The story of life
Travel through four billion years — from the first speck of life to you. Almost all of it is older than you can imagine.
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Hadean Eon
Earth is born
A ball of molten rock and endless lava, bombarded by asteroids. No air you could breathe, no water you could drink, and no life of any kind.
The word 'Hadean' comes from Hades, the Greek underworld. The name fits: surface temperatures were hot enough to keep rock glowing and molten.
Earth and everything on it — including every atom in your body — was built from dust left over from dead stars. You are, quite literally, stardust.
A world-sized collision makes the Moon
A planet the size of Mars slams into the young Earth. The debris flung into orbit clumps together to become the Moon.
Back then the Moon was up to 15 times closer, and a single day lasted only about six hours. It has been slowly drifting away — about 3.8 cm a year — ever since.
The Moon steadies Earth's tilt, which keeps our seasons stable. Without that collision, life might never have found a foothold.
The first oceans
As the surface cools, water vapour rains down for thousands of years and the first oceans form — the cradle where everything that follows begins.
Some of Earth's water may have been delivered by icy comets and asteroids crashing in from space.
The oldest things ever found on Earth are tiny zircon crystals about 4.4 billion years old — hinting that liquid water existed almost unbelievably early.
Archean Eon
The heavy bombardment
For hundreds of millions of years, asteroids and comets rain down relentlessly, scarring the young planet and its new Moon.
Almost every crater you can see on the Moon tonight is a scar from this era — frozen in place because the Moon has no weather to erase them.
Life begins
Somewhere in those oceans, the first single-celled life appears. Every living thing today — you included — descends from these first tiny cells.
All life shares the same genetic code and the same basic chemistry, which is why scientists think it all traces back to a single common ancestor, nicknamed LUCA.
For its first three billion years, life on Earth was nothing but microbes — invisible specks. The whole rest of this journey is squeezed into the final stretch.
Cyanobacteria invent photosynthesis
Microbes learn to turn sunlight into food, breathing out oxygen as waste. It will take over a billion years, but this slowly remakes the entire planet.
Stromatolites — layered mounds built by these microbes — are the oldest fossils on Earth, and a few colonies are still being built today in places like Western Australia.
The first continents
Volcanic islands grow and collide, slowly assembling the first true continents and rafting them across the globe — a dance of land that never stops.
The plates of rock you live on are still drifting, about as fast as your fingernails grow. Given enough time, that's enough to rearrange the entire planet.
Proterozoic Eon
The Great Oxidation — the first catastrophe
Oxygen floods the air for the first time. To most life back then it was a deadly poison: this 'Oxygen Catastrophe' wiped out countless species.
Oxygen in the air, over time
All that oxygen rusted the iron dissolved in the oceans, which sank to the seabed in vast red layers. Much of the iron we mine today was laid down in this single event.
Oxygen may have triggered the planet's first great freeze, by destroying the greenhouse gas methane that had kept the young Earth warm.
Cells with a nucleus
A bigger, more complex cell appears — one with a nucleus and inner machinery. Every animal, plant and fungus is built from this kind of cell.
The powerhouses inside your cells, called mitochondria, were once free-living bacteria that got swallowed and never left. You're a partnership billions of years old.
The 'Boring Billion'
For roughly a billion years, almost nothing dramatic happens. The climate is stable, the oceans are calm, and life ticks along, quietly preparing for what's next.
Scientists really do call it the Boring Billion. But it wasn't wasted time — this is when complex cells quietly perfected the tricks that complex life would later need.
Many cells, and sex
Cells begin teaming up into multicellular life, and sexual reproduction appears — shuffling genes and supercharging how fast life can change.
Before sex, life mostly just cloned itself. Mixing two parents' genes meant every offspring was a fresh experiment — and evolution suddenly had far more to work with.
The supercontinent Rodinia
Almost all the land on Earth fuses into a single giant supercontinent called Rodinia, surrounded by one world-spanning ocean.
This is not the first or the last time. Earth's continents have gathered into a supercontinent and broken apart again several times — a slow heartbeat lasting hundreds of millions of years.
Snowball Earth
The whole planet freezes over — ice reaches all the way to the equator. Life clings on under the ice, waiting out one of the harshest chapters in Earth's story.
Ice may have been over a kilometre thick at the equator. From space, Earth would have looked like a giant white marble.
Volcanoes kept pumping out CO₂ until the greenhouse effect finally cracked the ice. The thaw that followed may have helped kick off the rise of animals.
The first animals
Among the earliest animals are simple sponges — no brain, no muscles, no organs, just filter-feeding bodies anchored to the seafloor.
Sponges are still here today, barely changed. You are more closely related to a sea sponge than that sponge is to any plant.
The first large animals
Strange, soft, frond-like creatures sprawl across the seafloor — the Ediacaran biota. They are the first big animals, with no mouths, eyes, or bones.
These creatures are so alien that scientists still argue about which were animals at all. Many left no descendants — a lost first draft of complex life.
Phanerozoic Eon · Cambrian
The Cambrian Explosion
In a geological blink, almost every animal body plan alive today appears. Eyes, shells, legs and predators arrive — and the world is never quiet again.
The very first eyes evolved here. Once some animals could see, the race between hunter and hunted began — and it has never stopped since.
Almost every major group of animals alive today, from insects to fish to you, can trace its blueprint back to this single burst of invention.
The weird wonders
The Cambrian seas teem with bizarre experiments: Opabinia with five eyes and a nozzle for a mouth, Hallucigenia walking on spikes. Evolution is throwing everything at the wall.
Hallucigenia was so strange that scientists first reconstructed it upside-down and back-to-front, mistaking its legs for spines and its head for its tail.
Trilobites rule the seas
Armoured trilobites scuttle across the seafloor. They'll thrive for nearly 300 million years — far longer than the dinosaurs ever did.
Some trilobites had eyes made of calcite — actual stone lenses. They saw the world through crystal.
There are more than 20,000 known species of trilobite. They are one of evolution's all-time success stories — yet not a single one survives today.
Ordovician
Giants in a cone-shaped shell
Orthocones — squid-like animals in long straight shells, some many metres long — become the top predators of the Ordovician seas.
These were cousins of today's octopus and squid. Their modern relative, the nautilus, still drifts the oceans in a coiled version of the same shell.
The first vertebrates
Jawless fish appear — the first animals with a backbone. This humble blueprint leads, eventually, to every fish, dinosaur, bird and human.
These first fish had no jaws — they sucked and filtered food. Jaws, one of evolution's great inventions, came tens of millions of years later.
Mass extinction #1
An ice age strikes and about 85% of species vanish — the first of the 'Big Five' mass extinctions. Life is repeatedly almost erased, then recovers.
The Big Five — % of species lost
Every one of the Big Five was an apocalypse for the life of its day. But each also cleared the stage for something new — the dinosaurs and, much later, us, are children of these disasters.
Plants conquer the land
Low mosses and the first plants creep out of the water onto bare rock — turning a grey, lifeless landscape green for the very first time.
Before plants, the land was bare rock and dust for over four billion years. Imagine a whole planet with no green anywhere.
Animals crawl ashore
Following the plants, the first animals — tiny millipedes and early bugs — leave the water and take their first steps onto dry land.
For millions of years the land belonged entirely to plants and creepy-crawlies. There were no animals with backbones on land at all yet.
Sea scorpions
Giant sea scorpions prowl the shallows — some over 2.5 metres long, the largest arthropods that have ever lived.
An arthropod is any animal with an exoskeleton and jointed legs — insects, crabs, spiders. None today comes close to the size of these ancient sea scorpions.
The first forests
The first true trees grow tall and the world sprouts forests, reaching toward the sky and pulling carbon out of the air on a massive scale.
As forests spread, they pulled so much CO₂ from the air that they may have helped chill the whole planet — proof that life itself reshapes the climate.
Devonian · Age of Fishes
Armour-plated terror
Dunkleosteus, a fish up to 6 metres long with a head of bony armour, rules the seas. Instead of teeth it had self-sharpening bony blades.
Its bite was among the most powerful of any fish ever — strong enough to slice other armoured fish clean in half.
Fish crawl onto land
A fish like Tiktaalik, with stubby limb-like fins and a neck, hauls itself onto the shore. Its descendants — including you — will become the four-limbed animals.
Look at your wrist, elbow and shoulder: that same set of bones first appeared in the fins of fish like this, getting ready to walk.
Mass extinction #2
A long series of die-offs — the Late Devonian extinction — devastates ocean life, especially the reefs and the armoured fish.
Ironically, the spread of land plants may have helped cause it: their roots and nutrients washed into the seas, starving the water of oxygen.
Carboniferous
Coal forests & giant insects
Vast swampy forests bury so much carbon they become today's coal. Oxygen hits ~35%, and insects grow huge — dragonflies with the wingspan of a hawk.
Insects breathe through tiny tubes, not lungs. The oxygen-rich air let them grow enormous: think millipedes nearly 2 metres long.
Almost all the coal we burn today is the fossilised remains of these forests. Every lump of coal is a piece of a 300-million-year-old swamp.
The egg conquers the land
The first reptiles evolve a tough, self-contained egg that can be laid on dry land — finally cutting the cord that tied animals to water to breed.
This waterproof egg was a game-changer. For the first time, animals with backbones could move deep inland, far from any pond or sea.
One supercontinent: Pangaea
All the world's land grinds together into a single supercontinent, Pangaea. You could, in theory, walk from pole to pole without crossing an ocean.
The land drifts together, then apart
This is why you can find matching fossils and rock layers on coastlines now separated by entire oceans — they were once joined.
Permian
The sail-backed hunter
Dimetrodon, with its huge skin sail, dominates the land. Despite looking like one, it's NOT a dinosaur — it's actually a distant relative of yours.
Dimetrodon is a synapsid, the same branch that led to mammals. It's more closely related to you than to any dinosaur — which wouldn't appear for another 60 million years.
Mesozoic Era · Triassic
The Great Dying
Massive volcanic eruptions trigger the worst extinction ever: up to 90% of all species die. Life comes closer to ending here than at any other moment.
The Big Five — % of species lost
Volcanoes in Siberia erupted for hundreds of thousands of years, poisoning the air and acidifying the oceans. It took life around 10 million years to fully recover.
This catastrophe finally finished off the trilobites — after they had survived in the seas for nearly 300 million years.
The first dinosaurs — and mammals
From the ashes, the first dinosaurs rise. Alongside them appear the first tiny mammals: shrew-sized creatures that scurry in the shadows.
For their first 150 million years, mammals stayed small and mostly nocturnal, hiding from the dinosaurs. We waited in the wings for a very long time.
The sky is conquered
Pterosaurs take to the air — the first vertebrates ever to truly fly, long before birds. Some later grew wingspans the size of a small plane.
The largest, Quetzalcoatlus, stood as tall as a giraffe and may have had a 10-metre wingspan — the largest flying animal we know of.
Jurassic
Mass extinction #4
Another mass extinction clears out many big competitors — and the dinosaurs seize the opening, exploding in size and number to rule the world.
Sometimes the winners of history are simply the survivors of a catastrophe. The age of dinosaurs began with a disaster that happened to spare them.
Giants and the first bird
Dinosaurs grow colossal — long-necked giants taller than a house. And a feathered dinosaur, Archaeopteryx, takes to the air: the first bird.
Birds didn't come after the dinosaurs — they ARE dinosaurs. Every sparrow and pigeon today is a living, feathered dinosaur.
The biggest sauropods may have weighed as much as ten elephants, yet their eggs were barely bigger than a football.
The world bursts into bloom
Flowering plants appear and spread explosively, painting a once-green world in colour and striking a deal with insects that still feeds us today.
Flowers and their pollinators evolved together. Nearly everything you eat — fruit, grains, coffee, chocolate — exists because of this ancient partnership.
Bigger than T. rex
Spinosaurus, a sail-backed giant longer than a bus, hunts in the rivers — the largest predatory dinosaur known, and a fearsome swimmer.
It's the only known dinosaur built for a life largely in water, with a paddle-like tail and crocodile-like jaws full of conical teeth.
Cretaceous
Coiled monsters of the deep
While dinosaurs rule the land, the seas swarm with ammonites — coiled-shell relatives of squid — and giant marine reptiles longer than a bus.
Ammonites are so common as fossils, and changed so fast, that geologists use them like clocks to date the rocks they're found in.
Tyrannosaurus rex
The most famous predator of all time stalks the land: T. rex, with teeth like bananas and a bite that could crush a car. Triceratops faces it down.
T. rex lived closer in time to us than to Stegosaurus. More than 80 million years separated those two famous dinosaurs.
Its bite force was around 35,000 newtons — the strongest of any land animal ever, able to bite straight through bone.
The day the sky fell
A 10-km asteroid slams into Earth. Firestorms, tsunamis and a years-long winter wipe out the non-bird dinosaurs — and three-quarters of all species. (Tap it.)
It hit what is now Mexico with the force of billions of atomic bombs, throwing up so much dust that the Sun was blotted out and the food chain collapsed.
The dinosaurs that survived were the small feathered ones — the birds. Their descendants now outnumber mammals two to one.
Cenozoic Era
The largest snake ever
In the steamy post-dinosaur jungles slithers Titanoboa — a snake up to 13 metres long and over a tonne, big enough to swallow a crocodile whole.
A snake that size needed a very hot climate to stay warm. Titanoboa is a clue that the tropics back then were even hotter than today.
The age of mammals
With the giant dinosaurs gone, mammals seize the empty world — growing bigger and bolder, spreading into every corner the dinosaurs left behind.
Freed from hiding, mammals exploded in variety in just a few million years: the ancestors of horses, whales, bats, elephants and primates all appear around now.
Horses the size of a cat
The first horses appear — but they're no bigger than a small dog, with several toes, tiptoeing through the forests.
Over millions of years they grew larger, lost toes, and ended up running on a single giant toe on each foot. A horse's hoof is really one enormous toenail.
Mammals return to the sea
Some four-legged mammals walk back into the ocean and become whales — their ancestors had crawled onto land 300 million years earlier.
Whales' closest living land relative is the hippopotamus. And buried in a whale's flippers are the bones of a hand — five fingers, hidden inside.
Grass takes over the world
Grasses spread into vast open plains. This new, tough food source reshapes evolution, favouring fast runners with grinding teeth — from horses to antelope.
Grass is one of the most successful plants on Earth, and one of the youngest. Wheat, rice, corn and the lawns of the world are all grasses.
The first apes
In the warm forests, the first apes swing through the trees — the family that will eventually include gibbons, gorillas, chimps and us.
You share about 98–99% of your DNA with a chimpanzee. The differences that make us human are written in a tiny sliver of our genome.
We split from the chimps
Our ancestors and the ancestors of chimpanzees go their separate ways. The human branch — the hominins — begins its own long story.
Many different human-like species lived and died along the way. For most of this story, several kinds of 'human' walked the Earth at the same time.
Walking upright
An ape like Australopithecus — 'Lucy' — walks upright on two legs across the African grasslands. The human story is finally taking shape.
Lucy's skeleton, found in Ethiopia in 1974, was nicknamed after the Beatles song playing at the camp that night. She stood barely over a metre tall.
The Ice Age
Great ice sheets advance and retreat. Woolly mammoths and sabre-toothed cats roam, while early humans learn to make stone tools and tame fire.
We're technically still in an ice age — there's permanent ice at both poles. We just happen to live in one of its warmer in-between spells.
Fire and the first journeys
Homo erectus tames fire, cooks food, and becomes the first human to walk out of Africa, spreading across Asia and Europe.
Cooking unlocked far more energy from food, which may have helped fuel the growth of the big, hungry human brain.
Homo sapiens appears
Our own species arrives — about 300,000 years ago. On the scale of this whole journey, that is the last few hairs' width of the entire road behind you.
We shared the planet with other humans — Neanderthals, Denisovans — for most of our existence. Many people today still carry a little of their DNA.
We spread across the world
About 60,000 years ago, modern humans sweep out of Africa and reach every continent. Soon after, the giant ice-age animals begin to vanish.
Wherever humans arrived, the largest animals — mammoths, giant sloths, moas — tended to disappear within a few thousand years.
Farming changes everything
As the last ice age ends, humans start farming. Settling down to grow food leads to villages, then towns, then everything that followed.
Before farming, every human who ever lived was a hunter-gatherer. In just 12,000 years — a blink — we went from that to spaceflight.
Everything you've ever heard of
Writing, cities, pyramids, every empire, every war, every person in every history book — all of it happened in the last 5,000 years. A single pixel.
If this whole journey were a 24-hour day, the entire span of recorded human history would flash by in the final fraction of the very last second.
4 billion years · thinky.fun
You scrolled through the whole story of life on Earth.
Every creature you passed lived and died so that the next could exist. All of recorded human history fit into the final fraction of that journey — and you're the first kind of animal that ever got to look back at all of it.
Take a friend through 4 billion years