HAIR

A hair-follicle scientist offers an edifying look at the biology, physiology, and history of hair.

A former professor of pathology and dermatology at Yale University School of Medicine and former director of skin biology for Johnson & Johnson, Stenn brings considerable expertise and lively curiosity to this wide-ranging inquiry into what hair is, how it evolved, and what it has meant culturally, personally, and economically. Hair, notes the author, is present on all skin surfaces, although on humans, much of it is hardly noticeable. Even an individual who appears to be bald has “frightfully small, only microscopically visible” hair follicles and hair shafts. Scientists disagree regarding why humans lost the dense hair cover that characterized earlier hominids; the author believes less density evolved “to protect their uniquely temperature-sensitive brain” and dissipate heat through sweat glands. Besides human hair, Stenn considers the significance of fur, which functioned as protective covering for early humans living in cold climates. Indigenous North Americans understood that late autumn was the best time to collect beaver skins because the animal’s fur was thickest in anticipation of winter. In 16th-century Europe, beaver hats were so coveted that trappers exhausted the beaver populations of Northern European forests, turning energetically to the New World, where fur trading became economically beneficial to native peoples. In the 14th century, England was renowned for wool production, which continued as the nation’s most profitable export for many centuries. Stenn investigates some arcane practices involving hair, notably the hair-hang act, where a female acrobat is suspended from rafters by a shank of hair, a feat made possible because of hair’s amazing tensile strength. Other uses for hair include artists’ brushes; violinists’ bows, which use about 130 to 150 straight shafts, constructed in a painstaking process; and as forensic evidence for solving crimes.

A spirited, informative history of a fascinating fiber.