Human evolution questioned: 'Big brain gene found humans, not chimps'

A single gene may have paved the way for the rise of human intelligence by dramatically increasing the number of brain cells found in a key brain region.

This gene seems to be uniquely human: It is found in modern-day humans, Neanderthals and another branch of extinct humans called Denisovans, but not in chimpanzees.

By allowing the brain region called the neocortex to contain many more neurons, the tiny snippet of DNA may have laid the foundation for the human brain's massive expansion.

"It is so cool that one tiny gene alone may suffice to affect the phenotype of the stem cells, which contributed the most to the expansion of the neocortex," said study lead author Marta Florio, a doctoral candidate in molecular and cellular biology and genetics at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.

Still, it's likely this gene is just one of many genetic changes that make human cognition special, Florio said.

An expanding brain

The evolution from primitive apes to humans with complex language and culture has taken millions of years.

Some 3.8 million ago, Australopithecus afarensis, the species typified by the iconic early human ancestor fossil Lucy, had a brain that was less than 30 cubic inches (500 cubic centimeters) in volume, or about a third the size of the modern human brain.

By about 1.8 million years ago, Homo erectus was equipped with a brain that was roughly twice as big as that of Australopithecus.

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Human evolution questioned: 'Big brain gene found humans, not chimps'

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