How Does Eye Color Affect Vision? Experts Explore Potential Advantages of Blue Eyes in Dim Light Conditions

Eye color is entirely determined by genes, influencing common eye conditions. While generally not a risk factor for vision issues, exceptions like albinism exist. Iris color can slightly affect how you perceive the world.

Approximately one in ten individuals worldwide possess eye colors that resemble nature. In certain European populations, this ratio can soar to three out of four people. The persistence of blue eyes, competing with darker-pigmented irises, has sparked speculation. UK anthropologists now suggest that blue eyes may offer a slight advantage in dimly lit conditions.

Genetics Behind Eye Color

Eye color is primarily determined by the pigmentation of the iris, a structure surrounding the pupil that regulates light entry. The iris color spans from light blue to dark brown, typically categorized as blue, green/hazel, or brown, with brown being the most prevalent worldwide. Genetic variations contribute to eye color by influencing the production, transport, and storage of melanin, a pigment crucial for iris pigmentation.

A pivotal role in eye color determination is played by a region on chromosome 15, housing the OCA2 and HERC2 genes. The OCA2 gene produces the P protein, vital for melanosomes' maturation, influencing melanin quantity and quality.

Formerly, eye color inheritance was oversimplified, assuming a single gene and straightforward dominance of brown over blue eyes. However, multiple genes interact to determine eye color, leading to a more nuanced inheritance pattern. While predictions based on parental eye colors are often accurate, genetic variations can yield unexpected outcomes.

Several eye color-related disorders exist, such as ocular albinism and oculocutaneous albinism, characterized by reduced iris pigmentation and vision problems. Heterochromia, featuring different-colored eyes in one individual, can result from genetic changes, developmental issues, or acquired conditions, highlighting the complexity of eye color determination.

READ ALSO: Color Blindness: Why Are Men More Likely To Acquire It?

Advantages of Blue Eyes in Dim Light

Anthropologists in the UK suggest in their new paper available in the preprint serve bioRxiv that blue eyes might confer a slight advantage in dimly lit conditions.

In a preliminary experiment led by Kyoko Yamaguchi and her student Faith Erin Cain from Liverpool John Moores University, 39 adult volunteers underwent a brief 30-second eye test as light intensity decreased. Participants self-reported and verified their eye colors, resulting in 25 individuals with various grades of blue eyes and 14 with light or dark brown eyes.

The analysis revealed that those with blue eyes could read codes on a wall under significantly lower light conditions (0.7 lux on average) than their brown-eyed counterparts (0.82 lux).

While this study has a preliminary nature, a relatively small sample size, and awaits peer review, its findings align with the theory that the loss of iris pigmentation evolved in certain populations to optimize vision in low-light environments. Irises, with their unique hues, consist of canvases splashed with proteins like melanin.

Higher melanin levels darken the eyes, while decreasing pigmentation scatters light, giving the iris a bluer tone. Evolution likely favored pigmented irises for their protective qualities, with darker-eyed individuals exhibiting lower rates of conditions such as cancer and macular degeneration.

A mutation in the gene associated with albinism, occurring in an individual around the advent of settled agriculture, led to the dilution of melanin in their eyes. This genetic change carried through bloodlines across ages, is present in millions globally. The persistence of this mutation might be linked to factors such as prestige, beauty, protection against low moods in dark seasons, or resource efficiency in harsh conditions.

RELATED ARTICLE:  Blue-Eyed People Share One Ancestor That Developed the Mutation 6,000 to 10,000 Years Ago

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