Human Origins

26 Apr 2010

One of the big consensus theories is that human origins are closely bound up with the Out of Africa theory. Conventional science outlets and the popular media, such as the BBC, constantly cite the theory as fact as if there was no alternative anthropological ideas. The theory is especially vexious to some as it assumes a pure Homo sapiens strain migrated out of the African continent at some point between 100,000 and 50,000 years ago and all other human groups, including Neanderthals for example, or Homo erectus, have no imput in modern genes. Yet, they have produced no mechanism to explain why earlier human groups became extinct, in order for Homo sapiens to fill the niche left behind. Neo-catastrophism could of course provide the perfect answer - but as far as I know is not on the agenda of any anthropologist. What we do have are a number of arguments on whether Homo sapiens is a pure strain - or it has been subject to a limited amount of admixture with earlier humans.

At http://johnhawks.net/weblog/ there are a number of articles on anthropology and they are updated regularly as and when papers appear in journals or hit the mainstream media - usually in a garbled fashion. This, apparently, was the case with the Boskop big brain people (see post a couple of weeks ago on an article in Discover magazine). Hawks takes the journalism to task, and the authors of the work the article was based on. Apparently, they wrote the piece as if anthropological discussion of Boskop people had stuck in the 1920s when in fact quite a bit of research has been done in recent years.

In another post he refers to the subject of another In the News posting - on the Current Biology special issue on global genetic history of Homo sapiens (see also www.cell.com/current-biology/specialissue ) which had seven papers. Hawks thinks the geneticists are reading the archaeology selectively. For example, an editorial by Colin Renfrew (see http://dx.doi:10.1016/j.cub.2009.11.056 ) where it notes that there is now an abundance of data about genetic variation in living people that has been gathered in the last ten years but a 'new synthesis' is not emerging. The application of archaeo-genetics to the Holocene period is not being applied.

In one post, 'Competitive Exclusion and the extinction of Neanderthals: should we believe it?' is a reference to ideas concerning the disappearance of the Neanderthals and their replacement by Homo sapiens. It examines climate before and after the disappearance, or what is known about it which is of course highly restricted. European ecology was not dramatically different it was decided and the range of the Aurignacians (early European Homo sapiens tool culture) is geographically identical with the Mousterian (Neanderthal tool culture). Hawks claims many factors are being ignored in such studies - yet around 35,000 years ago the latter died out and the former replaced them - right across their range (and provides a map of the distribution of Mousterian and Aurignacian sites). It should be noted here that it is primarily tool cultures that are being used in the study and assumptions associated with technological differences between the two groups. 

A posting on March 27th 2010, 'More X-Woman Thoughts' is John Hawks opinion on the finger bone found in Russian Siberia and assigned to an unknown woman that co-existed with Neanderthals (see In the News posting on this topic). Hawks describes some of the difficulties encountered in attempts to define how much Neanderthal genetic material has survived in modern European and Western Asian humans. He has put together a Mathematica demonstration of the difficulties, 'Coalescent Gene Genealogies' at http://demonstrations.wolfram.com/CoalescentGeneGenealogies/ that generates random gene trees.

His post on April 21st, 'Multi Regional Evolution Lives' is a reference to the claim in a Nature paper that Neanderthals may have interbred with modern humans. The researchers studied genetic data from nearly 2000 individuals from 99 populations around the world and analysed 614 sections of the genome to be used like fingerprints. An evolutionary tree was then created by computer modelling to explain the observed genetic variations in 614 sections of the genome and it emerged that there would have been two periods of interbreeding between humans and either Neanderthals or Heidelbergensis predecessors. These findings are along the lines of what John Hawks favours but in spite of this he is also critical - but read the post.

On April 24th, 'Population models and testing human origins' is in response to a study that estimated 5 per cent of the modern gene pool is derived from ancestral non-Africans. However, there is a lot of literature out there, he admits, that contradicts this line of research - and still favours a purity in the Homo sapiens ancestry - and it is still being published (and quotes a paper in the April PLoS ONE journal. Such divergence of opinions result from what is fed into the models as all studies appear to proceed on the basis of an assumption - computer simulation does not work without human input and a specific agenda. Some models use Bayesian statistical methodology. It is not so much that such statistics are infallible but that the people using them are clever and argumentative. The simulation models have around 18 parameters which can be reshuffled endlessly in a variety of ways - so why does zero admixture always come out winning he asks. Intuitively, he feels, this is wrong ... but read the rest of the post.

Finally, while we are on the subject, at www.physorg.com/print191172239.html there is another article. 'What can we learn from Neanderthal DNA?' ... contrary to their image as knuckle dragging brutes the Neanderthals on television play tennis, attend cocktail parties, and sell insurance. In reality they died out 30,000 years ago, it continues, but their DNA is being extracted from skeletons found in a cave in Croatia.