There are many theories about how man is separate from the animals. The most recent one is that fire was the difference—not in a Ringo Starr fights the other tribe way, but in a new way: cooked food. Cooking let man absorb more calories from the same amount of food, giving him free time to think and energy to develop a new organ. It follows similar theories about using tools and opposable thumbs, both of which fail the “but don’t other animals do that too?” test.
For the best account I’ve ever read on human evolution, read Bruce Chatwin’s The Songlines. It’s a great piece of writing, and it addresses evolution obliquely, while studying nomads.
Bonus evolutionary fact: some turtles breathe throught their butts.
