Paleogenetics

Paleogenetics is the study of the past through the examination of preserved genetic material from the remains of ancient organisms.Emile Zuckerkandl and the physical chemist Linus Carl Pauling introduced the term "paleogenetics" in 1963, in reference to the examination of possible applications in the reconstruction of past polypeptide sequences. The first sequence of an ancient DNA, isolated from a museum specimen of the extinct quagga, was published in 1984 by a team led by Allan Wilson.

Paleogeneticists do not recreate actual organisms, but piece together ancient DNA sequences using various analytical methods. In many ways, an organism's genetics are "the only direct witnesses of extinct species and of evolutionary events".

Similar sequences are often found along protein polypeptide chains in different species. This similarity is directly linked to the sequence of the DNA (the genetic material of the organism). Due to the improbability of this being random chance, and its consistency too long to be attributed to convergence by natural selection, these similarities can be plausibly linked to the existence of a common ancestor with common genes. This allows polypeptide sequences to be compared between species, and the difference between two genetic sequences can be used to determine - within error - the time at which a common ancestor existed.

Using the thigh bone of a Neanderthal female, 63% of the Neanderthal genome was uncovered and 3.7 billion bases of DNA were decoded. It showed that Homo neanderthalensis was the closest living relative of Homo sapiens, until the former lineage died out 30,000 years ago. The Neanderthal genome was shown to be within the range of variation of those of anatomically modern humans, although at the far periphery of that range of variation. Paleogenetic analysis also suggests that Neanderthals shared more DNA with chimpanzees than homo sapiens. It was also found that Neanderthals were less genetically diverse than modern humans are, which indicates that Homo neanderthalensis grew from a group composed of relatively few individuals. DNA sequences suggest that Homo sapiens first appeared between about 130,000 and 250,000 years ago in Africa.

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