We are the most complex creature on this planet. A big brain, two legged mammal. We've risen from the raw materials of the earth to dominate and shape it.
Wind the clock backwards, and the story of how we got to be us is a puzzle that defies all logic. Through nearly 4 billion years of evolutionary twists and turns, disasters strike. Predators threaten to wipe us out.
From rodent to reptile, we face extinction at every turn. From the land into the water, fighting to survive every step of the way. From fish to worm, back to the very first spark of life. to a single simple cell. This is the most extraordinary and probable story ever told.
The story of mankind rising. Four billion years ago, a ball of rock and dust spins in the frozen vacuum of space. This isn't Mars or Venus.
This hell is Earth. This seething lifeless mass of molten lava will become home to nearly 9 million living species. But generating life from this will take a chain of events that defies the laws of probability.
There are many theories. Nobody knows exactly how or where life began. But it couldn't happen without water.
Experts believe asteroids or comets delivered it here. The water is churning with chemicals and organic compounds. Lightning strikes the chemical soup at the right place and the right time.
Billions of volts of electricity trigger a chain of improbable coincidences. The chemical's atoms join up in a precise sequence, creating a bundle of genetic material. These fragile genes don't stand a chance in this extreme environment.
But luck strikes again. A blob of oily material engulfs a single chain to create the first ever cell. Now, the genes send out messages, chemical instructions.
And 3.5 billion years ago, they do something extraordinary. They copy themselves and the cell to create a perfect clone. This is the very first living thing. Every human, every animal, every bug, every plant can trace its origins to this single cell. The genes tell each cell to reproduce, guaranteeing their survival as they pass from one generation to the next.
For two billion years, the only living things are simple single cells. But a random accident changes everything. Two cells merge.
Their genes combine. The merged cell clones itself. Its offspring contains genes from not one, but two cells, two parents.
We call this accident sex. Sex introduces variation. Occasionally, things go wrong. As the cells re- Produce genes get deleted, duplicated. These cells are mutants.
Mutations pile up. Differences increase. Until the cells become so different, they're separate species. The tree of life branches out into billions of species, but only one will lead to us.
Mutating and diversifying. spreading out through the oceans, getting bigger, more complex, until our ancestor is a three-inch long water worm. This is us 550 million years ago.
Mutations create distinct male and female sexes. We produce more offspring, passing on more genes. Mars and Venus.
Boy meets girl. It all starts here. But finding a partner is almost impossible when every living thing is blind. In this sea of darkness, the ability to see will give us a critical advantage. Nature's most perfect innovation begins to take shape.
A handful of skin cells mutate. Now, we can tell dark from light, find more prey, dodge more predators. We live longer.
and produce more offspring. Soon, creatures with light-sensitive cells dominate the population. Over countless generations, more mutations refine the cells. This is natural selection in action. The process that allows every living thing to adapt to the world.
And that gives our ancestor eyes. We can see. And everything we can see is descended from that first single cell.
But we need to make sense of what we're seeing. Behind our eyes, a tiny collection of nerve cells cluster together. They're no bigger than a pinhead.
One day, this will be nature's most complex and mysterious organ. 521 million years ago, this is the very first brain. We are a fish-like creature called Myloconmingia.
Our brain can make simple decisions, process basic information. But we can't outwit. or outrun this. Anomalacaris, the great white of the ancient oceans.
Our odds of extinction are far higher than survival. Of all the species that have ever lived, 99% of them are extinct. Lucky roll of the genetic dice helps Milo toughen up. Your jaws, your teeth, they exist because over 400 million years ago we faced the wrath of a primeval monster.
Jaws and teeth mean more food and a bigger stronger body. Until 375 million years ago we're a footlong armored fish. But we're not.
Now, the choice is simple. Get out of his way or die. We're safe in the shallow water. Or are we? The water's stagnant.
There's not enough oxygen. Starved of oxygen, cells shut down. Toxic carbon dioxide saturates the blood.
We can't go back. We can't stay here. There's only one place left for us to go.
It takes over three billion years for our ancestor to evolve from a single cell to a foot-long armored fish. Our future looks bleak. Natural selection throws us a lifeline.
Over millions of years, thousands of generations, our body adapts until we do something no fish has done before. Breathe air. The air travels into a new organ. A lung.
Take a breath and remember it's because a monster fish chased our ancestor into the stagnant water, forcing them to breathe air. We're in Icthio Stega. We can breathe air or water, closing off our windpipe to switch between lungs and gills.
Today our gills are gone, but the mechanism remains. And sometimes it spasms, giving us the hiccups. 365 million years ago, we stick our head out of the water.
There's a swamp behind us, paradise ahead. The choice is simple, but the consequences are immense. We pull ourselves out of the water and change the course of history. This is the moment we leave the water for a new life on land.
But all this food comes at a price. The fierce sun dries out our skin. The hard terrain tears at our soft feet.
Ichthyostega is a fish out of water. We dodged extinction in a stagnant swamp, only to slam straight into another deadly environment. Countless creatures perish, but natural selection helps our ancestor adapt. Thicker skin protects us from the sun.
And tough claws that will one day become our fingernails help us move across the rough terrain until we're cassonaria. We've adapted to life on land, but our eggs haven't. They need a tough shell to stop them drying out in the sun.
The problem is males can't fertilize an egg through a tough shell, but they can fertilize it before the shell forms, inside the female's body. Sex as we know it starts here. The result is a masterpiece of evolution.
An egg in a tough shell, with all the nutrients the embryo needs sealed inside. Sex is the best way to increase genetic variety and keep our species alive. Thanks to sex, 340 million years ago, Cassinaria becomes the first of our ancestors to live entirely on land.
It's a new world, different from anything we've experienced up to now. We breathe air, support our own weight, and wrestle with an onslaught of new smells, sounds, sights. Bombarded with information, our brains evolve.
We're smart. And we need to be. From that first creature to set foot on land, millions of species have evolved. More competitors mean less food to go round.
A mutation gives us bigger, more powerful jaw muscles. It's a critical advantage. We can eat more food, faster.
And it shows. We're Varanaps, a slab of pure meat-eating power. This little creature is a Proterosaurus. Once a competitor, now he's prey.
With Varanops for an ancestor, our success seems certain. But our story is a roller coaster ride, and there's a big dip coming. 250 million years ago, thousands of miles away in Siberia, the Earth tears itself apart.
A giant plume of magma surges up from deep inside the planet. Molten rock oozes through cracks in the Earth's crust, covering an area the size of the United States, under a layer 1,000 feet deep. And it continues for half a million years.
Trillions of tons of noxious carbon dioxide trap the sun's heat inside the atmosphere. Temperatures soar to over 100 degrees. Plants, the plant eaters, and eventually Eventually the meat eaters perish. 95% of all species die.
Only a tiny handful hang on. Among them, us and another species that will one day become the dinosaurs. As the fight for survival winds down, the battle for supremacy begins.
30 million years since volcanic eruptions wiped out 95% of all living things. When the eruptions struck, we looked like a large lizard. Now we're a cat-sized creature covered in fur called Ectoninion.
Imagine you've survived the apocalypse and today is the day it's finally safe to venture out of hiding. You discover you're not alone. The last thing you want to see is a dinosaur.
a five foot tall Herrerasaurus. She evolved from one of the small reptiles that survived the mass extinction. Her ancestors adapted faster than ours, putting the dinosaurs ahead in the game and leaving us playing catch up.
We're staring down the barrel of an evolutionary gun. I hope. Natural selection.
Over millions of years, we get smaller. So we're harder to catch. We become nocturnal, making us harder to see. We're cold.
Cold and scared. Tiny muscles around the base of each hair contract, making our fur stand on end, trapping air as insulation. That's why today, when we're cold or startled, we get goosebumps.
Our senses sharpen so we can see, hear, and smell a dinosaur, before a dinosaur sees us. Inside our brain, a new structure evolves, the neocortex, the home of complex thought. that allows us to analyze a situation and respond. It will one day give us the power to imagine, create, and communicate.
66 million years ago, we're Batadon, a two-inch long shrew-like creature living on our wits in the ancient forests of Montana. Humanity's future depends on Batadon's sharp senses. and supercharged brain.
If these fail, we may never exist. The dinosaurs may be the best thing that ever happened to us. Thanks to them, we have powerful senses and brilliant brains. Without them, we could still be laying eggs.
To protect our offspring from hungry dinosaurs, we evolved to give birth to live young. Instead of leaving them to fend for themselves, we nurture them with milk. Sweat glands evolve to become mammary glands. It's a major milestone in our journey from cell to human.
The birth of a new kind of animal. One that will branch out into more than 4,000 species. From the smallest mouse, to the largest whale, to us.
The mammals have arrived. The dinosaurs help shape who we are. But we lost the battle for supremacy. The dinosaurs reigned for over 165 million years. Nothing can stop them.
Or so it seems. Montana, 65 million years ago. An asteroid strikes 1,800 miles away off Mexico's Yucatan Peninsula. A small rat-like mammal is about to face the fight of his life. Lose, and humans may never exist.
Pulverized rock and dust engulf the entire planet. The only way out is to dig. Smoke and ash from the fires block out the sun. Temperatures plummet.
Vegetation dies. The local disaster becomes a global disaster. Global catastrophe. For the dinosaurs, it's a disaster. They're big creatures with big appetites.
And now, that's a big problem. As the mighty fall, the small rise to the top. Bugs. Tough enough to survive the worst catastrophe.
Gorge on the dead and decaying. And they make the perfect snack. Next time you're about to squash a bug, remember that we wouldn't be here without them.
64 million years ago, our bug-eating ancestor is purgatorious. Just under six inches long, this little creature and the rest of his mammal family are the unlikely inheritors of the dinosaur's crown. Mammals become the dominant animals on land. They spread out across the newly formed continents.
Our future rests on their tiny shoulders. From the ashes of destruction, new life begins to sprout. 60 million years ago, fruit ripens on the trees. Packed full of nutrients, the more fruit we eat, the longer we live.
We leave solid ground for a new life in the trees. A new world demands a new body. We've come a long way from that first single cell. Now, at last, we're beginning to glimpse a family resemblance. We're Altiatlassius, one of the first members of a new group of mammals, the primates, by 56 million years ago.
We've adapted to our world. But that world is about to change. Again. Over 10 million years, extreme temperature shifts ravage the forests.
Forests get smaller. Food gets harder to reach. Natural selection intervenes again.
Our tail shrinks back to the base of the spine, where it stays, as the coccyx. A reminder of our days spent leaping through the trees. Instead of leaping, we stretch. Our arms grow long and flexible.
Changing temperatures changed our ancestors. And us. Forever. But the planet's not finished yet.
Deep underground, the African and Arabian plates pull apart. The land between them drops to form the East African Rift Valley. Along its edge, a 3,500-mile-long mountain chain rises up. Rains from the Indian Ocean once watered all of Africa.
Now the mountains block their path. The trees get even further apart, the food harder to reach. We're starving, desperate. 4.4 million years ago, the will to survive that's driven us from a single cell in the ocean to a complex primate in the forests of Africa is about to make us do something extraordinary, something no primate has ever done before. After three billion years of evolution, we hit an evolutionary dead end.
We're Ardipithecus ramidus. Four feet tall, at 80 pounds, with a brain the size of an orange. Our dense rainforest home has become patchy forest.
We can stand on branches, move along them, but to reach more food, we need to let go. 4.4 million years ago. These are our first steps on two legs. Walking takes us to the food. And leaves our hands free to pick it.
It catches on. fast. Artipithecus is smart enough to copy and learn.
Walking gets passed from parent to child. Over the next 1.2 million years, our body evolves so that we can walk further and faster. Finding shelter, a mate, and food gets easier, but childbirth gets harder.
With a narrower pelvis, giving birth to a fully developed infant becomes impossible. Babies have to come out early, when their heads are smaller and they're barely developed. That's why we are one of the few species to spend years caring for our offspring, protecting them, feeding them, and keeping them out of trouble. 3.2 million years ago, we're an Australopithecan.
Our brain is the size of a grapefruit, and we walk on two legs all the time. We got lucky. The lion has already eaten.
This time. We can't outrun our predators. The only way to survive is to outthink them. The smarter we get, the longer we live.
Natural selection promotes the mutations that improve our brain power. Like weaker jaw muscles. Released from the muscle's vice-like grip, the brain is free to grow. It doubles in size. 2.3 million years ago.
This is Homo habilis, also known as handyman. Walking on two legs with a big brain, we're the first of an entirely new type of creature. We're the first man. We're bigger, stronger, and hungrier than ever before.
There's food out there, but it's more likely to eat us before we can eat it. We're a scavenger, working alone. We eat whatever we can find.
The edge is razor sharp. We have just made the very first tool. Armed with this, we will change the world.
East Africa 2.3 million years ago. After over 3 billion years of evolution, we take our fate into our own hands. We are the first species to make tools. In this hostile environment, we need every advantage we can get. We must fight off predators, starvation, There's no meat left.
It looks like we're going hungry again. But there's bone marrow locked inside, packed with energy. The tool is the key to a whole new way of life.
We'll use it to grow crops, build cities, and travel into space. Our thumbs become stronger. Hold a cup.
Pick up a pen. We can do this because two million years ago, tool use changed our bodies and the course of evolution. We've pieced together our ancestors'story from their bones.
But from the vastness of Africa, all the bones of our early human ancestors ever found would fit into the back of a pick-up. Less than one bone in a billion becomes a fossil. Factor in the chances of finding those bones across millions of square miles, and it's clear.
Most of what has lived has been lost. Our family tree is a giant puzzle, with most of the pieces missing. But 1.8 million years ago, a piece falls into place, and we find a new species on the scene, Homo erectus. Until this point, we were scavengers. But now, we're hunters.
And we've learned how to work with other members of our species. The hunt is on. The Impala can run fast, but we can run further. Low shoulders and long torsos stabilize us. Powerful buttock muscles contract, expand and push us forwards.
Sweat stops us from overheating. Covered in fur, the Impala is exhausted. Fire. It sparks an idea that will make our ancestors human.
Warmth, light, safety is within reach. Nature's power is in our hands. Protected from the terrors of the dark, our extended family gather round.
By working together, these earliest families get food more often, so we live longer. This is the advantage of family life, the reason most of us live as we do today. Meat is too precious to waste. And cooked meat is easier to chew.
The powerful molars used to chew tough raw food retreat back into the gums, where they'll stay, as our wisdom teeth. 35% of us never even grow them, a sign that they may be evolving out of existence. With less energy spent on chewing, our ancestors have energy to spare. The brain increases to the size of a softball, 50% larger than before the invention of cooking.
Erectus, is the cleverest, most cooperative ancestor to date. But with several adult males in an extended family, rivalries are inevitable. Communicate, and we'll live longer. Natural selection kicks in.
Our tongue changes shape and moves down our throat carrying the larynx with it allowing us to form different shapes in our mouths making different sounds and ultimately words. Speech is our greatest tool. It's the last piece of the puzzle that turns our ancestors into us.
200,000 years ago, after a 3.3 billion year battle for survival, we've arrived. We are Homo sapiens, meaning wise man. Pound for pound, we have the largest brain of any creature on Earth.
Armed with tools, speech, and superior intelligence, we spread out across every continent. We evolve and adapt to new environments, new challenges, until we become the undisputed masters of the world. Wind the clock of life back to the beginning, and the chances of us evolving again are practically zero.
Change one thing, one predator, one life. lucky mutation and we wouldn't be here to tell the tale, to piece together the extraordinary story of our four billion year journey.