No one in evolution says that we came from monkeys. They say that we and monkeys share a common ancestor. At some point in time, one of our ancestors began hunting on the plains instead of sticking to the trees. Because they fulfilled separate ecological niches, there was no competition, so the tree dwelling monkeys and the land based primates diverged, evolutionarily speaking. Over time, various other land based primates evolved, but were out competed by other species better adapted to living on the land. Homo Erectus, Neanderthals, and Cro-Magnon were all examples of land based hominids that had ventured down the evolutionary trail of land-walking hominids. Meanwhile, the tree-dwelling apes, like Chimps and Orangutans, or land apes with suitable geographic isolation, like gorillas, did not compete directly with the land hominids, therefor survived.
From Yahoo but it's a good explanation.
at 10:26 PM on Jan. 1, 2013