Abstract
In this lecture, we discussed the evidence suggesting that adaptation most often takes the form of polygenic selection, i.e. acting on a phenotype whose variation arises from numerous alleles each with a small effect on phenotype and fitness. We then discussed approaches that are beginning to be developed to identify the fingerprints of these polygenic adaptations, and cautions that are important to remember when interpreting their results. The lecture ended by discussing the very different conception of adaptation suggested by these recent studies : a pattern in which new selection pressures act simultaneously on many correlated phenotypes, and adaptation occurs (at least in the first instance) through subtle changes in allele frequencies at many loci distributed throughout the genome.
