Why Do Humans Have Big Butts? [Video]

We have big butts and we cannot lie.  LOL!!  Did you ever wonder why humans have big butts?  Well, the Smithsonian appears to have the answer.  Check out this video from the Smithsonian Channel on YouTube.  It's pretty cool and, honestly, I would never have guessed this to be reason why there's so much junk in our trunks.