Genetic Secrets of the Jomon
Ancient DNA indicates that the Jomon people who inhabited the Japanese islands between 16,000 and 3,000 years ago carried specific genetic variations to survive the biting cold of the Ice Age. These individuals did not possess a single cold-adaptation gene. Instead, they relied on a mix of adaptations involving non-shivering thermogenesis, lipid metabolism, and temperature sensing. Researchers identified these traits by analyzing 42 Jomon genomes and comparing them against a modern panel of 9,290 Japanese genomes to fill in missing gaps.
Hiroki Oota, a professor at the University of Tokyo who led the research, suggests that these genetic signals represent an archive of how ancient hunter-gatherers managed life in extreme conditions. The team found that the Jomon possessed a version of the UCP1 gene tied to increased heat production through brown fat. About 70 percent of their genetic samples at the relevant site contained this heat-boosting variant, a significant increase compared to modern East Asian populations.
Mechanisms of Heat Production
Brown fat plays a role in burning energy for warmth rather than storing it. The Jomon also showed distinct patterns in the TRPM8 gene, which regulates cold sensing. Roughly 75 percent of their samples carried the variant associated with colder environments. These biological markers, when paired with archaeological findings of seafood-rich diets in pottery from 15,000 to 11,800 years ago, point to a population highly specialized for their environment.
The findings show that two genes, FTO and APOA5, provided the strongest evidence of natural selection during the glacial period. FTO is known to influence how the body stores and uses weight, while APOA5 governs the breakdown of triglycerides in the bloodstream. In an experiment involving human-variant mice, the FTO version found in the Jomon helped the animals maintain stable body temperatures despite exposure to the cold. Nearly 90 percent of Jomon samples carried a variant of APOA5 that promotes high triglyceride levels, suggesting a system built to store energy effectively and burn it rapidly for heat.
Modern Health Impacts and Lingering Questions
Many of these ancient variants remain present in modern populations in Japan. Recent health data tracking over 170,000 individuals suggests that higher levels of Jomon ancestry correspond to a higher body mass index. This aligns with the theory of thrifty genes, where biological traits that assisted survival in unpredictable, cold environments may contribute to modern health challenges in more stable settings. Oota emphasizes that researchers must remain cautious, as these physiological traits are complex and influenced by many environmental factors.
Despite the findings, the study highlights clear limits to current knowledge. Every individual sampled lived thousands of years after the glaciers retreated, meaning the earliest Ice Age ancestry remains inferred. The team acknowledges that they cannot definitively confirm how these bodies functioned in the cold without older DNA samples from the deepest parts of the glacial period. Researchers hope to recover remains from Hokkaido to bridge this gap, as that region holds the key to the earliest populations. The findings were published in the journal Science Advances.