The sequencing of the Neanderthal genome revealed that Neanderthals were the closest relatives of anatomically modern humans among all known archaic human lineages.

The split between the two lineages occurred somewhere between 500,000 and 700,000 years ago, based on genetic analysis.

After that split, the lineages evolved in geographic separation — Neanderthals in Europe and western Asia, modern human ancestors in Africa — developing the distinct anatomical and behavioral profiles that make them identifiable in the archaeological record.

That separation was not total or permanent.

The genetic evidence documents at least two episodes of significant interbreeding: an earlier event in the Middle East, roughly 100,000 years ago, when a group of modern humans moved out of Africa and encountered Neanderthals, and a later, more substantial episode beginning around 60,000 to 70,000 years ago during the major modern human expansion out of Africa.