2025/10/10 by Leah C Redmond, Claire A. Higgins
Medicine · Biochemistry, Genetics and Molecular Biology · #Hair Growth and Disorders #Skin and Cellular Biology Research #melanin and skin pigmentation
paper · doi:10.1093/bjd/ljaf395
A striking characteristic that sets modern humans apart from their ancestors is the lack of a thick fur coat. Despite being popularly dubbed 'the naked ape', humans are covered in 2-3 million vellus hair follicles producing tiny hair fibres. This review explores why humans evolved thinner body hair, with a focus on the need for an effective cooling mechanism. We address anthropological evidence and traits that developed in parallel with humans losing their fur. We then discuss the differences between thick terminal hairs and thin vellus hairs, and the role of the dermal papilla in the regulation of hair fibre thickness. Taking inspiration from genes involved in hirsutism, hypertrichosis and hair thickness, and expression of these genes in the dermal papilla, we propose a linear switch regulator hypothesis of how humans have evolved to not develop terminal hair on their bodies.