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Tibetans inherited their high altitude tolerance from Denisovans

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posted on Jul, 2 2014 @ 03:59 PM
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A new study shows that Tibetans inherited their ability to live at high altitudes from Denisovans.
From Dienekes Anthropology blog.

As modern humans migrated out of Africa, they encountered many new environmental conditions, including greater temperature extremes, different pathogens and higher altitudes. These diverse environments are likely to have acted as agents of natural selection and to have led to local adaptations. One of the most celebrated examples in humans is the adaptation of Tibetans to the hypoxic environment of the high-altitude Tibetan plateau1, 2, 3. A hypoxia pathway gene, EPAS1, was previously identified as having the most extreme signature of positive selection in Tibetans4, 5, 6, 7, 8, 9, 10, and was shown to be associated with differences in haemoglobin concentration at high altitude. Re-sequencing the region around EPAS1 in 40 Tibetan and 40 Han individuals, we find that this gene has a highly unusual haplotype structure that can only be convincingly explained by introgression of DNA from Denisovan or Denisovan-related individuals into humans. Scanning a larger set of worldwide populations, we find that the selected haplotype is only found in Denisovans and in Tibetans, and at very low frequency among Han Chinese. Furthermore, the length of the haplotype, and the fact that it is not found in any other populations, makes it unlikely that the haplotype sharing between Tibetans and Denisovans was caused by incomplete ancestral lineage sorting rather than introgression. Our findings illustrate that admixture with other hominin species has provided genetic variation that helped humans to adapt to new environments

dienekes.blogspot.com...


This finding has implications for the dispersal of AMH in east Asia and the Americas.
If the only populations that have it are Tibetans and Han Chinese, then it casts doubt on the accepted origins of native Americans.
If it's not found in native Americans then they either separated from before the admixture event or the admixter event was very recent,




posted on Jul, 2 2014 @ 05:04 PM
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a reply to: punkinworks10

"A comparison of the genomes of 50 Tibetans and 40 Han Chinese shows that ethnic Tibetans split off from the Han less than 3,000 years ago"
newscenter.berkeley.edu...

Seems to suggest that Denisovans may have existed in tibetan mountains until very recently.

edit on 2 7 2014 by glend because: (no reason given)



posted on Jul, 2 2014 @ 05:29 PM
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Interesting find for science, hopefully another piece in the giant jigsaw of human evolution and migration.

Some more about it here.

www.newscientist.com...


Studies have linked their altitude adaptation to several genes including EPAS1, part of the system that helps the body react to low levels of oxygen. The Tibetan version of EPAS1 came from ancestors of the Nepalese Sherpa people and spread rapidly through the population 30,000 years ago, suggesting it is beneficial.




Now Rasmus Nielsen of the University of California, Berkeley, and his colleagues have compared Tibetan genomes with populations from around the world. No other modern group carries the Tibetan variant of EPAS1.

But they found the same gene variant in the genome of a Denisovan, an extinct species of human known only from a cave in the Altai mountains in east-central Asia.




"The study shows that one of the most spectacular cases of [genetic] adaptation in humans has its roots in Denisovans," says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "It is very satisfying to see that gene flow from Denisovans, an extinct group of archaic humans that we discovered only four years ago, is now found to have had important consequences for people living today."

The Tibetan EPAS1 probably got there by interbreeding, but more evidence is needed to confirm which archaic humans were the source, says David Reich of Harvard Medical School in Boston. "There is no proof in the paper that the origin of the [DNA] is Denisovan." He says it could just as easily have come from Neanderthals, whose EPAS1 looks similar to the Tibetans'. That might make more sense as they were common on mainland Asia, whereas the Denisovan heartland seems to have been in South-East Asia.



posted on Jul, 2 2014 @ 05:37 PM
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a reply to: glend
Thanks for posting that, it seems to contradict other evidence,
but there is evidence for archaic persistence in Asia.
Hmmmm



posted on Jul, 2 2014 @ 11:59 PM
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a reply to: glend

So... Yetisovans?



posted on Jul, 3 2014 @ 04:41 AM
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I disagree. I think they inherited it from their ancestors.



posted on Jul, 3 2014 @ 04:56 AM
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a reply to: punkinworks10

Hmm. That is interesting. Some one above mentioned the Native Americans and their origins. So what about the Peruvians or any South American Native that lived in higher altitudes? They have the same gene or a variant that afforded the same characteristics?

Kratos



posted on Jul, 3 2014 @ 09:08 AM
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a reply to: Kratos40

There's a bit of a difference. Cuzco is at 11,000', but the average elevation of the Tibetan plateau is 15,000'.



posted on Jul, 3 2014 @ 10:49 AM
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a reply to: Kratos40
If I've read the paper correctly, the gene is not found in any other modern population.
Whether or not the Andean people are represented in the worldwide samples, but he fact that the Han have it and it is not found in the new world suggests that native Americans split off before this admixture event.
The Andean people have adapted to the high altitude via very definitive physiological adaptations, like larger lungs and slower heartbeats.



posted on Jul, 3 2014 @ 10:58 AM
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a reply to: punkinworks10

It doesn't imply isolated genes exclusive to Denisovan and / or in a particular geographical location.

As has been suggested, the origin of the gene could be from Neanderthal, the report doesn't offer any proof of it being Denisovan, just that there is a commonality.

If it is from Neanderthal, it could mean many variations on interbreeding, migrations etc. and doesn't necessarily imply an admixture event, it could be simple inheritance, given that the picture of human evolution is extremely patchy guesswork so far.

www.newscientist.com...-_ldWSp


The Tibetan EPAS1 probably got there by interbreeding, but more evidence is needed to confirm which archaic humans were the source, says David Reich of Harvard Medical School in Boston. "There is no proof in the paper that the origin of the [DNA] is Denisovan." He says it could just as easily have come from Neanderthals, whose EPAS1 looks similar to the Tibetans'. That might make more sense as they were common on mainland Asia, whereas the Denisovan heartland seems to have been in South-East Asia.




Denisovans are one of at least two extinct hominin species that humans mated with, the other being Neanderthals. Many of us carry bits of DNA from these other species.

The new finding adds to the evidence that this interbreeding had significant effects on our evolution. For instance, Neanderthal DNA is particularly common in genes relating to keratin, a protein found in hair, skin and nails. Another Neanderthal gene found in modern Eurasians may increase the risk of type 2 diabetes.

Humans interbred with Neanderthals soon after moving out of Africa, when we were ill-equipped to cope with Eurasian diseases. However Neanderthals had been hanging out in Europe and Asia for much longer, so their immune systems had adapted. There is evidence that humans snagged some of the Neanderthals' immunity genes when the two mated, perhaps helping us to spread across the planet.

edit on 3-7-2014 by theabsolutetruth because: (no reason given)



posted on Jul, 3 2014 @ 10:19 PM
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Awesome stuff! Thanks for posting.

I really believe we are just starting to scratch the surface on how complex and convoluted our history is.



posted on Jul, 4 2014 @ 11:32 PM
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originally posted by: punkinworks10
a reply to: Kratos40
If I've read the paper correctly, the gene is not found in any other modern population.
Whether or not the Andean people are represented in the worldwide samples, but he fact that the Han have it and it is not found in the new world suggests that native Americans split off before this admixture event.
The Andean people have adapted to the high altitude via very definitive physiological adaptations, like larger lungs and slower heartbeats.


Not necessarily. It said that the Han have it in very small frequencies, and founding populations can themselves be miniscule.



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