Pleistocene

Our ancestors were little more than walking apes when the Pleistocene began, nearly 2.6 million years ago. Those proto-humans, called “habilines”, were limited to a single continent—Africa—and created only the crudest of stone tools. When the Pleistocene ended, less than 12 thousand years ago, fully modern humans had established complex societies across every continent but Antarctica. Often we think of this transition as a linear “March of Progress”, where the “walking apes” steadily became more and more human. But our true family history is no simple procession from there to here—it is great tangle of twisting branches.

The “habilines” had brains barely larger than those of chimpanzees. Some of their descendants did not change much in this regard—the “hobbits” of Indonesia (Homo floresiensis) and the “Star Men” of southern Africa (Homo naledi). But other descendants, the “erectines”, developed larger brains. Their greater intellect is reflected in their more sophisticated stone tools. And about a million years ago, they gave rise to people with even larger brains: the “archaics”.

“Archaics” spread out across the Old World, rapidly splitting into several major groups. In West Eurasia lived the Neandertals (Homo neanderthalensis), the “cave men” of popular culture. In East Asia we find scant remains of a mysterious group: the Denisovans. And in Africa, during the Middle Pleistocene, a new species arose. Compared to the others, they had soft, graceful, child-like features. They were us: Homo sapiens.

By the end of the Pleistocene, Homo sapiens was the only species left. The small-brained relicts, “hobbits” and “Star Men”, died out as we rose to dominance. But the large-brained “archaics” did not entirely vanish. Although everyone today owes over 90% of their ancestry to the early Homo sapiens of Africa, a small percentage comes from the “archaics”: Neandertals, Denisovans, and various African lineages. The remnants of a more diverse era are written into our DNA.

After parting ways nearly a million years ago, modern humans and “archaics” found each other again in the Late Pleistocene. Were these first meetings violent? Peaceful? Both? We can only wonder.