Tibet has the highest average aggrandisement of any other region in the world , at 4900 m above ocean point . There have been modern humans in Tibet for at least 21,000 year , with the ancestors of the current inhabitant move in around 3000 BCE . A late survey led by Rasmus Nielsen of UC Berkeley suggests that Tibetans ’ success at that high altitude may be partially accredit to genes picked up when their ancestor interbred with an out first cousin of humans , the Denisovans . The results of the field were published inNature .
The decreased air pressure at high altitudes pee-pee it arduous to intake oxygen . Many people are able to temporarily cover for the altitude by inspissate the blood , though it can negatively pretend the cardiovascular system after a while . However , occupant of Tibet have been able to deal with the lessen oxygen for good . This ability seem to be due to a variant of a gene that came from the Denisovans , an extinct group of humankind that lived in Siberia and drop dead out around 40,000 year ago .
“ We have very clear grounds that this version of the gene come from Denisovans , ” Nielson said in apress departure . “ This picture very clearly and directly that humans evolved and adapted to newfangled environments by getting their gene from another species . ”
The gene in question is EPAS1 , which is regulated by oxygen . Prior genetical analysis of Denisovan DNA take from a finger’s breadth bone fragment revealed a mutation of this cistron which boosts hemoglobin and red stock cell output only slightly , avoiding the negative cardiovascular effects seen by those with other variants of the cistron that stimulate thicker blood .
“ We incur that part of the EPAS1 gene in Tibetans is almost monovular to the cistron in Denisovans and very different from all other humans , ” Nielsen said . “ We can do a statistical analysis to show that this must have come from Denisovans . There is no other way of explaining the data . ”
This rarified variation was institute in 87 percent of Tibetans who were examine for the study , equate to only 9 percent of Han Chinese , who share a common ancestor with the Tibetans , though they exist at lower elevations . The factor would have been more advantageous on the Tibetan plateau , where oxygen tier are about 40 percent lower than at sea level . It would not have been selected for at lower superlative , which is likely why it is so rare for non - Tibetans .
“ There might be many other specie from which we also get DNA , but we do n’t know because we do n’t have the genome , ” Nielsen said . “ The only reason we can say that this bit of DNA is Denisovan is because of this lucky accident of sequence DNA from a lilliputian bone obtain in a cave in Siberia . We found the Denisovan species at the DNA stage , but how many other species are out there that we have n’t sequenced ? ”
coping double “ Jentsa ” by tsemdo.thar via flickr , used in accord withCC BY - NC - ND 2.0 .
