Researchers used non-invasive magnetic resonance imaging (MRI) to create data-driven maps of the human and chimpanzee brain. They analyzed scans from 189 chimpanzees aged 9 to 50 and 480 humans aged 20 to 74. Results showed that the brains of both species were generally symmetrical and shared many similar clusters of anatomical structures, particularly in the prefrontal cortex. The researchers then measured how much gray matter – a marker of aging – shrank over time in chimpanzees under 50 and humans under 58. In humans, they found the greatest reduction in the frontal cortex, including the prefrontal cortex, while in chimpanzees, the striatum, a structure involved in habit formation and reward-seeking behavior, showed the most significant decline. Brain regions associated with visual processing and motor skills were less susceptible to aging in both species. Finally, the researchers assessed which regions of the human brain expanded the most compared to chimpanzees and compared scans of same-aged, same-sex humans and chimpanzees. The results indicated that the fastest evolutionary expansion occurred in the prefrontal cortex, one of the regions most vulnerable to aging.
