Why Do We Lie?

Everyone lies. Even you and even me. We lie about small things and we lie about big things. We lie to help ourselves and we lie to protect others. Powerful people lie, all the way down to little kids telling fibs. Why do we do this if we're supposed to be the most socially developed species on Earth? Why can't we tell the truth? Are we doomed to lie? Well, maybe. Here's why.