Editing Hair (section)

===Texture===

====<span id="curly"></span>Curly hair====
[[File:Yellow curly hair and scalp from body which had long black wig over hair. Parts of wig plait remains. From Egypt, Gurob, probably tomb 23. 18th-19th Dynasty. The Petrie Museum of Egyptian Archaeology, London.jpg|thumb|Yellow curly hair and scalp from body which had long black wig over hair. Parts of wig plait remains. From Egypt, Gurob, probably tomb 23. 18th–19th Dynasty. The Petrie Museum of Egyptian Archaeology, London]]
[[File:David Luiz ConfedCup2013Champions17.jpg|thumb|Man with curly hair ([[David Luiz]], Brazilian footballer)]]
[[File:PSM V52 D323 Global hair texture map.png|thumb|Global hair texture map]]
{{More citations needed section|date=August 2016}}
Jablonski<ref name=Jablonski06/> asserts head hair was evolutionarily advantageous for pre-humans to retain because it protected the scalp as they walked upright in the intense African (equatorial) [[UV light]]. While some might argue that, by this logic, humans should also express hairy shoulders because these body parts would putatively be exposed to similar conditions, the protection of the head, the seat of the brain that enabled humanity to become one of the most successful species on the planet (and which also is very vulnerable at birth) was arguably a more urgent issue (axillary hair in the underarms and groin were also retained as signs of sexual maturity). Sometime during the gradual process by which ''Homo erectus'' began a transition from furry skin to the naked skin expressed by ''Homo sapiens'', hair texture putatively gradually changed from straight hair{{Citation needed|date=September 2010}} (the condition of most mammals, including humanity's closest cousins—chimpanzees) to [[Afro-textured hair]] or 'kinky' (i.e. tightly coiled). This argument assumes that curly hair better impedes the passage of UV light into the body relative to straight hair (thus curly or coiled hair would be particularly advantageous for light-skinned hominids living at the equator).

It is substantiated by Iyengar's findings {{citation needed|date=November 2024}}(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.

Jablonski's assertions<ref name=Jablonski06/> suggest that the adjective "woolly" in reference to Afro-hair is a [[misnomer]] in connoting the high heat insulation derivable from the true wool of sheep. Instead, the relatively sparse density of Afro-hair, combined with its springy coils actually results in an airy, almost sponge-like structure that in turn, Jablonski argues,<ref name=Jablonski06/> more likely facilitates an increase in the circulation of cool air onto the scalp. Further, wet Afro-hair does not stick to the neck and scalp unless totally drenched and instead tends to retain its basic springy puffiness because it less easily responds to moisture and sweat than straight hair does. In this sense, the trait may enhance comfort levels in intense equatorial climates more than straight hair (which, on the other hand, tends to naturally fall over the ears and neck to a degree that provides slightly enhanced comfort levels in cold climates relative to tightly coiled hair).

Further, it is notable that the most pervasive expression of this hair texture can be found in sub-Saharan Africa; a region of the world that abundant genetic and paleo-anthropological evidence suggests, was the relatively recent (≈200,000-year-old) point of origin for modern humanity. In fact, although genetic findings (Tishkoff, 2009) suggest that sub-Saharan Africans are the most genetically diverse continental group on Earth, [[Afro-textured hair]] approaches ubiquity in this region. This points to a strong, long-term selective pressure that, in stark contrast to most other regions of the genomes of sub-Saharan groups, left little room for genetic variation at the determining loci. Such a pattern, again, does not seem to support human sexual aesthetics as being the sole or primary cause of this distribution.

[[File:Blackhair10.jpg|thumb|Straight black hair]]

==== The EDAR locus ====
A group of studies have recently shown that genetic patterns at the EDAR locus, a region of the modern human genome that contributes to hair texture variation among most individuals of East Asian descent, support the hypothesis that (East Asian) straight hair likely developed in this branch of the modern human lineage subsequent to the original expression of tightly coiled [[natural afro-hair]].<ref>{{cite journal|pmid=18065779|last1=Fujimoto|first1=A|year=2008|pages=835–43|issue=6|volume=17|last2=Kimura|first2=R|journal=Human Molecular Genetics|last3=Ohashi|first3=J|last4=Omi|first4=K|last5=Yuliwulandari|first5=R|last6=Batubara|first6=L|last7=Mustofa|first7=MS|last8=Samakkarn|first8=U|last9=Settheetham-Ishida|first9=W|last10=Ishida|first10=T.|last11=Morishita|first11=Y.|last12=Furusawa|first12=T.|last13=Nakazawa|first13=M.|last14=Ohtsuka|first14=R.|last15=Tokunaga|first15=K.|title=A scan for genetic determinants of human hair morphology: EDAR is associated with Asian hair thickness|doi=10.1093/hmg/ddm355|display-authors=8|doi-access=free}}</ref><ref>{{cite journal|pmid=18704500|last1=Fujimoto|first1=A|year=2008|pages=179–85|issue=2|volume=124|last2=Ohashi|first2=J|journal=Human Genetics|last3=Nishida|first3=N|last4=Miyagawa|first4=T|last5=Morishita|first5=Y|last6=Tsunoda|first6=T|last7=Kimura|first7=R|last8=Tokunaga|first8=K|title=A replication study confirmed the EDAR gene to be a major contributor to population differentiation regarding head hair thickness in Asia|url=http://www.tulips.tsukuba.ac.jp/dspace/bitstream/2241/103672/1/HG_124-2.pdf|doi=10.1007/s00439-008-0537-1|access-date=14 December 2010|archive-url=https://web.archive.org/web/20110205011119/http://www.tulips.tsukuba.ac.jp/dspace/bitstream/2241/103672/1/HG_124-2.pdf|archive-date=5 February 2011|url-status=dead|hdl=2241/103672|s2cid=20084816|hdl-access=free}}</ref><ref>{{cite journal|last1=Mou|first1=C|last2=Thomason|first2=HA|last3=Willan|first3=PM|last4=Clowes|first4=C|last5=Harris|first5=WE|last6=Drew|first6=CF|last7=Dixon|first7=J|last8=Dixon|first8=MJ|last9=Headon|first9=DJ|year=2008|title=Enhanced ectodysplasin-A receptor (EDAR) signaling alters multiple fiber characteristics to produce the East Asian hair form|url=https://www.pure.ed.ac.uk/ws/files/8264337/Mou_et_al_EDAR_and_Asian_Hair_2008_supplementary_material.pdf|journal=Human Mutation|volume=29|issue=12|pages=1405–11|doi=10.1002/humu.20795|pmid=18561327|hdl=20.500.11820/0b35a959-86c8-44e5-b100-20639dd6bbf1|s2cid=37696013|access-date=30 January 2019|hdl-access=free}}</ref> Specifically, the relevant findings indicate that the EDAR mutation coding for the predominant East Asian 'coarse' or thick, straight hair texture arose within the past ≈65,000 years, which is a time frame that covers from the earliest of the 'Out of Africa' migrations up to now.