Researchers have discovered that a minute change in brain biochemistry, occurring about half a million years ago, may be crucial to our species’ evolutionary success. This change affects the stability and genetic expression of the enzyme adenylosuccinate lyase (ADSL), involved in DNA and RNA production.
The ADSL enzyme differs by just one amino acid between modern humans and Neanderthals and Denisovans. This substitution reduces the enzyme’s stability, but its effect on behavior is complex. In a study published in PNAS, scientists found that female mice with this substitution accessed water more frequently than their littermates when thirsty, suggesting an advantage in competing for scarce resources.
Further research identified genetic variants in the ADSL gene present in nearly all modern human genomes. These variants show strong evidence of positive selection among humans and further diminish ADSL activity, especially in the brain. The researchers suggest that these evolutionary pressures may have reduced ADSL activity to provide specific behavioral advantages while avoiding deficiency disorders.
The study opens up many questions about human behavior and evolution. Future research will explore the role of ADSL in behavior and investigate how combinations of genetic changes may affect our metabolism over time.
Source: https://phys.org/news/2025-08-brain-chemistry-humanity-family-tree.html