The fifth installment of The Year in Evolutionary Biology series includes reviews on: gene loss, thermogenesis, and the origin of birds; sexual selection in the light of molecular evolutionary genetics; the nine-spined stickleback (Pungitius pungitius), an emerging model in evolutionary biology; the evolutionary consequences of interspecific aggression; specific-gene studies of evolution in an age of genome-wide surveying; and biodiversity and evolutionary history: expanding the PD phylogenetic diversity assessment framework.