The main thought of human evolution is that humans and apes share a common ancestor. Humans did not come from apes, though the first 99.87% of human’s and ape’s ancestral lines are the same. Humans started as single-celled organisms just like everything else, and everything is related. Behaviorally, modern humans have only been on Earth for 0.01% of its history, yet we had the fastest development and colonization of any species in the world. In 1859, Charles Darwin published The Origin of the Species, and in 1871, he published The Descent of Man, which said that humans and apes must share a common ancestor. Finally, in 1872, he published The Expression of the Emotion in Man and Animals which stated links in the way that humans and animals expressed emotion.