Lineage separation· Where Sapiens lives

The east-west split

49 ka

About 46,000 years ago, the populations outside Africa split into the ancestors of West Eurasians and those of East Asians, from whom the Americas and the Pacific would later be peopled.

Deepest division among populations outside Africa: on one side the ancestors of West Eurasians, on the other those of East Asian populations and of all who will later reach the Americas and the Pacific. Everything the timeline represents east of the Levant proceeds from that second set.

What the evidence shows

The model carrying this branching is a phylogeny fitted to the allele frequencies of East Asian, Australasian and American populations together with ancient western and northern Eurasians, the archaic groups being included. It resolves into a primary bifurcation between an eastern and a western set, with a small number of admixture episodes, and its authors present it as a null model and not as a conclusion. A supertree assembled from 257 genetic and linguistic trees recovers the same grouping, the populations of Sahul and Oceania, East Asia and Beringia-America falling together on the eastern side. What the model does not supply is an age: 45,000 years is the youngest value the bifurcation can take and not its date.

Dating & uncertainty

Reviews place the major divergences among non-African populations between 50,000 and 40,000 years, that is, later than the interval represented here. The disagreement bears not on the separation of the eastern and western lineages, but on how much of that separation had already occurred at the time of the crossing to Sahul.