A new Yale study provides a fuller picture of the genetic changes that shaped the evolution of the human brain, and how the process differed from the evolution of chimpanzees.

For the study, published Jan. 30 in the journal Cell, researchers focused on a class of genetic switches known as Human Accelerated Regions (HARs), which regulate when, where, and at what level genes are expressed during evolution.

While past research theorized that HARs may act by controlling different genes in humans compared to chimpanzees, our closest primate relative, the new findings show that HARs fine-tune the expression of genes that are already shared between humans and chimpanzees, influencing how neurons are born, develop, and communicate with each other.