We Didn't Evolve To Work Out, But It's Still Good For Us

So many New Year's resolutions involve fitness and exercise. But keeping those fitness goals can be difficult. In part, because we didn't evolve to work out. We actually evolved to be, well, lazy.

In Daniel Lieberman's new book, "Exercised: Why Something We never Evolved to Do Is Healthy and Rewarding," he writes about why we should get off the couch and find a way to make exercise fun so we'll do it for our health and longevity. Lieberman is a professor in the Department of Human Evolutionary Biology at Harvard University.