Human Ancestors Interbred with Related Species

By Matt Kaplan
Via Nature News
Analysis suggests genetic mixing occurred in Africa around 35,000 years ago.

Our ancestors bred with other species in the Homo genus, according to a study published today in the Proceedings of the National Academy of Sciences1. The authors say that up to 2% of the genomes of some modern African populations may originally came from a closely related species.

Palaeontologists have long wondered whether modern humans came from a single, genetically isolated population of hominins or whether we are a genetic mix of various hominin species.

Last year, an analysis comparing the Neanderthal genome sequence to that of modern H. sapiens showed that some interbreeding did take place between the two species in Europe some time between 80 and 30,000 years ago and that, to a certain extent, Neanderthals ‘live on’ in the genes of modern humans2.

It has been a mystery whether similar genetic mixing took place among Homo species even earlier, before the populations that became modern humans left Africa.

To find out, evolutionary biologist Michael Hammer at the University of Arizona in Tucson and his colleagues studied DNA from two African hunter-gatherer groups, the Biaka Pygmies and the San, as well as from a West African agricultural population known as the Mandenka.

Each of these groups is descended from populations that are thought to have remained in Africa, meaning they would have avoided the genetic bottleneck effect that usually occurs with migration. This means the groups show particularly high genetic diversity, which makes their genomes more likely to have retained evidence of ancient genetic mixing. Read story at Nature News

References

  1. Hammer, M. F. et al. Proc. Natl Acad. Sci. USAhttp://dx.doi.org/10.1073/pnas.1109300108 (2011).
  2. Green, R. E. et al. Science 328, 710-722 (2010).
Related:
Svante Paabo: DNA clues to our inner neanderthal

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