Opposite-sex friendships can have non-romantic benefits. And not just for people, but for our primate cousins, too. A 35-year study of 542 baboons finds that males that have close female friends have higher rates of survival. Previous studies have assumed that males befriend females to protect their offspring, or to boost their chances of mating later on. But the new study points to an additional benefit: female friends may help them live a longer life.