![]() Hair coloration may also provide thermoregulatory benefits. Color signalling plays a role in sexual communication as well as species, kin, and individual recognition, which is evinced from studies of primate faces. The strongest of these, crypsis, likely contributes to both drab and conspicuous coloration. Nonetheless, we know that crypsis, signalling, and physiology all drive the evolution of coloration in wild mammals. Yet, we know little about the evolutionary origin of this phenotype. Incremental greying is thus a progressive increase towards more depigmented hairs over time. Phenotypically, the perception of grey hairs comes from an increase in depigmented hair shafts relative to the number of pigmented hair shafts (i.e., salt and pepper look in brunettes). Therefore, melanin can no longer be deposited into hair shafts once melanocytes die. Hair greying occurs from a permanent and irreversible loss of melanocytes (i.e., melanin-producing cells) in each hair follicle as humans age. However, the age of hair greying onset and its progression throughout life are now known to vary between human populations and geographical origin. An early study found that at least 50% of the aged (>50 years old) population has at least 50% grey (depigmented) scalp hair. ![]() Head hair greying is one of the most important phenotypic markers for human aging, especially after mid-life. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. ![]() This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: The data underlying the results presented in the study are available from doi: 10.5061/dryad.f7m0cfxs7.įunding: Funding for this study was from George Washington University, Yale University, and NSF (BCS-1546730). Received: DecemAccepted: JPublished: July 14, 2020Ĭopyright: © 2020 Tapanes et al. related to conspecific communication), is unclear and worthy of more detailed examination across populations and taxa.Ĭitation: Tapanes E, Anestis S, Kamilar JM, Bradley BJ (2020) Does facial hair greying in chimpanzees provide a salient progressive cue of aging? PLoS ONE 15(7):Įditor: Nicoletta Righini, Universidad de Guadalajara, MEXICO Whether this reflects neutral differences in senescence, or potential differences in selection pressures (e.g. Thus, chimpanzee facial hair greying is unlikely a progressive indicator of age beyond mid-life, and thus facial greying in chimpanzees seems different from the pattern observed in humans. Our results highlight that chimpanzee pigmentation likely exhibits substantial variation between populations, and that both 'grey' and pigmented phenotypes exist across various age classes. Our data suggest that chimpanzee head and facial hair generally greys with age prior to mid-life (~30 years old), but afterwards, greying ceases to increase incrementally. Digital facial photographs representing three chimpanzee populations (N = 145 ages 1–60 years) were scored for hair greying on a scale of one to six. We examined the relationship between pigmentation loss in facial hair (greying) to age, population, and sex in wild and captive chimpanzees ( Pan troglodytes). ![]() Yet, whether humans are unique in our pattern of age-related hair depigmentation is unclear. In wild mammal populations, greying can change with life history or environmental factors (e.g., sexual maturity in silverback gorillas). They, however, get around by climbing and swinging from tree to tree.The greying of human head hair is arguably the most salient marker of human aging. They sometimes feed on other wildlife like monkeys or small antelope.Ĭhimpanzees usually walk on all fours, but also have the ability to walk on two feet. Chimpanzee diet includes seeds, leaves, roots, insects and honey. They, however, have a special liking for fruits. They also use tree branches to scratch their backs.Ĭhimpanzees feed on a variety of food, both plant and animals. Rocks and twigs are some of the rudimentary tools they use to search for food. New smaller units often form as the animals forge new relationships.Ĭhimpanzees make use of self-made tools in order to feed and protect themselves. They live in groups where the membership size and composition changes over time. This causes a close familial bond, even during maturity.Įxtended family groups can grow as large as 20 to 120 chimpanzees, and can have strict hierarchies, with just one dominant alpha male as the leader. Infant chimpanzees often cling on to their mothers' fur and ride on their backs until the ages of three to five. Most chimpanzee pregnancies carry one child.
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