Title: Blacks, whites and Asians have different ancestors – and did not come from Africa, claims scientist Source:
Article Safari URL Source:http://www.articlesafari.com/2010/0 ... ians-did-not-come-from-africa/ Published:Sep 12, 2010 Author:articlesafari Post Date:2010-10-21 04:10:51 by X-15 Keywords:None Views:185 Comments:12
Geographer claims the races evolved from different ancestors.
A public claim by a fellow of the prestigious Royal Geographic Society that humans did not all come from Africa — and that blacks, whites and Asians have different ancestors — has been dismissed by world experts as “dangerous”, “wrong” and “racist”.
In a paper widely trumpeted and due for release in book form, Akhil Bakshi, the leader of a recent major scientific expedition supported by India’s prime minister, claims that “Negroid”, “Caucasian” and “Mongoloid” peoples are not only separate races but separate species, having evolved on different continents. Responding to the claims — developed while Bakshi led the Gondwanaland expedition from India to South Africa — Professor Lee Berger, a leading palaeoanthropologist at the University of the Witwatersrand, immediately insisted that, there were no fundamental differences between the races and that all humans had the same genetic and physical roots in Africa.
The prevalent scientific theory of modern humans — the “Out of Africa” model — is that they left Africa just 55000 years ago and replaced the last remnants of other ancient hominids living in Europe, Asia and elsewhere.
The old biological racial distinctions of “Caucasian”, “Negroid” and “Mongoloid” have recently been abandoned by mainstream scientists — removed, for instance, from the US National Library of Medicine in 2003.
Bakshi has become a self-declared champion of a minority scientific view called “multiregionalism”, which claims that modern humans evolved from separate hominid populations. Hominids encompass all humans and the ancient family of human-like ancestors, including large-brained ancient ancestors and unsuccessful species such as Neanderthals. However, Bakshi — who has no training as an anthropologist — has linked to this model a theory that these populations evolved according to the genetic material left behind when the prehistoric supercontinents, the northern Laurasia and the southern Gondwanaland, broke up. An influential figure in India, Bakshi is also a filmmaker and author who has led four major scientific expeditions since 1994. Bakshi admitted to the Sunday Times that “some of my points may prove to be wrong, and may be seen as politically incorrect.
He claims indigenous “Negroid” populations occur in places like Australia, India, Sri Lanka, the Philippines and the Andaman Islands not because they moved there from Africa, but because all these land masses were once part of Gondwanaland — and that all evolved separately. Whites, according to Bakshi, are from Laurasia and blacks are from Gondwanaland. He argues that, 60000 years ago, humans could not have crossed vast oceans and deserts to reach remote places like Australia and North America, and they must therefore have evolved there.
“His is a highly confused argument which jumps enormous levels, which are quite impossible to link,” Tobias said. However, he added that the true picture of modern humanity’s precise departure from Africa was far from clear-cut.
According to King (1993, p 30) “the most functionally obvious difference between biological species is the attainment of reproductive isolation.” There are many factors that may cause this isolation. Some, like geographical, seasonal, behavioural, mechanical or physiological, are prezygotic (medical-dictionary.thefreedictionary.com/prezygotic). Other barriers are postzygotic and largely based around hybrid non-viability
However it could be argued that only postzygotic mechanisms are ‘real’ and permanent. For example geographical barriers can disappear. Some human ‘races’ are a good example of this. Whilst geographically separated for thousands of years gene flow between some populations was all but stopped. But even that was not enough for speciation to have occurred, and viable hybrids (possibly even fitter than their parents) have resulted now that technology has brought the species so close together again.
Prezygotic reproductive isolation creates an opportunity for speciation but something more is needed for it to actually occur and become fixed. Even species recognition and other, e.g. morphological, pre-mating barriers in the field may potentially be overcome in the laboratory.
It is important to keep in mind, however, that in the field these barriers are real. King (1993 p 208) himself, a chief proponent of chromosomal speciation, reminds us that “chromosome change is not a sin qua non for speciation.”
Central to issue of genetic reproductive isolation is the viability of hybrids. King (1993, p 32-33) specifies the importance of including the absence of F2 generation or backcross hybridisation in defining this barrier and promotes Key’s (1981 p 455) definition of reproductive isolation.
“.. the relationship between two populations that do not hybridise in the field, although in contact with each other, or, if they do, whose F1 hybrids leave no progeny of reproductive age, i.e. are infertile interse and in every backcross.”
Before we investigate how chromosome change may result and how it might effect the interbreeding of populations we must first get a background to their function and how they are organised. To do so we will focus in on the organisation of the human genome.