Primates are relatively hairless compared to other mammals, and hominini such as chimpanzees, have less dense hair than would be expected given their body size for a primate. [48] Evolutionary biologists suggest that the genus Homo arose in East Africa approximately 2 million years ago. [49] Part of this evolution was the development of endurance running [50] and venturing out during the hot times of the day [51] that required efficient thermoregulation through perspiration. The loss of heat through heat of evaporation by means of sweat glands is aided by air currents next to the skin surface, which are facilitated by the loss of body hair. [52]

Hindmarsh, J.T. Caveats in hair analysis in chronic arsenic poisoning. Clin. Biochem. 2002, 35, 1–11. [ Google Scholar] [ CrossRef] Weber, R.J.M.; Southam, A.D.; Sommer, U.; Viant, M.R. Characterization of isotopic abundance measurements in high resolution ft-icr and orbitrap mass spectra for improved confidence of metabolite identification. Anal. Chem. 2011, 83, 3737–3743. [ Google Scholar] [ CrossRef] [ PubMed] For freehand techniques such as balayage: There’s nothing quite like Blondor Freelights. We formulated it specifically for freehand, foil-free strokes, complete with an adhesive mass that ensures it stays in place. This means you don’t have to worry about blurring or bleeding while the lightener develops.Hair: its power and meaning in Asian cultures. Alf Hiltebeitel, Barbara D. Miller. Albany: State University of New York Press. 1998. ISBN 0-7914-3741-8. OCLC 37254408. {{ cite book}}: CS1 maint: others ( link) Rebora, Alfredo (2010). "Lucy's pelt: when we became hairless and how we managed to survive". International Journal of Dermatology. 49 (1): 17–20. doi: 10.1111/j.1365-4632.2009.04266.x. ISSN 1365-4632. PMID 20465604. S2CID 21484729. Ruben, J.A.; Jones, T.D. (2000). "Selective Factors Associated with the Origin of Fur and Feathers". Am. Zool. 40 (4): 585–596. doi: 10.1093/icb/40.4.585. Hair-follicle cycling Hair grows at different speeds and different lengths. Its composition causes different colors and textures, which influence how long the hair strands grow. Marianne Ernst, a German "Long hair model".

For pin-straight, divide each layer into small sections. Glide the straightener only a few times over each section before moving along. [5] X Research source 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. Toth, Maria (29 December 2017). Hair and fur atlas of Central European mammals. Pars Ltd. p.307. ISBN 978-963-88339-7-6 . Retrieved 8 July 2019.Bubenik, George A. (1 September 2003). "Why do humans get "goosebumps" when they are cold, or under other circumstances?". Scientific American . Retrieved 4 May 2010. Teerink, BJ (2003). Hair of West European Mammals: Atlas and Identification Key. Cambridge University Press. p.224. ISBN 9780521545778. As long as new hair cells continue to grow in the hair bulb, the hair continues to grow longer. This growth phase is also called the anagen phase. At any point in time, about 90 percent of a person’s total amount of hair is in this growth phase. Borella, P.; Rovesti, S.; Caselgrandi, E.; Bargellini, A. Quality control in hair analysis: A systematic study on washing procedures for trace element determinations. MikroChim. Acta 1996, 123, 271–280. [ Google Scholar] [ CrossRef] Castaing, R.; Slodzian, G. Optique corpusculaire-premiers essais de microanalyse par emission ionique secondaire. J. Microsc. 1962, 1, 395–399. [ Google Scholar]

Wu, Dong-Dong; Irwin, David M. (2018), Plowman, Jeffrey E.; Harland, Duane P.; Deb-Choudhury, Santanu (eds.), "Evolution of Trichocyte Keratin Associated Proteins", The Hair Fibre: Proteins, Structure and Development, Advances in Experimental Medicine and Biology, Singapore: Springer, vol.1054, pp.47–56, doi: 10.1007/978-981-10-8195-8_5, ISBN 978-981-10-8195-8, PMID 29797267 , retrieved 4 March 2023 Niedźwiedzki, Grzegorz; Bojanowski, Maciej (July 2012). "A Supposed Eupelycosaur Body Impression from the Early Permian of the Intra-Sudetic Basin, Poland". Ichnos. 19 (3): 150–155. Bibcode: 2012Ichno..19..150N. doi: 10.1080/10420940.2012.702549. S2CID 129567176. Heads were shaved in concentration camps, and head-shaving has been used as punishment, especially for women with long hair. The shaven head is common in military haircuts, while Western monks are known for the tonsure. By contrast, among some Indian holy men, the hair is worn extremely long. [67] [68] [69] [70]a b c "Hair type, texture and density | Hairdressing Training". Hairdressing.ac.uk. Archived from the original on 12 February 2015 . Retrieved 28 January 2015. the hair shaft, which is the hard filamentous part that extends above the skin surface. A cross section of the hair shaft may be divided roughly into three zones. The Andre Walker Hair Typing System is the most widely used system to classify hair. The system was created by the hairstylist of Oprah Winfrey, Andre Walker. According to this system there are four types of hair: straight, wavy, curly, kinky. Klausz, G.; Keller, E.; Rona, K. Hair analysis of abused drugs with gas-chromatography mass spectrometry. Acta Pharm. Hung. 2009, 79, 47–56. [ Google Scholar] [ PubMed]