Convoluted human evolution: variation and interbreeding (Introduction)

by David Turell @, Tuesday, May 26, 2015, 14:57 (1239 days ago) @ David Turell

There has been a fair amount of interbreeding in the fossils that are available, and much variation within species:

"One of the great revelations from population genetics over recent decades is the surprisingly common occurrence of interspecies mating: hybridisation.

"At least 10% of primate species interbreed naturally, in the wild, and hybridisation is now widely regarded to be a source of evolutionary novelty and to even play a role in the formation of new species.

"In 2010, with the first draft sequence of a Neanderthal genome by Richard Green and co-workers, we began to learn that the ancestors of all living non-Africans had in fact mated with our Neanderthal cousins.

"The result was that 1-4% of our genome is Neanderthal in origin, although, slightly earlier estimates from studies of the human genome by Jeffrey Wall and his team suggested the contribution of archaic human DNA could be least 6%, and perhaps up to 14%.

"The amount varies also between human populations with some East Asians having 40% more Neanderthal DNA than Europeans, according to other research published by Wall and co-workers.

"And yet further work by Jeffrey Wall has shown evidence in the genome of some living Africans for interbreeding with another species there, around 35,000 years ago. One we haven't yet identified from the fossils.


"One of the emerging surprises from the fossil record from the period roughly 50,000-10,000 years ago is the remarkably large number of 'enigmatic' remains that have and continue to be discovered.

"By enigmatic I mean that 'overall' they resemble modern humans (H. sapiens) but also possess a surprisingly large number of features that we would normally associate with archaic groups like the Neanderthals.

"I've seen this in my own work with the 'Red Deer Cave people' in Southwest China.

"And its a compelling explanation for the mixed anatomy of the Iwo Eleru remains from West Africa, Nazlet Khater 2 skull from Egypt, Lukenya Hill fossil from Kenya, and in Europe, the Mezzena jaw and Pestera cu Oase remains from Romania, among others.

"A recent news report in Nature announced that DNA had been successfully sequenced from a 35,000 year old jaw from Pestera cu Oase, as described at the Biology of Genomes meeting in Cold Spring Harbor in New York.

"Qiaomei Fu, a palaeogenomicist at Harvard Medical School, and her team apparently found that between 5% and 11% of the DNA of this individual (a man) was Neanderthal, including large chunks of several chromosomes."

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