Many species of birds and other vertebrates form pair bonds and mate with just one other individual for much of their lives. But the unions don’t always work out. Scientists want to know the underlying factors.

Evidence from various sciences reveals that there are diverse ways of being male, female, or both. An anthropologist argues that embracing these truths will help humans flourish.

Across the animal kingdom, dominance isn’t the only way for a male to score. Colluding, sneaking around, or cross-dressing can work, too.

Do fish have personalities?