Abstract

Evolutionary analysis at the genome level may detect the action of natural selection in genes and groups of genes, which are linked to phenotypes. For that, it is necessary to understand the molecular pathways of gene products. This analysis targets the molecular basis of complex adaptations. By comparing genomic data between species, or different populations of the same species, we can distinguish between selection at large or small scales, allowing the detection of natural selection in the form of positive selection and purifying selection. One of the interesting evolutionary challenges is to discover the genetic bases of adaptive phenotypes, but the greatest challenges are complex adaptations. In humans, selection has not acted equally throughout evolutionary history: genes with higher numbers of interactions are more likely to have been targeted by recent positive selection during recent human evolution. Our results indicate that the relationship between centrality and the impact of adaptive evolution depends to a high degree on the evolutionary time-scale. Most likely, network adaptation occurs through intraspecific adaptive leaps affecting key network genes, followed by the fine-tuning of adaptations in less important network regions. These results reshape the profile of traditional evolutionary landscapes.