Brain Development in Chimpanzees Provides Insight into the Evolution of the Human Brain
The development of brain regions crucial to learning occurred before apes evolved into humans.
Social learning and cognition occurred earlier in the evolutionary process than previously thought, according to researchers from the Icahn School of Medicine at Mount Sinai. The findings, which are published in June in the Proceedings of the National Academy of Sciences, indicate that development of brain regions crucial to learning occurred before apes evolved into humans.
Macaque monkeys, which share a last common ancestor with humans from approximately 25 million years ago, have served as the predominant comparative model for human brain development. However, there is a significant lack of evidence about similarities in brain development between humans and more closely-related apes, such as chimpanzees, creating a gap in understanding about when during evolution humans acquired social learning practices and language skills. As a result, researchers at Mount Sinai and George Washington University evaluated chimpanzees to help establish a timeline of when evolutionary changes in the neocortex, a brain region crucial for cognition, occurred in humans and chimpanzees.
“We know that brain development in humans is characterized by an extended period of growth of synapses, the points of contact between nerve cells, into mid-childhood, and a delayed nerve cell maturation of the prefrontal cortex, the region responsible for higher cognitive abilities,” said Patrick Hof, MD, Professor of Neuroscience at the Icahn School of Medicine at Mount Sinai. “In order to establish when during the evolutionary process this development happened, we evaluated chimpanzees to identify similarities with humans and to assess whether this type of development happened before or after the chimpanzee-human evolutionary split.”
By evaluating tissue from the brains of chimpanzees, Serena Bianchi, MSc, and Chet Sherwood, PhD, at the George Washington University, and Dr. Hof found that chimpanzee brain development in the neocortex is very similar to that of humans in timing and duration. Unlike macaques who are born with a more mature cerebral cortex, chimpanzees undergo this development between ages three and five, similar to humans. These observations indicate that evolutionary changes in a brain region crucial for cognition likely occurred earlier than the chimpanzee-human divergence.
“These findings, when placed in the context of primate evolution, provide important insights not only about the developmental origins of human-specific cognitive and social skills, but importantly also on possible mechanisms leading to the emergence of neuropsychiatric illnesses that selectively affect our own species,” said Dr. Hof.
This research was supported by grants from the National Science Foundation, the National Institutes of Health, and the James S. McDonnell Foundation.
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