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According to a professor of immunology and microbiology at Stanford University, humans were able to survive, spread and expand their populations once they left Africa because of immunities to disease they acquired from Neanderthals and Denisovans, who had lived in Europe and Asia already for hundreds of thousands of years.
A review of the new research appears in the online science magazine Discover under the date of June 20, 2011. The professor's name is Peter Parham.
Crux of the matter, according to Royal Society report
- Parham began by taking a close look at a family of genes called human leukocyte antigens (HLAs), which play a central role in our body’s immune responses. We are able to react to a wide array of diseases because our HLA genes are highly variable, each containing dozens of alleles (forms of genes).
- Our ancestors in Africa, however, would have had a small number of HLA alleles because they likely traveled in small bands and had little contact with other groups. Moreover, their HLAs would have only protected them against African diseases.
- When Parham compared the HLAs of modern humans with those of Neanderthals and Denisovans, he noticed some overlaps. In particular, he found that HLA-C*0702, an allele common in Europeans and Asians but nonexistent in Africans, was also present in the Neanderthal genome. Similarly, HLA-A*11, which is found in modern Asians but not in Africans, popped up in Denisovan DNA.
- Overall, about 50 percent of HLA Class I alleles in Europeans seemed to come from Neanderthals, 70 to 80 percent in East Asians from Denisovans, and 90 to 95 percent in Papuans from Denisovans, Parham said at a recent Royal Society meeting.
DNA Consultants introduced its Neanderthal Index, a measure of affinity with archaic populations of Europe and the Middle East, one year ago this month.
Dr. Donald Yates says he is planning a visit to Vindija cave near Varazdin in Croatia this month to see firsthand the world's most important site for the discovery of Neanderthal bones and lifeways, dating to about 30,000 years ago.
Human history changed drastically with the 1974 Neanderthal discoveries at Vindija Cave. Photo Tomislav Kranjcic.
Comments
When we finally do have a thorough understanding of the human story, I believe we will find a very complex evolutionary history of many different groups who have a common ancestor as far back as 1.5 to 2 million years ago.