evolutionary arms race between the sexes sexual conflict

Because only a single gamete of each type is required to produce an offspring, there will be an excess of male gametes that will not fertilize any eggs. Sex roles are defined by differences in gametes: females produce relatively few, highly nutritious (usually non-motile) gametes, whereas males produce comparatively abundant, smaller, motile gametes. In the 40 years since, there has been much progress in our understanding of how sexual selection operates. However, the idea of female mate choice was received with ridicule, and was not seriously reconsidered until nearly 80 years later (Cronin 1991).

The idea of cumbersome traits evolving to aid males in competition during aggressive encounters was readily accepted by scientists shortly after Darwin's publication. He recognized two mechanisms of sexual selection: intrasexual selection, or competition between members of the same sex (usually males) for access to mates, and intersexual selection, where members of one sex (usually females) choose members of the opposite sex. He suggested that such traits might evolve if they are sexually selected, that is if they increase the individual's reproductive success, even at the expense of their survival (Darwin 1871).ĭarwin noted that sexual selection depends on the struggle between males to access females. However he noted that there were many examples of elaborate, and apparently non-adaptive, sexual traits that would clearly not aid in the survival of their bearers. The primary mechanism he proposed to explain this fact was natural selection: that is, that organisms better adapted to their environment would benefit from higher rates of survival than those less well equipped to do so. Charles Darwin proposed that all living species were derived from common ancestors.

Evolutionary arms race between the sexes sexual conflict