Posted on 02/28/2007 1:34:33 PM PST by blam
Contact: Preston M. Moretz
pmoretz@temple.edu
215-204-7476
Temple University
New DNA study helps explain unique diversity among Melanesians
Small populations of Melanesians — among the most genetically diverse people on the planet — have significant differences in their mitochondrial DNA that can be linked to where they live, the size of their home island and the language they speak, according to a study being published in the new online journal, Public Library of Science ONE (http://www.plosone.org).
The study, "Melanesian mtDNA complexity," was lead by Jonathan Friedlaender, emeritus professor of anthropology at Temple University. The study appears in the Feb. 28 issue.
Friedlaender and his collaborators from Binghamton University, the Institute for Medical research in New Guinea and the University of Pennsylvania, examined mitochondrial DNA sequences from 32 diverse populations on four Melanesian islands, an island chain north and northeast of Australia that includes Fiji, New Caledonia, Vanuatu, the Solomon Islands, and New Guinea. The islands that were intensively covered were Bougainville, New Ireland, New Britain and New Guinea. "Mitochondrial DNA has been a focus of analysis for about 15 years," says Friedlaender. "It is very interesting in that it is strictly maternally inherited as a block of DNA, so it really allows for the construction of a very deep family tree on the maternal side as new mutations accumulate over the generations on ancestral genetic backgrounds.
"In this part of the world, the genealogy extends back more than 35,000 years, when Neanderthals still occupied Europe," he adds. "These island groups were isolated at the edge of the human species range for an incredible length of time, not quite out in the middle of the Pacific, but beyond Australia and New Guinea. During this time they developed this pattern of DNA diversity that is really quite extraordinary, and includes many genetic variants that are unknown elsewhere, that can be tied to specific islands and even specific populations there. Others suggest very ancient links to Australian Aborigines and New Guinea highlanders."
Friedlaender also says that the study gives a different perspective on the notion of the "apparent distinctions between humans from different continents, often called racial differences. In this part of the Pacific, there are big differences between groups just from one island to the next — one might have to name five or six new races on this basis, if one were so inclined. Human racial distinctions don’t amount to much."
### The study was funded by grants from the National Science Foundation, the Wenner-Gren Foundation for Anthropological Research, the National Geographic Society Exploration Fund and the Penn Faculty Research Fund.
"Unique Diversity"?.....
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The ones who are Muslim have been inbreeding for centuries.
So, any explanantion for this seeming contradiction in mtDNA diversity? Would polygamy 'splain it?
Hey--I figgered you were our resident expert in genetics.
Cousins marrying cousins and uncles marrying aunts/nieces does lead to severe mental and physical maladies...and Muslims exhibit all them.
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I'm not physically or mentally deficient. Nor am I Muslim. But genealogy is fun for me because so many of my lines converge on common ancestors. Us Southerners had ancestors who lived in rural areas with limited access to new blood. We did ok.
Contradiction? I think marriage arrangements don't influence things,only the egg has mtDNA.
Indeed--the cytoplasm of the sperm is negligible, so (essentially) all the mtDNA comes from the ova. The contradiction would be why, in this limited area, would there be so much diversity of mtDNA? One way to possibly explain it would be for the dominant males to raid other islands and bring captive women back--women who would have different genetic lines.
You cannot compare your situation (amongst "Southerners" but simlar to many rural communities in all parts of the US) with first cousin marriage as a normal routine occurence among Muslims.
Many of my ancestors are married first cousins. Three of my father's four grandparents were cousins to each other, two of them first cousins. The practice has gone back to nearly three hundred years that I can uncover, and I suspect it's longer than that.
Interbreeding wouldn't result in specific mtDNAs on "specific islands and even specific populations". This has to be the result of population isolation and I'm guessing long isolation at various locals. Long isolation accounts for the high number of mtDNA mutations not found in other populations.
FWIW Melanesians have the greatest genetic distance from Africans according to Cavalli-Sforza.
Yes--isolation and then rearranging the female lines through raids. It's also interesting to note that Africans have a great amount of genetic diversity.
I don't see any evidence here that the female lines move around. If the female lines were rearranged wouldn't the mtDNAs be spread all over Melanesia instead of isolated to islands and even sections of populations? The total genome of Melanesia may have a lot of diversity but apparently at any particular local it's not diverse.
OK--I see your point. But in Africa, they take the high level of diversity as meaning that they are the oldest populations, but if as you say the Melanesians are the farthest from the Africans, it does not make sense that the Melanesians would be a very old line.
I was told that Africa has more genetic diversity than the rest of the world combined. I guess Melanesia must be second. If you believe in molecular clocks, than the oldest population will have the DNA that the daughter populations will have variants of. Since it takes time to accumulate mutations, the more recent populations splits will have fewer variants and the older population splits will have more. Melanesians have more therefore they're older.
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