Interesting new research provides evidence that the out of Africa model is not correct, and that modern humans share a common ancestor originating in southeast Asia. Paper linked below in case anyone is interested to read it.
Out of Africa is based significantly on the theory of “molecular clock” which is the idea that random genetic mutations occur more or less at the same pace in all living species over time. Because modern African people have the most genetic diversity compared to humans of other races and geographies, it is assumed that Africans have been around the longest. However, this is challenged by pointing out that by using the maximum genetic diversity model it makes more sense that a newly evolved species will saturate its genetic content with new mutations and then relatively quickly slow down the rate of new mutations, quite simply because there exists stabilizing selection pressure on the genome to minimize the spread of new mutations in the new organism. The idea is that genetic mutations = random noise, and the level of noise is synonymous more or less not with how long a species has existed in its present form but rather the inverse of this.
It is argued that African people, because they have the highest amount of genetic diversity within their race compared to other races, are actually among the most recently evolved of modern humans because they still have yet to coalesce and stabilize their genome. They still have a relatively high level of mutational difference amongst people of their race, implying that they have not been subject to as long a period of stabilizing selection pressure that would tend over time to reduce random noise (genetic diversity) within the genome of the species.
Another point has to do with neotany, the propensity for species to evolve over time toward extending those phenotypes more resembling the characteristics of infants or youth of the species. This indicates a tendency toward slowing down of the rate of aging which would result naturally from a longer period of stabilizing selection pushing that species more toward K-strategy (slow life) rather than r-strategy (fast life) in terms of life history strategy. It is well known that Africans are more r-selected and Asians are more K-selected, with Europeans being somewhere in the middle. Neotany would also have been selected for (and is still being selected for) in humans because we (especially men, but women do this too) tend to sexually select for features indicating youth as opposed to advanced age. Youth is a secondary indicator of sexual fertility and health when compared to being older, therefore it is natural that we prefer younger as opposed to older mates. The longer a group has been in existence the longer it would have been sexually selecting for whatever traits it happens to preference, resulting in our case as humans in a slow shift toward more neotanous features in the population. Asian people tend to have the most neotanous features (larger eyes, appearance that looks younger, flatter faces, less body hair, shorter height, “cuter” appearance, etc.). Asian women are often rated as the most physically attractive compared to women of other races, which makes sense from a standpoint of neotany. In contrast, while Asian people tend to have the most neotanous features African people tend to have the least neotanous features. European people are again somewhere in-between when it comes to their levels of phenotypical neotany.
They also go over some other evidence involving Y chromosome and mitochondrial DNA. I didn’t review all of this, I was focused mainly on the idea of molecular clock and the meaning of random genetic mutation/noise within a context of selection pressures (Darwinian purifying selection and stabilizing selection (stabilizing the various and most important gene structures around their most optimized forms) and neotany.
Interesting ideas presented here, feel free to post your own thoughts about this issue or other relevant scientific data.