{"label":"Wikipedia — White Sea assemblage","url":"https://en.wikipedia.org/wiki/White_Sea_assemblage"}],"minAge":4,"yearEnd":-550000000},{"id":"ediacaran-kimberella-first-grazer","emoji":"🐌","title":"An early grazer on the seabed","explanation":"Among the White Sea fossils, dated to about 555 to 558 million years ago, the slug-like Kimberella probably grazed on microbial mats, scratching the surface as it fed. It is recognised as the oldest well-documented bilaterian, an animal that moved across the seabed as it ate.","year":-555000000,"place":{"lat":65.5,"lon":40,"label":"White Sea coast, Russia"},"links":["biodiversity"],"edge":"enabled","weight":0.84,"sources":[{"label":"Wikipedia — Kimberella","url":"https://en.wikipedia.org/wiki/Kimberella"}],"minAge":4},{"id":"ediacaran-cloudina-first-skeletons","emoji":"🐚","title":"The first shells and the dawn of predators","explanation":"Near the end of the Ediacaran, tube-building Cloudina were among the earliest creatures with mineralized skeletons, and in some places up to 20% of their fossils carry predatory borings. That arms race between predators and armour is commonly cited as a cause of the explosion of animal life in the Cambrian.","year":-550000000,"place":{"lat":-25,"lon":16.5,"label":"Nama Group, Namibia"},"links":["biodiversity"],"edge":"caused","weight":0.85,"sources":[{"label":"Wikipedia — Cloudinidae","url":"https://en.wikipedia.org/wiki/Cloudinidae"}],"minAge":7},{"id":"cambrian-burrowers-churn-seafloor","emoji":"🪱","title":"The first diggers plough the seafloor","explanation":"Early Cambrian animals began burrowing into the once-still microbial mats of the seabed, a change called the 'agronomic revolution'. Burrowing let water and oxygen reach deeper below the surface, making the upper seafloor habitable for a much wider range of organisms, and the mixing of sediment is proposed to have raised the sulfate in seawater.","year":-538000000,"links":["biodiversity","oxygen"],"edge":"caused","weight":0.83,"sources":[{"label":"Wikipedia — Cambrian substrate revolution","url":"https://en.wikipedia.org/wiki/Cambrian_substrate_revolution"},{"label":"Canfield & Farquhar 2009, Animal evolution, bioturbation, and the sulfate concentration of the oceans (PNAS)","url":"https://doi.org/10.1073/pnas.0902037106"}],"minAge":4},{"id":"ordovician-moss-weathering-chill","emoji":"🌱","title":"The first land plants and an ice age","explanation":"The first land plants appear about 470 million years ago, known from tiny spores like those of modern liverworts. The spread of land plants and of microscopic plankton, which consumed carbon dioxide, may have weakened the greenhouse effect and helped tip the climate into the Late Ordovician glaciation. The cause is heavily debated: the weathering of rising mountains also drew CO2 down.","year":-470000000,"links":["vegetation","co2","temperature","ice-cover"],"edge":"enabled","weight":0.88,"sources":[{"label":"Wikipedia — Evolutionary history of plants","url":"https://en.wikipedia.org/wiki/Evolutionary_history_of_plants"},{"label":"Wikipedia — Late Ordovician mass extinction","url":"https://en.wikipedia.org/wiki/Late_Ordovician_mass_extinction"},{"label":"Wikipedia — Hirnantian glaciation","url":"https://en.wikipedia.org/wiki/Hirnantian_glaciation"}],"minAge":4},{"id":"andean-saharan-glaciation-sahara-ice","emoji":"🧊","title":"Glaciers on the Sahara","explanation":"In the Late Ordovician the giant southern continent Gondwana sat over the South Pole, and glaciation left its mark in the rocks of what is now the Sahara. Ice volumes likely equalled or exceeded those of the last Ice Age maximum, and the sea-level fall drained shallow seas and eliminated the habitat of many species, a glaciation typically blamed for the first pulse of the Late Ordovician mass extinction.","year":-450000000,"yearEnd":-440000000,"place":{"lat":25,"lon":10,"label":"Sahara (Gondwana over the South Pole)"},"links":["ice-cover","sea-level","biodiversity"],"edge":"caused","weight":0.87,"sources":[{"label":"Wikipedia — Hirnantian glaciation","url":"https://en.wikipedia.org/wiki/Hirnantian_glaciation"},{"label":"Wikipedia — Late Ordovician mass extinction","url":"https://en.wikipedia.org/wiki/Late_Ordovician_mass_extinction"},{"label":"Finnegan et al. 2011, The magnitude and duration of Late Ordovician-Early Silurian glaciation (Science)","url":"https://doi.org/10.1126/science.1200803"}],"minAge":7},{"id":"paleozoic-ozone-shield","emoji":"🛡️","title":"The sky grows a sunscreen","explanation":"As photosynthesis pumped oxygen into the air, ultraviolet light turned some of it into ozone (O3), which collected in a layer high up. The ozone layer is thought to have formed about 500 million years ago, when oxygen reached about 20% of the air. It absorbs most of the Sun's harmful ultraviolet; without it, ultraviolet would have caused unsustainable mutation in exposed cells, so it let life colonise the ocean surface and eventually the land.","year":-500000000,"links":["oxygen","biodiversity"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Ozone layer","url":"https://en.wikipedia.org/wiki/Ozone_layer"},{"label":"Wikipedia — History of Earth","url":"https://en.wikipedia.org/wiki/History_of_Earth"}],"minAge":4},{"id":"devonian-first-forests-build-soil","emoji":"🌳","title":"The first forests dig in","explanation":"In the Devonian, Archaeopteris trees grew woody trunks and the first extensive root systems. Their roots broke up the upper layers of bedrock and held a deep layer of soil, and soil promotes weathering; the new forests drew carbon out of the air, and the spread of land plants matches a long-term fall in CO2.","year":-385000000,"place":{"lat":42.4,"lon":-74.4,"label":"Cairo & Gilboa fossil forests, New York"},"links":["vegetation","co2"],"edge":"caused","weight":0.87,"sources":[{"label":"Stein et al. 2020, Mid-Devonian Archaeopteris Roots Signal Revolutionary Change in Earliest Fossil Forests (Current Biology)","url":"https://doi.org/10.1016/j.cub.2019.11.067"},{"label":"Wikipedia — Archaeopteris","url":"https://en.wikipedia.org/wiki/Archaeopteris"},{"label":"Wikipedia — Late Devonian mass extinction","url":"https://en.wikipedia.org/wiki/Late_Devonian_mass_extinction"},{"label":"Wikipedia — Devonian","url":"https://en.wikipedia.org/wiki/Devonian"}],"minAge":4},{"id":"devonian-fish-to-land","emoji":"🐟","title":"Fish learn to walk","explanation":"In the warm, oxygen-poor waters of Devonian lakes and streams, some early fish developed lungs and the ability to crawl out of the water for short periods. Tiktaalik, about 375 million years ago, had fins with a wrist-like joint that could prop it up in shallow water, a link between swimming fish and four-legged vertebrates.","year":-375000000,"place":{"lat":78.5,"lon":-82,"label":"Ellesmere Island, Canada (Tiktaalik)"},"links":["biodiversity","oxygen"],"edge":"enabled","weight":0.9,"sources":[{"label":"Daeschler, Shubin & Jenkins 2006, A Devonian tetrapod-like fish and the evolution of the tetrapod body plan (Nature)","url":"https://doi.org/10.1038/nature04639"},{"label":"Wikipedia — Tiktaalik","url":"https://en.wikipedia.org/wiki/Tiktaalik"},{"label":"Wikipedia — Devonian","url":"https://en.wikipedia.org/wiki/Devonian"}],"minAge":4},{"id":"devonian-kellwasser-forest-anoxia","emoji":"🟢","title":"Did forests choke the seas?","explanation":"As deep-rooted forests spread in the Late Devonian, their soils sped up weathering and released nutrients such as phosphates. The relatively sudden input of nutrients into rivers may have caused algal blooms whose decay used up the oxygen. Widespread ocean anoxia accompanied the Kellwasser event about 372 million years ago, which hit reef-builders hardest. One study ties the spread of plants to carbon dioxide drawdown and anoxia, but another blames rivers rather than plants, and the link has long been conjectural.","year":-372000000,"links":["vegetation","biodiversity","oxygen","co2"],"edge":"enabled","weight":0.88,"sources":[{"label":"Wikipedia — Late Devonian mass extinction","url":"https://en.wikipedia.org/wiki/Late_Devonian_mass_extinction"}],"minAge":7},{"id":"devonian-hangenberg-cold-snap","emoji":"❄️","title":"A green world tips into ice","explanation":"Spreading land plants drew carbon dioxide out of the air, which would have cooled the world and brought glaciation by the late Devonian. Then the Hangenberg event, about 13 million years after the Kellwasser crisis, brought a cooling episode and a sea-level fall of more than 100 metres in Morocco, and the armoured placoderm fish died out completely.","year":-359000000,"links":["co2","temperature","biodiversity"],"edge":"triggered","weight":0.85,"sources":[{"label":"Wikipedia — Hangenberg event","url":"https://en.wikipedia.org/wiki/Hangenberg_event"},{"label":"Wikipedia — Late Devonian mass extinction","url":"https://en.wikipedia.org/wiki/Late_Devonian_mass_extinction"}],"minAge":7},{"id":"permian-pangaea-megamonsoon","emoji":"🏜️","title":"A supercontinent breeds a super-monsoon","explanation":"Scientists think the supercontinent Pangaea had a 'megamonsoon', with winds that reversed with the seasons. It is already apparent in Early Permian rocks, kept strengthening as the continents drew together, and reached its maximum in the Triassic, when Pangaea's land area was largest. The interior was immensely arid, with very hot days and frigid nights, nearly uninhabitable for land life, while the coasts swung between rainy summers and dry winters.","year":-298900000,"yearEnd":-201400000,"place":{"lat":10,"lon":5,"label":"Pangaea interior (equatorial supercontinent)"},"links":["vegetation"],"edge":"caused","weight":0.86,"sources":[{"label":"Wikipedia — Pangean megamonsoon","url":"https://en.wikipedia.org/wiki/Pangean_megamonsoon"},{"label":"Wikipedia — Permian","url":"https://en.wikipedia.org/wiki/Permian"},{"label":"Wikipedia — Triassic","url":"https://en.wikipedia.org/wiki/Triassic"}],"minAge":4},{"id":"permian-capitan-reef-boom","emoji":"🪸","title":"The Capitan Reef","explanation":"Along the margin of a shallow Permian sea grew the Capitan Reef, a giant reef that may have stood 200-300 feet (61-91 m) above the sea floor, now fossilized and exposed in Texas and New Mexico. Its middle beds hold an abundant fossil assemblage of sponges, brachiopods, bryozoans and molluscs, and the complex has been described as the largest, best-preserved, most accessible, and most intensively studied Paleozoic reef complex in the world.","year":-265000000,"place":{"lat":31.9,"lon":-104.9,"label":"Guadalupe Mountains, Texas (Capitan Reef)"},"links":["biodiversity"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Capitan Formation","url":"https://en.wikipedia.org/wiki/Capitan_Formation"},{"label":"Wikipedia — Guadalupe Mountains National Park","url":"https://en.wikipedia.org/wiki/Guadalupe_Mountains_National_Park"}],"minAge":7},{"id":"triassic-lethal-heat-recovery","emoji":"🥵","title":"The world stays deadly hot","explanation":"After the Great Dying, the Early Triassic, from about 252 to 247 million years ago, was the hottest stretch of the whole Phanerozoic. Temperatures in equatorial latitudes were too high for life, driving most plants and animals out of the tropical land and leaving almost no fish in the equatorial Tethys sea, which held back the recovery of life. Temperatures finally fell by about 6°C between 248 and 247 million years ago.","year":-251902000,"yearEnd":-247000000,"place":{"lat":0,"lon":95,"label":"Equatorial Tethys Ocean"},"links":["temperature","biodiversity","co2"],"edge":"constrained","weight":0.9,"sources":[{"label":"Sun et al. 2012, Lethally Hot Temperatures During the Early Triassic Greenhouse (Science)","url":"https://doi.org/10.1126/science.1224126"},{"label":"Wikipedia — Triassic","url":"https://en.wikipedia.org/wiki/Triassic"},{"label":"Wikipedia — Early Triassic","url":"https://en.wikipedia.org/wiki/Early_Triassic"}],"minAge":7},{"id":"pangaea-rift-atlantic-opens","emoji":"🌊","title":"Pangaea splits and the Atlantic is born","explanation":"The break-up of Pangaea began in the central Atlantic, between North America and Northwest Africa, where rift basins opened during the Late Triassic and Early Jurassic, about 200 to 170 million years ago, as the Atlantic Ocean began to open. It was set off by the eruption of the Central Atlantic Magmatic Province, one of the most extensive volcanic provinces in Earth's history, which is associated with the Triassic–Jurassic extinction. Faster seafloor spreading widens the mid-ocean ridges, which displaces seawater and can raise sea level over millions of years.","year":-200000000,"yearEnd":-170000000,"place":{"lat":25,"lon":-45,"label":"Central Atlantic rift"},"links":["sea-level","biodiversity"],"edge":"caused","weight":0.92,"sources":[{"label":"Wikipedia — Atlantic Ocean","url":"https://en.wikipedia.org/wiki/Atlantic_Ocean"},{"label":"Wikipedia — Jurassic","url":"https://en.wikipedia.org/wiki/Jurassic"},{"label":"Wikipedia — Mid-ocean ridge","url":"https://en.wikipedia.org/wiki/Mid-ocean_ridge"}],"minAge":4},{"id":"mesozoic-marine-revolution","emoji":"🦀","title":"An arms race remakes the seafloor","explanation":"Through the Mesozoic, shell-crushing predators - marine reptiles, bony fish, mantis shrimps and crabs - attacked shelled sea animals more and more. This arms race was once thought to belong to the Cretaceous, but it may have begun as early as the Triassic. The prey had to develop defences or face extinction, and many shifted to living buried in the sediment, remaking life on the seafloor.","year":-247000000,"yearEnd":-66000000,"links":["biodiversity"],"edge":"caused","weight":0.82,"sources":[{"label":"Wikipedia — Mesozoic marine revolution","url":"https://en.wikipedia.org/wiki/Mesozoic_marine_revolution"},{"label":"Wikipedia — Anisian","url":"https://en.wikipedia.org/wiki/Anisian"}],"minAge":7},{"id":"angiosperm-flowering-revolution","emoji":"🌸","title":"Flowers take over the world","explanation":"Flowering plants appeared in the Early Cretaceous (the earliest widely accepted pollen is about 134 million years old) and became the dominant group of plants by the end of the Cretaceous as many gymnosperm groups declined. Researchers say their rise triggered a revolution on land between about 100 and 50 million years ago, the Angiosperm Terrestrial Revolution, which drove modern biodiversity.","year":-100000000,"yearEnd":-50000000,"links":["vegetation","biodiversity"],"edge":"caused","weight":0.91,"sources":[{"label":"Benton et al., The Angiosperm Terrestrial Revolution and the origins of modern biodiversity (New Phytologist)","url":"https://doi.org/10.1111/nph.17822"},{"label":"Wikipedia — Cretaceous","url":"https://en.wikipedia.org/wiki/Cretaceous"}],"minAge":4},{"id":"cretaceous-ocean-anoxic-events","emoji":"⚫","title":"When the oceans ran out of air","explanation":"Many scientists think bursts of volcanic CO₂ warmed the world and sent nutrients into the sea, feeding plankton. Large expanses of ocean then ran short of dissolved oxygen, and black, carbon-rich shale built up on the seafloor - bands of shale that have been tied to the world's oil reserves.","year":-120000000,"yearEnd":-93000000,"place":{"lat":43.36,"lon":12.58,"label":"Bonarelli Level, Gubbio, Italy"},"links":["oxygen","co2"],"edge":"triggered","weight":0.88,"sources":[{"label":"Wikipedia — Anoxic event","url":"https://en.wikipedia.org/wiki/Anoxic_event"}],"minAge":7},{"id":"flower-pollinator-coevolution","emoji":"🐝","title":"Flowers and their insect partners","explanation":"As flowering plants spread, insect partners followed. Bees are estimated to have first appeared about 123 million years ago, and all the major bee groups arose in the Middle to Late Cretaceous, when flowering plants became the dominant land plants. Researchers describe flowers and pollinators as coevolving.","year":-120000000,"yearEnd":-90000000,"links":["vegetation","biodiversity"],"edge":"enabled","weight":0.85,"sources":[{"label":"Cardinal & Danforth 2013, Bees diversified in the age of eudicots (Proceedings of the Royal Society B)","url":"https://doi.org/10.1098/rspb.2012.2686"},{"label":"Benton et al., The Angiosperm Terrestrial Revolution and the origins of modern biodiversity (New Phytologist)","url":"https://doi.org/10.1111/nph.17822"}],"minAge":4},{"id":"cretaceous-chalk-plankton","emoji":"🐚","title":"Plankton build the white cliffs","explanation":"Cretaceous seas were home to tiny algae called coccolithophores, each wearing a skeleton of calcite plates called coccoliths. Their remains piled up into chalk - more chalk formed in the Cretaceous than in any other period of the Phanerozoic, including the Chalk Group that forms the white cliffs of Dover.","year":-100000000,"yearEnd":-66000000,"place":{"lat":51.12,"lon":1.37,"label":"White Cliffs of Dover"},"links":["biodiversity"],"edge":"caused","weight":0.84,"sources":[{"label":"Wikipedia — Cretaceous","url":"https://en.wikipedia.org/wiki/Cretaceous"},{"label":"Wikipedia — Chalk","url":"https://en.wikipedia.org/wiki/Chalk"}],"minAge":7},{"id":"cretaceous-polar-forests","emoji":"🌲","title":"Forests and dinosaurs at the poles","explanation":"The Cretaceous world was largely ice-free, and forests extended to the poles. There is evidence of polar rainforests at 82° S, warm-adapted plant fossils are known as far north as Alaska and Greenland, and dinosaur fossils have been found within 15 degrees of the Cretaceous south pole.","year":-100000000,"yearEnd":-70000000,"place":{"lat":70,"lon":-151,"label":"Prince Creek Formation, Arctic Alaska"},"links":["temperature","ice-cover","vegetation"],"edge":"enabled","weight":0.85,"sources":[{"label":"Wikipedia — Cretaceous","url":"https://en.wikipedia.org/wiki/Cretaceous"}],"minAge":4},{"id":"ceno-eocene-greenhouse-peak","emoji":"🌴","title":"The hothouse peak of the Eocene","explanation":"From about 54 to 49 million years ago the Early Eocene Climatic Optimum was the hottest sustained interval of the Cenozoic. Estimates of carbon dioxide vary widely: one study of fossil plankton puts it around 1,400 parts per million, other geochemical evidence suggests only 700 to 900, and climate models need about 1,680 to match the heat. Palms grew in what is now British Columbia, crocodile relatives lived in Canada's Western Arctic, and little to no ice was present on Earth.","year":-54000000,"yearEnd":-49000000,"links":["temperature","co2"],"edge":"caused","weight":0.9,"sources":[{"label":"Anagnostou et al. 2016, Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate (Nature)","url":"https://doi.org/10.1038/nature17423"},{"label":"Wikipedia — Early Eocene Climatic Optimum","url":"https://en.wikipedia.org/wiki/Early_Eocene_Climatic_Optimum"},{"label":"Wikipedia — Eocene","url":"https://en.wikipedia.org/wiki/Eocene"}],"minAge":4},{"id":"ceno-himalaya-weathering-cooldown","emoji":"⛰️","title":"The mountains that may have cooled the world","explanation":"When India collided with Asia, the Himalaya and the Tibetan Plateau began to rise. One idea is that the uplift sped up the chemical weathering of rock, which may have drawn carbon dioxide out of the air over the past 40 million years and helped bring the global cooling that grew large ice sheets in both hemispheres.","year":-50000000,"yearEnd":-2580000,"place":{"lat":29.5,"lon":88,"label":"Tibetan Plateau"},"links":["co2","temperature"],"edge":"enabled","weight":0.9,"sources":[{"label":"Raymo & Ruddiman 1992, Tectonic forcing of late Cenozoic climate (Nature)","url":"https://www.nature.com/articles/359117a0"},{"label":"Wikipedia — Eocene","url":"https://en.wikipedia.org/wiki/Eocene"},{"label":"Wikipedia — Earth system interactions across mountain belts","url":"https://en.wikipedia.org/wiki/Earth_system_interactions_across_mountain_belts"},{"label":"Wikipedia — Quaternary glaciation","url":"https://en.wikipedia.org/wiki/Quaternary_glaciation"}],"minAge":4},{"id":"ceno-circumpolar-current-ice","emoji":"🌀","title":"A current that froze a continent","explanation":"As Antarctica separated from Australia and South America, the Tasmanian and Drake passages opened and a current began to circle the pole, keeping warm ocean water away from the continent. The Tasmanian Seaway opened about 33.5 million years ago; when Drake Passage opened is disputed, and one study found Pacific water flowing through it about 41 million years ago. Many researchers credit the current with the glaciation of Antarctica, but in one climate model the opening of these gateways played a secondary role to falling carbon dioxide.","year":-34000000,"place":{"lat":-58,"lon":-63,"label":"Drake Passage"},"links":["ice-cover","temperature","co2"],"edge":"enabled","weight":0.91,"sources":[{"label":"Scher & Martin 2006, Timing and Climatic Consequences of the Opening of Drake Passage (Science)","url":"https://doi.org/10.1126/science.1120044"},{"label":"Wikipedia — Antarctic Circumpolar Current","url":"https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current"},{"label":"Wikipedia — Drake Passage","url":"https://en.wikipedia.org/wiki/Drake_Passage"},{"label":"DeConto & Pollard 2003, Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2 (Nature)","url":"https://doi.org/10.1038/nature01290"}],"minAge":4},{"id":"ceno-eocene-oligocene-chill","emoji":"❄️","title":"The great chill and the Grande Coupure","explanation":"About 34 million years ago, as carbon dioxide fell, a large permanent ice sheet formed on Antarctica and the world cooled abruptly. In Europe a turnover of mammals followed that was so sharp it is called the 'Grande Coupure', the great cut: many native groups died out and new ones arrived from Asia. The cooling is one suggested cause, alongside competition from the newcomers and large asteroid impacts, and few scientists argue for a single cause.","year":-34000000,"links":["temperature","ice-cover","biodiversity"],"edge":"triggered","weight":0.86,"sources":[{"label":"Coxall et al. 2005, Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean (Nature)","url":"https://doi.org/10.1038/nature03135"},{"label":"Wikipedia — Eocene–Oligocene extinction event","url":"https://en.wikipedia.org/wiki/Eocene–Oligocene_extinction_event"}],"minAge":7},{"id":"ceno-whales-return-to-sea","emoji":"🐋","title":"Whales grow giant on a churning ocean","explanation":"Modern whales arose and diversified about 30 to 40 million years ago, and their diversity rose and fell in step with ocean plankton called diatoms and with changes in climate. Much later, in the Plio-Pleistocene, baleen whales began trending towards huge sizes just as seasonal upwelling started packing coastal waters with prey - changes that may have opened a path to gigantism.","year":-40000000,"yearEnd":-2580000,"place":{"lat":-60,"lon":0,"label":"Southern Ocean"},"links":["biodiversity","temperature"],"edge":"enabled","weight":0.82,"sources":[{"label":"Marx & Uhen 2010, Climate, Critters, and Cetaceans: Cenozoic Drivers of the Evolution of Modern Whales (Science)","url":"https://doi.org/10.1126/science.1185581"},{"label":"Slater, Goldbogen & Pyenson 2017, Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics (Proc. R. Soc. B)","url":"https://doi.org/10.1098/rspb.2017.0546"},{"label":"Wikipedia — Pliocene","url":"https://en.wikipedia.org/wiki/Pliocene"}],"minAge":4},{"id":"ceno-horse-grass-teeth","emoji":"🐎","title":"Grass reshapes the horse's mouth","explanation":"Grass contains phytoliths, silica-rich granules that wear teeth away quickly. As grasses spread, horses' diets shifted from leaves to grass, and the extra wear selected for bigger, tougher teeth; Merychippus, in North America from about 16 to 5.3 million years ago, is the first horse known to have grazed. But high-crowned teeth evolved out of step with the spread of grasslands, and the 'grit, not grass' hypothesis holds that soil swallowed while grazing was the main driver.","year":-15970000,"yearEnd":-5330000,"place":{"lat":41,"lon":-101,"label":"North American Great Plains"},"links":["vegetation","biodiversity"],"edge":"enabled","weight":0.81,"sources":[{"label":"Wikipedia — Evolution of the horse","url":"https://en.wikipedia.org/wiki/Evolution_of_the_horse"},{"label":"Wikipedia — Hypsodont","url":"https://en.wikipedia.org/wiki/Hypsodont"},{"label":"Wikipedia — Merychippus","url":"https://en.wikipedia.org/wiki/Merychippus"}],"minAge":4},{"id":"ceno-miocene-warm-optimum","emoji":"🌡️","title":"The Miocene's warm interlude","explanation":"Between about 17 and 14 million years ago the long Cenozoic cooling paused for the Middle Miocene Climatic Optimum, a warm spell believed to have been driven mainly by carbon dioxide from huge volcanic eruptions in what is now the northwestern United States. When it ended, the East Antarctic Ice Sheet grew back and the planet cooled again.","year":-17000000,"yearEnd":-14000000,"links":["temperature","co2"],"edge":"caused","weight":0.83,"sources":[{"label":"Wikipedia — Middle Miocene Climatic Optimum","url":"https://en.wikipedia.org/wiki/Middle_Miocene_Climatic_Optimum"},{"label":"Wikipedia — Middle Miocene disruption","url":"https://en.wikipedia.org/wiki/Middle_Miocene_disruption"}],"minAge":4},{"id":"ceno-grassland-c4-spread","emoji":"🌾","title":"Grasslands take over the world","explanation":"Between 8 and 6 million years ago, plants using efficient 'C4' photosynthesis suddenly became much more abundant across Asia, Africa, North America and South America, as the carbon in fossil tooth enamel shows. It may be linked to falling carbon dioxide, though later work finds the causes more complex than first assumed.","year":-8000000,"yearEnd":-6000000,"links":["vegetation","co2"],"edge":"enabled","weight":0.88,"sources":[{"label":"Cerling et al. 1997, Global vegetation change through the Miocene/Pliocene boundary (Nature)","url":"https://www.nature.com/articles/38229"},{"label":"Edwards et al. 2010, The Origins of C4 Grasslands: Integrating Evolutionary and Ecosystem Science (Science)","url":"https://doi.org/10.1126/science.1177216"}],"minAge":4},{"id":"ceno-rift-drying-upright-apes","emoji":"🚶","title":"A shrinking forest and our upright ancestors","explanation":"The savannah hypothesis holds that as tropical forests retreated with a changing climate, our ancestors left the trees and took to walking upright. The open-grassland version is now mostly dismissed: early fossils such as 7-million-year-old Sahelanthropus point to a mosaic of habitats from forest to grassland, and the change from forest to savanna was probably more gradual than once thought. Still, climate change and its effects on African ecosystems may have played a key role in human evolution.","year":-7000000,"place":{"lat":0.5,"lon":36,"label":"East African Rift Valley"},"links":["vegetation"],"edge":"enabled","weight":0.87,"sources":[{"label":"deMenocal 2011, Climate and Human Evolution (Science)","url":"https://doi.org/10.1126/science.1190683"},{"label":"Wikipedia — Savannah hypothesis","url":"https://en.wikipedia.org/wiki/Savannah_hypothesis"}],"minAge":4},{"id":"ceno-panama-isthmus-glaciation","emoji":"🌊","title":"A land bridge that helped start the ice ages","explanation":"As the Isthmus of Panama rose and the seaway between the Americas grew shallower, ocean circulation was reorganised from about 4.6 million years ago: the Gulf Stream intensified and carried warm, salty water to high northern latitudes. The extra moisture this brought is proposed as a necessary precondition for the great Northern Hemisphere ice sheets, which grew strongly between 3.1 and 2.5 million years ago. Scientists still debate the exact timing.","year":-4600000,"yearEnd":-2500000,"place":{"lat":9,"lon":-79.5,"label":"Isthmus of Panama"},"links":["ice-cover","temperature"],"edge":"enabled","weight":0.89,"sources":[{"label":"Haug & Tiedemann 1998, Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation (Nature)","url":"https://www.nature.com/articles/31447"}],"minAge":4},{"id":"ceno-american-biotic-interchange","emoji":"🦥","title":"Two Americas swap their animals","explanation":"As the Isthmus of Panama rose and joined North and South America by land, migration between them accelerated dramatically about 2.7 million years ago. Camels, tapirs, deer, horses, cats, dogs and bears moved south, while armadillos, opossums and ground sloths moved north, mixing two long-separate worlds of life.","year":-2700000,"place":{"lat":9,"lon":-79.5,"label":"Isthmus of Panama"},"links":["biodiversity"],"edge":"enabled","weight":0.85,"sources":[{"label":"Wikipedia — Great American Interchange","url":"https://en.wikipedia.org/wiki/Great_American_Interchange"},{"label":"Woodburne 2010, The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens (Journal of Mammalian Evolution)","url":"https://doi.org/10.1007/s10914-010-9144-8"}],"minAge":4},{"id":"glacial-cycles-human-evolution","emoji":"🌗","title":"Climate swings may have shaped the human mind","explanation":"Over the last 2.5 million years, the swings in global temperature and glacial ice grew larger than ever, and at Kenya's Olorgesailie an ancient lake rose and fell and sometimes dried up. The variability selection hypothesis says our ancestors did not specialise in one habitat but became more adaptable, and that a big, flexible brain, which grew fastest over the past 800,000 years, helped them cope.","year":-2500000,"yearEnd":-12000,"place":{"lat":0.5,"lon":36,"label":"East African Rift"},"links":["temperature","ice-cover"],"edge":"enabled","weight":0.86,"sources":[{"label":"Smithsonian Human Origins Program — Climate Effects on Human Evolution","url":"https://humanorigins.si.edu/research/climate-and-human-evolution/climate-effects-human-evolution"}],"minAge":4},{"id":"fire-cooking-bigger-brains","emoji":"🔥","title":"Fire, cooking and the growing brain","explanation":"Some scientists argue that cooking made food easier to chew and digest, so a smaller, more efficient gut freed up energy for a bigger brain; the primatologist Richard Wrangham argues that Homo erectus emerged about two million years ago as a result. Critics doubt the fire evidence is that old. The earliest secure evidence of burning in an archaeological context is from about 1 million years ago, at Wonderwerk Cave.","year":-1000000,"place":{"lat":-27.85,"lon":23.55,"label":"Wonderwerk Cave, South Africa"},"links":[],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Catching Fire: How Cooking Made Us Human","url":"https://en.wikipedia.org/wiki/Catching_Fire:_How_Cooking_Made_Us_Human"},{"label":"Berna et al. 2012, Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa (PNAS)","url":"https://doi.org/10.1073/pnas.1117620109"}],"minAge":4},{"id":"beringia-land-bridge-americas","emoji":"🦣","title":"A frozen bridge to a new world","explanation":"During the last ice age the sea fell by about 60 to 120 metres, uncovering a wide land of grassy steppe and tundra that linked Siberia to Alaska. People and animals crossed this land bridge, and by about 15,000 years ago humans had reached the Americas.","year":-20000,"yearEnd":-15000,"place":{"lat":65.7,"lon":-168.7,"label":"Bering Strait / Beringia"},"links":["sea-level","population","ice-cover"],"edge":"enabled","weight":0.93,"sources":[{"label":"Goebel, Waters & O'Rourke 2008, The late Pleistocene dispersal of modern humans in the Americas (Science)","url":"https://doi.org/10.1126/science.1153569"},{"label":"Wikipedia — Peopling of the Americas","url":"https://en.wikipedia.org/wiki/Peopling_of_the_Americas"},{"label":"Wikipedia — Beringia","url":"https://en.wikipedia.org/wiki/Beringia"}],"minAge":4},{"id":"younger-dryas-cold-snap","emoji":"❄️","title":"The world plunges back into cold","explanation":"Just as the last ice age was ending, the ocean currents that carry warmth north slowed or shut down, possibly after a huge outburst of meltwater, and the Northern Hemisphere turned cold again for over a thousand years. Some scholars link this chill to the start of farming in the Near East, though that is still debated.","year":-10900,"yearEnd":-9700,"place":{"lat":72.6,"lon":-38.5,"label":"Greenland ice cores"},"links":["temperature","vegetation"],"edge":"triggered","weight":0.85,"sources":[{"label":"Wikipedia — Younger Dryas","url":"https://en.wikipedia.org/wiki/Younger_Dryas"}],"minAge":7},{"id":"holocene-stability-cities","emoji":"🌾","title":"A calmer climate helps farming begin","explanation":"When the ice age ended about 11,700 years ago (9,700 BCE), Earth entered the Holocene. Greenland ice cores suggest a more stable climate than in the ice age before, although it still varied. Some researchers argue that this steadier climate helped farming begin, and farming made a larger population possible as people settled in villages and towns. The earliest known civilization developed in Sumer about 6,500 years ago.","year":-9700,"yearEnd":-4500,"links":["temperature","population","urbanization"],"edge":"enabled","weight":0.92,"sources":[{"label":"Wikipedia — Holocene","url":"https://en.wikipedia.org/wiki/Holocene"},{"label":"Wikipedia — Neolithic Revolution","url":"https://en.wikipedia.org/wiki/Neolithic_Revolution"}],"minAge":4},{"id":"green-sahara-to-nile","emoji":"🐊","title":"A green Sahara dries and people move to the Nile","explanation":"After the ice age the Sahara turned green: the African humid period began about 14,600 years ago, and the eastern Sahara was settled after a sudden onset of wetter conditions around 8500 BCE, a land of lakes, rivers, grass and herders. As it gradually dried from about 5300 BCE, people left the desert for places with more reliable water, such as the Nile Valley, and this helped trigger the rise of ancient Egyptian civilization.","year":-8500,"yearEnd":-3500,"place":{"lat":26,"lon":30,"label":"Sahara & the Nile Valley"},"links":["vegetation","population"],"edge":"caused","weight":0.87,"sources":[{"label":"Kuper & Kröpelin 2006, Climate-controlled Holocene occupation in the Sahara: motor of Africa's evolution (Science)","url":"https://doi.org/10.1126/science.1130989"},{"label":"Wikipedia — African humid period","url":"https://en.wikipedia.org/wiki/African_humid_period"}],"minAge":4},{"id":"neolithic-demographic-transition","emoji":"👶","title":"Farming triggers a baby boom","explanation":"When people settled down to farm they had more food and no longer had to keep moving, and birth rates jumped in what scholars call the Neolithic Demographic Transition, by an estimated two extra births per woman. It came first in Southwest Asia, from about 9500 BCE, and thousands of years later elsewhere. Living close to animals and to each other also spread diseases, which eventually pushed death rates up again.","year":-9500,"yearEnd":-2500,"links":["population","life-expectancy"],"edge":"caused","weight":0.84,"sources":[{"label":"Bocquet-Appel 2011, When the world's population took off: the springboard of the Neolithic Demographic Transition (Science)","url":"https://doi.org/10.1126/science.1208880"},{"label":"Wikipedia — Neolithic demographic transition","url":"https://en.wikipedia.org/wiki/Neolithic_demographic_transition"}],"minAge":7},{"id":"doggerland-drowned","emoji":"🌊","title":"Britain becomes an island","explanation":"As the ice sheets melted, rising seas gradually submerged Doggerland, the land that joined Britain to mainland Europe, and by around 6500 BCE Britain was cut off. One hypothesis says that around 6200 BCE a tsunami from an undersea landslide off Norway flooded much of the coastal land that remained.","year":-6500,"yearEnd":-6200,"place":{"lat":54.5,"lon":3,"label":"Doggerland, North Sea"},"links":["sea-level","population"],"edge":"caused","weight":0.83,"sources":[{"label":"Wikipedia — Doggerland","url":"https://en.wikipedia.org/wiki/Doggerland"}],"minAge":7},{"id":"cuneiform-writing-first-states","emoji":"✍️","title":"Writing is born to run a city","explanation":"In the Uruk period, southern Mesopotamia grew large temple-centred cities with over 10,000 people and central administrations that had to keep accounts of livestock and goods. Writing grew out of that accounting: clay tokens used for counting gave way to signs recorded on clay tablets, and the first unequivocal written documents come from Uruk from about 3300 BCE. By the late 4th millennium BCE Sumer was divided into many independent city-states, each centred on a temple.","year":-3300,"place":{"lat":31.32,"lon":45.64,"label":"Uruk, Sumer"},"links":["literacy","urbanization"],"edge":"caused","weight":0.9,"sources":[{"label":"Wikipedia — Cuneiform","url":"https://en.wikipedia.org/wiki/Cuneiform"},{"label":"Wikipedia — Sumer","url":"https://en.wikipedia.org/wiki/Sumer"}],"minAge":4},{"id":"akkad-42ka-drought","emoji":"🏜️","title":"The drought that toppled an empire","explanation":"Around 2200 BCE the climate of the Near East turned sharply drier, and the dry spell most likely lasted through the 22nd century BCE. Archaeologists found that people abandoned the farmland of northern Mesopotamia, and in 1993 Weiss and colleagues argued that this abrupt change, which they said followed a volcanic eruption, caused the collapse of the Akkadian Empire. Other scientists disagree, citing evidence that the event was not a global drought and had no clear timeline.","year":-2200,"yearEnd":-2100,"place":{"lat":36.96,"lon":41.5,"label":"Tell Leilan, northern Mesopotamia"},"links":["temperature","population","urbanization"],"edge":"caused","weight":0.86,"sources":[{"label":"Weiss et al. 1993, The genesis and collapse of third millennium north Mesopotamian civilization (Science)","url":"https://doi.org/10.1126/science.261.5124.995"},{"label":"Wikipedia — 4.2-kiloyear event","url":"https://en.wikipedia.org/wiki/4.2-kiloyear_event"}],"minAge":7},{"id":"late-bronze-collapse-drought","emoji":"🏛️","title":"When the Bronze Age world fell apart","explanation":"Around 1200 BCE the Hittite Empire collapsed, the palace economy of Mycenaean Greece broke apart, and many palaces and fortified sites in the eastern Mediterranean were destroyed. Climate records suggest a prolonged drought and famine helped push this connected world over the edge, though it was probably not the only cause.","year":-1200,"yearEnd":-1150,"place":{"lat":35.6,"lon":35.78,"label":"Ugarit, Syrian coast"},"links":["temperature","population","urbanization"],"edge":"caused","weight":0.87,"sources":[{"label":"Kaniewski et al. 2013, Environmental roots of the Late Bronze Age crisis (PLOS ONE)","url":"https://doi.org/10.1371/journal.pone.0071004"},{"label":"Wikipedia — Late Bronze Age collapse","url":"https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse"}],"minAge":10},{"id":"arab-agricultural-revolution","emoji":"🍋","title":"The Arab Agricultural Revolution","explanation":"During the Islamic Golden Age (8th to 13th centuries), historian Andrew Watson argued, the trade of Arab and other Muslim merchants spread crops such as rice, sugar cane, cotton and citrus fruits across the Islamic world, including to Spain, alongside better irrigation such as the saqiyah water wheel. These changes made farming more productive, supporting population growth and urbanisation. Some historians disagree: Michael Decker argued that rice, cotton and other staples were already common under the Roman and Sassanid empires.","year":700,"yearEnd":1300,"place":{"lat":37.88,"lon":-4.78,"label":"Córdoba, al-Andalus"},"links":["population","vegetation"],"edge":"enabled","weight":0.85,"sources":[{"label":"Wikipedia — Arab Agricultural Revolution","url":"https://en.wikipedia.org/wiki/Arab_Agricultural_Revolution"}],"minAge":4},{"id":"islamic-paper-golden-age","emoji":"📜","title":"Paper and the Golden Age of books","explanation":"Papermaking spread from China into the Islamic world in the 8th century, and paper was being made in Baghdad by the late 8th century. Together with an easier writing system, paper democratized information so far that, probably for the first time in history, it became possible to make a living from writing and selling books. This was the Islamic Golden Age, understood to have begun under the caliph Harun al-Rashid (786-809) and said to have ended with the Siege of Baghdad in 1258.","year":786,"yearEnd":1258,"place":{"lat":33.31,"lon":44.36,"label":"Baghdad, Abbasid Caliphate"},"links":["literacy"],"edge":"enabled","weight":0.84,"sources":[{"label":"Wikipedia — Papermaking","url":"https://en.wikipedia.org/wiki/Papermaking"},{"label":"Wikipedia — Paper","url":"https://en.wikipedia.org/wiki/Paper"},{"label":"Wikipedia — Islamic Golden Age","url":"https://en.wikipedia.org/wiki/Islamic_Golden_Age"}],"minAge":4},{"id":"heavy-plough-three-field","emoji":"🐂","title":"The heavy plough feeds Europe","explanation":"In the later 8th and early 9th centuries, medieval Europeans began adopting the mouldboard plough, strong enough to work the heavy soils of northern Europe, together with the three-field system, a crop rotation that helped keep the soil fertile; the switch to three fields spread from the 9th to the 11th century. Together they raised farm productivity and created a surplus, and heavy ploughs led to greater food production, coinciding with a marked rise in the world's population in the second millennium AD.","year":800,"yearEnd":1100,"place":{"lat":51,"lon":4.5,"label":"Northern European plain"},"links":["vegetation","population"],"edge":"enabled","weight":0.86,"sources":[{"label":"Wikipedia — Plough","url":"https://en.wikipedia.org/wiki/Plough"},{"label":"Wikipedia — Three-field system","url":"https://en.wikipedia.org/wiki/Three-field_system"}],"minAge":4},{"id":"angkor-hydraulic-empire","emoji":"💧","title":"Angkor, the hydraulic empire","explanation":"From the 9th century the Khmer built vast reservoirs and canals around Angkor, a water network used for irrigation to offset the unpredictable monsoon and support a growing population. Angkor was the largest pre-industrial city in the world by surface area. In the 14th and 15th centuries decades-long droughts interspersed with intense monsoons, together with other factors, contributed to its decline.","year":900,"yearEnd":1431,"place":{"lat":13.41,"lon":103.87,"label":"Angkor, Khmer Empire"},"links":["urbanization","population","vegetation"],"edge":"caused","weight":0.84,"sources":[{"label":"Wikipedia — Angkor","url":"https://en.wikipedia.org/wiki/Angkor"},{"label":"Buckley et al. 2010, Climate as a contributing factor in the demise of Angkor, Cambodia (Proc. Natl. Acad. Sci.)","url":"https://doi.org/10.1073/pnas.0910827107"}],"minAge":7},{"id":"medieval-warm-period-greenland","emoji":"🌾","title":"The Medieval Warm Period opens Greenland","explanation":"From about 950 to 1250 CE a warm spell, the Medieval Warm Period, lay over the North Atlantic region. The common theory is that Norse settlers took advantage of ice-free seas to colonise Greenland, and around 985 they founded settlements there, keeping cattle, sheep and goats. After the climate turned colder and stormier around 1250 their diet shifted towards the sea, and the end of the colony is thought to have had many causes, climate among them.","year":950,"yearEnd":1250,"place":{"lat":60.99,"lon":-45.52,"label":"Brattahlíð, Eastern Settlement, Greenland"},"links":["temperature","population","vegetation"],"edge":"enabled","weight":0.9,"sources":[{"label":"Wikipedia — Medieval Warm Period","url":"https://en.wikipedia.org/wiki/Medieval_Warm_Period"},{"label":"Mann et al. 2009, Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly (Science)","url":"https://doi.org/10.1126/science.1177303"},{"label":"Dugmore et al. 2012, Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland (Proc. Natl. Acad. Sci.)","url":"https://doi.org/10.1073/pnas.1115292109"}],"minAge":4},{"id":"song-champa-rice-boom","emoji":"🍚","title":"Champa rice and the Song boom","explanation":"Around 1011 CE the Song emperor Zhenzong introduced fast-ripening, drought-resistant Champa rice from the Kingdom of Champa in Vietnam, which allowed two harvests a year instead of one. Officials gave the rice to peasants across China, and China's population doubled between the 10th and 11th centuries, growth made possible by expanded rice cultivation and early-ripening rice. Kaifeng and Hangzhou had populations of over a million, among the largest cities in the world.","year":1011,"yearEnd":1127,"place":{"lat":34.8,"lon":114.31,"label":"Kaifeng, Song China"},"links":["population","urbanization"],"edge":"caused","weight":0.9,"sources":[{"label":"Wikipedia — Champa rice","url":"https://en.wikipedia.org/wiki/Champa_rice"},{"label":"Wikipedia — Song dynasty","url":"https://en.wikipedia.org/wiki/Song_dynasty"}],"minAge":4},{"id":"cahokia-maize-city","emoji":"🌽","title":"Cahokia rises on maize","explanation":"Maize was successfully introduced to the region around 900 CE and is often credited with enabling Cahokia's early population growth, though newer research finds its people ate a varied diet. Around 1100 CE Cahokia was the largest urban center north of the great cities of Mexico, crowned by huge earthen mounds, with a population estimated at between 6,000 and 40,000. By 1350 CE it was abandoned, and scholars point to a mix of environmental and social causes.","year":1050,"yearEnd":1350,"place":{"lat":38.66,"lon":-90.06,"label":"Cahokia, Mississippi valley"},"links":["population","urbanization","vegetation"],"edge":"enabled","weight":0.82,"sources":[{"label":"Wikipedia — Cahokia","url":"https://en.wikipedia.org/wiki/Cahokia"}],"minAge":7},{"id":"polynesian-pacific-settlement","emoji":"🛶","title":"Voyagers reach the last islands","explanation":"Around 1190 to 1290 CE Polynesian navigators, using outrigger or double-hulled canoes, spread in one major pulse to all the remaining islands of East Polynesia, including New Zealand, the last habitable places on Earth colonised by humans. In New Zealand the giant flightless moa were driven to extinction by hunting and, to a lesser extent, forest clearance, within about 100 years of settlement; by 1445 CE all moa were gone.","year":1190,"yearEnd":1445,"place":{"lat":-41,"lon":174,"label":"Aotearoa / New Zealand"},"links":["population","biodiversity","vegetation"],"edge":"enabled","weight":0.83,"sources":[{"label":"Wilmshurst et al. 2011, High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia (Proc. Natl. Acad. Sci.)","url":"https://doi.org/10.1073/pnas.1015876108"},{"label":"Wikipedia — Polynesian navigation","url":"https://en.wikipedia.org/wiki/Polynesian_navigation"},{"label":"Wikipedia — Moa","url":"https://en.wikipedia.org/wiki/Moa"}],"minAge":7},{"id":"pax-mongolica-eurasian-trade","emoji":"🐎","title":"Pax Mongolica reconnects Eurasia","explanation":"After 1206 the conquests of Genghis Khan and his successors united much of Eurasia, from Southeast Asia to Eastern Europe, under Mongol rule, and the trade routes used by merchants became safe for travel. This \"Mongol Peace\" led to growth and expansion of trade from China to Britain, and goods such as silk, spices and gunpowder moved across the continent. Its end was marked by the breakup of the khanates and by the Black Death, which killed up to 50 million people and struck Europe from 1346 to 1353; where the plague began, and whether it travelled the Silk Road, is still disputed.","year":1206,"yearEnd":1353,"place":{"lat":39.65,"lon":66.96,"label":"Samarkand, Silk Road"},"links":["population"],"edge":"enabled","weight":0.89,"sources":[{"label":"Wikipedia — Pax Mongolica","url":"https://en.wikipedia.org/wiki/Pax_Mongolica"},{"label":"Wikipedia — Black Death","url":"https://en.wikipedia.org/wiki/Black_Death"}],"minAge":10},{"id":"mali-trans-saharan-gold","emoji":"🪙","title":"Mali's gold crosses the Sahara","explanation":"By the beginning of the 14th century the Mali Empire was the source of almost half the Old World's exported gold, and caravans of camels carried trade across the Sahara. When Mansa Musa made his pilgrimage to Mecca in 1324, his lavish gift-giving is said to have noticeably affected the value of gold in Egypt. He also took an interest in Timbuktu, a scholarly city where he turned Sankore into an Islamic university.","year":1235,"yearEnd":1400,"place":{"lat":16.77,"lon":-3,"label":"Timbuktu, Mali Empire"},"links":["gdp","urbanization","literacy"],"edge":"caused","weight":0.83,"sources":[{"label":"Wikipedia — Mali Empire","url":"https://en.wikipedia.org/wiki/Mali_Empire"},{"label":"Wikipedia — Mansa Musa","url":"https://en.wikipedia.org/wiki/Mansa_Musa"},{"label":"Wikipedia — Trans-Saharan trade","url":"https://en.wikipedia.org/wiki/Trans-Saharan_trade"}],"minAge":4},{"id":"great-famine-1315","emoji":"🌧️","title":"The Great Famine of 1315","explanation":"In spring 1315 unusually heavy rain began in much of Europe, and crop failures lasted until the summer harvest of 1317. The famine followed the end of the Medieval Warm Period, when Europe's population was at a historical high, and an estimated 10-25% of the population of many cities and towns died. Its effects also reached later events such as the Black Death, when an already weakened population suffered a further calamity.","year":1315,"yearEnd":1317,"place":{"lat":50.85,"lon":4.35,"label":"Low Countries / Flanders"},"links":["temperature","population","life-expectancy"],"edge":"triggered","weight":0.87,"sources":[{"label":"Wikipedia — Great Famine of 1315–1317","url":"https://en.wikipedia.org/wiki/Great_Famine_of_1315–1317"}],"minAge":10}]