In our travels we visit many museums and sites, and some are full of anthropology: old bones, stone tools, a reconstructed skull, a single famous fossil. The information is usually there, and often well explained. The trouble is time. There is more than you can absorb in one visit, and reading a panel once, on your feet in a gallery, is not the same as keeping it. And not keeping it just carries the problem to the next site and museum and your learning never progresses.

The same gap opens on a larger scale. You arrive somewhere and learn who lives there now, and often, if the museum is good, who came before them too. What you rarely get is how it all connects: how the same people also settled other regions, where they had come from before they arrived here, how this one place fits into a single, much larger story of movement. A place is not just its present, and not just its own local past. It is one point on a chain of arrivals that stretches across whole continents and back tens of thousands of years. That chain, followed all the way, is what we mean by peopling.

That is why we make these primers. Not to become experts, but to build the broad view once, in our own words, and carry it with us. Then the next display, and the next place, makes sense, and when a museum leaves us with a gap we can read the piece we need on the spot and go back to enjoying it. When a site teaches us something new, that is the signal to come back and improve the primer. This one, and others to follow, is our attempt to fill that gap with what we have learned. Our focus is the migration itself, the journey and its branches, not the wider study of humankind. The two are tied together, so we lean on that wider study where we must, but only as far as the journey needs. If we find we need to understand a piece more deeply, we may make a separate primer for it. Our primer post are different. They are not static. They are dynamic. We update them constantly. That is why we don’t broadcast them. But you can find them in our Never Stop Learning Section on the menu.

For North America we have already told this peopling story, up to just before Europeans arrived, in our Never Stop Learning video series (Peopling of the Americas and Pre-History of US and Canada Native Americans). The named tribes living there at that point, the ones who enter written history when the Europeans come, are a separate and later layer.

We will most likely cover them as written posts. From here on all of this work will be posts, not videos. Life on the road has taken away the time that films need, and the posts let us keep going.

Every person alive today came from Africa. Go back far enough, and every family line meets there. But most people carry something more exact. They descend from a small group of Homo Sapiens, hunter-gatherers who walked out of Africa. Over thousands of years, their descendants reached the far corners of the world. Not a nation. Not a tribe. A small band of people. Along the way they met other kinds of human, and mixed a little with them. Those others were not strangers: the Neanderthals and the Denisovans came from the same ancestor we did, Homo Heidelbergensis, or something close to it, whose children had spread across three continents and slowly grown apart into three kinds. We are the branch that stayed in Africa and became Homo Sapiens. This is the story of that journey, before anyone farmed, before anyone built a city, before anyone wrote a word. It is the part we all share, up to the point where the family split and each branch went its own way.

We know this story from two things: old bones, and ancient DNA. DNA is the set of instructions inside every living cell. A parent passes it to a child, and small changes build up over many generations. Around 2010, scientists learned to read the DNA of people who died tens of thousands of years ago. The old story had been built from skulls and stone tools alone. The DNA rewrote large parts of it. Some of the new story is now certain. Some is still argued over, and when it is, we say so.

A people, a culture, and a language are three separate things. A people is a group linked by shared ancestors. A culture is a way of life: the tools people make, the food they eat, how they bury their dead. A language is the words they speak. These three do not always move together. A group can learn a new language without gaining new ancestors. It can take up a new way of life without changing its language. For a long time people treated all three as one thing. That was the oldest mistake in this field, and the DNA is what finally pulled them apart.

Where in Africa?

The story begins in Africa. Almost every fossil of an early human comes from Africa. So does the deepest DNA of every person alive. That part has not changed in a long time. What has changed is where in Africa, and how.

For most of the twentieth century, the answer was East Africa. A long crack runs through the Earth’s surface there, called the Great Rift Valley. It cuts down through Ethiopia, Kenya, and Tanzania, and it has given up an amazing run of fossils: the oldest stone tools, the first members of our own branch of the family, and famous ancestors like Lucy, a skeleton more than three million years old. People called East Africa the cradle of humankind.

For the deep past, the name still fits. The Rift Valley holds our best evidence for where our earliest ancestors took shape. But the rock there happens to protect old bones well, and erosion brings them back to the surface. East Africa may look special only because it is one of the few places where old bones survive and can be found. We may see it clearly just because it is where we can see anything at all.

For our own kind, the picture has cracked open. Our own kind is called Homo Sapiens, which means modern humans, people like us. Scientists use the name to tell us apart from earlier kinds of human that are now gone. The old idea was simple. Modern humans began in one group in East Africa, around 200,000 years ago, and spread out from there.

That idea no longer holds. In 2017, scientists found fossils of Homo Sapiens at Jebel Irhoud, in Morocco — the far northwest of the continent, thousands of miles from the Rift. The bones were about 300,000 years old, older than anything then known from East Africa. The oldest known modern human skeleton, from Omo in southern Ethiopia, is around 230,000 years old. More early bones have turned up in the far south of Africa too. Our kind was already spread right across Africa, very early, not sitting in one corner.

Most scientists now picture our origin a new way, and they call it the pan-African model. Pan-African means all of Africa, not one corner of it. We did not come from a single group in a single place. Several early groups lived in different parts of Africa, only a little different from one another, and they stayed loosely joined, because people kept moving between them and having children across hundreds of thousands of years. Scientists sometimes call this a weakly structured stem: many linked strands rather than one trunk.

The DNA of people alive today still carries a trace of this. The oldest split between groups that we can still see happened around 120,000 to 135,000 years ago. Even that was not a clean break, because the groups kept mixing long after. There is no single birthplace. The whole of Africa is the cradle.

This is the leading idea, not the final word. Scientists still argue over how many groups there were, and how closely joined they stayed. But Africa held the deepest roots of humankind, and the widest variety, and it holds them still. The people who left were one branch of a much larger African family. Most of that family never left, and its descendants are in Africa today.

The Long Road to Us

Homo Sapiens was not the first human. Behind us lies a long line of ancestors and near-relatives, reaching back millions of years in Africa. This family tree is not a straight ladder. It is a branching bush, most of its branches dead ends now, and the links between the twigs get redrawn each time a new fossil comes out of the ground. What follows is the shape most scientists accept, with the biggest doubts flagged.

The road begins not with a human, but with an ape. Go back far enough and our line meets the line of other apes at a series of forks. Each fork is a shared ancestor, a single species that split into two. Around 13 million years ago, one of those ancestors split into the line that led to orangutans and the line that led to us. Around 8 million years ago, the next split sent off the line that led to gorillas. Around 6 million years ago, the one after that split again: one branch became the chimpanzees and bonobos, the other became us. That last shared ancestor is extinct, and we have no fossil of it. It was not a chimpanzee. Chimpanzees had the same millions of years to change as we did, and they went their own way. We and the chimpanzees are cousins, from a shared grandparent, not parent and child.

The Last Split From Our Nearest Cousins

On our side of that last fork, something set our branch apart, and it was not a big brain, and not tools. Those came much later. It was walking upright, on two legs. Somewhere around 7 to 6 million years ago, in Africa, our ancestors stood up. That is where our lineage begins, and for millions of years walking upright was almost the only thing that made them different from other apes.

How do we know an animal walked upright, when all that survives is old bone? Two kinds of evidence. The first is the shape of the skeleton. An upright walker’s body is built differently, and it can be recognized even in a single bone. Compare a chimpanzee to an early upright walker and the differences line up head to foot. The hole where the spine meets the skull sits underneath, so the head balances on top of the spine, instead of hanging forward as it does in a four-legged ape. The spine itself curves into a gentle S, which brings the body’s weight over the hips instead of slinging it forward. The hip bone is short and bowl-shaped, to carry that weight over the legs, rather than the long, narrow blade of an ape. The thigh bones angle inward, to bring the knees and feet under the body, instead of angling out. And the proportions change: an upright walker’s arms are shorter than its legs and no longer used to walk on, while an ape’s arms are longer and take its weight on the ground. A good hip or knee joint can do that job. For Lucy, whom we will meet soon, the hip and leg bones alone proved it.

The second kind of evidence is rarer, and more direct: footprints. At Laetoli, in Tanzania, a group of our ancestors walked across a layer of wet volcanic ash about 3.66 million years ago. The ash dried and hardened, and the tracks survived. They show an upright, striding walk. The heel lands first, and the weight rolls forward to push off from the toes. The big toe lines up with the others, instead of sticking out to the side like a thumb, the way an ape’s grasping foot does. These are the oldest sure sign of upright walking anywhere, and they are behavior caught in the act, not a shape guessed from bones. Some claim upright walking goes back further still, up to 7 million years ago, from bones alone. Those claims are argued over. The footprints are not.

The earliest candidates for that first upright branch are three very old African species, at the blurriest edge of the whole story. The oldest is Sahelanthropus, from Chad, around 7 million years ago, known from a single skull. The hole where its spine met the head sits in a spot that hints it stood upright, though one skull leaves plenty of room for doubt.

Next comes Orrorin, from Kenya, around 6 million years ago, known mostly from thigh bones that suggest walking.

Then Ardipithecus, from Ethiopia, around 4.4 million years ago. Its partial skeleton, nicknamed Ardi, shows a creature that walked on the ground but still had a grasping big toe for climbing trees. All three seem to have walked at least partly upright. But we do not know whether any of them is a true ancestor of ours, or just a cousin off to the side, or a dead end. Each new find reshuffles the argument. Upright walking is very old, older than our own group by millions of years. Which of them we come from, if any, we cannot say.

For these deep ancestors, and for everything older than a few hundred thousand years, we have only bones and footprints. Never DNA. DNA breaks down over time, and faster in heat, so it does not survive in fossils this old from warm Africa. Their whole story is read from the shape of what they left in the ground. Only for the recent, cold-climate humans, the Neanderthals and Denisovans we will meet later, does DNA survive, and even they sit near the limit.

Next come the Australopithecines, the southern (Austral) apes. They were small, upright creatures with brains only a little larger than a chimpanzee’s, and they walked the African grasslands from around 4 to 2 million years ago.

Lucy, the famous skeleton from Ethiopia, is one of them. Her species is called Australopithecus Afarensis, and she lived about 3.2 million years ago. Lucy proved that our ancestors walked upright long before their brains grew large. Walking came first. The big brain came much later.

Brain size is the second great trace of our story, after walking. There are two ways to measure brain size. The simple way is the raw size of the braincase, in cubic centimeters, read from the hollow of the skull. It is easy to get, and it is the number most often compared. But on its own it misleads. A larger body needs a larger brain just to run it, so raw size alone would rank a cow above a chimpanzee. The better measure is brain size set against body size. By that measure humans are extreme, carrying several times the brain our size would predict, more than any other animal. But this better measure is harder to pin down. Body weight has to be guessed from a partial skeleton, and the guess carries error. So the raw braincase numbers still do most of the visible work.

Either way, the record shows the same shape: a long slow start, then a sharp climb. For millions of years, even after our ancestors stood up, their brains stayed close to a chimpanzee’s, around 450 cubic centimeters in the australopithecines. The growth began with the first members of our own group, Homo, and sped up with Homo erectus, whose brain reached about 1,000. Modern humans average about 1,350. The Neanderthals had brains as large as ours, or a little larger. Two cautions. A bigger brain did not simply mean a cleverer creature necessarily: Homo erectus carried its larger brain for more than a million years while its stone tools barely changed. And the climb was not a smooth line rising in every species; some show no clear trend at all, and scientists still argue over the pattern. But from a walnut-sized brain to ours is roughly a tripling, and it marks our lineage as surely as walking does.

Around this same time, the family tree split. One branch led toward us. Another led to the Paranthropus species, often called the Robust Australopithecines. They had huge jaws, enormous back teeth, and cheekbones flared wide to hold powerful muscles. The biggest had a bony ridge along the top of the skull, like a gorilla’s, to anchor those muscles. One is nicknamed nutcracker man. All of this was for a diet of tough, gritty plants: roots, seeds, and hard stems. They lived across eastern and southern Africa for more than a million years, right alongside the first members of our own group. Then they died out, and left no descendants. They are not our ancestors. They are our cousins, a different answer to the same African world, and a reminder that our branch was one of several, not the point the others were heading toward.

From some Australopithecine group, around 2 to 3 million years ago, our own group appeared: the genus Homo. Genus is just the next level up from species, a cluster of close relatives. We are its only living member of that genus. The earliest members are usually called Homo Habilis, the handy man. It earned the name because its bones were found next to simple stone tools, the first clear sign of toolmaking in our line. Habilis had a slightly larger brain than the Australopithecines, and a hand better suited to a firm grip. But it kept a small body and long arms, and even its place in our group is argued over. Some scientists would sort it differently. Still, with Habilis the pattern of our genus begins: a growing brain, a working hand, and tools.

Then comes Homo Erectus, upright man, appearing around 2 million years ago. Erectus was the first of our line built much like us, tall and long-legged, made for walking and running across open country rather than climbing. It was the first to use fire in a steady way, the first to make a fine teardrop-shaped stone hand axe, and the first human of any kind to leave Africa. It lasted well over a million years, longer than any other human species, and spread across much of Asia. Two of the most famous human fossils ever found belong to it. One is Java Man, dug up in Indonesia in the 1890s. The other is Peking Man, found in a cave near Beijing in the 1920s. Each was given its own name at first. Only later did scientists realize the two were the same species, Homo erectus, found at opposite ends of Asia.

On the Indonesian island of Flores lived Homo Floresiensis, an adult barely three feet tall, nicknamed the hobbit. It survived until surprisingly late, perhaps 60,000 years ago. It shared its island with dwarf elephants and giant rats, yet it made stone tools and hunted. Most scientists think it descends from an early human, perhaps Homo erectus or something older still, that reached the island and shrank over generations, the way large animals often do when trapped on islands with little food. How it got there, across open sea, and exactly what it came from, are both still argued. It is a dead-end branch, not an ancestor of ours, but a reminder that ours was never the only human story running at once.

From Homo Erectus, later and larger-brained humans evolved. Around 800,000 to 500,000 years ago came Homo Heidelbergensis, a strong, big-brained human that lived in Africa and spread into Eurasia. Most scientists see heidelbergensis, or something close to it, as the shared ancestor of three later humans.

How one species became three is a story of distance and isolation. Heidelbergensis spread thin across three continents, from Africa into Europe and on into Asia. Groups that far apart rarely met, and the way between them kept closing: the Sahara swung from green to desert and back, and the ice ages broke populations into scattered pockets with empty, unlivable land between. Cut off from one another for hundreds of thousands of years, each group drifted down its own path. The ones in Africa became Homo Sapiens, ourselves. The ones in Europe and western Asia became the Neanderthals. The ones further east, across Asia, became the Denisovans. Same starting point, three long separations, three kinds of human.

This is about as far back as DNA reaches. From one cold cave in Spain, scientists have pulled scraps of genetic material about 400,000 years old, close to the oldest anyone has managed. For most humans this deep, the evidence is still only bone.

The Neanderthals were the cold-country humans of Europe and western Asia, stocky and strong, with brains as large as ours. The Denisovans were their eastern cousins across Asia, a people we know almost entirely from DNA rather than bones. Neither came out of Africa on its own. Both grew out of that earlier Heidelbergensis wave, in place, in Eurasia. And neither is wholly gone, because both mixed with us before they vanished. We will meet them properly in the next chapter. They were there, waiting, when we finally walked out.

Around 300,000 years ago, in Africa, that African branch became Homo Sapiens. Everything after that is the story of this post: how one branch of one African species walked out and filled the world, while its cousins, already spread across Eurasia, met it, mixed with it, and then were gone.

These species were not a single line, one turning neatly into the next. Several overlapped in time. Around two million years ago, the robust Paranthropus cousins were still living across Africa while the first members of our own group, Homo, were already on the scene. The two shared the same landscape for a long stretch before the robust branch died out. This is the shape of the whole story: not a ladder climbing toward us, but a bush, throwing out branches that mostly ended.

The human family at a glance

Species	When they lived	Where	Fate
Sahelanthropus	~7 million years ago	Chad	Unknown. One of the oldest candidates for the upright line; may be an ancestor or a side branch.
Orrorin	~6 million years ago	Kenya	Unknown. An early upright candidate; whether it is a true ancestor is unsettled.
Ardipithecus	~5.8–4.4 million years ago	Ethiopia	Unknown. May have led to the australopithecines, but debated like the two above.
Australopithecus	~4–2 million years ago	East and southern Africa	Evolved onward. One population became the first Homo. Lucy is of this group.
Homo habilis	~2.3–1.65 million years ago	East and southern Africa	Evolved onward, into Homo erectus (contested species).
Homo erectus	~2 million–110,000 years ago	Africa, then across Asia	Evolved onward in Africa; long-lasting, died out in Asia. First to leave Africa.
Homo heidelbergensis	~800,000–200,000 years ago	Africa and Eurasia	Split three ways: became Neanderthals, Denisovans, and Sapiens.
Homo floresiensis	~100,000–50,000 years ago	Flores, Indonesia	Died out. A tiny side branch, the “hobbit”; origin debated.
Neanderthals	~400,000–40,000 years ago	Europe and western Asia	Died out, but merged in part into us. Survive as 1–2% of non-African DNA.
Denisovans	known to ~40,000 years ago	Asia, Siberia to Tibet	Died out, but merged in part into us. Survive in Asian and Pacific DNA.
Homo sapiens (us)	~300,000 years ago to now	Africa, then worldwide	The only human left. Carries fragments of the others within.

Dates are approximate and some are debated; overlaps are real, several of these humans were alive at the same time.

The Ancient Waves: Out of Africa I

We were not the first of our line to leave Africa. Humans left in waves, across a very long span of time. Scientists call the ancient waves, together, Out of Africa I, and the later spread of our own species Out of Africa II. These are just handy labels, not an official system. On its own, the phrase “Out of Africa” usually means the modern human spread. But the two-part shape is real, as long as we remember that Out of Africa I was not one event. It was many, strung across nearly two million years.

The first humans to leave were not us, and they left long before us. The earliest firm sign of any human outside Africa comes from Dmanisi, in the country of Georgia, about 1.8 million years ago. The skulls found there belong to Homo Erectus. From this early exit, Homo Erectus spread widely across Asia. Its fossils turn up as far east as Zhoukoudian, near Beijing in China, where the bones once called Peking Man were found, and on the Indonesian island of Java, where the first erectus fossils were dug up in the 1890s. This human ranged across half the world and lasted more than a million years. Nothing before erectus ever left Africa, as far as the fossils show; the older ancestors, the Australopithecines and Homo Habilis, stayed on the continent. A few stone tools found outside Africa have been dated older than the oldest bones nearby, which would hint someone was out even earlier. But the dates are argued over, and tools without bones cannot say who made them. This stays an open question, not a known earlier journey.

There may have been an even earlier and more primitive exit, before erectus. Some think the Hobbit of Flores came from such an early wave, rather than from Erectus, which is part of why its origin stays argued over.

Later waves followed. Around 800,000 to 500,000 years ago, Homo Heidelbergensis spread out of Africa into Eurasia, the single great landmass of Europe and Asia. This was the second great exit, long after Erectus and long before us. It is the one that mattered, because those who left, and those who stayed, drifted apart into the three humans who would later meet: the Neanderthals, the Denisovans, and Sapiens.

The Cousins

These are the two cousins the Heidelbergensis split left in Eurasia. In the west, across Europe and the Near East, its groups became the Neanderthals. In the east, across Asia, they became the Denisovans. Neither came out of Africa in a migration of its own. Both are the Eurasian descendants of that earlier wave, and both took shape after it had already left. That Heidelbergensis was their shared ancestor is the mainstream view, but the names and exact links in this part of the family tree are argued over, and get redrawn as new bones appear.

We know these two peoples better than any other extinct humans, and their story runs straight into ours.

The Neanderthals lived across Europe and western Asia for more than 300,000 years, from Spain and Wales in the west to Iraq and deep into Siberia in the east. They were built for cold: short, broad, heavily muscled, with large noses and brains as big as ours. They were not the brutes of old cartoons. They made fine stone tools, controlled fire, hunted large and dangerous animals up close, and cared for their injured. At Shanidar Cave in Iraq, one Neanderthal lived for years with a withered arm, a damaged leg, and blindness in one eye; others must have fed and sheltered him. At Krapina in Croatia, a single site gave up over nine hundred Neanderthal bones, the largest such collection anywhere. And the whole people takes its name from one valley: the Neander Valley near Düsseldorf in Germany, where the first recognized Neanderthal bones were found in 1856. At several sites they seem to have buried their dead, though whether the burials were deliberate is still argued. This was a thinking, feeling kind of human.

The Denisovans we know the opposite way: their DNA in fine detail, but almost no bones. They are the first kind of human ever identified from DNA alone. The first Denisovan was recognized from the genetic material in a single finger bone, before anyone knew what these people looked like. Nearly everything comes from one place, Denisova Cave in the Altai Mountains of southern Siberia, and the people are named after it. The cave held Neanderthals, Denisovans, and modern humans at different times. It even gave up the bone of a girl whose mother was a Neanderthal and whose father was a Denisovan, direct proof that the two cousins met and had children together. Beyond a single jawbone found high on the Tibetan Plateau, which shows the Denisovans lived at extreme altitude, they have left almost no fossils at all. A gene that helps modern Tibetans breathe the thin mountain air was passed down to them from Denisovan ancestors. They remain the most mysterious humans we know of, a people known mostly from the DNA they left behind in us.

By the time our own species was ready to leave Africa, Eurasia was not empty. The west was Neanderthal country. The east was Denisovan country. They overlapped in the middle, and they mixed. We were the newcomers, walking into a world that already had humans in it.

Out of Africa II: Our Own Journey

Africa is not easy to leave. To the north is the Sahara. To the east are the deserts of Arabia. For most of history these were walls of sand that few could cross. But the desert does not stay the same. Over tens of thousands of years the Sahara swings between dry and green, as slow wobbles in the Earth’s orbit change how much sun falls on the land. When the rains came, grass and lakes spread across what is now sand, and people and animals could move through. When the desert returned, the door shut. People did not march out of Africa. They passed through in the wet windows, when the land let them.

There was more than one attempt. Our own species pushed out early, and more than once, and the fossils mark the failed tries. Modern human bones at Misliya Cave, in what is now Israel, date to around 180,000 years ago. Others at the nearby Skhul and Qafzeh caves date to between about 80,000 and 120,000 years ago. There is even evidence of modern humans reaching Arabia by around 85,000 years ago, and maybe China not long after. But these early waves faded. Maybe they died out. Maybe Neanderthals moving south ahead of the ice pushed them back. Maybe they were simply too few to last. Whatever happened, they left little or no trace in the ancestry of people alive today. The early exits did not people the world.

The wave that did came later, and it took a different door. Around 60,000 years ago, a group of Homo sapiens left Africa by the south. They most likely crossed the narrow mouth of the Red Sea, at the strait now called the Bab-el-Mandeb, at the Horn of Africa. A strait is a narrow neck of sea between two larger bodies of water. Back then the ice ages had locked up so much of the world’s water as ice that sea levels were far lower, and the strait was narrower than it is today. It could be crossed on simple rafts, maybe island to island. This is the favored path for the wave that succeeded, and it is called the Southern Route. From the Horn, these people spread fast along the coasts of southern Arabia and India, living off the shore. Nearly everyone whose ancestry lies outside Africa today traces back to this one wave. A northern branch of it, through the Levant, later carried people into the Near East and Europe. But the main push that peopled the world went along the southern coast. When we talk about the peopling of the world, this is the journey we mean.

The Meetings

This wave walked into the lands of the cousins. And again, meeting meant mixing. We carry the proof in our own genes.

People whose ancestry lies outside Africa carry a small amount of Neanderthal DNA today, between one and two percent. It is part of the shared inheritance of everyone descended from that wave. The main mixing traces to a single long window, beginning around 50,000 years ago and lasting some 7,000 years, while the two kinds of human overlapped in western Asia. A Denisovan share shows up too. It appears mostly in the ancestry of peoples across parts of Asia and out into the Pacific: New Guinea, Australia, and the islands. It marks where those meetings happened, not where anyone came from.

These traces are a map of ancient meetings. They are not a ranking. They do not measure how advanced, how pure, or how human any living people is. No one is more or less human for carrying a little more or a little less of this ancient DNA. Every living population is a blend, and these fragments are just part of the blend.

Within a few thousand years of that wave, the Neanderthals and the Denisovans were gone. The last firm Neanderthal traces date to around 40,000 years ago. The Denisovans’ last certain remains are a little older, around 50,000 years, though the DNA of people in New Guinea and Australia hints they may have lingered in Southeast Asia much later, perhaps to 25,000 years ago or beyond. We cannot yet say, because no late fossils survive in that warm, wet climate to prove it. Why they disappeared is not settled, and the honest answer is that we do not know. Climate stress, competition with our larger numbers, being absorbed through mixing, or some blend of all three. But they did not vanish completely. They live on, in fragments, inside us. The last of the other humans survives in the genes of the only human left.

There is no purer human anywhere. Everyone is a blend, and the blends are just made of different parts. People outside Africa carry Neanderthal DNA, and some carry Denisovan DNA as well. Africans carry old archaic DNA too. Some of it is Neanderthal, carried back into Africa by groups that had left, mixed in Eurasia, and returned. And the genes of several West African peoples point to mixing with an older African population, one we have no bones for and cannot yet name, known only as a shadow in the DNA. Whether that shadow was a separate archaic human, or just a very old, long-separated branch of our own species, is still argued. Either way, inside Africa and outside it, our species met older humans and took in a piece of them.

The modern human is not one pure thing that later picked up stray fragments. We are the mixture itself. Homo sapiens and its cousins, meeting and blending across tens of thousands of years, together made the humans alive today. No lineage stands outside this, and none stands above it. That is the deepest finding of this whole science, and the exact opposite of what the old racial myths claimed.

Reaching the Edges

From the coasts of southern Asia the wave pushed on. One thread went east, generation by generation, toward the rising sun and the islands of Southeast Asia. A northern branch turned up into the Near East, and from there into Europe, into the cold edge of the Neanderthals’ world, in their last years.

The most striking reach was to Australia. Getting there meant crossing open sea. At the height of the ice ages, so much water was locked in ice that sea levels fell, and Australia, New Guinea, and Tasmania joined into one landmass. Even then, a stretch of deep water still lay between that land and Asia. It could not be walked. It had to be crossed by boat. And it was, tens of thousands of years before anyone anywhere planted a field or built a wall. This is the oldest firm evidence of humans deliberately crossing the sea.

One great land was left, and it was reached last of all: the Americas. During the ice ages the sea was so low that a wide bridge of dry land joined Siberia to Alaska, where the Bering Strait now runs. Scientists call this lost land Beringia. People crossed it, or moved down the coast beside it, from Asia into a continent that had never held a human being. When they came is one of the liveliest arguments in the field. The old view said about 13,000 years ago, through a gap between the ice sheets. That view is now in doubt. Human footprints in New Mexico have been dated to between 21,000 and 23,000 years ago, and a site in southern Chile to at least 14,500, both far too early for the old route. Most researchers now favor a coastal path, people moving south by boat along the Pacific shore, living off the sea, well before the inland ice opened. The dates are still being worked out. However they came, they then spread the length of two continents with remarkable speed. We tell that story in full in its own place, and in our video on the peopling of the Americas.

Here is the journey laid out in time, though every date is rough and some are still argued over. From the crossing at the Horn of Africa, people reached Arabia by around 85,000 years ago in the early waves. The main coastal push reached India and the southern coast of Asia by roughly 65,000 to 60,000 years ago. It reached Australia by at least 50,000 years ago, and by some contested evidence closer to 65,000. It spread into eastern Asia and China across the same stretch, by around 50,000 to 45,000 years ago on the firm dates, though there are older, disputed Chinese finds. Europe was reached last of the Old World, by around 45,000 years ago, with modern humans across the northwest by about 43,000. The Americas came last of all, by at least 16,000 years ago and quite possibly earlier. These are rough milestones, and for each region the earliest date is usually the one still being argued over.

When modern humans reached each region

Region	First reached (modern humans)	Note
Near East (the doorway)	~55,000–50,000 years ago	The wave passed through here on its way out; a northern branch later turned toward Europe.
South Asia (India)	~65,000–60,000 years ago	Reached early by the main coastal push along the shore of southern Asia.
Australia (then part of Sahul)	at least 50,000 years ago	Required a sea crossing; some contested evidence points closer to 65,000.
East Asia (China)	~50,000–45,000 years ago	Firm dates; there are older, disputed Chinese finds.
Europe	~45,000–43,000 years ago	Reached last of the Old World, entering the Neanderthals’ country.
The Americas	at least 16,000 years ago	Last of all, via Beringia; footprints in New Mexico may push this to ~23,000.

All dates are approximate; for each region the earliest figure is usually the one still argued over.

The Ice

All of this happened during the ice ages. Great sheets of ice covered the north. Sea levels rose and fell as water locked into the ice and released again. The climate swung between cold and colder. At the peak of the last ice age, around 20,000 years ago, much of northern Eurasia could not be lived in, and people drew back into warmer refuges in the south to wait it out. When the ice retreated, they spread out again into the land it uncovered.

By now people looked different from one region to the next, shaped by tens of thousands of years apart, under different skies. But they were still, everywhere, hunter-gatherers: people who lived by hunting wild animals and gathering wild plants, rather than by farming. No one farmed yet. No one stayed in one place yet. The great changes were still ahead.

The End of the Shared Story

This is where the shared story ends. By around 15,000 to 12,000 years ago, human beings had reached almost every corner of the reachable world. Africa, where it began. Europe. All of Asia, to its farthest coasts. Australia. The whole Old World was peopled, and peopled by hunter-gatherers who lived, at root, in much the same way.

The Americas were the last to fill, reached near the end of the ice age, and their fuller story is told in its own place. With that final crossing, our species had touched every habitable continent on Earth.

Everywhere else, the journey out was over, and something new was about to begin. Cut off from one another by distance, ice, and sea, each of these groups started down its own road. One would learn to plant seeds. One would tame the horse. One would raise cities from mud. One would press the first written words into clay. From a single people walking out of Africa, the many peoples of the world were about to be born.

That is where we pick them up, one branch at a time.

Where to See This Story

This story is told in bones, and many of them can be visited. Some sites hold the original fossils. More often what is on display is a cast, an exact copy, because the true fossils are fragile national treasures kept in guarded storage. We mark which is which, so you know before you travel. The list runs roughly from the deep African past to the European sites closest to most travelers.

The African Originals:

• National Museum of Ethiopia, Addis Ababa — the home of Lucy. The original is normally locked away and the hall shows a cast, but the basement holds a genuine, world-class collection of early human fossils. The single best place to stand near the beginning of the story.
• Cradle of Humankind, near Johannesburg, South Africa — an open-air World Heritage site built around the Sterkfontein Caves, where many australopithecine fossils were found. Its Maropeng visitor center walks you through the whole of human evolution, and the caves can be toured.
• Laetoli, northern Tanzania — where our ancestors left their footprints in the ash 3.66 million years ago. The prints themselves are reburied to protect them, but the story is told nearby, and the same region holds Olduvai Gorge, one of the most famous fossil sites in the world, with its own museum.
• Cleveland Museum of Natural History, Ohio — a special claim on Lucy: she was discovered in 1974 by Donald Johanson, then the museum’s own curator. The fossil went back to Ethiopia, but the museum made the first casts of her bones, and nearly every other Lucy cast in the world descends from those. Its human skeletal collection is held with Case Western Reserve University. For anyone in North America, the closest you can get to the real Lucy.

The European Cousins:

• Neanderthal Museum, Mettmann, near Düsseldorf, Germany — stands on the very spot where the first Neanderthal was found and the species got its name. You can walk the valley itself.
• Krapina Neanderthal Museum, northern Croatia — beside the site that gave up the largest single collection of Neanderthal bones anywhere, with some of the best reconstructions of Neanderthal life made.
• Museum of Human Evolution, Burgos, northern Spain — displays fossils from the nearby Atapuerca caves, one of the richest records of early Europeans on the continent, reaching back nearly a million years. The caves can be visited too.

The Homes of Homo Erectus, in Asia.

• Zhoukoudian, near Beijing, China — where Peking Man was found, a World Heritage site with a modern museum. A real mystery hangs over it: the original skulls, dug up before the Second World War, were lost in 1937 while being moved for safekeeping and have never been found. What’s displayed are casts made before they vanished, alongside newer finds from the ongoing dig.
• Sangiran, Indonesia — near where Java Man was found, showing casts of the Java fossils and real animal bones from the same ancient ground. The site is still being excavated.

Summary

• Every human alive traces back to Africa — but we are neither the first humans nor the only ones. Behind us stretches a long, branching line of ancestors and cousins, most of them dead ends.
• Our branch split from the line leading to chimpanzees around 7 million years ago, and was set apart first by walking upright — long before big brains or tools. The oldest footprints of an upright walker are at Laetoli (Tanzania), 3.66 million years old.
• The earliest upright candidates were Sahelanthropus (Chad), Orrorin (Kenya), and Ardipithecus (Ethiopia) — all debated.
• From small, small-brained upright apes — the australopithecines, like Lucy (Australopithecus afarensis, Ethiopia, 3.2 million years old) — our own group, Homo, slowly emerged. A robust plant-eating cousin, Paranthropus, lived alongside early Homo and died out.
• The first of our group were Homo habilis (the toolmaker) and then Homo erectus, who tamed fire and, around 1.8–2 million years ago, became the first human to leave Africa — reaching Dmanisi (Georgia), Java (Indonesia), and Zhoukoudian (China).
• A later ancestor, Homo heidelbergensis, spread across three continents and was split apart by desert and ice into three kinds of human:
• Homo sapiens in Africa, the Neanderthals in Europe and western Asia, and the Denisovans across Asia. We are the African branch. Homo sapiens arose across Africa early — fossils at Jebel Irhoud (Morocco), ~300,000 years old, and Omo (Ethiopia), ~230,000 years old.
• The Neanderthals are known from sites like Shanidar (Iraq), Krapina (Croatia), and the Neander Valley (Germany); the Denisovans almost entirely from DNA at Denisova Cave (Siberia).
• When our species finally left Africa, around 60,000 years ago, crossing the Bab-el-Mandeb strait at the Horn of Africa, the other two were already there. We met them, and we mixed with them.
• That is why people outside Africa still carry 1–2% Neanderthal DNA (and Denisovan DNA across Asia and the Pacific) — and why no living people is purer or older than any other. Everyone is a blend.
• From that one wave, modern humans spread along the southern coasts of Asia, crossed open sea to Australia (by ~50,000 years ago), and reached the Americas last of all, across Beringia (by at least ~16,000 years ago).
• By roughly 12,000 years ago the world was peopled — everywhere, by hunter-gatherers who still lived, at root, the same way.
• That is where this story stops, and where all the separate histories of the world begin.