Researchers at Scripps Research Institute in California found that the bulk of the differences between the brains of humans and primates boils down to a gene duplication error.
In experiments on mice, the team found that this "error" caused the rodents' brain cells to move into place faster and enabled more connections between brain cells.
According to the scientists, when any cell divides, it first copies its entire genome. During this process, it can make errors. The cell usually fixes errors in the DNA, but when they aren't fixed, they become permanent changes called mutations, which are sometimes hurtful and sometimes helpful, though usually innocuous, they said.
One type of error is duplication, when the DNA-copying machinery accidentally copies a section of the genome twice. The second copy can be changed in future copies -- gaining mutations or losing parts, the researchers said.
In the study, published in the journal Cell, the team scanned the human genome for these duplications, and found that many of them seem to play a role in the developing brain.
"There are approximately 30 genes that were selectively duplicated in humans," study author Franck Polleux was quoted as saying by LiveScience. "These are some of our most recent genomic innovations."
An extra copy of a gene gives evolution something to work with: Like modelling clay, this gene isn't essential like the original copy, so changes can be made to it without damaging the resulting organism, the researchers said.
The researchers studied one specific gene, called SRGAP2, which they think has been duplicated at least twice during the course of human evolution, first about 3.5 million years ago and then again about 2.5 million years ago.
The second and recent duplication seems to be incomplete with only part of the gene being duplicated. The researchers think this partially duplicated gene is able to interfere with the actions of the original, ancestral copy of SRGAP2. (More)
