Sexual conflict occurs when males and females differ in their reproductive interests, is an inevitable consequence of sexual reproduction, and is enhanced by promiscuity when males and females have several partners. The study of sexual conflict and the impact it has on the evolution of male and female traits has become a rapidly developing field, in part because of disagreement over its importance. Sexual conflict can generate rapid anatagonistic coevolution between the sexes. This occurs when one sex, usually males, attempt to manipulate reproduction in the other sex, usually females, to the manipulators' benefit. If this manipulation is detrimental to females, females may go on the counteroffensive and selection would favor traits that help them resist this manipulation. Males may then be counterselected and evolve traits that, once again, allow them to manipulate females, while females again evolve measures to defend against manipulation, potentially setting off an endless evolutionary cycle of adaptation and counter adaptation. As with many exciting areas of biology, however, controversy exists over the details and generality of the scenario outlined. Sexual conflict is not in debate; what is being debated is whether this generates escalating arms races between the sexes, and if so, when, how often, and what is the effect of this on the sexes.
This special issue of The American Naturalist contains eight research papers from experts in this field that address these questions and attempt to provide some insights into the battle between the sexes.