Eye color is a fascinating human trait, often sparking curiosity due to its diverse range and unique appearances. Among the various hues, hazel eyes stand out for their complex and shifting appearance, which frequently leads to questions about their prevalence and defining characteristics. Understanding what makes hazel eyes distinct, how common they are, and the biological processes behind their color provides insight into this intriguing aspect of human variation.
Defining Hazel Eye Color
Hazel eyes are distinguished by their multi-tonal appearance, blending green, gold, and brown. Unlike solid-colored eyes, hazel irises often exhibit a “sunburst” effect, where different hues appear in various parts of the eye. Flecks of amber or blue can sometimes be present.
The exact mix of colors in hazel eyes can vary, leading to appearances that are either predominantly green or predominantly brown. If eyes are a solid copper or yellowish-gold with little green, they are considered amber, which is distinct from hazel. Green eyes tend to have a mostly solid green color throughout the iris, whereas hazel eyes are notably multicolored.
Prevalence and Rarity
Hazel eyes are considered relatively uncommon globally. Approximately 5% of the world’s population has hazel eyes. This makes them significantly less common than brown eyes, which are the most prevalent eye color, accounting for 70-80% of the global population. Blue eyes are the second most common, found in about 8-10% of people worldwide.
Hazel is more prevalent than green eyes, which are the rarest, occurring in only about 2% of the global population. Hazel eyes are most frequently found in regions with mixed ancestry, such as parts of Europe, particularly the Netherlands, the United Kingdom, and Spain, as well as the Middle East, North Africa, and Brazil. In the United States, the prevalence of hazel eyes is notably higher, estimated at around 18% of the population.
Genetics Behind Hazel Eyes
The color of hazel eyes is determined by a complex interplay of genetics and the presence of melanin in the iris. Melanin is the pigment responsible for coloring skin, hair, and eyes. There are two primary types of melanin involved in eye color: eumelanin, which produces dark brown pigment, and pheomelanin, which contributes reddish-yellow hues. Hazel eyes result from a moderate amount of melanin, more than blue or green eyes but less than brown eyes.
In hazel eyes, the distribution of melanin is uneven across the iris, contributing to its multicolored appearance. This unevenness, combined with the scattering of light within the iris, creates the distinct blend of brown, green, and gold tones. The scattering of light, particularly the Tyndall effect, plays a role in how lighter eye colors, including hazel, appear. Eye color is a polygenic trait, meaning multiple genes are involved in its determination.
Factors Influencing Perceived Hazel
The appearance of hazel eyes can seem to change based on various external factors, leading to observations of them appearing greener or browner at different times. This perceived shift is often influenced by lighting conditions. Certain lighting can emphasize green or gold flecks, making the overall color appear different.
Beyond lighting, factors such as clothing colors, makeup, and even the surrounding environment can affect how hazel eyes are perceived. These elements do not alter the actual pigment in the eye but rather create an optical illusion by reflecting certain colors or enhancing existing hues. While a person’s eye color generally stabilizes in early childhood, slight changes can occur with age due to natural variations in melanin levels, subtly altering the perceived shade.