Unlocking Survival: How a Genetic Mutation in Key Enzymes Helped Humans Thrive While Neanderthals Vanished

A tiny genetic change in an enzyme might explain why modern humans thrived while Neanderthals and Denisovans went extinct. Researchers from the Okinawa Institute of Science and Technology in Japan and the Max Planck Institute in Germany published these findings in the journal Proceedings of the National Academy of Sciences.

The enzyme in question is called adenylosuccinate lyase (ADSL). It plays a key role in producing DNA, RNA, and energy for cells. Interestingly, the human and Neanderthal versions of ADSL differ by just one amino acid out of 484. This minor tweak seems to have a big impact on brain function and behavior.

Dr. Xiangchun Ju, a lead researcher, mentioned that this genetic difference could have helped modern humans adapt better to challenges. The mutation exchanges a valine for an alanine, a change that is present in nearly all living humans but absent in Neanderthals and Denisovans.

Previously, studies indicated that this mutation made the human version of ADSL less stable and prone to breaking down faster. In their recent work, the team introduced the human variant into genetically modified mice. They found that these mice exhibited higher levels of ADSL’s substrates in their brains, suggesting reduced enzyme activity. This change seemed to affect their behavior positively.

For instance, when female mice with the human-like ADSL had to learn to connect sounds with water access, they learned faster than their counterparts. They were also quicker to find water when thirsty, suggesting they may have been better at competing for limited resources. Dr. Ju cautioned that while these findings are promising, drawing direct parallels to humans requires more research since mouse brains differ significantly from ours.

The research also identified other genetic changes in a region of the ADSL gene present in about 97% of modern humans. These variants further reduced enzyme function by lowering its RNA expression in the brain. Dr. Shin-Yu Lee pointed out that there seemed to be an evolutionary pressure to balance the enzyme’s activity. It needed to be low enough to provide these benefits while still preventing disorders associated with ADSL deficiency.

Interestingly, the behavioral advantages from the enzyme change were only noted in female mice. This raises questions about the role of gender in these genetic adaptations. Professor Izumi Fukunaga highlighted the complexity of brain processes involved in behaviors like seeking water, indicating more studies are needed.

Nobel Laureate Svante Pääbo, who was involved in the study, emphasized that even small genetic changes can shape species over time. He noted that such minor distinctions may have given modern humans an edge in adaptability and problem-solving, crucial for surviving changing climates and dwindling resources.

While this research can’t completely explain the extinction of Neanderthals and Denisovans, it sheds light on how small biochemical differences may have contributed to modern humans’ success. As climates shifted and resources became scarce, these subtle advantages might have made a critical difference for survival.

For more detailed insights, check the study in Proceedings of the National Academy of Sciences here.

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Denisovans,Evolution,Homo sapiens,Neanderthals