When we think of social animals-that is, animals who live together in well-defined groups, and form enduring relationships- we usually think of the great apes, of wolves and other members of the dog family, and, or course, of humans. Science considers bears to be solitary animals. But while bears don't live in established groups or obey rigid hierarchies as chimps and wolves do, they have amazingly complex social relationships.

Bears, it turns out, are a lot like humans. They form alliances with strangers, they make calculations about relative costs and benefits, they lay down rules and punish those who break them. They trade based on a clear system of reciprocity. They communicate using equal parts emotion, intention, and dependence on context-a combination that is essential for communication between strangers and in fact forms the basis for language.

Aggression in bears can be and often is a stepping stone to friendship. Friendship and alliances frequently develop by repeated interactions, with initial aggression that lessens over time.

Highly social animals like dogs and chimpanzees who live in small groups evolved to be more tolerant in subordinate roles. The fact that young bears behave more like young humans suggests common influences upon their social behaviour.