Conversation with Lluis Quintana-Murci. Part 2

So we can go from the origin of our species to very recent times too? Or we may just see very old events in our genome? The more recent we go in time, the more difficult it is to detect adaptation. Because of the power of the analysis we are using and also because biological adaptation takes a lot of time to be visible in our genomes. But there’s increasing evidence to suggest with new methods and thousands of genome sequences from different individuals that we can even detect biological adaptation in the last 2000 years. You are talking on the history of humans detected by the genome, but when the different human groups may encounter, can you also detect that?

Can you detect, let’s say, where the migrations, the interbreeding, introgression, this kind of things? This is a very important question, because when we have to adapt to a given environment there are several possibilities. Either we wait until a mutation will appear and this mutation will allow us to adapt to a new climatic or nutritional environment, or we just borrow this adaptive mutation – this advantageous mutation – through admixture with another population that is already adapted to the environment.

In the context of Africa, for example, we have recently shown that farmers, during their travel all across Sub-Saharan Africa —what’s called the Bantu expansion – they admixed with local populations - pygmies in the west, East African pastoralists in the east - from which they borrow adaptive mutations related to immune responses or to lactose tolerance. And in these cases in which you see this admixture of human groups, can you trace clearly the different origin of one group and the other? Well, in terms of geographic origins, yes. But still I think there is a lot to be done in term of many continents - including Africa - are absolutely under sampled.

So we can have some approximations of where and when these populations split from each other. In the case you have been saying now, on the Bantu expansion, may we mirror European descents that this expansion - a linguistic expansion at the very end - has had a very strong genetic impact? Yeah, I mean, in Europe there was like 10,000 years ago there was this movements from the Middle East towards Western Europe that probably brought – actually brought – the Indo-European languages to which extent Indo-Europeans getting into Europe admixed with local populations of hunter-gatherers from which they borrow even adaptive variants. This still remains to be investigated in detail in the era of the complete genomes.