[Innate immunity and human diseases: from archaic introgression to natural selection]

Throughout evolution, humans have had to face strong variation in environmental conditions, with pathogens being among the strongest threats that our species has encountered. The use of population genetic approaches provides novel insights into how natural selection imposed by pathogen pressures, in its different forms and intensities, has shaped the patterns of diversity of the human genome at the population level. These studies help to distinguish genes playing essential, non-redundant functions in host defence from genes variation in which has conferred selective advantages to specific human populations and/or has been acquired through admixture with archaic hominins, such as Neandertals. However, with the improvements in hygiene and the advent of antibiotics and vaccination, pressures imposed by pathogens have recently been relaxed. Accumulating evidence suggests that alleles having conferred an advantage against infection in the past may nowadays be associated with increased risk to develop immune-related disorders, such as autoimmunity and inflammation.