Geneticists Develop New Model for Ancient Human Relationships

VANCOUVER, CANADA—ABC News Australia reports that statistical geneticist Ryan Bohlender of the University of Texas MD Anderson Cancer Center and his team developed a new computer model to evaluate the possible relationships among the ancestors of modern humans, Neanderthals, and Denisovans. The tool varied estimations of population size and dates for when the populations stopped interbreeding, and accounted for inconsistencies in previous studies of genomes of modern and archaic humans. The analysis suggests that interbreeding occurred both within and outside of Africa, that the early population in Africa was 50 percent larger than had been thought, and that modern humans diverged from the family tree some 440,000 years ago. The study also suggests that the different populations may have interbred less frequently than previously thought, and in similar numbers in Europe and in East Asia. (It had been suggested that interbreeding occurred more frequently in East Asia.) And, according to Bohlender, Melanesians may carry a small amount of DNA from an unidentified, extinct human species. Future computer simulations will add additional populations into the mix to see how they affect the results.