Penn: We don't really know jack sh*t about people, but other primates sure aren't built for monogamy. Watch some chimps next time you're on safari or hang out at the zoo for a few days straight. Before they throw you out for some weird, obsessive monkey fascination, you'll notice a simple fact: they ALL f*ck each other. It's Mother Nature. They won't tell you that on the zoo tour, but it's true! And here's the thing...nobody seems to care.