Yann points to a new paper, new paper, Cystic Fibrosis: Cystic fibrosis and lactase persistence: a possible correlation (Open Access):
The simplest and most economical explanation is that a dairy-milk diet became established in a single area and remained restricted to that area for a period of time sufficient to allow the T and the F508del alleles to attain high values. Then, in a second phase, the population of that area exported to the rest of Europe its dairy-milk diet culture together with the two adaptive genes, that is, the adaptogen and the two genetic adaptations to it. These two alleles would have then been amplified in the recipient populations because of their adaptive value owing to the co-imported dairy milk diet.
The two models to explain the high frequency of the deleterious CF allele in Europeans are that it has a high mutational bias and heterozygote advantage for those with one copy. Most people would say that the latter is much more likely. The authors here propose that the derived CF allele was a really kludgey adaptive response to a new cultural regime predicated on raw milk consumption. Paul has some Ireland related thoughts (as usual!). I’ve never seen the term “adaptopgen” before. In any case, I need to think on this case more…but I do think that if human evolution has been on hyperdrive the last 10,000 years we should be many kludgey genetic responses laying around the adaptive landscape…..
Related: Lactase persistence posts. Another from Yann, Is there a fitness advantage to being a CFTR carrier?