Daniel Lieberman is a professor in the department of human evolutionary biology at Harvard. He says that the notion of "getting exercise" — movement just for movement's sake — is a relatively new phenomenon in human history. His new book is Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding.
In The Story of the Human Body, evolutionary biologist Daniel Lieberman explains how our bodies haven't adapted to modern conditions. The result is "mismatch diseases" -- ailments that occur because our bodies weren't designed for the environments in which we now live.