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Human genetic diversity 100,000 years ago
Human genetic diversity 100,000 years ago
seminar from group Science, Reason and Faith.
Daniel Turbón. Pamplona, May 29, 2013.
Daniel Turbón is Full Professor of the Anthropology Unit of the University of Barcelona. Some of his lines of research are: Bipedalism, encephalization, dental evolution and Neanderthals (Paleoanthropology); Mitochondrial DNA, Y chromosome, RFLPs, STRs and Paleogenetics (Molecular Anthropology).
summary:
The astonishing technological breakthrough in Genetics Molecular has provided, in the last few months, data scientific breakthroughs that were unthinkable only three years ago.
The programs of study of mtDNA lineages - that of the mothers who left offspring - in current human populations, had allowed a map of the current diversity Genetics and of the probable migratory routes, which arose mainly from Africa, to be constructed. New programs of study, using 3.2 million distinct single-locus genetic polymorphisms (SNPs), have managed to fill in the genetic map of present-day humans; and to calculate the oldest detected separation, estimated at over 100,000 since the present, between present-day Khoe-San Africans (formerly called Bushmen) and Melano-Africans speaking Bantu-rooted languages.
On the other hand, from programs of study palaeogenetics of Neanderthals we know that Neanderthals share more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neanderthals to non-African ancestors occurred before the divergence of present-day Eurasian groups from each other. Europeans have 2.5% of our genome inherited from Neanderthals.
The biggest surprise has been finding of the Denisovans, a new human group in the scientific panorama of human palaeogenetics. These are two skeletal remains found in Denisova, a cave in southern Siberia, near the Himalayas, in which, due to the low temperatures, the DNA has been well preserved. They are dated to 50,000 years ago. They were neither Neanderthals nor modern humans, although they coexisted with both, and even mated with Homo sapiens. It is very strange that, for being between 30,000 and 50,000 years old, the genome of the Denisovans is so well preserved. In Neanderthals of this age, it is common that only 1% of the genome we analyse is original and that the remaining 99% corresponds to microbes that have contaminated the sample, which makes it difficult and limits the work. In the case of Denisova, 70% of the genome is original. For those who study ancient genomes, this is a gem.
The finding that 5% of the genome of Melanesian populations is inherited from the Denisovans indicates that, at some point, they had to be somewhere where they encountered the ancestors of the Melanesians, and presumably this did not occur in southern Siberia. Denisovans are thought to have spread across Asia in a similar way to how Neanderthals spread across Europe and, like Neanderthals, became extinct after the arrival of modern humans.
Introgressions of Neanderthal and Denisovan genomes have been detected in our genome. Specifically, the highly polymorphic human leukocyte antigen (HLA) system class I - under intense natural selection pressure - sample how modern humans acquired the HLA-B *73 variant in West Asia through admixture with Denisovans. Homo sapiens (ancestors of modern humans), Denisovans and Neanderthals must have diverged about 400,000 years ago. Neanderthals migrated from Africa to Europe and western Asia; Denisovans left Africa for eastern Asia. The ancestors of modern humans left Africa only 65,000 years ago.