Human brains make synaptic connections throughout much of childhood, and the brain’s plasticity enables humans to slowly wire them based upon experiences, contrary to how chimpanzees develop. Humans and chimpanzees share 98.8% of the same genes, but scientists have been looking for what drives the unique cognitive and social skills of humans.

A new study, which was published today in Genome Research, that examined brain samples from humans, chimpanzees, and macaques, collected from birth up to the end of their life span, has found some key differences between the expression of genes that control the development and function of synapses, which are the connections between neurons through which information flows.