Analysis of the extent of natural selection in the human genome has proved crucial in identifying the genes responsible for the morphological and physiological diversity of populations, and has led to a better understanding of the nature of adaptive phenotypes. The adaptive history of our species can be divided into three major phases : (i) the differentiation of the Homo genus from its common ancestor with the chimpanzee, then its evolution until the appearance of our species (- 6 000 000 to - 150 000 years), (ii) the differentiation of human populations (- 60 000 to - 10 000 years) and (iii) the technological expansions associated with the appearance of agriculture (- 10 000 years to the present day). The aim of this lecture is to present the different forms of natural selection and the statistical tests used to detect them. Knowledge of the biological functions involved in the adaptation of populations to various environmental factors - climatic, nutritional, pathogenic - has greatly increased over the last ten years.
We will also discuss how a population's demographic history influences the effectiveness of selection in eliminating deleterious mutations, as well as the major biological functions that have been involved in the adaptation of humans to their environment. Iconic cases of genetic adaptation include genes involved in metabolism and adaptation to nutritional resources, genes linked to variations in skin pigmentation and adaptation to different types of habitat, and genes involved in resistance to infectious diseases. Finally, we will discuss the evolutionary trade-offs between past selection and adaptation, and current diseases, at the origin of the concept of " maladaptation ". A growing number of studies show that certain genetic variants that conferred better adaptation in the past are currently responsible for certain diseases, such as autoimmune and inflammatory diseases and diabetes.
