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 self this is the most extraordinary improbable 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 nine 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 suit at the right place and the right time billions of volts of electricity trigger a chain of improbable coincidences the chemicals 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 [Music] 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 copied 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 reproduce 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 [Music] 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 milo conningia our brain can make simple decisions process basic information but we can't outwit or outrun this anomalous 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 but a 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 foot long armored fish we look invincible but we're not now the choice is simple get out of his way or die [Music] 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 now our future looks bleak but 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 an ichthyostega 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 [Music] 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 [Music] 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 casanaria 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 [Music] thanks to sex 340 million years ago cassanaria 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 [Music] 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 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 a thousand feet deep and it continues for half a million years trillions of tons of noxious carbon dioxide trapped the sun's heat inside the atmosphere temperatures soar to over a hundred degrees plants the plant eaters and 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 percent of all living things when the eruption 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 [Music] this one's fast strong and hungry [Music] we're staring down the barrel of an evolutionary gun our only 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 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 batadong a two-inch-long shrew-like creature living on our wits in the ancient forests of montana humanity's future depends on vatadon's sharp senses and supercharged brain if these fail we may never exist my [Applause] [Music] 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 four thousand species from the smallest mouse to the largest whale to us the mammals have arrived the dinosaurs helped 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 1800 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 engulfed the entire planet [Music] 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 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 dinosaurs 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 [Music] we're alti atlassias one of the first members of a new group of mammals the primates by 56 million years ago we've adapted to our world [Music] but that world is about to change again over 10 million years extreme temperature shifts ravaged the forests forests get smaller food gets harder to reach natural selection intervenes our again 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 three and a half thousand mile long mountain chain rises up rains from the indian ocean once watered all of africa now the mountains blocked 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 artipithicus 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 [Music] [Music] 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 art epithecus 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 [Music] 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 australopithecuan our brain is the size of a grapefruit and we walk on two legs all the time [Music] so we got lucky the lion has already eaten this time we can't outrun our predators the only way to survive is to out-think 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 three 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 and our own relatives [Applause] [Music] 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 in 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 pickup 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 [Music] 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 [Music] 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 percent 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 will 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 men 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 lucky mutation and we wouldn't be here to tell the tale to piece together the extraordinary story of our 4 billion year journey