How many of the developments of the human brain peculiar to us, like the huge relative growth of the prefrontal cortex, are down to old genes that have existed throughout the mammals and beyond, but have become differently regulated - made to work harder - in humans, and how much is down to novel genes that have arisen only in mammals, some only in primates, and some only in the line leading to us from the common ancestor with the ancestors of chimpanzees? Until now, regulation of old conserved genes was thought to have been more important but the work reported here, from the University of Chicago, suggests otherwise. A surprising number of novel brain genes have arisen and the timing of their arrival fits very nicely with the increase in size and human-specific specialization of the human brain.
"“We were very shocked that there were that many new genes that were upregulated in this part of the brain,” said Long, who added that he was also taken aback by synchronicity of the origin of the genes and the development of novel brain structures. It seems that around the same time that the neocortex and the prefrontal cortex arose, and then expanded in humans, a large collection of genes also popped up."