New research has indicated that it is in the womb itself that human brains outpace those of chimps.

"Elucidating these differences in the developmental patterns of brain structure between humans and great apes will provide important clues to understand the remarkable enlargement of the modern human brain and humans' sophisticated behavior," Sakai said.
The researchers say they now hope to explore fetal development in particular parts of the brain, including the forebrain, which is critical for decision making, self-awareness, and creativity.
Source-Eurekalert