New research suggests that a partial duplication of a gene played a significant role in a major advance in human brain evolution that occurred a few million years ago.
The SRGAP2 gene has been duplicated at least twice during human evolution, first about 3.5 million years ago and again about 2.5 million years ago. The second duplication produced only a partial copy of the gene, the study authors said.
This partial copy acts at exactly the same time and place as the original gene, allowing the partial copy to interact with and block the original gene's function, according to the findings published online in the journal Cell.
The partial copy of the SRGAP2 gene seems to have appeared at the same time that the fossil records show a transition from our extinct Australopithecus ancestors to the genus Homo, which led to and includes modern humans.
Why humans are more intelligent
This point in human evolution is also when our ancestors' brains began to expand and major advances in intelligence likely occurred, according to Franck Polleux, an expert in brain development at Scripps Research Institute in La Jolla, Calif., and Evan Eichler, a genome scientist at the University of Washington in Seattle.
The researchers said that SRGAP2 and other human-specific gene duplicates may explain why humans are much more intelligent than other primates, despite few apparent differences in their genome sequences.
"We may have been looking at the wrong types of mutations to explain human and great ape differences," Eichler said in a journal news release. "These episodic and large duplication events could have allowed for radical - potentially earth-shattering - changes in brain development and brain function."
The findings also may provide clues to neurodevelopmental disorders, including autism, epilepsy and schizophrenia, the researchers said.
Gorilla sheds light on evolution
The U.S. Institute of Neurological Disorders and Stroke has more about the brain.
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