Southern Africa's bushmen, and their relatives the Khoe, veered off on their own path of genetic development 100,000 years ago, according to a new study.
The split, gleaned from an analysis of genetic data, is the earliest divergence scientists have discovered in the evolution of modern humans.
The Khoe and the San peoples - who speak click languages, and live across a wide swath of southern Africa from Namibia to Mozambique to South Africa - have long fascinated scientists.
The San, in particular, were one of the last remaining hunter-gatherer societies, living well into the 20th century in a style anthropologists think was similar to humans' most ancient ancestors.
The study published in the journal Science analyses the genes of 220 members of the Khoe and San groups. Researchers looked at 2.3 million genetic variations for each participant, learning important information about the Khoe-San and, more generally, the origins of modern humans.