The Bonobo Primate and Humans, 2 very similar species.

This video is incredible. It clearly shows how close we are to our early primate ancestors.
The Bonobo primates are a very interesting species and are more closely related to us humans than even Chimpanzees. Please watch this video and you can get a better picture of our human evolution.
Just because they did not take the same evolutionary process as humans and have not evolved at the same rate is part of the natural selection and other conditions, such as not migrating far from their origin.