A recent study has revealed fascinating differences in a protein that helps synthesize DNA between modern humans and our extinct relatives, the Neanderthals and Denisovans. This discovery offers insights into why Neanderthals and Denisovans disappeared while we thrived.
The study focuses on an enzyme called ADSL (adenylosuccinate lyase). This protein is crucial for creating purines, the building blocks of DNA. Modern humans have a variant of ADSL that differs from the versions found in Neanderthals and Denisovans by just one amino acid. This small change might have given us an edge in survival tasks.
Researchers from the Okinawa Institute of Science and Technology in Japan led this study. Xiangchun Ju, the study’s lead author, cautioned that linking mouse experiments directly to human behavior is tricky because mouse brains work differently from ours. However, data suggests that the modern version of ADSL might have provided advantages, especially in competing for scarce resources.
Experts point out that around 600,000 years ago, modern humans branched off from Neanderthals and Denisovans, but it’s unclear why we survived and they didn’t. ADSL is one of the few proteins that underwent significant evolutionary change, and its unique mutation appears to be exclusive to modern humans. Previous studies showed that this mutation caused the enzyme to break down more rapidly, possibly affecting brain function and behavior.
In newer experiments, mice carrying the modern human version of ADSL showed a notable ability to learn connections between cues, like lights and water rewards, better than their counterparts without this variant. Interestingly, only female mice benefited from this change, suggesting complexities in behavior influenced by genetics.
Statistical analyses have shown this mutation in ADSL occurred more often in modern human genomes than would be expected by random chance, hinting at its evolutionary importance. However, research also indicates that deficiencies in ADSL can lead to significant health issues in modern humans, raising questions about the trade-offs that shaped our evolution.
While some experts are skeptical about the direct implications for human evolution, they see promise in using animal models to further study the behavioral impacts of genetic differences. According to Mark Collard, a paleoanthropologist, this approach could open doors to new research on how our ancestors’ brains and behaviors evolved.
Future studies could elaborate on how changes in ADSL activity might link to specific behaviors and how various genetic factors interact to shape our capabilities. The quest to understand our past is just beginning, and as more research unfolds, we may uncover deeper insights into what truly sets us apart from our closest relatives.
For more details on the research, you can read the article published in the journal PNAS here or learn about the broader context of human evolution in related studies.
