Brain Size Brain size has increased threefold in the last 3 million years.

Social Intelligence OOne cause for greater brain size: –sSocial intelligence: –the ability to process information about the behavior of others and to react adaptively to their behavior. AAs group size grows, so do complexities PPrimates live in social groups that are more complex than those of other animals

Social Intelligence One ability that would have conferred a great advantage to survival and reproduction is the ability to predict other individuals’ behavior. “The world of higher primates – of monkeys, apes, and humans – is quintessentially a game of social chess, a keen intellectual challenge. The challenge is keener yet than the ancient board game itself, because the pieces not only unpredictably change identity – knights becoming bishops, pawns becoming castles, and so on – they occasionally switch colors to become the enemy…” (Leaky and Lewin 1992)

Theory of Mind: A chimpanzee is as likely to beg for food from a person who is unable to see the gesture as from one who is watching

Clark’s nutcracker

Astatotilapia burtoni