The human fabric

old woman’s face with blue and red scarf on head
Divyesh Sejpal

"It isn't good to take for granted something as important as skin," writes Nina G. Jablonski.

With the publication of her most recent book, Skin: A Natural History (University of California Press), Jablonski—professor and head of Penn State's anthropology department—delivers a thought-provoking remedy to our nonchalance about the human body's largest organ. Her book, which she describes as "more an idiosyncratic guidebook" than a "systematic treatise or manual" is an engaging tour of skin's evolutionary history and cultural significance.

Jablonski devotes the first half of the book to her principal research interests, primate evolution and human pigmentation. A teacher of human anatomy for many years, the author opens with a discussion of how skin is put together and how it functions. Illustrations underscore Jablonski's message: the human dermis is a highly specialized, sophisticated mosaic of cells providing our most basic needs of physical protection, temperature regulation, radiation deflection, and vitamin D absorption. "Our skin is not perfect," Jablonski writes, "but it does a remarkably good job. Our fabric doesn't wear out, our seams don't burst, we don't spontaneously sprout leaks, and we don't expand like water balloons when we sit in the bathtub."

After this brief primer in "Skin 101," Jablonski moves on to discuss why we humans—or "naked apes"—are relatively hairless among the animal kingdom. The answer, Jablonski argues, lies in our eccrine sweat glands. Under selective evolutionary pressure, humans became "proficient eccrine sweat machines," she says. Although many animals sweat, the evaporative cooling of wet fur is an inefficient way to keep the body's core cool. Says Jablonski, "For an active primate living in a hot environment, having a functionally naked and actively sweating skin is the best may to maintain a steady body temperature and—literally—a cool head."

In the quest for survival, it turns out that cooler heads really do prevail. As anyone who has had a fever knows, "your abilities to think, reason and communicate are compromised when the brain is even slightly overheated...," reminds Jablonski. Our large brain size ("the largest brain of all animals relative to body size") makes an efficient body cooling system a necessity. "Behind every large human brain," quips Jablonski, "there is a potentially very sweaty human body."

Skin delves into such fascinating areas as the cultures of tattooing, ceremonial scarring and the modern skin care industry, as well as speculating on the development of artificial electronic skin that may provide robots of the future "with a sense of touch and, perhaps, a sense of self." However, the most passionately argued topic of Jablonski's book may be her discussion of skin color. "The evolution of different skin colors is one of the most engaging and important stories in all of human evolution," writes Jablonski. Despite the fact that skin color has been used to classify people into "purportedly genetically distinct geographic groups or 'races,'" Jablonski argues, "...this method of classifying people doesn't make sense." Whatever your hue, it developed as "a product of evolution by natural selection, based on the solar environment of our ancestors," especially the different levels of ultraviolet radiation around the globe. (The higher melanin content of dark skin confers a natural sun protection equivalent to SPF 10-15 and allows darker-skinned people to tolerate longer sun exposure than the light-skinned.) Skin color does not equal race, Jablonski asserts. It tells us about "the nature of the past environments in which people lived, but skin color itself is useless as a marker of racial identity."

This highly-readable natural history reminds us that although "clothing and shelter are fairly recent inventions in human history," our skin is our first and most essential home, and shield. "Through our naked, sweaty, marked-up skin, we tell the world who we are," Jablonski concludes. "Our skin is us."

Nina Jablonski, Ph. D., is professor and head of anthropology in the College of the Liberal Arts, ngj2@psu.edu. Skin: A Natural History was published in October 2006 by University of California Press.

Last Updated August 01, 2007