BACKGROUND Whereas early studies of animal evolution focused principally on the
adaptations of different species to their physical environment, more recent studies have …

During the latter half of the last century, evidence of reproductive competition between males
and male selection by females led to the development of a stereotypical view of sex …

Research on sexual selection shows that the evolution of secondary sexual characters in
males and the distribution of sex differences are more complex than was initially suggested …

Darwin developed the theory of sexual selection to account for the evolution of weaponry,
ornamentation and other secondary sexual characters that are commonly more developed …

Although competition between females is one of the cornerstones of the theory of natural
selection, most studies of reproductive competition have focussed principally on mating …

Numerous field researchers have described cooperative hunting in social carnivores, but
experimental evidence of cooperative problem solving typically derives from laboratory …

The associations between social status and endogenous testosterone and corticosterone
have been well-studied across taxa, including rodents. Dominant social status is typically …

The intestinal microbiota plays a major role in host development, metabolism, and health. To
date, few longitudinal studies have investigated the causes and consequences of microbiota …

Sexual selection theory predicts that competitors or potential mates signal their quality or
relatedness to conspecifics. Researchers have focused on visual or auditory modes of …

In male song sparrows (Melospiza melodia), territorial challenges during the breeding
season can rapidly increase circulating levels of testosterone (T). During the non-breeding …