1. It really is a popularity contest: Rhesus macaques that have large, strong social networks tend to belong to families of similarly amiable macaques. Not only that, but playing nice with others tends to yield greater reproductive success. A corollary shows that the most aggressive monkeys have greater reproductive success—but so do the most passive monkeys. The loser? The monkey in the middle.
2. Yawning is contagious: Jingzhi Tan, an evolutionary anthropology Ph.D. student, has found that showing bonobos a video of a yawning bonobo from an unknown social group will prompt the same reaction. The xenophilic bonobo is one of the two closest relatives of Homo sapiens and is a bellwether of our more sociable tendencies. (Our other closest relative is the notoriously xenophobic and aggressive chimpanzee.)
3. Coalitions— they’re not just for government: Speaking of chimpanzees, males that successfully enter strategic alliances are more likely to mate and rise in rank. Central positions in a coalition are most beneficial. Chimps use these coalitions to direct aggression at one or more targets, further asserting dominance.
4. ’Tis almost as good to give as to receive: When given the opportunity to give or receive a squirt of juice, rhesus macaques usually keep it for themselves. But they choose to give away the juice if the choice is that or nothing for themselves. Turns out, the same region of the brain is active when this animal receives a reward or simply watches another receive it instead.
5. Hitting the share button: Though plenty are quick to dismiss the “sharing” zeitgeist as an expression of narcissism, our ancestors might beg to differ. Bonobos will share their food with or even give up their own meal to total strangers, as long as the stranger offers social interaction. (Chimps, on the other hand, possess no compunction.)