Re: DNA Change That Accounts For White Skin
Posted By: kristine In Response To: DNA Change That Accounts For White Skin *LINK* (kristine)
Date: Saturday, 10 June 2006, at 4:16 p.m.
In Response To: DNA Change That Accounts For White Skin *LINK* (kristine)
~Neanderthal yields nuclear DNA
"However, the researcher is also working to extract and read Neanderthal DNA by the traditional method. About 75,000 base-pairs have been sequenced this way so far. They show that Neanderthals diverged from the evolutionary line that led to modern humans about 315,000 years ago.
Neanderthals lived across Europe and parts of west and central Asia from approximately 230,000 to 29,000 years ago. It is unclear what factors led to their demise, but climate change and competition from modern humans may have played a role."
~Letter From New York: The New Neandertal
"Modern human specimens are also being digitized, allowing us to assess bone shape and size variations and understand their significance in anatomical evolution. In a remarkable contribution at the conference, Katerina Harvati and Tim Weaver of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, looked at skull variation in modern humans from different climates and cultures. They found that the shape of the face is linked to local environmental conditions, which fits well with the current belief that the Neandertal's projecting face is a cold-climate adaptation. By contrast, the shape of the brain case, particularly the temporal bone (on the side of the skull), proved to be a good indicator of genetic closeness among populations."
"Although this number is small, the evidence gives us insight into the demography of the Neandertals. The limited variability of their DNA suggests that there were times, perhaps during glacial advances, when their population was greatly reduced, resulting in genetic bottlenecking. The population recovered in size afterward but with fewer surviving different genetic lines. In this respect, humans--modern, Neandertal, and others--strongly contrast with African apes, which evolved in a much less stressful environment during the last several hundred thousand years, and therefore have much greater genetic variability."
"There is no evidence that the last Neandertals were evolving toward a physical appearance like our own, but the issue of the possible contribution of Neandertals to the modern European genetic makeup is still fervently debated. Even if Neandertals represented a distinct, although very close, species separate from modern humans, we know that in nature, hybridization is a common process under such circumstances. At the conference, Trenton Holliday of Tulane University surveyed the zoological evidence, pointing out many hybrids among large mammals including members of the camel, horse, dog, and cat families. Did Neandertals and modern humans interbreed? It is quite possible in some instances, but it had no major biological results."
~Fossil find recharts the journey of modern man
"Africa may be the cradle of humanity, but humans have a long history of leaving it. An earlier, more ape-like human species called Homo erectus started leaving Africa for Asia as long as 1.8 million years ago; its fossils and skulls have been found throughout China and Indonesia. Similarly, primitive human species were in Europe a million years ago. By at least 300,000 years ago, they had evolved into a short, stocky, brutish-looking creature called Neanderthal man."
~Molecular clockwork and related theories
"The controversial recombination factor is providing new directions for research and interpretation. In 1997, Svante Pääbo of the Max Planck Institute of Evolutionary Anthropology in Leipzig retrieved Neanderthal DNA over 50,000 years old, which he determined to have not contributed in any way to the mtDNA of modern humans. But the possibility of recombination suggests to Erika Hagelberg that Neanderthals might be more closely related to modern humans than Pääbo’s mtDNA data shows. Pääbo partially agrees, but feels recombination has not yet been effectively proven. MtDNA shows Neanderthals equally distant from both modern Europeans, whom they may be ancestral to, and unrelated populations.
Further research on mtDNA evolution should serve to identify and eliminate the specific genes which mutate at abnormally fast or slow rates. Jody Hey and Eugene Harris of Rutgers University suggest that future work should increasingly concentrate on the more complex nuclear genes. A recent study by Hey and Harris (1999) on the mutation rate of PDHA1 genes in the X Chromosome, thought to have a steady rate of mutation, has identified two populations at least 200,000 years old ancestral to modern humans. To determine the mutation rate of the gene, these were compared to the differences between human and chimpanzee PDHA1 genes, diverging at least 5-6 million years ago. They found that prior to 200,000 years ago, one form of this gene existed only in Africa and led to types only in modern Africans. Another existed only outside of Africa with one variant found in some modern Africans and another which split ca. 200,000 years ago into two haplotypes found in non-Africans.
Milford Wolpoff of the University of Michigan, a long-time opponent of the oversimplified use of molecular clocks (1988), supports the recent findings of Hey and Harris. If this evidence is not to make “Out-of-Africa II” theories obsolete, they may nevertheless need to evolve significantly themselves, to accommodate Asian and European populations originating in Africa but leaving considerably earlier than 100,000 to 200,000 years ago."
~Ginger gene makes redheads more sensitive to the cold
"Simon Cheetham of Red and Proud, a website that claims to represent redheads, welcomed the research, but said it shattered the myth of the tough, ginger Scottish male.
"The stereotype of a Celt is a wild, kilted man with red hair who takes no notice of the temperature," he said. "In fact most redheads don't really like extremes of temperature." "
~Human Genome Shows Proof of Recent Evolution, Survey Finds
"Genes related to physical characteristics also showed strong evidence of selection, with interesting differences among the three populations.
"We found five different genes involved in skin pigmentation in the European population," Pritchard said.
He noted that, for humans living far from the equator, lighter skin is important for producing vitamin D, which is often formed in the body following exposure to the sun's ultraviolet rays.
Pritchard says evidence of recent pigmentation changes in Europeans may be the tail end of a much older process underway since modern humans first moved out of Africa or Asia to higher latitudes.
But the genetic changes could also be a reflection of more recent northward migrations following the last Ice Age, about 14,000 years ago, he says."
~Neanderthal man floated into Europe, say Spanish researchers
"Spanish investigators believe they may have found proof that neanderthal man reached Europe from Africa not just via the Middle East but by sailing, swimming or floating across the Strait of Gibraltar.
Prehistoric remains of hunter-gatherer communities found at a site known as La Cabililla de Benzú, in the Spanish north African enclave of Ceuta, are remarkably similar to those found in southern Spain, investigators said. Stone tools at the site correspond to the middle palaeolithic period, when neanderthal man emerged, and resemble those found across Spain."
Messages In This Thread
Rastafari Speaks Archive is maintained by Administrator with RastafariSpeaks.com 5.12.
FAIR USE NOTICE:
This site may at times contain copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.
For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml