What let Homo erectus walk out of Africa a million years before us?

What got Homo erectus out of Africa was probably its body, not its brain. It was the first hominin with a body plan like ours. It had long legs and a human-like stride. Fossil footprints in Kenya suggest it walked much as we do. Researchers link that efficient walking to its spread across Africa, Asia and Europe.

The proof sits in Dmanisi, in the country of Georgia. Hominins lived there about 1.8 million years ago. These are the oldest human remains found outside Africa. Their skulls were primitive and their brains small. But their spines and legs were built for long-distance walking. One of them had lost all but one tooth, yet lived on for years. Others probably cared for them.

Those travellers were not carrying fancy kit either. Homo erectus would later invent big Acheulean handaxes. Yet the Dmanisi group left Africa with only simple Oldowan-style tools. Fire was not the key either. It only becomes common in the record about 400,000 to 300,000 years ago.

Was Homo erectus really the first to leave? Probably, but not for certain. Stone tools in Jordan and China may be 2.48 and 2.1 million years old. If those dates hold, an earlier hominin left first.