One of the neatest new sciences that has arisen in the last decade is Paleogenetics. DNA degrades quite rapidly so recovering useable sequences beyond a few thousand years in age has been quite problematic. New advances in DNA sequencing however have now allowed the recovery of DNA snippets going back hundreds of thousands of years. The current record is the recovered DNA from a Pleistocene horse approx. 700,000 years old.
This has huge ramifications for our understanding of human origins history since we can now sequence the DNA of our extinct sister species. Last year a major milestone was accomplished with the sequencing of a complete Neanderthal genome. Research published last week now shows non-African humans got some critical genes, particularly those involved in skin and hair development, from interbreeding with Neanderthals.
For reference, humans and Neanderthals last shared a common ancestor around 600,000 years ago. The interbreeding is though to have taken place between 45,000 and 60,000 years ago. Neanderthals went extinct about 30,000 years ago.
Next on the list to be sequenced and analyzed are Homo floresiensis who lived as recently as 12,000 years ago in Indonesia and the mysterious Denisonans who lived about 40,000 years ago in Siberia. The results should give new insight into the tangled bush of human evolution.
Interesting stuff!
This has huge ramifications for our understanding of human origins history since we can now sequence the DNA of our extinct sister species. Last year a major milestone was accomplished with the sequencing of a complete Neanderthal genome. Research published last week now shows non-African humans got some critical genes, particularly those involved in skin and hair development, from interbreeding with Neanderthals.
The genomic landscape of Neanderthal ancestry in present-day humans
Sankararaman et al
Nature, doi:10.1038/nature12961 29 January 2014
Abstract: Genomic studies have shown that Neanderthals interbred with modern humans, and that non-Africans today are the products of this mixture. The antiquity of Neanderthal gene flow into modern humans means that genomic regions that derive from Neanderthals in any one human today are usually less than a hundred kilobases in size. However, Neanderthal haplotypes are also distinctive enough that several studies have been able to detect Neanderthal ancestry at specific loci. We systematically infer Neanderthal haplotypes in the genomes of 1,004 present-day humans. Regions that harbour a high frequency of Neanderthal alleles are enriched for genes affecting keratin filaments, suggesting that Neanderthal alleles may have helped modern humans to adapt to non-African environments. We identify multiple Neanderthal-derived alleles that confer risk for disease, suggesting that Neanderthal alleles continue to shape human biology. An unexpected finding is that regions with reduced Neanderthal ancestry are enriched in genes, implying selection to remove genetic material derived from Neanderthals. Genes that are more highly expressed in testes than in any other tissue are especially reduced in Neanderthal ancestry, and there is an approximately fivefold reduction of Neanderthal ancestry on the X chromosome, which is known from studies of diverse species to be especially dense in male hybrid sterility genes. These results suggest that part of the explanation for genomic regions of reduced Neanderthal ancestry is Neanderthal alleles that caused decreased fertility in males when moved to a modern human genetic background.
link
Sankararaman et al
Nature, doi:10.1038/nature12961 29 January 2014
Abstract: Genomic studies have shown that Neanderthals interbred with modern humans, and that non-Africans today are the products of this mixture. The antiquity of Neanderthal gene flow into modern humans means that genomic regions that derive from Neanderthals in any one human today are usually less than a hundred kilobases in size. However, Neanderthal haplotypes are also distinctive enough that several studies have been able to detect Neanderthal ancestry at specific loci. We systematically infer Neanderthal haplotypes in the genomes of 1,004 present-day humans. Regions that harbour a high frequency of Neanderthal alleles are enriched for genes affecting keratin filaments, suggesting that Neanderthal alleles may have helped modern humans to adapt to non-African environments. We identify multiple Neanderthal-derived alleles that confer risk for disease, suggesting that Neanderthal alleles continue to shape human biology. An unexpected finding is that regions with reduced Neanderthal ancestry are enriched in genes, implying selection to remove genetic material derived from Neanderthals. Genes that are more highly expressed in testes than in any other tissue are especially reduced in Neanderthal ancestry, and there is an approximately fivefold reduction of Neanderthal ancestry on the X chromosome, which is known from studies of diverse species to be especially dense in male hybrid sterility genes. These results suggest that part of the explanation for genomic regions of reduced Neanderthal ancestry is Neanderthal alleles that caused decreased fertility in males when moved to a modern human genetic background.
link
Next on the list to be sequenced and analyzed are Homo floresiensis who lived as recently as 12,000 years ago in Indonesia and the mysterious Denisonans who lived about 40,000 years ago in Siberia. The results should give new insight into the tangled bush of human evolution.
Interesting stuff!
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