New research reveals why humans have different skin colors

With the help of a study of the common zebrafish, whose cell composition is similar to ours, the researchers discovered that the change in skin color is due to a mutation in a certain key gene

The light zebra fish and the dark zebra fish: normal zebra fish (A) and a mutation of the fish (B). In fish with the mutation, the black stripes are paler than normal and their bodies are yellower. The researchers showed that the version of the gene in the goldfish changed the production of melanosomes, black pigments that give the skin its color

A gene responsible for fair skin tone in Europeans and dark skin tone in Africans was discovered by researchers from the University of Pennsylvania in the USA. The study, published last week in the journal "Science", found that this gene has two versions: one is found in 99% of Europeans, and the other in 93%-100% of Africans.

The discovery is unusual, as humans are known to generally share different versions of genes, although a particular version may be more common in one race than another. The exception to this exception is the version of the gene named after Duffy, which prevents malaria and is found almost exclusively in members of one race - sub-Saharan Africans.

The new gene belongs to the same category as the Duffy gene, and may shed light on the evolutionary changes Europeans underwent when their ancestors, who were probably brown-skinned, migrated north about 40 years ago.

Humans developed dark skin in Africa about 1.5 million years ago. At that time, humans lost a significant part of their body hair and therefore needed new protection from the strong sunlight. The ultraviolet rays of the sun destroy folic acid, and a lack of this acid causes birth defects. The dark skin tone provided the same protection. But when modern humans migrated out of Africa and settled in northern lands, they needed more sunlight to enable the chemical reaction that produces vitamin D.

The new gene was first identified not in humans, but in a mutation of zebrafish, a small, striped fish common in aquariums. The fish with the mutation are called "golden", because their stripes, which are mostly black, are paler than normal and their bodies are yellower.

Dr. Keith Cheng and his colleagues showed that the gene in the golden version of the fish altered the production of melanosomes, tiny black pigment particles that give the skin its color. Then the researchers discovered that in humans, who have their own version of the gene, the version common among Africans enabled the production of larger melanosomes, which tend to cluster together, while the version common in Europeans produced smaller, more scattered melanosomes.

According to Chen, people of Asian descent have the same version found in Africans, so it seems that their light skin tone evolved thanks to some other gene, which also affects skin color. Mark Schreiber, who was a partner in the research, said that in his laboratory an attempt was made to estimate when the European version of the gene became so widespread, and to find its geographical origin.

It is possible that the strong selective pressure that caused the version to become universal among the Europeans, also included selection in the choice of the spouses. "In Africa, humans are much darker than they need to be to protect themselves from ultraviolet radiation, so I think sexual selection was also at work here," Schreiber said. In other words, black skin may have been preferred by African men and women in their sexual partners, just as Europeans and Asians preferred light skin in sexual partners.

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A team of experts from the University of Pennsylvania discovered that the SLC24A5 gene found in our bodies is the cause of our different skin colors. The BBC reported that the researchers came to this conclusion after a long study of zebrafish. Although the gene was known, only today can it be linked to skin color.

Advertisement The zebrafish is ideal for such research, as many of its genes are identical to human genes. And many of their pigmentation cells contain containing melanosomes, which are also present in the cells of the human body. The researchers found that lighter skin in zebrafish was caused by a mutation of the SLC24A5 gene. Adding a certain protein to the light fish strain, caused the fish to become darker, and spawn darker fry. The researchers then conducted the same study in humans, and discovered a similar pattern.

It turns out that in the European region, most people carry only one mutation of the gene, and it is the one that causes lighter skin among Europeans.

The researchers claim that the research has an importance that extends beyond understanding where our skin color comes from, which is one of the great scientific mysteries of medicine. The research is important for discovering a treatment for skin cancer (melanoma). Also, it will be possible to understand why we have different eye colors, different hair color, etc.

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