We are the biggest sissies in the jungle. Every other animal is stronger than we are — they have fangs, they have claws, they have nimbleness, they have speed. We think Usain Bolt is fast — Usain Bolt can get his ass kicked by a squirrel.

This quote is from journalist and runner Christopher McDougall's 2010 TED Talk in which he explores the mysteries that compel humans to run. In this quote, McDougall is talking about how surprising it is that humans were able to hunt and kill animals two million years before we invented weapons. Says McDougall, we are not strong or fast compared to other animals and we don't have any natural weapons like fangs or claws. So how did we do it? Well, humans evolved as a "hunting pack animal" that could run very long distances, McDougall explains later in the Talk. Watch the full TED Talk here: Christopher McDougall - Are We Born to Run?

“Are We Born to Run?” TEDxPennQuarter. Jul. 2010. Conference Presentation.