Friday, 15 March 2013
Why is Albert Perry's DNA so interesting?
Many people researching their family history are interested in finding as much as possible about the paternal line – and have resorted to DNA testing of the Y chromosome, which passes from father to son, and which is not found in women. Because small copying errors occur between one generation and the next it is possible to find out how closely related and two men are. Fossil evidence suggests that modern man came into existence about 200,000 years ago and that all living men shared a common “Adam” ancestor somewhere between 60 and 140,000 years ago.
That is until Albert Perry's DNA was sent for testing by a relative – and the laboratory carrying out the genealogical tests on his DNA were puzzled – as it didn't fit. Further investigation suggested that his Y chromosome was so different to yours or mine that the “Human” paternal ancestor we shared with Albert lived about 340,000 years ago – over 100,000 years before the beginnings of the modern human species.
In the talk How Evolution made us the way we are I gave earlier this year I suggested that interbreeding of homo species played an important part in our evolution I got excited – as the most likely explanation is that one of Albert's ancestral mother's mated with the male of a different homo species and the Y chromosome has passed down the male line to Albert.
Albert (who apparently died before the importance of his unusual DNA was discovered) was an African-American whose ancestors probably came from a small village in Cameroon, where 11 other men with the same unusual Y gene have now been discovered. Interestingly this is only a few hundred miles from the Iwo Eleru rock shelter where excavated remains suggest that a cousin human species was still living as recently as 15,000 years ago. As we already know that early modern man had interbred with both Neanderthal and Denisovan cousin species (in Europe and Asia) we now appear to have another example from Africa of inter-species breeding in the last 50,000 years. This helps to support my suggestion that some human “features” may have developed in different cousin species – and then come together by later interbreeding – possibly on many different occasions with many different cousin species over the 3-6 million years.
[Based on article in this week's New Scientist and information on the Iwo Eleru rock shelter in Stringer's book “The Origin of the Species”.
The New Scientist also contained details of some research which suggests that Neanderthals had bigger eyes and that more of their brain was devoted to processing optical information that occurs in modern humans. It is suggested that as their brain was about the same size this may have left less room for “intelligent” thinking. There is no comment (at least in the press reports) as to the amount of brain devoted to speech so as far as I can see the argument could well be that they lost out because their language skills were less well developed. Evidence elsewhere suggested the children matured faster – meaning a shorter “learning” time to absorb language skills and culture. (See Royal Society report)