"Two studies published online today in Cell1, 2 suggest that DNA duplication errors that happened millions of years ago might have had a pivotal role in the evolution of the complexity of the human brain. The duplications — which created new versions of a gene active in the brains of other mammals — may have endowed humans with brains that could create more neuronal connections, perhaps leading to greater computational power.
The enzymes that copy DNA sometimes slip extra copies of a gene into a chromosome, and scientists estimate that such genetic replicas make up about 5% of the human genome. (...)
“Ten years after the human genome was sequenced and declared done, we’re still finding new genes in new places that are really important to human brain function and evolution,” Eichler’s team calculates that SRGAP2C appeared roughly 2.4 million years ago, around the time that big-brained species of Homo evolved in Africa from smaller-skulled Australopithecines, and around the time that stone tools appeared in the fossil record. These ancient hominins eventually gave rise to Homo erectus, which were the first human ancestors to wander beyond Africa, roughly 1.8 million years ago. (...)
“If you’re increasing the total number of connections, you’re probably increasing the ability of this network to handle information,” Polleux says. "It’s like increasing the number of processors in a computer."