Humans are more intelligent than their nearest living cousins — the chimpanzees — because we undergo a massive explosion in white matter growth during the first two years of life, scientists say.
A new study sheds light on why humans have much bigger brains and are, as a species, much more intelligent, despite sharing 98% of the DNA with chimps.

“What’s unique about us is that our brains experience rapid establishment of connectivity in the first two years of life,” Chet Sherwood from George Washington University said.

Researchers carried magnetic resonance imaging (MRI) brain scans of three baby chimps as they grew to 6 years of age. They then compared the data with existing brain-imaging scans for six macaques and 28 Japanese children.

They found that chimpanzees and humans both had much more brain development in early life than macaques.