The most common eye color in Japan is brown. According to a survey conducted by the Ministry of Health, Labour and Welfare in Japan in 2018, around 90% of the Japanese population has brown eyes.
Eye color is determined by the amount and type of pigments in the iris. The iris is the colored part of the eye that controls the amount of light that enters the eye. The color of the iris is determined by the amount of melanin, which is a dark pigment that also determines skin and hair color. There are three types of melanin: eumelanin, pheomelanin, and neuromelanin. Eumelanin is responsible for brown and black hair. Eye color, while pheomelanin is responsible for red and blonde hair and some variations of green and hazel eyes. Neuromelanin is found in the brain and has no effect on eye color.
The prevalence of brown eyes in Japan is due to genetic factors. The majority of the Japanese population has East Asian ancestry, and the genetic makeup of East Asians is distinct from other ethnic groups. Studies have shown that the TYRP1 gene, which is responsible for the production of melanin, is more common in East Asians than in other populations. The TYRP1 gene produces a form of eumelanin that results in brown eyes.
However, it is worth noting that eye color is not solely determined by genetics. Environmental factors such as sunlight exposure can affect the production of melanin, leading to changes in eye color over time. Additionally, some individuals may have eye color that is not common in their ethnic group due to genetic mutations or a mixture of ancestry.
In conclusion, the most common eye color in Japan is brown. Which is determined by the amount and type of melanin in the iris. The prevalence of brown eyes in Japan is due to genetic factors, particularly the TYRP1 gene. However, eye color is not solely determined by genetics. Environmental factors such as sunlight exposure can also play a role.