Human Evolution: Our Brains and Behavior

Dunbar (How Many Friends Does One Person Need?), a professor of evolutionary psychology at Oxford, ponders what it is “to be human (as opposed to being an ape)” and asks, “How did we come to be that way?” He suggests the answer began with a cooling climate 1.8 million to 2.5 million years ago, which led to fewer lush forests and more harsh grasslands. Because human ancestors were bipedal, they left trees for dangerous open spaces more easily than other primates. This left them vulnerable to predators, so social bonding became crucial for mutual protection. But as groups grew in size to improve safety, bonding became more complex and difficult to sustain. To adapt, did hominids begin evolving to replace grooming—most primates’ time-consuming bonding mechanism—with laughter, singing, and speech, simply because such bonding methods took less time? Did such increasingly sophisticated communication methods lead to bigger brains, spawning more sophisticated technology (cooking and hunting tools) and thus even more sophisticated communication methods (culture and religion), and in turn even larger brains? In light of such questions, Dunbar devised mathematical “time-budget” models to support his “social brain hypothesis.” Dunbar’s idea has gained in popularity among scholars, and his narrative is so mesmerizing it may attract many general readers, too. [em](Nov.) [/em]