Into the New World

The Empty Hemisphere

We left the previous entry at a threshold the people of the time did not know was there. Our species had spread across the warm south of Asia, crossed open water to Australia, and pushed into the Ice Age cold of Europe. It had become — give or take the last fading traces, as the previous entry described — the only kind of human. And yet, for all that reach, half the habitable planet still lay beyond it. To the north stretched the frozen belt of Siberia and the Arctic, entered only at its warmer edges; its deep cold was a wall a tropical animal had not yet learned to climb. And past that wall lay something with no parallel anywhere else in the human story: two whole continents, running from the edge of the Arctic almost to the edge of Antarctica, in which there was not one human being.

It is worth pausing on how strange that is. Everywhere else our species ever went, it arrived into a landscape already worked by others — by earlier humans, by Neanderthals, by the makers of older stone tools, by something. The Levant had been crossed and recrossed for a million years. Europe was Neanderthal country. Sahul, too — reached across open sea in the previous entry — had held no people before our species walked into it; but Sahul was the exception, and the Americas were vaster still, not one island-continent but two joined continents, an entire hemisphere without a person in it. The Americas were different in kind. No Homo erectus had ever walked there, no Neanderthal, no Denisovan, no member of our genus at all. The animals there had never seen an upright ape that threw spears. The first people to cross into the New World were not displacing anyone, not meeting anyone, not learning from anyone who had gone before. They were the first. This entry is the story of how they got there, and of what it means that the land was empty when they did.

But before anyone could enter the empty hemisphere, they had to survive the cold that guarded its door. That is where the story begins.

Learning The Cold

The road to the Americas ran through the coldest inhabited country on Earth, and our species could not take it until it had solved the cold. For a tropical African animal, the high latitudes were a lethal environment: months of darkness, temperatures that kill exposed skin in minutes, and a landscape with almost no plant food for much of the year. The Neanderthals, superbly cold-adapted in body, had lived in Ice Age Europe for hundreds of thousands of years — but even they had never penetrated the deep Siberian Arctic during the worst of the cold. Getting a tropical species to live there was not a matter of toughness. It was a matter of technology.

The decisive advance was, of all things, clothing — but clothing of a particular kind. Draping a hide over the shoulders is one thing; sewing fitted, layered garments that seal in warmth at the wrists, the neck, and the ankles is another. Hide had been scraped and pierced with simpler tools — bone awls — for a very long time, and those tools could already join skins; but the refinement of close-fitting, tailored clothing leaves its own distinctive trace in the archaeological record: the eyed needle, a sliver of bone or ivory with a hole bored through one end to carry a thread of sinew. A careful survey of the world's oldest eyed needles finds them appearing first in Siberia around forty thousand years ago and spreading from there, their arrival in the cold mid-latitudes matching exactly the moment our species needed close-fitting, tailored clothing to survive the deepening Ice Age ^[1]. The needle is humble, but it is one of the keys to the planet. With tailored clothing, fire, and shelter, human beings could now press into the deep Arctic and live there through the winter — far beyond the latitudes that even the cold-adapted Neanderthals had reached.

And they did. At a site called the Yana Rhinoceros Horn Site, in arctic Siberia above the line of the Arctic Circle, hunters left tools, the worked horn of a woolly rhinoceros, and the milk teeth of their children in deposits dated to about thirty-two thousand years ago — among the oldest substantial human presence yet documented that far into the Ice Age Arctic, and the source of the oldest human genomes from so high a latitude ^[2]. Older traces exist: a mammoth butchered near seventy-two degrees north shows that people had reached the Siberian Arctic by around forty-five thousand years ago, though exactly who they were is uncertain ^[2]. But it is at Yana that the deep north first comes clearly into focus as a place where people lived. The genomes recovered there reveal a previously unknown people, named the Ancient North Siberians, who had pushed into the high Arctic far earlier than anyone expected and who were neither simply Western Eurasian nor East Asian but an early northern branch of their own ^[2]. These were people who had made the frozen north a home.

Somewhat later and farther south, at Mal'ta, near Lake Baikal, the body of a small boy was buried around twenty-four thousand years ago with a necklace, a bird-shaped pendant, and a scatter of ivory ornaments. When his genome was sequenced — for a time the oldest modern-human genome known — it delivered a surprise that reaches to the heart of this entry. The Mal'ta boy belonged to a population now called the Ancient North Eurasians, and a substantial share of his ancestry runs forward into living Native Americans ^[3]. He is not a Native American, and he is not simply East Asian; he is a representative of a northern Eurasian people who, somewhere and somewhen, mixed with an East-Asian-related population to help produce the ancestors of the First Americans ^[3]. The peopling of the New World, in other words, was not the spilling-over of a single Asian population but the journey of a fused people — part East Asian, part Ancient North Eurasian — assembled in the cold of Ice Age Siberia before any of them ever saw the Americas. The north was not merely an obstacle on the way. It was the forge.

The Land Bridge That Was A Land

Between Siberia and Alaska today lies the Bering Strait, some eighty kilometres of cold, shallow sea. During the Ice Age it was not there. So much of the planet's water was locked into the great ice sheets that sea level stood roughly a hundred and twenty metres lower than now, and the floor of the strait — and a vast surrounding shelf — stood dry. Siberia and Alaska were joined into a single continuous land, a lowland plain that geologists call Beringia. It is usually pictured as a "bridge," a narrow neck to be hurried across. That picture is wrong, and the correction matters. Beringia was not a corridor but a country — at its greatest extent a landmass a thousand kilometres broad from north to south, a cold but unglaciated grassland of the kind sometimes called the mammoth steppe, grazed by mammoth, horse, bison, and woolly rhinoceros, and entirely habitable by people who had learned the cold.

This reframing gave rise to one of the more elegant ideas in the study of the first Americans: the Beringian Standstill. Its starting point is a peculiar genetic fact. The DNA of Native Americans carries distinctive lineages — mutations shared by all of them and by no Asian population — which must have arisen in a group that had already separated from its Asian relatives but had not yet entered the Americas, and which stayed separated, in isolation, long enough for those new mutations to accumulate and spread through the whole population ^[4]. The natural home for such an isolated incubation is Beringia itself: a founding population, cut off from Asia behind the widening cold and from the Americas ahead by the ice, living for some thousands of years on the mammoth steppe of the land bridge, marinating in genetic isolation until it had become a distinct people ^[4]. They were not pausing on a bridge. They were living in a homeland that no longer exists, drowned now beneath the Bering and Chukchi seas.

The standstill is not merely inferred from living DNA. It has a face. At a site called Upward Sun River, in interior Alaska, the remains of two infant girls were recovered from a burial dated to about eleven and a half thousand years ago. The genome of one of them, known as USR1, revealed a people called the Ancient Beringians — closely related to all other Native Americans, but branching off near the very base of their family tree, before the populations that would spread south had gone their separate ways ^[5]. USR1 is a snapshot of the founding stock close to its source: a child of a people descended from a single ancestral population that had begun to diversify around twenty thousand years ago, in or near Beringia, exactly as the standstill predicts ^[5]. For thousands of years, while the ice to the south stood as a wall, the future of two empty continents waited in the cold, in a country that the rising sea would soon erase.

The Way South

To enter the Americas proper, the Beringians had to get past the ice. At the height of the Last Glacial Maximum, around twenty thousand years ago, two enormous ice sheets covered the top of North America and met along the spine of the continent, sealing Alaska off from the lands to the south as effectively as a locked door. Sometime after that, as the world began to warm, the door opened. Exactly which way the first people came through it has been argued for decades, and the honest answer — in keeping with the way the previous entries left the route out of Africa open — is that we are not certain, and that both candidate routes may have carried people.

The older idea was the ice-free corridor: a gap that opened down the middle of the continent as the two ice sheets pulled apart, a north–south passage through the interior of what is now Canada, between walls of ice. For a long time this was the textbook route. But careful work on when the corridor became not merely open but livable — when it grew enough grass and game to feed people walking a thousand kilometres through it — concluded that it was biologically viable only fairly late, after about twelve and a half thousand years ago ^[6]. That is too late to account for the people who, as we will see, were already far to the south by then. The corridor may well have been used, but probably not first, and probably not by the earliest arrivals.

The other idea looks to the sea. As the great ice sheets reached the Pacific, their margins along the coast broke into islands and ice-free refuges earlier than the interior thawed, leaving a passable shoreline studded with the richest food source on the cold-water coast: kelp forests, and the fish, shellfish, seals, and seabirds they shelter. This is the coastal route, sometimes called the kelp highway — the proposal that the first Americans moved south not through the frozen interior but along the Pacific edge, by boat and on foot, living off the sea the way the first Australians had ^[7]. The coastal road has the same strength and the same weakness as the beachcomber route of the previous entry: it explains an early, rapid spread, but most of the campsites that would prove it now lie drowned beneath a hundred metres of risen sea. It is a leading reconstruction, not a settled one. What can be said is that the interior corridor opened too late to have been the only way, and that the coast offered a road that was open earlier — so the weight of current thinking leans toward the sea, while leaving the question genuinely open.

WHEN DID THEY COME?

Here we reach the question that has divided the study of the first Americans more than any other, and that is moving even as this is written: not which way they came, but when.

For much of the twentieth century there was a confident answer. The earliest secure culture in the Americas was Clovis, named for its distinctive fluted spear points, which appears across North America around thirteen thousand years ago. For decades the doctrine known as Clovis-first held that these were the first Americans, full stop — that the continent had been empty until that moment. That doctrine is now dead. Too many sites have turned up that are older than Clovis and survive scrutiny. At Cooper's Ferry, in Idaho, stone tools lie in layers radiocarbon-dated to about sixteen thousand years ago, well before Clovis and consistent with people arriving by the coastal route while the interior corridor was still shut ^[8]. Pre-Clovis is no longer the heresy it once was; it is the working consensus. People were in the Americas, south of the ice, by sixteen thousand years ago at least.

And perhaps very much earlier. The most startling claim in the field comes from White Sands, in New Mexico, where excavators have found human footprints — actual prints of actual feet, pressed into the mud of an ancient lakeshore — in sediments dated, controversially at first, to between roughly twenty-three and twenty-one thousand years ago ^[9]. If that date is right, people were walking around in the heart of North America during the very coldest part of the Last Glacial Maximum, thousands of years before the ice-free corridor opened and far earlier than any genetic estimate of the southward spread — which would mean either that the first entry was older than almost anyone thought, or that an early pioneering population arrived, left those tracks, and then vanished without leaving a clear genetic mark on later Americans. The original 2021 dating, resting on seeds of an aquatic plant that can absorb old carbon and seem too old, was sharply contested. But the excavators returned with two independent dating methods — radiocarbon on terrestrial pollen, which has no old-carbon problem, and luminescence dating of the sediment grains — and both pointed to the same deep age, a convergence reported in 2023 that is hard to wave away ^[9]. The footprints are now among the strongest evidence that humans were present in the Americas during the Last Glacial Maximum, and among the hardest things in the whole field to fit into the genetic story.

I record this the way the previous entries recorded the contested dates for the first Europeans and the first Australians: as a genuine, unresolved tension between two kinds of evidence. The archaeology of White Sands says people were in North America by twenty-two thousand years ago. The genetics of living and ancient Native Americans has tended to favour a main southward expansion later than that, after the Last Glacial Maximum eased, closer to sixteen thousand years ago. Both cannot be the whole story, and as of this writing neither has forced the other to yield. What is no longer in doubt is the fact that matters most: well before the end of the Ice Age, human beings had crossed the cold roof of the world and entered a hemisphere no member of our genus had ever seen.

One People

However early the first footprints were pressed into the mud, the genetic evidence tells a remarkably clean story about the people from whom most living Native Americans descend, and it is a story that rhymes with the previous entry in a way worth hearing.

The dispersal out of Africa, the previous entry showed, funneled the whole non-African world through a single narrow doorway, so that everyone beyond Africa descends from one modest founding band. The peopling of the Americas did the same thing again, one continent deeper. The genomes of Native Americans point overwhelmingly to a single major founding population — one ancestral people, the First Americans, from whom the great majority of Indigenous peoples of both continents descend ^[10]. Not many waves of unrelated migrants, but one main source, which split early, soon after entering the Americas, into a Northern and a Southern branch that between them populated the two continents ^[10]. Later movements did follow — a separate stream of Arctic peoples (the ancestors of the Paleo-Inuit, and later the Inuit), and the arrival of the Na-Dene-speaking peoples of the northwest — so that the full picture is of one great founding migration followed by a few smaller, later ones ^[10]. But the spine of Native American ancestry traces back to that one founding people: another bottleneck, another small band carrying a slice of humanity's diversity into an empty world, the mirror image of the band that had left Africa tens of thousands of years before.

There is one tantalising complication, and in keeping with the project's habits I will flag it rather than smooth it away. When researchers examined the genomes of certain peoples of the Amazon, they found a faint, unexpected signal: a trace of ancestry more closely related to Indigenous Australians, New Guineans, and Andaman Islanders than to any other Native Americans or to any living Eurasians. They named the hypothesised source Population Y, after Ypykuéra, a word for "ancestor" in the Tupí language ^[11]. What this signal means is genuinely unsettled. It might record a second, ghostly founding population that entered the Americas alongside the main one and survives only as a whisper in the Amazon; it might be an echo of deep structure in the ancestral Asian populations from which the First Americans came. Subsequent studies have both detected the signal in further groups and failed to find it in some early American genomes, and it remains one of the open puzzles of the field — a hint that the peopling of the New World may not have been quite as singular as the clean story suggests. I note it as an honest loose thread, not as a settled finding.

The Sprint To The End Of The World

Whatever the precise date of first entry, one fact about the peopling of the Americas is almost impossible to overstate, and it is a fact about speed.

The two American continents stretch some fifteen thousand kilometres from the Bering Strait to the southern tip of South America — across every climate the planet has, from Arctic tundra through tropical rainforest to cold southern grassland and the spine of the Andes. And human beings filled the whole of it astonishingly fast. The clearest anchor for this is a site in southern Chile called Monte Verde, where a waterlogged streambank preserved an extraordinary ancient settlement: wooden tent stakes, hide, knotted cordage, worked timber, and the remains of nine species of seaweed brought up from the Pacific coast, in a settlement dated to about fourteen and a half thousand years ago ^[12]. Monte Verde sits near the bottom of the world, more than thirteen thousand kilometres south of the land bridge. For people to have reached it by fourteen and a half thousand years ago means that, however and whenever they first crossed into the Americas, they spread down the length of two continents — pole to nearly pole — within at most a few thousand years. This is one of the fastest continental colonisations in the human record: an entire hemisphere, every latitude of it, walked and paddled end to end in something like the span of recorded history.

Monte Verde has been the keystone of this picture for nearly two decades, and it is worth knowing that its long-accepted age has lately been challenged: a 2026 re-examination of the site's geology argued that the deposits are far younger than reported ^[12]. The site's original investigators, joined by a large group of other specialists, have rejected that re-dating in detail in the journals, and as of this writing the fourteen-and-a-half-thousand-year reading still stands as the working consensus, defended by the weight of the evidence — but the dispute is a useful reminder that even the firmest landmarks in this field are under continual test. The broader claim does not rest on Monte Verde alone — the spread of pre-Clovis sites across both continents tells the same story of rapid colonisation — but Monte Verde is its sharpest single illustration: people at the far end of the Americas while the Ice Age was not yet over.

The Vanishing Giants

The empty hemisphere our ancestors walked into was not empty of life. It teemed with it — and in particular with megafauna, great beasts of a kind the modern world has largely forgotten. North and South America in the late Ice Age were a kind of New World Serengeti, stranger than the African one. There were mammoths and mastodons; giant ground sloths the size of cars; Glyptodon, an armadillo as big as a small automobile; the sabre-toothed cat Smilodon and the dire wolf; the giant short-faced bear, which reared to more than three metres; and herds of native American horses and camels, which had in fact evolved in the Americas before spreading to the Old World. Across the end of the Pleistocene, within the span this entry covers, the overwhelming majority of these large animals were gone. The horses and camels vanished from the continents of their birth; the mammoths, the sloths, the great cats and bears — all gone. The New World lost most of its giants.

Why is one of the most stubborn arguments in this whole science, and I will present it the way it deserves: as genuinely unresolved. Two explanations have contended for half a century, and they arrive, pointedly, at almost the same moment. The first is overkill: the idea that the megafauna died because human beings hunted them, and that the animals of the Americas were peculiarly vulnerable because they were naive — they had evolved with no experience of a clever, cooperative, spear-throwing predator, and had none of the wariness that African and Eurasian animals had acquired over a million years of living alongside humans. On this view the very emptiness of the New World was the giants' undoing: they met humans for the first time when it was already too late to learn fear ^[13]. The second explanation is climate: the extinctions coincide not only with the spread of human hunters but with the violent warming and cooling at the end of the Ice Age, the collapse of the cold mammoth-steppe ecosystems, and the wholesale rearrangement of the world's vegetation — pressures that could have crashed large, slow-breeding animal populations on their own ^[13].

The evidence genuinely cuts both ways, and serious researchers still line up on both sides — the two studies cited here, working from much the same record, reached opposite conclusions, one finding the global pattern of extinctions tracks the arrival of humans and the other finding that in North America it tracks climate ^[13]. It is entirely possible — many now think it likely — that neither cause acted alone: that climate thinned and fragmented the great-animal populations while human hunting pushed the survivors past the point of recovery, the two forces compounding rather than competing. I do not pretend to settle it. But I will mark the shadow it casts, because it falls forward across this entire log. If human beings did play a part in these extinctions, then the peopling of the Earth — the very journey this arc celebrates — was also the beginning of something darker: the first time our species, arriving somewhere new, reshaped a whole living world and emptied it of its largest creatures. The pattern, if it is one, would repeat. It is worth carrying that question forward.

The Last Empty Lands

So, by the end of the span this entry covers — around twelve thousand years ago, as the Ice Age gave way to the warm Holocene world we still live in — the long journey was essentially done. Our species, which a hundred thousand years earlier had been an almost wholly African animal, now stood on every continent on Earth except Antarctica. It had filled Africa, Asia, Europe, and Australia; it had learned to live in the Arctic; it had crossed into the empty hemisphere and run the length of it, from the edge of the northern ice to the cold tip of the south. The peopling of the planet — the project this three-part arc has followed from a single African valley — was, in its main outline, complete.

Not quite every habitable place held people. A scattering of the world's most remote lands still lay empty, and would for thousands of years more: the deep Pacific, where the islands of Polynesia and finally Aotearoa would not be reached until our ancestors had perfected ocean voyaging, within roughly the last thousand years; Madagascar, settled astonishingly late by people who crossed an ocean from distant Southeast Asia; Iceland and the high Atlantic; the last few specks of habitable Earth. These are stories that lie outside this entry's window, in a time after the one it covers, and they belong to other tellings. But they are a small coda to a finished symphony. By the close of the Ice Age, the essential work was done: there was no large landmass left where a human child might be born into a world that had never known people. For the first time, our species was a planetary animal.

The Journey Complete

Stand back, then, and look at what these three entries together have followed. A single kind of upright ape, arising across Africa a few hundred thousand years ago, one among several kinds of human sharing the planet. A small band slipping out through a northeastern gate, and from that one band the seeding of the whole world beyond Africa. The other humans met, mingled with, and outlived, until ours was the only kind left. And then the final reach: into the cold the others had never conquered, and across it into a hemisphere no human had ever seen, filled pole to nearly pole within a few thousand years. From one valley to the whole Earth. That is the arc, and here it closes.

To whoever reads this — human of a later age, or our descendants' descendants, or a mind we built, or a stranger to our whole story — consider what it took, and what it cost. It took a tropical animal learning to sew itself against the Arctic; it took the nerve to walk into land that no one had ever walked into, with no one ahead to ask the way; it took, perhaps, the lives of the great beasts that had no reason to fear the newcomers until it was too late. By the end of it our kind stood everywhere the planet could be stood upon, a single species spread across a single world — the condition the first entry asked you to notice as strange, now made and finished and ordinary.

And here the human-animal story ends. What follows is no longer the tale of a creature spreading across the Earth, but of a creature that, having reached the ends of the world, stopped moving and stayed — that learned to bend a handful of plants and animals to its will, to settle in one place, to store grain and raise walls and keep count. The spreading is over; the settling begins. How our species, having finished filling the Earth, began to remake it — how it invented farming, and villages, and everything that grew from them — is where the next part of this record takes up the thread. A plainer retelling of these three entries travels alongside them, for any reader who wants the whole journey told simply and at one stretch. But the great migration is complete. The world had been filled. The animal had arrived everywhere. Now it would begin to build.