This happened to me when I was in my senior year at college. I was standing outside our Computer Centre, thinking about nothing in particular and watching the monkeys. One particular pair caught my attention: it was a male monkey trying to get it on with a female one (no, our campus was not so culturally advanced then for gay monkeys to come out of the closet). This male monkey (let's call him Jack) kept trying to do you-know-what, and the female monkey (Jill) kept shifting position, effectively frustrating Jack's designs.
After repeated tries, our hero had enough of it. No, he didn't say "Screw you!" and walk away with his dignity intact. Instead, he chose to question the very essence of Jill's feminity, by lifting up her tail and peering under it to really ensure that Jill's anatomy was as his friends had advised him it would be.
May be this just goes to show that the male of the species will not take no for an answer and would go to any lengths to protect their self-image. In that case, monkeys may be as dumb as humans.