Sexual Selection Comes at a Cost

Abstract

Males evolved extravagant plumage, towering antlers, and frenetic mating displays, Darwin proposed, because that’s what females like. Why such preferences evolved is still controversial—one view holds that flashy males beget sexy sons with more chance of attracting mates—but it’s generally thought that sexual selection provides some type of indirect genetic benefit leading to higher intrinsic fitness of the offspring. Selection on secondary sexual characteristics often results in sexually dimorphic traits being tailored toward the specific reproductive needs of each sex. Sexual dimorphism typically arises because selection operates in different directions on each gender—selecting for large males and compact females, for example—promoting sex-specific gene expression.