Friday, July 03, 2015

What is your body's biggest organ?

Steve Paulson has some questions in Nautilus about our skin. He writes,
Skin may seem like a superficial human attribute, but it’s the first thing we notice about anyone we meet. Nina Jablonski came to this realization many years ago when she was teaching a human anatomy class to young medical students in Hong Kong. When faced with dissecting a dead body, they flinched at the thought of cutting into or even touching it. But they lost their inhibitions once they opened up the cadaver. Without skin, the corpse no longer looked human.

Jablonski got hooked on all things related to human skin. As a primatologist and paleobiologist, she wanted to understand why humans—alone among the primates—evolved to become the naked ape, and why skin comes in so many different hues and shades around the world. Once she started investigating the science of skin color, Jablonski was pulled into the sordid history of racism, and she saw how even great thinkers like Kant and Thomas Jefferson believed people with dark skin were innately inferior to light-skinned people like themselves.

Why did we lose our fur?

We think it occurred because of the need to keep ourselves cool when we were moving around very vigorously in a hot environment. Around 2 million years ago, we see the evolution of the first members of the genus Homo. These ancestors were tall, strapping, strong walkers, vigorous runners, and all those activities under equatorial sun generate a lot of heat. Primates, including humans, dissipate heat through the surface of their skin. We can’t really pant like dogs, so we have to lose heat either through radiant heat loss from the surface of our bodies or by sweating. So we evolved the ability to sweat copiously and lost most of our fur.

So early humans in equatorial Africa developed dark skin as protection against the sun?

That’s right. The sun is great, but it has a lot of injurious rays, especially ultraviolet radiation. Most animals protect themselves from UV radiation with fur. What we did in our lineage was turn on pigmentation genes that allowed us to produce more permanent pigmentation in our skin cells. This was really an important revolution in human history because it allowed us to continue to evolve in equatorial environments and thrive and disperse. It really made it possible for us to continue along the trajectory toward modern humans, Homo sapiens, in Africa.

...What do you make of studies that have linked IQ and race?

The studies are flawed in the way they’ve been conducted, in the nature of the samples that have been used, in the tests that have been given. The people who have undertaken these studies have gone in with an agenda in mind. This is dangerous, and we know in the history of science that when people come in with an idea they want to prove, this is not science.

There have been studies of relatively small numbers of individuals, with much better controls for educational background, socioeconomic background, and all environmental variables. What these small, careful studies have shown is that there’s no difference in intelligence between the so-called races and that all differences that develop are due to cultural differences. Some of these may be due to differences in diet. Most have to do with differences in learning patterns that result from a child’s cultural framework. In other words, we are all born basically with equal potential and what happens after birth is what really determines our so- called intelligence.

Pale skin is clearly not as prized as it once was. How do you see the politics of skin color in today’s world?

We live in a strange world where many light-skinned people want to be darker—or at least tanned to look healthy and like they’ve just enjoyed a vacation on the Riviera. A lot of darkly pigmented people want to look lighter because lightness is associated with higher status. So we have a paradoxical situation where many light people want to be darker and many dark people want to be lighter. Humans are motivated by diverse sets of ideas. They usually aspire to an appearance that confers higher status. Once we recognize that it’s a pretty stupid thing to do, we can adjust our cultural sights and say, “Hey, let’s just live with the skin color that we have. Let’s protect it, let’s cherish it, let’s make sure that we are healthy with it.”
Read more here.

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