From The New York Times:
For the past two decades, Kay E. Holekamp has been chronicling the lives of spotted hyenas on the savannas of southern Kenya. She has watched cubs emerge from their dens and take their place in the hyena hierarchy; she has seen alliances form and collapse. She has observed clan wars, in which dozens of hyenas have joined together to defend their hunting grounds against invaders. Throughout her career, Dr. Holekamp has remained vigilant against anthropocentrism. She does not think of the hyenas as long-eared people running around on all fours. But the lives of spotted hyenas, she has concluded, share some profound similarities with our own. In both species, a complex social world has driven the evolution of a big, complex brain.
Scientists have long puzzled over the enormous size of the human brain. It is seven times larger than one would predict for an average mammal of our size. Many of our extra neurons are in a region called the frontal cortex, where much of the most sophisticated thought takes place. To understand how we ended up with such a strange organ, many scientists have turned to our fellow primates. They also have large brains, although not as large as our own. It turns out that primates with a big frontal cortex tend to live in large groups.