The evolution of human intelligence is closely tied to the evolution of the human brain and to the origin of language. The timeline of human evolution spans approximately 9 million years, from the separation of the genus Pan until the emergence of behavioral modernity by 50,000 years ago. The first 3 million years of this timeline concern Sahelanthropus, the following 2 million concern Australopithecus and the final 2 million span the history of the genus Homo in the Paleolithic era.

Many traits of human intelligence, such as empathy, theory of mind, mourning, ritual, and the use of symbols and tools, are somewhat apparent in great apes, although they are in much less sophisticated forms than what is found in humans like the great ape language.

 

Note:   The above text is excerpted from the Wikipedia article Evolution of human intelligence, which has been released under the GNU Free Documentation License.