How did Homo sapiens spread out of Africa and across the world?

Homo sapiens spread out of Africa in waves, mostly along coasts, and crossed the sea to reach Australia. The wave that lasted began roughly 70,000 to 50,000 years ago. Its exact dates and routes are still argued over, and new finds keep shifting them.

Some groups left much earlier. Homo sapiens fossils in Israel's Misliya Cave are about 194,000 to 177,000 years old. But those early pushes seem to have failed. Neanderthals may have replaced them.

The lasting move was small. A group from East Africa, maybe fewer than 1,000 people, crossed the Bab-el-Mandeb strait into Yemen. That happened sometime after 75,000 years ago. Their descendants followed the coast around Arabia and Persia. They reached South Asia before 55,000 years ago.

Along the way, they met Neanderthals and, farther east, Denisovans. They had children together. Traces of that mixing are still in people's DNA today.

Then came a bold step. Sea levels were lower, but open water still separated Asia from Australia and New Guinea. Some gaps were 90 kilometres wide. Homo sapiens crossed them by roughly 65,000 to 50,000 years ago. That took real seafaring skill. It was the first time humans went beyond where Homo erectus had lived.

The map then filled in. Europe came around 40,000 years ago, and the Americas about 20,000 years ago. Arctic Canada and Greenland followed about 4,000 years ago. The far islands of Polynesia came last, within the past 2,000 years.