It is substantiated by Iyengar's findings (1998) that UV light can enter into straight human hair roots (and thus into the body through the skin) via the hair shaft. Specifically, the results of that study suggest that this phenomenon resembles the passage of light through fiber optic tubes (which do not function as effectively when kinked or sharply curved or coiled). In this sense, when hominids (i.e. Homo erectus) were gradually losing their straight body hair and thereby exposing the initially pale skin underneath their fur to the sun, straight hair would have been an adaptive liability. By inverse logic, later, as humans traveled farther from Africa and/or the equator, straight hair may have (initially) evolved to aid the entry of UV light into the body during the transition from dark, UV-protected skin to paler skin. Innes, William C. (2021). Religious hair display and its meanings. Cham, Switzerland. ISBN 978-3-030-69974-1. OCLC 1249505982. {{ cite book}}: CS1 maint: location missing publisher ( link)

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The high interspecific variability of the size, color, and microstructure of hair often enables the identification of species based on single hair filaments. [43] [44] Naked mole-rat ( Heterocephalus glaber) in a zoo.

Author Contributions

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