It is not correct to say that we "descend" from the monkeys. The orangutan, the gorilla, the chimpanzee and we are primates. But the evolution of each species was different. We all probably came of a common trunk that, far behind, 70 million years ago, in the period called Paleocene, began to divide. The first hominoids, biological family to which we belong, appeared during the Miocene, from 24 to 5millions of years ago.