I’ve always been somewhat fascinated by the abundance of different skin colors in our world. We all originated from the same part of the world, so why do we all differ so much in our skin tones? I wanted to know more about the science and evolution behind it all.
So like I said, we all came from the same place. About 50,000 to 80,000 years ago (scientists argue about exactly how long ago), humans migrated from Africa out into the rest of the world. Something happened between then and now to change our skin colors and, as many intelligent people could probably infer, it has to do in part with where each group of people ended up settling and the characteristics of those places.
According to this article, there are three main factors that led to the emergence of multiple skin colors. Differences in skin tones correlate very closely with the following:
- Geography
- Ultraviolet (UV) radiation from the sun
- And! A third factor many would most likely not think of: diets that are rich in seafood (another way to get vitamin D than from the sun).
As can be inferred, geography plays a big part because, of course, climates are in no way consistent all across the globe. The temperatures and environments found in Africa are entirely different than those in, say, Northern Ireland. So, when humans began to migrate from one climate to another, their bodies needed to cope with the significant changes. For example, dark skin came from the need to stay cool. As humans settled into hot, wide open environments like those in Africa or Australia, they eventually evolved to have an increase of sweat glands on the skin as well as a decrease in body hair. Both of these things served to make cooling off easier in hotter temperatures. However, these humans now lacked the dark body hair needed to protect them from the sun’s rays (UV rays in specific). Instead, they evolved to have permanently dark skin to protect from the dangers the sun’s rays posed. This dark skin came from an abundance of melanin, a brown pigment found in our skin that acts as that protection from the sun.
Now on the other hand, we have the groups of people who moved further north. Up north, further away from the equator, there’s a lot less UV rays to cause damage to the human body. We need a healthy dose of vitamin D from the sun in order to stay healthy, and darker skin prevented early northern settlers from getting it. So natural selection favored the genes that carried pale skin and fair features. That’s why the further north you travel, the lighter skinned people get. Take me, for example. I’m half Italian, so I’ve got dark hair and eyes and somewhat tan skin. But, I’m also Irish, so that means that I’ve got lighter skin than my father, who is full-blooded Italian. Why? Because Ireland is more north than Italy, and people there have lighter skin tones than found in a southern European country like Italy.
The human body is a fascinating thing, huh? Just think for a moment about how incredible it really is that evolutionary advances like this happen entirely on their own.
And what about that third factor? How does sea food have anything to do with skin color? That’s what I was wondering. It all comes back to vitamin D. Seafood is very rich in vitamin D. This means that native coastal people whose diets consisted mostly of seafood didn’t need to depend on the sun to get their daily dose of vitamin D. This explains why the people who settled in Arctic environments like Alaska or Canada could afford to have darker skin than others. Even though they lived in these low UV places, they still were able to get enough vitamin D through the seafood they ate. And another interesting detail that same article from above mentions is that their dark skin also helped protect them from UV rays that would reflect off of ice or snow!
So what’s the take away from all of this? Just remember that we all came from the same place. We really are not that different, some of us are simply better protected from the sun then others!
Picture Source:
http://anthro.palomar.edu/adapt/adapt_4.htm
Sources:
http://anthro.palomar.edu/adapt/adapt_4.htm
http://www.livescience.com/50326-what-is-ultraviolet-light.html