A persistent, directional preference for lighter-coloured females as marriage partners has been recognized during historic times in some east- and south-Asian cultures, and it is likely that this has contributed to the greater sexual dimorphism in coloration observed [ 2187 ]. Like skin, the coloration of human hair and eyes is determined primarily by the amount and type of melanin produced and stored in melanosomes [ 8889 ].
Iris pigmentation is also influenced by structural features within the eye itself and by the degree of pupillary dilation [ 90 — 92 ]. Although skin coloration varies according to the intensity and seasonality of UVR on a global scale, no such regular geographical pattern is observed with hair and eye coloration [ 93 ].
In fact, little variation in hair and eye coloration occurs in indigenous populations outside of Europe for hair and outside of Europe, North Africa, the Middle East, Central Asia and South Asia for eyes [ 888994 ]. The lack of variation in hair and eye coloration in Africa has been assumed to be caused by the importance of eumelanin in affording protection, as it does in the case of skin coloration, but this has not been empirically established. Hair and eye coloration appear to have not been under as strong natural selection as skin coloration, and loss of genetic variation at one or more population bottlenecks probably contributed to the patterns of phenotypic variation observed in the hair and irises of modern people [ 95 ].
Scalp hair in most non-European populations is very dark brown, with little phenotypic variation [ 96 ].
Many genes appear to contribute to the dark brown hair colour phenotype [ 8893 ], and the relative importance of different loci is not yet known. The relatively high prevalence of blond hair in Northern Island Melanesia has been traced to the 93C allele of the TYRP1 gene [ 9798 ], which has been dispersed throughout the region in the course of human colonization of the Southwest Pacific.
In Europe, blond hair has been traced to establishment of variation in a regulatory enhancer of the KITLG gene, while red hair is produced by a specific range of variants of the MC1R locus [ 99 — ]. Sexual selection is thought to have influenced the high prevalence of blond- and red-hair phenotypes in Europe [ 93 ], but this has not been established empirically.
The nature and coloration of human male facial hair—beards and moustaches—have been a matter of curiosity and speculation, but little formal research [ 16, ]. Male facial hair, manifested as moustaches, cheek hair whiskers and beards, occurs in some male primates and appears to represent secondary sexual characteristics that evolved as amplified visual signals of rank, dominance and attractiveness [ 8]. This supports claims that age-related changes in human beard and moustache coverage and colour on the male face serve as honest signals of age or social dominance [ ], and that they evolved as products of contest competition between males [ ].
Beards augment the effectiveness of human aggressive facial displays, but are rated as ambivalent or unattractive by females . Until very recently, studies of human iris coloration focused primarily on European populations, where the greatest range and variety of eye colours—from dark brown to pale blue—are found. Iris colour phenotypes are determined by amounts of melanin and by the ratio of eumelanin to phaeomelanin in the iris, with brown eyes having a higher ratio than light eyes [ 8889 ].
Other categorical eye colours, such as blue, green and hazel, are common in Europe and parts of the Middle East, and Central and South Asia, with Europeans having the lightest eye colours [ 88 ]. The sets of genetic markers associated with variation in iris coloration in Europe, South Asia and East Asia are distinct, and relatively little is known of the combination of evolutionary forces—including natural and sexual selection—that influenced their distribution [ 89 ].
Dark iris coloration is associated with less scattering of intraocular light, a trait that may be protective under conditions of bright sunlight and high UVR. Blue eye coloration, on the other hand, is associated with greater intraocular light scattering and a higher level of melatonin suppression, traits that may have been adaptive under highly seasonal sunshine regimes in northwestern Eurasia [ ].
Blue-eyed women have been found to be preferred by blue-eyed men, possibly as a manifestation of a male adaptation for the detection of extra-pair paternity based on eye colour, as a phenotypically based assurance of paternity [ ]. Arguments for the action of natural and sexual selection on iris colour need to be examined with great care as more data on the genetic basis of the trait are revealed. A recent study showing that the genetic markers associated with iris coloration are also associated with skin and hair pigmentation traits suggests that iris coloration was a pleitropic effect associated with selection on pigmentation genes whose primary effect was skin or hair pigmentation, not iris coloration [ 89 ].
The genetic basis of human coloration is complex because some genetic variants affect all pigmentary systems—skin, hair and eyes—through pleiotropic effects, while others affect only one type [ ] and because different genes and gene combinations can create similar coloration phenotypes.
Despite the technical difficulties of such studies, the fascination of humans with their own coloration phenotypes will certainly continue to propel research forward quickly. Skin, hair and eye coloration in humans is variable, and has been influenced by different combinations of evolutionary forces. Skin coloration has been strongly influenced by natural selection, globally and throughout human prehistory, because of the importance of melanin as a natural sunscreen on naked skin. The role of natural selection in the evolution of hair and eye coloration appears to have been negligible, but genetic bottlenecks followed by sexual selection may have played more significant roles in establishing the patterns of variation recognized outside of Africa.
In recent centuries, humans have migrated faster and over longer distances than during any time in prehistory. Many of these movements have brought people into regions with markedly different solar regimes than their homelands. Many people now live under levels of solar radiation that are much stronger, or much weaker and more seasonal, than those under which their ancestors evolved.
These rapid changes in living circumstances have created significant health problems resulting from too much UVR exposure skin cancer, accelerated ageing of the skin and from too little UVR exposure vitamin D deficiency and its many sequelae that have greatly impacted individual well-being and public health.
Mitigating these problems is now the focus of considerable attention in many health professions [ — ]. Rapid, long-distance migrations have also brought people together from disparate and widely separated places, creating unprecedented and novel opportunities for gene flow.
The twenty-first century world contains a sepia rainbow of human skin colours, created from old and new combinations of skin colour—related genetic markers. The effects of these new genetic admixtures on health are not known.
More significant to health and overall human well-being, however, are the problems of social segregation and behavioural bias that are rooted in cultural constructions of skin colour—based race categories [ 87 ].
Humans are visually oriented primates, and our varied colours are badges of our recently shared evolutionary history. Our skin colours unite us, not divide us. Tim and two anonymous reviewers provided excellent suggestions for improvement of this contribution. We thank Theresa Wilson of Penn State for providing comprehensive support and assistance to our research programme, including the maintenance of our reference library and preparation of this manuscript.
The authors contributed equally to the conception and design of this paper and to the drafting and revising of the article for important intellectual content; they also gave the final approval of the version to be published. National Center for Biotechnology InformationU. Published online May Nina G. Jablonski and George Chaplin. Author information Article notes Copyright and License information Disclaimer. Accepted Dec 9. This article has been cited by other articles in PMC.
Abstract Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory. Keywords: eumelanin, phaeomelanin, ultraviolet radiation, natural selection, sexual selection, genetic drift. Introduction Discussions of the cardinal features of the human lineage usually focus on bipedalism, relative brain size, language and technology, and ignore the remarkable distinctions of the integument and eyes that have figured importantly in human evolution.
Human coloration in context Like most mammals, primates have hair covering most of their bodies. Variation in human skin coloration is mostly a product of natural selection Skin colour as measured by skin reflectance and levels of UVR are highly correlated.
Hair and eye coloration are not under strong natural selection Like skin, the coloration of human hair and eyes is determined primarily by the amount and type of melanin produced and stored in melanosomes [ 8889 ]. Conclusion Skin, hair and eye coloration in humans is variable, and has been influenced by different combinations of evolutionary forces.
Authors' contributions The authors contributed equally to the conception and design of this paper and to the drafting and revising of the article for important intellectual content; they also gave the final approval of the version to be published. Competing interests We have no competing interests. Funding We received no funding for this study. References 1. Caro T. The colours of extant mammals. Cell Dev. Walsberg GE. Consequences of skin color and fur properties for solar heat gain and ultraviolet irradiance in two mammals.
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Treating hyperpigmentation using a combination of hyaluronic and succinic acids
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Treating dark spots on the face
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Walter HV. Remarks on the environmental adaptation of man. Humangenetik 1385— However, this combination is not available in any medicinal products in France. In addition, hydroquinone is not authorized in Europe in cosmetic products, and the only possibility for use remains within the framework of magistral preparations prescribed by a dermatologist.
In this case, it is a medical prescription that requires careful monitoring. Products used to camouflage them must suffice. When combined with vitamin C and exfoliating agents, alpha-arbutin yields interesting results by blurring dark spots and unifying the complexion. Whether the melasma has been in place for some time or if the objective is preventing it due to promoting factors dark skin, family history, hormonal contraceptives, pregnancy, repeated sun exposuregood sun protection on the face, neck and chest is a salutary reflex.
This colorless, non-sticky and non-oily cream can be used regularly without being seen no chalky effect. Treating dark spots on the face. La marque Les produits Les préparations magistrales Le Mag. Français Español Italiano. Journal page Archives Contents list. Amici, V. Article Article Outline. Access to the text HTML. Access to the PDF text. Recommend this article. Save as favorites. Service d'aide à la décision clinique Votre service d'aide à la décision clinique.
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