Timescale Geological Timescale

Geological Timescale 44

• 4600 Ma – 4500 Ma Formation of the Earth Accretion from solar nebula Earth forms from colliding planetesimals; Moon-forming giant impact occurs shortly after.
• 4500 Ma Formation of the Moon Giant impact with Theia A Mars-sized body collides with proto-Earth, ejecting material that forms the Moon.
• 4404 Ma Jack Hills Zircons Oldest minerals on Earth Zircon crystals dated at 4.404 Ga are the oldest known minerals on Earth.
• 4400 Ma First Liquid Water Oceans begin to form Zircon crystals (Jack Hills) suggest liquid water existed on Earth as early as 4.4 Ga.
• 3800 Ma – 3700 Ma First Life Earliest evidence of life Chemical signatures suggest life existed by at least 3.7 Ga, likely chemosynthetic bacteria near hydrothermal vents.
• 2450 Ma – 2320 Ma Great Oxidation Event Oxygen fills the atmosphere Cyanobacteria flood the atmosphere with oxygen, rusting the oceans and enabling complex aerobic organisms.
• 2100 Ma First Eukaryotes Cells with a nucleus appear First cells with a true nucleus and organelles — ancestors of all plants, animals and fungi.
• 717 Ma – 660 Ma Snowball Earth — Sturtian First global glaciation Glaciers advance to the equator, freezing the entire ocean surface. Life survives in isolated refugia.
• 650 Ma – 635 Ma Snowball Earth — Marinoan Second global glaciation Second global glaciation; its dramatic end triggers the Ediacaran explosion of animal life.
• 575 Ma First Animals Ediacaran biota appear First unambiguous multicellular animals — soft-bodied Dickinsonia and Charnia, preserved as seafloor impressions.
• 538.8 Ma – 521 Ma Cambrian Explosion Most animal body plans appear Rapid diversification of complex multicellular life with hard body parts.
• 252.5 Ma – 251.5 Ma Siberian Traps Volcanism Triggers Great Dying Massive flood basalt volcanism releases CO2 and SO2, causing runaway climate change.
• 251.902 Ma End-Permian Extinction The Great Dying — 96% of marine species lost Largest mass extinction; caused by Siberian Traps volcanism, ocean acidification and anoxia.
• 150–148 Ma · Late Jurassic Archaeopteryx The first known bird The iconic transitional fossil between dinosaurs and birds. Archaeopteryx had feathers and wings like a bird but teeth, clawed wings and a bony tail like a dinosaur. Found in Solnhofen limestone, Germany.
• 68–66 Ma · Late Cretaceous Tyrannosaurus rex King of the tyrant lizards The most famous dinosaur of all — Tyrannosaurus rex was 13 metres long, weighed up to 9 tonnes and had the most powerful bite of any land animal. It lived in the last 2 million years before the K-Pg extinction.
• 66 Ma Chicxulub Impact Asteroid ends the Mesozoic 10 km asteroid strikes Yucatan; triggers mass extinction.
• 66 Ma End-Cretaceous Extinction K-Pg event — dinosaurs go extinct Chicxulub asteroid impact ends the Mesozoic. Non-avian dinosaurs, mosasaurs and ammonites disappear.
• 0.3 Ma – present Homo sapiens Modern humans evolve Anatomically modern Homo sapiens appears in Africa, eventually spreading to every continent.
• 12,000–10,000 BC Megafauna Extinctions Woolly mammoth and others disappear The great megafauna — woolly mammoths, mastodons, cave lions, giant sloths — go extinct across the world, likely from a combination of climate change and human hunting.
• ~11,700 years ago Younger Dryas Ends Ice age abruptly ends The last cold snap of the Ice Age ends around 11,700 years ago; global temperatures rise 10°C in decades. Glaciers retreat, sea levels rise, and modern climate conditions begin.
• ~9,500 BC Göbekli Tepe World's oldest temple complex Hunter-gatherers in southeastern Turkey construct Göbekli Tepe — massive stone pillars in circles, predating agriculture. Suggests complex religion and social organisation far earlier than thought.
• ~9,000 BC Agriculture Begins Farming invented in the Fertile Crescent Humans begin deliberately cultivating wheat, barley and lentils in the Fertile Crescent. The most transformative change in human history begins.
• ~9,000–8,000 BC First Domesticated Animals Sheep, goats and dogs tamed Sheep, goats, pigs and cattle are domesticated in the Middle East, providing reliable food, wool and labour.
• ~8,000 BC Jericho Founded One of the world's first cities Jericho develops into one of the earliest permanent settlements, with mud-brick houses, a stone tower and defensive walls — remarkable for 9000 BCE.
• ~7,000–5,000 BC Catalhoyuk Largest Neolithic city Catalhoyuk in Turkey becomes one of the world's largest settlements with up to 8,000 inhabitants — a remarkable proto-urban society.
• ~7,000–5,000 BC Pottery Invented Fired clay vessels transform food storage Ceramic pottery is independently invented in multiple regions, enabling cooking, food storage and trade.
• ~6,000–4,000 BC Farming Spreads to Europe Agriculture reaches the Mediterranean Farming communities spread westward from Anatolia into Greece and the Balkans, then across Europe, displacing or absorbing hunter-gatherer populations.
• ~6,000–3,000 BC Holocene Climate Optimum Earth's warmest post-glacial period Global temperatures peak 1-2°C above present. The Sahara is green with lakes and wildlife. African and Asian monsoons are stronger, supporting large populations in now-arid regions.
• ~6,000–2,000 BC Sahara Green Period The Green Sahara The Sahara Desert is replaced by savannah, grassland and lakes, supporting hippos, crocodiles, elephants and large human populations. Rock art from this period survives across the region.
• ~5,000–4,000 BC Copper Smelting First metal technology Humans discover that copper ore can be smelted to produce metal tools — the first use of metallurgy. Marks the transition from Stone Age to Copper Age.
• ~3,500 BC First Writing Cuneiform invented in Mesopotamia The Sumerians develop cuneiform writing on clay tablets to record trade. The invention of writing marks the beginning of recorded history.
• ~3,500 BC Wheel Invented Transformative transport technology The wheel is invented in Mesopotamia, initially for pottery then transport. Combined with the axle, it transforms trade, warfare and agriculture across Eurasia.
• ~3,000 BC Bronze Age Begins Tin and copper alloyed into bronze Metallurgists discover that adding tin to copper creates bronze — harder and more durable. Bronze tools and weapons spread across Eurasia, transforming warfare and agriculture.
• ~2,560 BC Pyramids of Giza Ancient Egypt's greatest monuments The Egyptian pharaohs construct the Great Pyramid of Giza — for 3,800 years the tallest structure ever built, representing the peak of Old Kingdom engineering.
• ~2,500 BC Stonehenge Completed Iconic megalithic monument The final phase of Stonehenge is completed in southern England — massive sarsen stones with precise astronomical alignments, suggesting sophisticated calendar knowledge.
• ~1,200 BC Iron Age Begins Iron replaces bronze Iron smelting technology spreads across the Old World, producing harder and cheaper tools than bronze. Iron ore is far more abundant than tin or copper, democratising metalwork.
• 500–300 BC Classical Greece Democracy, philosophy and science Ancient Greece produces democracy, philosophy, drama and science. Socrates, Plato, Aristotle, Euclid and Archimedes lay the intellectual foundations of Western civilisation.
• 27 BC – 476 AD Roman Empire Largest western empire of antiquity The Roman Empire at its height controls 5 million km² and 70 million people, spreading Latin, Roman law and engineering across Europe, North Africa and the Middle East.
• 1347–1351 AD Black Death Deadliest pandemic in human history The bubonic plague kills 30-60% of Europe's population between 1347 and 1351. It reshapes European society, labour relations and the relationship between Church and state.
• 1440 AD Printing Press Gutenberg's moveable type Gutenberg's printing press (1440) revolutionises the spread of information, enabling the Protestant Reformation, the Scientific Revolution and the spread of literacy.
• 1760–1840 AD Industrial Revolution Steam power transforms civilisation The Industrial Revolution begins in Britain around 1760, powered by steam engines and coal. It transforms manufacturing, transport and urban life, launching sustained economic growth.
• 1750–present Climate Crisis Human-caused global warming accelerates Burning of fossil fuels raises atmospheric CO₂ to levels not seen in 3 million years, driving rapid global warming, sea level rise and extreme weather events.
• 1914–1945 AD World Wars Two global conflicts reshape the world The First and Second World Wars (1914-18, 1939-45) kill over 80 million people and redraw the world map, leading to decolonisation, the United Nations and the nuclear age.
• 1960–present Digital Revolution Computing and the internet transform life Computers, the internet and smartphones create a new information age. By 2000, the world is more interconnected than at any point in history.