'Big Brain' Gene Responsible for Human Intelligence, Not Found in Chimps

A "big brain" gene may be responsible for human intelligence, according to researchers who found that the factor is not present in chimpanzees.

The gene, scientists believe, appears to be unique to humans and can also be found in Neanderthals and extinct humans called Denisovans, according to LiveScience.com. The DNA allowed a part of the brain called the neocortex to house many more neurons, allowing for the human brain's massive growth.

"The neocortex is so interesting because that's the seat of cognitive abilities, which, in a way, make us human — like language and logical thinking," Marta Florio, a doctoral candidate at the Max Planck Institute of Molecular Cell Biology and Genetics in Germany, told LiveScience.com.

Scientists have been able to use the DNA to grow the brains of mice significantly larger, Debra Silver, a neurobiologist at Duke University Medical School, told National Public Radio.

"It's likely to be one of many DNA regions that's critical for controlling how the human brain develops," Silver said.

NPR wrote that the genetic code between human and chimpanzees is 95-percent identical. Katie Pollard, of the Gladstone Institutes and the University of California, San Francisco, told NPR her lab is studying the differences between the two DNAs.

"We can now actually generate the equivalent of embryonic brain cells and tissues that are human or chimpanzee," Pollard said. "And, using genome engineering techniques, we can start to study the effects of switching the human and the chimp sequences in these primate cell lines."

Ruth Faden, of Johns Hopkins Berman Institute of Bioethics, told NPR that no one should be worried about someone trying to use the technology to make nonhuman animals more humanlike or more intelligent. Faden said, though, it is something scientists should try to avoid tinkering with, according to NPR.

"The prospect of, sort of, tearing down the barriers between humans and other nonhuman species in ways that really threaten our sense of ourselves as special is disturbing," Faden said.

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