Sex is an inherently fascinating aspect of life. As researchers learn more and more about it, surprises regularly emerge.

Sexual selection doesn’t end when females choose a mate. Females and males of many animal species employ an array of tactics to stack the deck in their reproductive favor.

Scientists propose a new model for how homosexuality develops, but observers say it will be difficult to test.

Traits that help one sex but hurt the other are not sufficient for maintaining genetic variation.