In search of the molecular basis of adaptations

Thanks to these approaches, dozens of very interesting examples have been identified, most of which relate to immune response, skin pigmentation and diet. But in the end, these cases represent relatively few examples, and almost none relate to the phenotypes that arguably most distinguish humans from other primates, namely bipedalism or our cognitive and linguistic abilities. Yet these adaptations too must have a genetic basis located somewhere in the genome. So where are they hiding ? The most likely hypothesis is that these adaptations are not detectable because they do not conform to the models we rely on to detect adaptations, i.e. they do not arise from a small number of alleles with large effects on fitness, but rather from a large number of alleles with small effects on fitness. However, if the selective advantage associated with an allele is small, this allele has no distorting effect on the diversity of linked sites, or at least not enough to be detected by existing methods.