Why are monkeys' faces all so bizarrely different?

New World Monkeys are the strangest-looking primates on Earth — and they all look nothing like each other, from the bald-headed, demon-like Uakari to the lion-maned golden marmoset to the massively mustachioed emperor tamarin up top. What's behind this insane variety? » 1/11/12 4:49pm 1/11/12 4:49pm