Why the human form varies so little, although humanity has managed to occupy every imaginable habitat and persisted within specific habitats for generations, is today answered through a study of the human genome - the genetic makeup of the human race - as compared to the chimpanzee. At the genetic level, humans are remarkably homozygous. Chimpanzees show as much as 10 times the genetic variation that humans possess, showing that humanity as a whole, be they African or Chinese, arose from a small stock of common ancestors (Wilson & Cann, 1992) and were subject to some heavy selection and specialization while surviving. One may remark that, considering the low degree of variation in the mitochondrial DNA of humans (Reader, 1988), the differences to be found between human races is quite remarkable, suggesting quite rigorous sexual and natural selection having been exerted upon humanity! I present the modified energetic Lotka-Volterra model (MELV model) in this book, suggesting that natural selection promotes differentiation as a response to differing environments, while sexual or social selection reduces this difference. Interestingly, at the genetic level, studies of mitochondrial DNA (mtDNA) has shown that the African populations have the greatest genetic variation, providing confirming evidence that humanity originated in Africa. A small group of people must have populated the rest of the world or the migrating humans were subject to heavier selective pressures (or both). Concerning similarities between apes, the myoglobin protein, found in muscle tissue and made of 154 amino acid subunits, differs between humans, gorillas and chimps, by only one amino acid! Baboons differ by only five, so this difference is not as remarkable as it initially appears.
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http://www.ecotao.com/holism/hu_sap.htm#Genetics
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