Dr. Trevor Cousins of Cambridge University's Department of Genetics: For a long time, it was assumed that we evolved from a single continuous ancestral line. Today, the best-fit model suggests an initial divergence of 1.7 Ma into two populations. Numerous authors have presented evidence that modern humans, especially West Africans, have recent additions of genes from unknown archaic ancestors. Parametric estimates vary, although all models of West African population structure suggest that admixture occurred less than 150,000 years ago, and some suggest less than 50,000 years ago. In addition, the inferred time of population divergence is always estimated to be later than 1 million years ago. Although this appears to be a different event than the one we describe, unavailable to all modern humans, these findings suggest a likely reason why the maximum likelihood estimates of the time of partitioning and admixture in West Africans inferred by the cobras are later than the CML estimate. Our research clearly indicates that our evolutionary origins are more complex, involving different groups that evolved separately for more than a million years and then returned to form the modern human species, said co-author Professor Richard Durbin, also of the Department of Genetics.