September 25, 2008

Deshpande et al. (2008) on Out of Africa

This is an important new paper which adds some complexity to the Out of Africa theory. Much existing work has focused on a "tree-like" story of the emergence of modern humans, with an African source population at the root, and other populations being less diverse the further they are (geographically) from the source.

This new model is not limited on colonization, i.e., the movement of a subset of a territory's population into a new uninhabited territory, but also on "lateral" gene exchange between pre-established populations.

From the paper:
Unlike previous models, ours separated colonization events from the continued exchange of people between occupied territories. Our estimates of the exchange rate between neighbouring populations were very low (below 0.01), with carrying capacities ranging from approximately 600 to 1200. Assuming that the census size is three times this effective population size, we derive a census size of approximately 1800–3600 people in each deme. Since each deme has dimensions of 125x125 km, this corresponds to a population density of approximately 0.11–0.23 persons m-2, well within the range for hunter–gatherers referred to by Liu et al. (2006).

Related: Geographic and genetic distance in human populations, A Geographically Explicit Genetic Model of Worldwide Human-Settlement History

Proceedings of the Royal Society B doi: 10.1098/rspb.2008.0750

A serial founder effect model for human settlement out of Africa

Omkar Deshpande, Serafim Batzoglou, Marcus W. Feldman, L. Luca Cavalli-Sforza





mathilda said...

The very iffy assumption of a 50k to 60k OOA date here. How is the Liujiang skull explained then?

Kosmo said...

From The Bradshaw Foundation:


Apparently they're just ignoring the Liujiang skull. At their peril, I think.