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Friday, 11 August 2017

Is Homo sapiens only one species?

The European Neanderthal became extinct some 40,000 years ago. The Asian Homo floresiensis was still alive some 50,000 years ago. The surge of the behavioral modern homo sapiens around 40,000–50,000 years ago, seems to have wiped out all other human species. Is Homo sapiens the only species left? Actually, this question is much harder than it seems like.

The 1st problem is definition as there is "no true type specimen of Homo sapiens" (Smithsonian). In the absence of a default specimen of Homo sapiens, the 2nd problem is human diversity. This is the reason why race became an issue as people were separated amongst colour. The Out-of-Africa migration theories I and II ended the scientific debate but not the racial debate. 

Diversity once again became a scientific debate following human genetic clustering. Research revealed that DNA diversity outside Africa was much less than within Africa. On the one hand, this supported the Out-of-Africa theory through the serial founder-effect: "the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population" (eg, 2009 study).

On the other hand, this research also revealed the existence in Africa of "14 ancestral population clusters that correlate well with self described ethnicity and shared cultural or linguistic properties" (2010 study). This finding reopened the racial debate on scientific grounds. 

"In the late 1990s Harvard evolutionary geneticist Richard Lewontin stated that "no justification can be offered for continuing the biological concept of race. [] Genetic data shows that no matter how racial groups are defined, two people from the same racial group are about as different from each other as two people from any two different racial groups. This view has been affirmed by numerous authors and the American Association of Physical Anthropologists since." (Wiki)

The DNA comparisons revealed another issue. Nat Geo: "Everyone living outside of Africa today has a small amount of Neanderthal in them, carried as a living relic of these ancient encounters. A team of scientists comparing the full genomes of the two species concluded that most Europeans and Asians have between 1 to 2 percent Neanderthal DNA. Indigenous sub-Saharan Africans have none, or very little Neanderthal DNA because their ancestors did not migrate through Eurasia."

Other studies revealed that some "populations in East Africa, including Ethiopian highlanders who live near Mota Cave, carried the highest levels of Eurasian ancestry". This back-to-Africa gene flow was revealed in a 4,500-year-old man from Ethiopia (eg, Nature, 2016). The last Ice Age of 25,000 to 13,000 years ago, and the subsequent melting of ice causing the Great flood of 11,000 BC - 4,000 BC, probably drove people back to higher and warmer areas, like Ethiopia.

"Few men are of one plain, decided colour; most are mixed, shaded, and blended; and vary as much, from different situations as changeable silks do from different lights." Quote by Lord Chesterfield (1694-1773)

Human Beings (1998) by Seal - artist, FB, lyrics, video, Wiki-1, Wiki-2