Appearance
3.6 — The Ice Age World and the Peopling of the Earth
At the peak of the last glacial period, about 21,000 years ago, you could walk from France to England, from Siberia to Alaska, from Malaysia to Java, and from New Guinea to Australia. Sea level was about 120 metres lower, and the exposed continental shelves of Chapter 1.11 were the flattest, best-watered, most game-rich land available.
Almost all of it is now under water. That is the single most important thing to know about the archaeology of this period: the places people most wanted to live are precisely the places we cannot easily dig.
The world as it was
Colder, and much drier. With so much water locked in ice and colder oceans evaporating less, global rainfall dropped. The Sahara and the Thar were larger. The Amazon and Congo forests were smaller and broken into patches. Aridity, not cold, was the main constraint over most of the inhabited world.
Windier and dustier, because a bigger temperature difference between the tropics and the ice sheets drives stronger winds. Ice cores from that period contain far more dust.
Lower carbon dioxide — about 180 parts per million against 280 in the following interglacial. This is low enough to limit plant growth, and it is one of the more interesting arguments about why farming did not happen earlier: at 180 ppm, the return on tending a plant is measurably poorer.
And Beringia was not a bridge. It is habitually called a land bridge, which suggests a narrow causeway. It was up to 1,600 kilometres wide from north to south — a subcontinent of dry grassland, unglaciated because it was too arid for ice sheets to form, supporting mammoth, horse, bison and the people who hunted them.
The peopling of the world, region by region
Australia, by around 65,000 years ago. The oldest widely accepted site is Madjedbebe in northern Australia, with dates around 65,000 that remain debated. Whatever the exact figure, arrival required deliberate sea crossings (Chapter 3.4). Aboriginal Australians therefore represent one of the longest continuous cultural traditions on Earth, and genetic work indicates deep continuity in the continent since that arrival.
Europe, from around 45,000 years ago. Modern humans entered a continent already occupied by Neanderthals, and the two overlapped for several thousand years before Neanderthals disappeared around 40,000 years ago. This is the period of Chauvet, the flutes and the Sungir burials.
East Asia, from around 45,000 years ago at least, with earlier claims from Chinese sites that remain contested.
Siberia, from around 45,000 years ago at the Arctic margins. The Yana site in northern Siberia, above the Arctic Circle at 71 degrees north, dates to about 32,000 years ago. Living there requires tailored clothing, controlled fire, substantial shelter and the ability to store food — all four of Chapter 3.4's technologies working together.
The Americas: the argument in full.
For most of the twentieth century the accepted story was "Clovis first": people crossed Beringia and came south through an ice-free corridor between the two North American ice sheets around 13,000 years ago, and their distinctive fluted Clovis spear points spread across the continent within a few centuries.
That model has collapsed, and the replacement is not yet settled.
The problems came one at a time. Monte Verde in southern Chile, excavated by Tom Dillehay, was dated to about 14,500 years ago and — after years of resistance — accepted by a visiting team of sceptics in 1997. That is earlier than Clovis and it is at the far southern end of the Americas, which requires arrival substantially earlier still. The ice-free corridor, when its geology and biology were examined properly, turns out not to have been passable — not vegetated enough to feed travellers — until after the earliest southern sites.
So the leading model is now a coastal route, down the Pacific shore by boat and on foot, using marine resources, which explains reaching Chile early and leaves few traces because the coastline of that period is now under water.
And some claims go much further back. Footprints at White Sands in New Mexico were dated in 2021 to between 21,000 and 23,000 years ago, using seeds in the sediment layers. The dating was challenged on grounds that aquatic plants can absorb old carbon; subsequent work using pollen and quartz dating supported the original range. This book's position: the White Sands dates are serious and are not yet the consensus. Other very early claims, such as Cerutti Mastodon in California at 130,000 years, are not accepted by most specialists.
What is not in dispute: people were widely present in the Americas by around 15,000 years ago, the ancestry is overwhelmingly Siberian with a distinctive component that separated from East Asians and mixed with an ancient North Eurasian population, and there were probably multiple pulses.
The Pacific, last of all, and the most impressive. Near Oceania — New Guinea and the nearby islands — was reached with Australia. Remote Oceania required crossing hundreds and then thousands of kilometres of open ocean. The Lapita culture reached Fiji, Tonga and Samoa around 3,000 years ago. Then, after a long pause, Polynesian voyagers reached the Society Islands, then Hawaii, Rapa Nui and New Zealand, the last of these around 1300 CE.
They did this in double-hulled canoes without instruments. The navigational system — reading star paths, swell patterns refracting around islands, cloud formations over land, and bird flight at dawn and dusk — was believed lost until it was demonstrated in the 1970s by Mau Piailug, a navigator from Satawal in Micronesia, who sailed a replica canoe from Hawaii to Tahiti without instruments. Rapa Nui is about 3,500 kilometres from the nearest inhabited land, and they found it.
What the ice did to the map
Doggerland, the land that is now the southern North Sea, was inhabited plain with rivers, lakes and forests. Trawlers still bring up worked flint, antler tools and mammoth bone from it. It drowned progressively between about 18,000 and 7,000 years ago, with a final catastrophic component from the Storegga submarine landslide off Norway around 8,200 years ago, which sent a tsunami across the remaining low islands.
Sundaland, in Southeast Asia, joined Sumatra, Java and Borneo to the mainland, and its drowning created the modern Indonesian archipelago.
India's coastline was well out beyond its present position. The Gulf of Khambhat was dry land, the Palk Strait between India and Sri Lanka was walkable, and large parts of the western continental shelf were coastal plain. Any coastal settlement of that period is now offshore.
Rates were not gentle. During periods called meltwater pulses, sea level rose at up to 4 centimetres per year — four metres per century. That is fast enough for a coastal community to be forced to move within a lifetime, repeatedly, over thousands of years. It is very likely the origin of the flood stories that appear independently in Mesopotamian, biblical, Indian and many other traditions, and Chapter 3.10 handles that carefully.
The Younger Dryas: a warning shot
About 12,900 years ago, with the world well into its warming, the northern hemisphere abruptly returned to near-glacial conditions for roughly 1,200 years. The leading explanation is the mechanism from Chapter 2.6: a vast glacial lake in North America, Lake Agassiz, drained catastrophically into the North Atlantic; the sudden freshwater input reduced surface salinity, stopped the sinking that drives the overturning circulation, and shut down the northward heat transport.
Then it ended, in the Greenland record, within perhaps a few decades. A temperature jump of several degrees in a human lifetime.
Why this matters for the next chapter. In the Levant, the Natufian people had by then become largely settled, living in permanent stone-founded villages, harvesting wild cereals with flint sickles, and storing grain — all without farming. The Younger Dryas made their wild harvests fail. Population had grown on the assumption of abundance, and the abundance stopped. The archaeological record shows sites abandoned, mobility increasing, and then — as conditions improved again — the first cultivated cereals.
Whether the cold snap caused agriculture is argued and probably too strong a claim. What the sequence shows is a population that had become dependent on dense stands of wild grain, hit by a crisis that made those stands unreliable, and which then began managing the plants deliberately. Chapter 3.7 takes it from there.
Where this shows up in your life
Your ancestry, whoever you are, includes at least one of these journeys. If you are Indian, your ancestry includes the coastal route east from Africa, the later expansions from Iran and the steppe that Chapter 6.2 examines, and much mixing since.
The archaeology of coastlines is a genuine gap in what we know. When someone claims that "civilisation is much older than we are told" and points at drowned coasts, the physical premise is correct — a great deal of habitation is under water. What does not follow is any specific claim about advanced lost civilisations, because the drowned land was inhabited by people at the same technological stage as those inland, and no evidence of anything else has been recovered. The honest statement is: we are missing a lot, and being missing is not evidence for anything in particular.
And the Younger Dryas is the single best reason to take abrupt climate change seriously. It shows that this planet's climate can flip between states within decades when a threshold is crossed, and that the trigger can be small compared with the effect. Part 14 returns to it.
What the next page covers
Around 11,700 years ago the climate stabilised, and within a couple of thousand years people in at least eleven separate regions of the world — with no contact between most of them — began planting crops. Chapter 3.7 is about that: where and when it happened, which plants and why those, why people would take up work that made them shorter, sicker and busier, and why it was almost certainly not a choice anyone made deliberately. It is the hinge on which the rest of this volume turns.