out-of-Africa hypothesis finds cranial support

Just as Mark Elbroch describes, osteology in combination with DNA analysis is a powerful tool for evolutionary biologists. Witness the recent study cementing the out-of-Africa hypothesis:

The genetic evidence has always strongly supported the single origin theory, and now results from a study of more than 6,000 skulls held around the world in academic collections supports this case.

"We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area in Sub-Saharan Africa," said Andrea Manica of the University of Cambridge's Department of Zoology.

Manica and colleagues wrote in the journal Nature that variations in skull size and shape decreased the further a skull was away from Africa, just like variations in DNA.

The decrease reflects the fact that, while the original African population was stable and varied, only a small number of people embarked on each stage of the multi-step migration out of Africa. This effectively created a series of "bottlenecks", which reduced diversity.

As an aside, Mike Dunford discusses why mitochondrial Eve and Y-chromosome Adam never knew each other.