The most common eye color among Asians is brown. However, there is significant diversity in eye color across different Asian ethnicities. Factors like genetics, environment, and diet influence eye color prevalence in Asia.
Distribution of Eye Colors in Asia
The distribution of eye colors across Asia is complex due to the continent’s ethnic, genetic, and geographic diversity. However, some broad patterns emerge:
- Brown eyes are overwhelmingly the most common, especially in East and Southeast Asia.
- Dark brown eyes predominate in countries like China, Japan, Korea, Vietnam, Thailand, Philippines, Malaysia, and Indonesia.
- Lighter brown eyes are more common in parts of South and Central Asia like India, Pakistan, Afghanistan, Iran.
- Hazel, amber, green, gray, and blue eyes occur at low frequencies in most Asian groups.
- Central Asian countries like Kazakhstan show higher levels of lighter eye colors due to historical mixing with European populations.
These distributions reflect the underlying genetics and ancestral origins of different Asian ethnicities. However, even within groups stereotyped as having “dark brown” eyes, there is measurable variation in lightness and hue.
Genetic Basis of Eye Color in Asians
The main gene influencing eye color in humans is OCA2 on chromosome 15, which codes for a protein involved in melanin production. The SNP rs12913832 in OCA2 accounts for over 70% of variation in eye color globally. The brown eye versions (G/G or G/C genotypes) of this SNP predominate in Asian populations.
However, other genes also influence eye color, including:
- HERC2 – regulates OCA2 expression
- SLC24A4 – codes for a calcium transporter affecting melanogenesis
- SLC45A2 – encodes a melanosome transporter protein
- TYR – codes for the enzyme tyrosinase essential for melanin synthesis
Many of these show signatures of selection in East Asians, indicating adaptive evolutionary pressures have shaped the genetic architecture of eye color in Asia. Unique variants in OCA2 and HERC2 likely contribute to the prevalence of brown eyes.
Geographic Variation in Eye Color in Asia
Geography correlates significantly with eye color variation within Asia. Some patterns:
- Siberian/Central Asian groups show more light eyes due to European ancestral mixing.
- Northern East Asians exhibit more light brown eyes than Southern groups.
- Southeast Asia displays very high frequencies of dark brown eyes.
- South Asia harbors more light brown compared to Northeast Asia.
Clinal gradients in allele frequencies centering on OCA2/HERC2 variants likely drive this geographic distribution. Environment may also play a role, with UV radiation proposed to exert selective pressure.
Environmental & Dietary Determinants of Asian Eye Color
Beyond genetics, some environmental and dietary factors may influence Asian eye color distributions:
- Low UV intensity promotes lighter eyes while high UV favors dark pigmentation.
- Latitude correlates with eye color gradients in Asia, with darker eyes near equator.
- Coastal groups tend to have darker eyes compared to inland mountain populations.
- Diet affects carotenoid intake, which influences melanin deposition in iris.
- Children’s eyes get darker from 1-7 years old, implicating environment/diet.
However, large-scale studies isolating the effects of environment versus genetics on eye color remain limited in Asia. Most variation appears strongly heritable, but climate and nutrition still modulate ocular phenotypes.
Eye Color Frequencies Among Major Asian Ethnic Groups
| Ethnicity | Brown (%) | Amber/Hazel (%) | Green (%) | Blue/Gray (%) |
|---|---|---|---|---|
| Chinese | 99 | 1 | 0 | 0 |
| Japanese | 99 | 1 | 0 | 0 |
| Korean | 100 | 0 | 0 | 0 |
| Filipino | 97 | 2 | 1 | 0 |
| Vietnamese | 99 | 1 | 0 | 0 |
| Thai | 99 | 1 | 0 | 0 |
| Indian | 89 | 5 | 2 | 1 |
| Pakistani | 90 | 5 | 3 | 1 |
| Kazakh | 70 | 10 | 10 | 5 |
This table summarizes reported frequencies of major eye colors among key Asian ethnicities. Brown eyes predominate across the board, but lighter traits emerge at higher rates in Central, South, and Southeast Asia.
Conclusion
In summary, brown eyes overwhelmingly predominate among Asian ethnicities, particularly in East Asia. Lighter eye colors occur at low to moderate frequencies in other parts of Asia. Genetics determines eye color distributions, but environment and geography also modulate outcomes. More research is needed to fully characterize the complex genetic architecture and adaptiveness of Asian iris pigmentation.
