The biggest brains on the block

Relative to their bodies, primates (the group that includes monkeys, apes and humans) have brains far larger than most mammals. Within primates, human brains take the cake—they’re the largest of the group, and impressively wrinkly.

In primates, brain size seems to be related to group size. For their body size, baboons have larger brains even than our close relatives, the chimpanzees. Chimps spend most of their time in the jungle, but baboons usually live in the open savannah, just like the ancestors of humans. Baboons (and early humans) probably began to live in larger groups to cope with the increased threats and challenges of life outside the protection of the forest. Baboon troops may be as large as two hundred individuals, but humans went on to form towns and cities with thousands or millions of people. To live in such large and complex groups, humans developed new abilities to cooperate and communicate, and brain size may have increase proportionately.

As you can see, a human’s brain is about three times the size of a chimp’s brain. And that makes sense—scientists think that a chimp can keep close track of about fifty individuals, while people can track about three times that number individuals.

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