The Fascinating Differences of the Japanese Human Body: Between Myths and Realities

1. Origins and Genetic Diversity: A Unique Mosaic The Japanese people are the product of a rich migratory history. Two main ancestral populations contributed to the current Japanese genetics: the Jomon, present on the archipelago since around 13,000 BCE, and the Yayoi, who arrived from Korea in the 3rd century BCE. In 1991, anthropologist Kazuro Hanihara proposed a dual structure model to explain this genetic fusion. Today, about 15% of modern Japanese DNA comes from the Jomon. However, recent studies suggest the existence of a third, unnamed genetic group, challenging the idea of “pure blood” of the Yamato people.
2. Physical Adaptations: From Small Chests to Protected Eyes The Japanese are often identified by certain physical characteristics:
   • Small Chests and Lack of Curves: These traits are linked to pulling muscles, a result of a millennia-old rice farming culture requiring specific physical efforts.
   • Slanted Eyes: This adaptation, inherited from ancestors living in Siberia, protects against the strong reflection of the sun on snow and ice.
   • Missing ALDH2 Enzyme: About 50% of Japanese lack an enzyme to process alcohol, causing rapid skin redness when consumed.
3. Hygiene and Sweating: Hidden Superpowers Contrary to popular belief, the Japanese do sweat, but in a different manner. They mostly have eccrine sweat glands (present all over the body) and few or no apocrine sweat glands (responsible for body odor). About 90% of Japanese have almost odorless sweat, a rare genetic trait compared to Caucasians.
4. Digestive Peculiarities: From Rice to Seaweed Japanese dietary habits have shaped their digestive system:
   • Longer Stomach: The Japanese stomach is longer, allowing for better digestion of cereals like rice.
   • Intestine Longer by a Meter: This trait favors the absorption of hard-to-digest nutrients.
   • Bacteroides plebeius: This bacterium, present in the Japanese intestine, helps digest seaweed, an essential element of their diet.
5. The Mongoloid Spot and Other Curiosities Almost all Japanese babies are born with a blue spot on their buttocks, known as the Mongoloid spot. This phenomenon, common among Asian peoples, usually disappears with age and remains without a precise scientific explanation.
6. Environmental Impact and Modern Adaptations Rapid urbanization and environmental changes have left marks on Japanese health. For example, pollen allergy, mainly due to the massive planting of Japanese cedars after World War II, affects 42.5% of the population. This situation is so severe that it impacts national productivity, pushing the government to consider drastic solutions, such as reducing cedar plantations.
7. Cultural and Physiological Constellation The physical and genetic differences of the Japanese are also influenced by their culture and lifestyle. Habits like Seiza (sitting on the heels) and the Asian squat shape their posture and bone structure. These positions, often difficult for non-habituated people, are beneficial for bodily health and maintaining good posture.

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The peculiarities of the Japanese human body are the result of a rich history and continuous adaptation to their environment. Between genetics, culture, and evolution, these differences illustrate the fascinating diversity of the human species. By better understanding these specificities, we learn to appreciate the nuances that make each human group a unique marvel.