Human brains exhibit more plasticity, the tendency to be modeled by the environment, than chimpanzee brains, which may account for part of human evolution, according to a study which may provide insight into why humans are capable of adapting to various environments and cultures. The stud examined the inherited genetic factors of brain organization in humans compared to their closest living relatives.

The research team studied 218 human brains and 206 chimpanzee brains to compare two things: brain size and organization as related to genetic similarity. The study found that human and chimpanzee brain size were both greatly influenced by genetics.

In contrast, the findings related to brain organization revealed key differences between chimpanzees and humans. In chimpanzees, brain organization is also highly inherited, but in humans this is not the case.

"We found that the anatomy of the chimpanzee brain is more strongly controlled by genes than that of human brains, suggesting the human brain is extensively shaped by its environment no matter its genetics," said Aida Gómez-Robles, postdoctoral scientist at the George Washington University Center for the Advanced Study of Human Paleobiology and lead author on the paper.

These findings could also have important implications regarding human susceptibility to degenerative diseases.

"Though our findings suggest that the increased plasticity found in human brains has many benefits for adaptation, it is also possible that it makes our brain more vulnerable to many human-specific neurodegenerative and neurodevelopment disorders," said William Hopkins, professor in the Neuroscience Institute at Georgia State.

In the study, the human brains were from twins (identical and fraternal) or siblings, while the chimpanzee brains had a variety of kinship relationships, including mothers and offspring or half siblings. MRI scans were used to measure brain volume and reconstruct 3D models of the cortical surface. Chimpanzees used in the study were housed at the Yerkes National Primate Research Center in Atlanta and at the University of Texas MD Anderson Cancer Center in Bastrop, Texas.