Primate Brain Evolution Explained as Consequence of Same Genetic Program

Scientists have made a breakthrough when it comes to studying brain evolution. They've found that differences between primate brains--from marmosets to humans--can largely be explained as consequences of the same genetic program. The findings could allow researchers to better understand how our own brains evolved over time.

In order to better understand primate brains, the researchers employed computer models. Using publicly available brain maps, MRI imaging data and modeling software, the researchers compared the sizes of different brain areas in humans and three monkey species which included marmosets, capuchins and macaques. They found that two regions, the lateral prefrontal cortex and the temporal parietal junction, expand disproportionally to the rest of the brain. While the prefrontal cortex is related to long-term planning, personality expression and decision making, the temporal parietal junction is related to self-awareness and other self-other distinction.

In fact, the scientists discovered that this substantial enlargement of some areas of the human brain, vital to advanced cognition, reflects a consistent pattern that is seen across primate species of all sizes. It's possible that these neural circuits responsible for traits that we consider uniquely human could have emerged simply as a natural consequence of the evolution of large brains.

"We found that the larger the brain is, the larger these areas get," said Tristan Chaplin, the lead author of the new study, in a news release. "When you go from a small to big monkey--the marmoset to macaque--the prefrontal cortex and temporal parietal junction get larger relative to the rest of the cortex, and we see the same thing again when you compare macaques to humans. This trend argues against the view that specific human mutations gave us these larger areas and advanced cognition and behavior, but are a consequence of what happens in development when you grow a larger brain."

The findings reveal a little bit more about primate brain evolution. The first computational comparative study conducted across several primate species, this research shows that humans may not be all that special. Instead, their size could be what really determines how humans think and reason.

The findings are published in the Journal of Neuroscience.