A study of artificial human and chimpanzee nerve cells revealed how faster-evolving DNA gives neurons the ability to build increasingly complex brain power.
How did humans evolve brains capable of complex language, civilization, and more?
The answer could lie in exceptional DNA. Scientists at UC San Francisco found that parts of our chromosomes have evolved at breakneck speeds to give us an edge in brain development compared to apes. But it might also put us at risk for uniquely human brain disorders.
The study, which was supported by grants from the National Institutes of Health, appears in Nature on Feb. 26.
The research focused on parts of chromosomes known as human accelerated regions (HARs), which have evolved most rapidly since humans split from chimpanzees on the evolutionary tree – changing 10 times faster than the expected rate of evolution in mammals.
The scientists, led by Yin Shen, PhD, professor in the UCSF Weill Institute for Neurosciences and the UCSF Institute for Human Genetics, studied the effects of HARs in artificial neurons derived from human and chimpanzee cell lines.
The human and chimpanzee genomes are 99% similar. HARs make up a big portion of the 1% difference, which can lead to dramatically different outcomes in human and chimp neurons in petri dishes. The human neurons grew multiple neurites, or wiry projections that help the nerve cells send and receive signals. But the chimp neurons only grew single neurites. When human HARs were engineered into artificial chimp neurons, the chimp neurons grew many more of these wires.
More neurites during development could mean more complexity in our neural networks. These networks facilitate the transmission of signals in the nervous system and support our higher cognitive functions. But disruptions in their development may contribute to neurodevelopmental disorders like autism."
Yin Shen, PhD, professor in the UCSF Weill Institute for Neurosciences and the UCSF Institute for Human Genetics
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Journal reference:
Cui, X., et al. (2025). Comparative characterization of human accelerated regions in neurons. Nature. doi.org/10.1038/s41586-025-08622-x.
Understanding the World Beyond DNA and Genes