February 21, 2014

Evolution equally efficient in removing deleterious variants in Europeans and West Africans

...but apparently not in Denisovans who accumulated deleterious mutations at a higher rate than modern humans. This may account for the fact that we haven't been able to find many Denisovans in the archaeological record as they may simply be a population that "failed" -- although apparently some distant relatives of the single Denisovan genome did admix into Australasians.

arXiv:1402.4896 [q-bio.PE]

No evidence that natural selection has been less effective at removing deleterious mutations in Europeans than in West Africans

Ron Do et al.

Non-African populations have experienced major bottlenecks in the time since their split from West Africans, which has led to the hypothesis that natural selection to remove weakly deleterious mutations may have been less effective in non-Africans. To directly test this hypothesis, we measure the per-genome accumulation of deleterious mutations across diverse humans. We fail to detect any significant differences, but find that archaic Denisovans accumulated non-synonymous mutations at a higher rate than modern humans, consistent with the longer separation time of modern and archaic humans. We also revisit the empirical patterns that have been interpreted as evidence for less effective removal of deleterious mutations in non-Africans than in West Africans, and show they are not driven by differences in selection after population separation, but by neutral evolution.



Unknown said...

Couldn't the higher rate of non-synonymous mutations in the Denisovan genome be from their admixture with the unidentified archaic species?

Tom Bridgeland said...

We have what, two denisovan samples? Or is it still only one? From an extremely inbred family. I don't think we can say that the denisovans as a species had a higher or lower level of retained deleterious mutations.

Raimo Kangasniemi said...

The comment above made me think about this: Based on the recent evidence that modern human & Neanderthal hybrids suffered from reduced fertility and male humans might have been sterile, two questions that I think should be asked are that what relationship the fact that late Denisovans were hybrids (having mixed with both their Neanderthal cousins and that unknown species) had with their higher rate of mutations and observed decrease in population? So, could the decrease in population point towards these hybridization events?