Evolution Of Human Skin

I watched a documentary the other night about the evolution of skin color. I had always thought that evolution was responsible for the differences in skin color among humans but didn't know the extent of the evidence.

Skin color is determined by the concentration and type of melanin found in the skin. So why do people from the northern parts of Europe have light skin and people from east africa have dark skin. Well, melanin is produced by the body to protect us from harmful UV radiation. It is then not surprising that when you overlay a chromatic distribution of skin color with that of UV radiation you get a 90% match. Essentially those humans living in high UV radiation areas have a higher concentration of the melanin type which causes dark skin color. When humans started migrating away from the equator around 120,000 years ago the amount of melanin required for protection was less. This is why people from the northern parts of Europe have fair skin.

In order to show that human skin color evolved over time scientists had to prove that protection against UV radiation increased the reproductive success amongst humans. Whilst working in WA Dr Nina Jablonski discovered a link between UV radiation protection and reproductive success. Folate is a chemical which is important for embryonic development and also for sperm production. It is also very susceptible to prolonged or intense UV radiation. So humans which are exposed to high levels of UV radiation without the necessary protection have a lower chance of reproductive success.

UV radiation isn't all bad for humans. Type b UV radiation is essential in the production of Vitamin-D. This was discovered at the turn of the last century when there was an epidemic of rickets amongst children in the UK. So humans living in areas with lower levels of UV radiation needed to absorb more radiation in order to produce Vitamin-D. What's also interesting is that African Americans living in the northern parts of America have been found to have high levels of Vitamin-D deficiency. In this case they are not getting enough UV radiation because there skin is so good at blocking it.

The final and most impressive piece of evidence was the discovery of a specific genetic mutation which suppresses melanin production. The discovery was first found in a small fish and then the same mutation was found in Europeans with fair skin. The significance of the discovery was not fully realised until the discovery of a similar mutation in the DNA of a Neanderthal. Neanderthal's share a similar ancestor to the modern day human, migrated from Africa to Europe and were fair skinned. This discovery shows that the skin color of both Neanderthal and modern day humans evolved in the same way.

What a great doco. Thanks SBS. If you want to watch the whole thing go here.