Since I've been talking about the possibility of admixture with "archaics" (I'm starting to think the term is a bit too H. sapiens sapiens-centric, is the Neandertal genome turning out to have more ancestral alleles?) I thought I'd point to a paper out in PLoS ONE which reiterates the basic fact that the overwhelming genetic evidence today suggests a massive demographic expansion from an African population within the last 100,000 years. Study after study has supported this contention since the mid-1980s. The question is whether this is the exclusive component of modern human genetic ancestry, which is a somewhat more extreme scenario. In any case, the paper is Formulating a Historical and Demographic Model of Recent Human Evolution Based on Resequencing Data from Noncoding Regions: