Evolution

Evolution refers to changes in the heritable traits of successive generations of living populations due to natural or sexual selection. Evolution can lead [Page 790]to entirely new species or alter the representation of traits within a species. A basic assumption of evolutionary theory is that both physical and psychological traits will be selected over time if they enhance an individual’s ability to survive and successfully reproduce. Natural selection refers to the selection of traits that enhance an individual’s chances of surviving to reproductive age; sexual selection refers to traits that enhance one’s attractiveness to mates and therefore increase reproductive success. Sometimes natural selection and sexual selection are at odds, as in the case of the peacock’s tail. Elaborate plumage is metabolically costly and places a ...