What is the origin of hazel eyes and why did they develop in the first place? Also, how can you tell if you have hazel eyes vs green eyes or amber eyes or brown eyes? I will answer these and many other questions in this video. Now around 5% of the worlds population have hazel eyes, with around 18% of the US population having them. They are the joint 3rd most popular eye colour in the world along with amber eyes, with brown being the most common and blue the second most common. Out of interest, do you have hazel eyes, please let me know below. In general, there are two main types of hazel eyes: those with brown as the dominant color in the iris and those with green as the dominant color. While all hazel eyes will have a combination of green and brown colors, the difference in dominant colors is why they can appear either mostly green or mostly brown. Given this, hazel eyes can quite often be confused with other eye colours in certain lighting conditions and in different environments. Hazel eyes can sometimes be confused with amber eyes for instance, but they are two separate eye colors. Although hazel eyes may contain specks of amber or gold, they usually tend to have many other colors, including green, brown and orange, while amber eyes are of a solid gold hue. Also, hazel eyes may appear to shift in color and consist of flecks and ripples. Hazel eyes are also sometimes confused with green eyes. One of the main differences between green and hazel eyes however is that green eyes usually have a solid green hue with more or less a single color throughout the iris. Hazel eyes are multi-coloured on the other hand, with a shade of green and a characteristic burst of brown or gold radiating outwards from around the pupil. Some people also confuse hazel eyes with brown eyes. Brown eyes however are mainly brown and may show only slight hints of green or other colors, whereas hazel eyes often have a combination of various colors. Now the reason why hazel eyes have more variation of colors than brown eyes is because they have less melanin as well a different distribution of melanin in the layers of the iris. This lower level of melanin compared to brown eyes allows for more light to be scattered, in similar way to how blue and green eyes get their color, and why the sky is blue, and this process gives rise to the various beautiful colors that you often see in hazel eyes. Hazel eyes do have more melanin than green, blue and gray eyes however. In general, a complex genetic process that scientists are still trying to figure out is involved in how much melanin is produced by the iris, with at least 16 different genes responsible for eye color, with the HERC2 and OCA2 genes particularly important in this process, which are located on chromosome 15. Different clothing can also sometimes change how your eyes look, and if you’re trying to figure out what color eyes you have, looking into a mirror wearing a white t-shirt can help according to some sources online. Now before looking at some of the reasons for hazel eyes, let’s turn our attention to their origin? Well the term hazel comes from the color of a hazelnut and is recorded describing eyes as early as the 1690s. Today, Hazel eyes are most common in Spain (with 55.2% of people in Spain having hazel-green eyes according to a 2009 study), as well as in North Africa, the Middle East, and Brazil. Now as far as the precise origin of hazel eyes, it is unknown who the first person with hazel eyes was and where they originated from, and more research is need to determine this. One point to note however relates to geography. It is interesting that hazel eyes are most common today in relatively connected regions of the globe, in Spain, North Africa, the Middle East, and Brazil. North Africa and the Middle East are obviously close to each other geographically, so a genetic trait could spread between these regions quite easily through the movement of people. Spain is also close by and is also connected to North Africa through the Moors and other peoples who had a major influence on the Iberian peninsula down through history. And Brazil also has strong connections to the Iberian peninsula through Portugal. Although this is just speculation, you can perhaps make the argument that there is a geographical connection linking hazel eyes. Perhaps there was a genetic mutation for hazel eyes in this general area around North Africa that persisted and impacted other areas around it due the movements of people over the centuries and millennia. This is just a thought however, and hopefully future research can provide more insights into the origin of hazel eyes. We do know that they have featured in mythology for thousands of years however. Some ancient cultures believed that individuals with hazel eyes possessed special powers, such as the ability to ward off evil spirits. As far as the reason for hazel eyes, a 2015 paper that looked at the inheritance of hazel eye colour in North India had some interesting findings. Their results indicated that hazel eyes are probably the result of more than just genetics, and that climate and the environment probably had an impact on hazel eyes developing. “Our pedigree study suggested that the hazel eye colour inheritance does not follow the Mendelian inheritance patterns. It also showed that the hazel eye colour is not sex-linked and moreover, that it is neither autosomal dominant nor autosomal recessive. One case from Kangra, Himachal Pradesh, a region with mild temperate climate, showed higher occurrence of hazel eyes in the family, with many lineages showing continuous expression of hazel eyes for three generations and in some for even four generations. The other two cases involving families from other regions with humid subtropical climate had a comparatively lesser number of persons with hazel eyes, showing continuous expression of hazel eyes for only two generations in a few lineages. Thus, climate might have a role in eye pigmentation due to differential expression of the genes responsible for eye colour. Since, there are many genes responsible for the production of eye colour like OCA2, BEY2, GEY, HERC2 etc., primarily the expression of these genes might produce the eye colour but the climate/environment might have its own influence on the expression of these genes.” So from this study in India at least, it seems that hazel eyes were more common in a region with a milder climate (relatively speaking for India that is) I live in Scotland after all 😊 If we look globally as well, it would make sense that as the melanin concertation of hazel eyes is somewhere in between brown and blue, it would make sense that hazel eyes are most common not too far south and not too far north. Spain, North Africa, the Middle East, and Brazil are all somewhat in the middle geographically. This paper from India in 2015 nicely details one way the environment make impact eye color given the climate and the level of light in different parts of the world: “The blue or green eye colour are rare in India. Unlike India, in the European and American populations, the blue or green eye colour is more common. This difference in the eye colour may be due to environmental influences. The melanin protects the cells from the harmful effects of the UV radiations from the sun. In countries like India, where temperature remains higher throughout the year in most parts of the country, this pigment might have a role in protection of our skin and eyes. In colder countries, where the sun rays do not fall direct, and the climatic conditions are mild when compared to other parts of the world at the same latitude, we come across people with lighter skin and eye pigmentation.” Although there are obviously various genetic mechanisms involved here, it is interesting that environmental factors do probably play a role in eye color. Another reason for hazel eyes being selected for over time could be to do with sexual attractiveness. In general, humans tend to value things that are rare or perceived to be rare, whether that is in the economic sphere such as valuing precious metals such as gold, jewellery, diamonds and fine art, or as far as physical traits. Given that only around 5% of the global population has hazel eyes, and they have probably also been relatively rare down through history, combined with being filled with various beautiful colors such as green and gold, its easy to see why hazel eyes would be valued and admired down through the ages. In general though, there needs to be more research into hazel eyes, as there wasn’t as much proper research as I had hoped, and not as much as compared to blue or green eyes for instance. Hazel eyes are often confused with green eyes. To find out more about why green eyes developed and what parts of the world they are most common, please click here. I would be interested to know your thoughts below as well on hazel eyes, so please let me know in the comments. 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