As an anthropologist with training in comparative biology, Jablonski is particularly interested in the natural history of humans: how did humans evolve to gain the varied appearances we see today? In particular, she investigates how our skin developed into a covering that is unique among animals in three ways: (1) it is naked--effectively hairless--and sweaty, (2) we come in a wide array of colors (not just the traditional four), and (3) we use our skin as a surface for decoration, a "social placard," which we cover or bare at will, and on which we put make-up, tattooes, scarifications, and piercings, all ways of expressing cultural and personal values.

Our ability to sweat allowed us to cast off the usual mammalian fur coat and to be active even in the heat of the day (when many creatures take shelter). Humans, therefore, could do more and be more as thinkers, builders, and social creatures.

As to our color variations, Jablonski argues that the main root of modern humans came out of East Africa; these people were black, because a lot of melanin in their skin was the best way to avoid too much ultraviolet radiation, although some is needed to create Vitamin D. As humans migrated to the north and the south, Darwinian selection favored lighter skin pigmentation in order to use the lower levels of sunlight.

Jablonski writes, "Dark skin or light skin, therefore, 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" (p. 95). And, noting an irony: "Naturally dark people in many parts of the world are increasingly seeking ways to lighten their skin, while the naturally light-skinned are trying to find new ways to darken theirs" (p. 159).

We often take our skin and all its functions for granted; our consciousness can change quickly, however, if we experience a skin disease, a sunburn, or a thermal burn (see Carter and Petro, Rising from the Flames: The Experience of the Severely Burned). Jablonski discusses a variety of illnesses, including burns, dermatitis, and skin cancers. Other topics include the importance of touch, how skin relates to emotion and sex, and experiments in artificial skin, useful for covering patients with severe burns.

Jablonski presents a dozen color plates, 44 figures, and maps to enliven her text.