非洲人、尼安德特人、和我们，耶和华到底造了谁？

在美一方

新的基因证据表明，凡是非洲以外的人，体内都有尼安德特人的基因片段。由此推断，人类在走出非洲之后，与尼安德特人有基因交换，physically的意思，就是有杂交。
http://www.sciencedaily.com/releases/2011/07/110718085329.htm

Science News

Non-Africans Are Part Neanderthal, Genetic Research Shows

ScienceDaily (July 18, 2011) — Some of the human X chromosome originates from Neanderthals and is found exclusively in people outside Africa, according to an international team of researchers led by Damian Labuda of the Department of Pediatrics at the University of Montreal and the CHU Sainte-Justine Research Center. The research was published in the July issue of Molecular Biology and Evolution.

"This confirms recent findings suggesting that the two populations interbred," says Dr. Labuda. His team places the timing of such intimate contacts and/or family ties early on, probably at the crossroads of the Middle East.

Neanderthals, whose ancestors left Africa about 400,000 to 800,000 years ago, evolved in what is now mainly France, Spain, Germany and Russia, and are thought to have lived until about 30,000 years ago. Meanwhile, early modern humans left Africa about 80,000 to 50,000 years ago. The question on everyone's mind has always been whether the physically stronger Neanderthals, who possessed the gene for language and may have played the flute, were a separate species or could have interbred with modern humans. The answer is yes, the two lived in close association.

"In addition, because our methods were totally independent of Neanderthal material, we can also conclude that previous results were not influenced by contaminating artifacts," adds Dr. Labuda.

Dr. Labuda and his team almost a decade ago had identified a piece of DNA (called a haplotype) in the human X chromosome that seemed different and whose origins they questioned. When the Neanderthal genome was sequenced in 2010, they quickly compared 6000 chromosomes from all parts of the world to the Neanderthal haplotype. The Neanderthal sequence was present in peoples across all continents, except for sub-Saharan Africa, and including Australia.

"There is little doubt that this haplotype is present because of mating with our ancestors and Neanderthals. This is a very nice result, and further analysis may help determine more details," says Dr. Nick Patterson, of the Broad Institute of MIT and Harvard University, a major researcher in human ancestry who was not involved in this study.

"Dr. Labuda and his colleagues were the first to identify a genetic variation in non-Africans that was likely to have come from an archaic population. This was done entirely without the Neanderthal genome sequence, but in light of the Neanderthal sequence, it is now clear that they were absolutely right!" adds Dr. David Reich, a Harvard Medical School geneticist, one of the principal researchers in the Neanderthal genome project.

So, speculates Dr. Labuda, did these exchanges contribute to our success across the world? "Variability is very important for long-term survival of a species," says Dr. Labuda. "Every addition to the genome can be enriching." An interesting match, indeed.

The study was supported by grants from the Canadian Institutes of Health Research.

Story Source:

    The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Montreal.

Journal Reference:

    V. Yotova, J.-F. Lefebvre, C. Moreau, E. Gbeha, K. Hovhannesyan, S. Bourgeois, S. Bedarida, L. Azevedo, A. Amorim, T. Sarkisian, P. H. Avogbe, N. Chabi, M. H. Dicko, E. S. Kou' Santa Amouzou, A. Sanni, J. Roberts-Thomson, B. Boettcher, R. J. Scott, D. Labuda. An X-Linked Haplotype of Neandertal Origin Is Present Among All Non-African Populations. Molecular Biology and Evolution, 2011; 28 (7): 1957 DOI: 10.1093/molbev/msr024

也和话

以前问过了，在这里：

http://www.hutong9.net/forum.php ... &extra=page%3D6

面瓜

我问个问题啊,
非洲原始人跑到欧洲以后,怎么变白的?

在美一方

回复 面瓜 的帖子

呵呵，我首先问你一个，你怎么知道非洲最原始的人本来就黑？

面瓜

在美一方 发表于 2011-7-24 17:17
回复 面瓜 的帖子

呵呵，我首先问你一个，你怎么知道非洲最原始的人本来就黑？

那非洲人后来怎么黑的？

在美一方

回复 面瓜 的帖子

我又没说非洲人原本不黑。你怎么那么机械啊。自己狗一下去。

在美一方

你懒，我狗来你看：
Evolution of skin color

Rogers et al. (2004) performed an examination of the variation in MC1R nucleotide sequences for people of different ancestry and compared the sequences for chimpanzees and humans from various regions of the Earth. Rogers concluded that roughly five million years ago, at the time of the evolutionary separation of chimpanzees and humans, the common ancestors of all humans had light skin that was covered by dark hair. Over time the hair disappeared to allow better heat dissipation through sweating[3] and the skin tone grew darker to protect from folate depletion to the increased exposure to sunlight.[4] By 1.2 million years ago, shortly after the final speciation of homo sapiens from homo ergaster[dubious – discuss], the ancestors of all people living today had exactly the same receptor protein as modern Africans.[43] Evolutionary pressure meant that any gene variations that resulted in lighter skin were unable to survive under the intense African sun, and human skin remained dark for the next 1.1 million years.

Approximately 70,000–100,000 years ago modern humans began to migrate away from the tropics to the north where they were exposed to less intense sunlight, possibly in part due to the need for greater use of clothing to protect against the colder climate. Under these conditions there was less photodestruction of folate and so the evolutionary pressure stopping lighter-skinned gene variants from surviving was reduced. In addition, lighter skin is able to generate more vitamin D (cholecalciferol) than darker skin so would have represented a health benefit in reduced sunlight if there were limited sources of vitamin D.[3] Hence the leading hypothesis for the evolution of human skin color proposes that:-

    From ~1.2 million years ago to less than 100,000 years ago, the ancestors of all people alive were as dark as modern Africans.
    As populations began to migrate, the evolutionary constraint keeping skin dark decreased proportionally to the distance North a population migrated, resulting in a range of skin tones within northern populations.
    At some point northern populations experienced positive selection for lighter skin due to the increased production of vitamin D from sunlight and the genes for darker skin disappeared from these populations.

The genetic mutations leading to light skin, though different among East Asians and Europeans,[25] suggest the two groups experienced a similar selective pressure due to settlement in northern latitudes.[5]

There is a long-standing hypothesis that the selection for lighter skin due to higher vitamin D absorption occurred soon after the Out of Africa migration sometime before 40,000 years ago. A number of researchers disagree with this and suggest that the northern latitudes permitted enough synthesis of vitamin D combined with food sources from hunting to keep populations healthy, and only when agriculture was adopted was there a need for lighter skin to maximize the synthesis of vitamin D. The theory suggests that the reduction of game meat, fish, and some plants from the diet resulted in skin turning white many thousands of years after settlement in Europe and Asia.[44][45] This theory is supported by a study into the SLC24A5 gene which found that the allelle associated with light skin in Europe may have originated as recently as 6,000–10,000 years ago[23] which is in line with the earliest evidence of farming.[46]

http://en.wikipedia.org/wiki/Human_skin_color