UV radiations and melanin production

UV radiations and melanin production

Humans and chimpanzees had the same ancestor about seven million years ago. The changes occur with the passage of time and each of the species evolved individually; the chimpanzees are, however, less evolved because they lived in their original environment. As our history can be related, it is observed that chimpanzees commonly have white skin which is covered with hair. So, it can be predicted that humans had white skin. The lifestyle of humans and chimpanzees is different because they live in different environments. Humans worked hard, like hunting, after they were fed up with picking fruit. This active lifestyle of humans developed their brains, and it is also a hypothesis that this used a lot of energy and heat was produced. This resulted in the formation of a lot of sweat glands, and the white skin was then affected by the harsh sunlight and new skin problems were discovered.

Ultraviolet (UV) light from the sun is dangerous for human skin as it can cause mutations in the DNA sequence of the skin cells. As a result of these changes, the production of melanin in the human skin started as it is a natural sunscreen and protects the human skin from UV and its harmful effects. Now every human has an ability to produce these pigments because of evolution. The difference in skin color is due to the difference in the amount of pigment in the skin. People with dark skin have more melanin, so they can absorb more UV rays, and melanin protects their skin from getting damaged. More melanin means a darker skin tone. The white color is genetically transferred to the next generation but the amount of melanin in a parent can be different from offspring as it is not genetic.

If we look at the globe and analyze it, then we will conclude that the area near the equator receives more solar energy (UV) than the poles. This is due to the low latitudes near the equator, which receive high UV radiation all year round, while at the poles we can observe that, due to the low angle of the sun and the high latitudes, fewer UV rays fall on the poles. Due to this fact, the countries near the equator, e.g., Colombia, Brazil and Congo, have a large population of dark-skinned people, while the countries at high latitudes, like Canada, Denmark and Norway, have a smaller population of dark-skinned people.

Background (added October 26, 2026). Sunlight contains three bands of ultraviolet (UV) radiation: UVA (315–400 nm), UVB (280–315 nm) and UVC (100–280 nm). The atmosphere absorbs all UVC and most UVB, so the UV reaching the ground is mostly UVA with a little UVB (WHO). Melanocytes make melanin inside small compartments called melanosomes and pass it to nearby skin cells, where it shields their DNA from UV. Eumelanin (brown to black) absorbs UV; pheomelanin (yellow to red) can instead produce reactive oxygen species under UVA. Tanning is part of the skin’s response: UVB damages DNA in skin cells, which triggers signals (including the hormone α-MSH) that make melanocytes produce more melanin (Yardman-Frank and Fisher, NIH PMC). Tyrosinase is one of the enzymes involved; another Odinity lab studies it in detail: Enzyme Kinetics: Determination of the Kinetic Parameters for Tyrosinase. This section is educational, not medical advice.

Editor’s note (October 26, 2026): The student’s essay is kept as written, apart from spelling and grammar fixes and a few word corrections (“infected” to “damaged,” since melanin protects cells from UV damage, not infection; “slight angle” to “low angle”; “near poles” to “at high latitudes”; “causes mutation” to “can cause mutations”). Four statements still need correcting:

• No species is “less evolved.” Humans and chimpanzees share a common ancestor from about 8 to 6 million years ago, and each lineage has evolved differently since (Smithsonian Human Origins Program). On natural selection, see The Evolution of the Theory of Evolution and these selections from Charles Darwin.
• Melanin production did not “start” with humans. Chimpanzees and other primates also make melanin in the hairless parts of their skin, such as the face, and chimpanzee facial skin darkens with age and UV exposure. Researchers propose that early hominids had lightly pigmented skin under dark hair, like chimpanzees, and that naked, darkly pigmented skin, which protected sweat glands from UV-induced injury, evolved early in the genus Homo (Jablonski and Chaplin, 2000).
• Skin color is largely genetic. Melanin “is not genetic” is incorrect: constitutive skin color is the genetically determined level of melanin in the skin, while tanning is a separate response to UV (Brenner and Hearing, NIH PMC, 2008).
• Skin color is not just the amount of pigment. People have similar numbers of melanocytes; differences come mainly from how much melanin they make, its type, and how the melanosomes are sized and packaged (Brenner and Hearing, 2008). The latitude pattern above matches research on indigenous peoples (Jablonski and Chaplin, 2000), who excluded populations known to be admixed or to have recently migrated; countries’ populations today can differ from this pattern because of migration.