•Primates mostly live in stable social groups and have long life histories.•Social touch, mostly grooming, promotes social bonding in primates.•Grooming is a social service that can be traded as a ...commodity in primate groups.•Social touch contributes to healthy emotional development in young primates.•Humans and nonhuman primates deprived of social touch exhibit stress.
Primates are long-lived, highly social mammals who maintain long-term social bonds and cohesive social groups through many affiliative mechanisms, foremost among them social touch. From birth through adulthood, social touch – primarily mutual grooming – creates and maintains relationships of trust and reliance, which are the basis for individual physical and emotional well-being and reproductive success. Because social touch helps to establish, maintain, and repair social alliances in primates, it contributes to the emotional stability of individuals and the cohesion of social groups. In these fundamental ways, thus, social touch supports the slow life histories of primates. The reinforcing neurochemistry of social touch insures that it is a pleasurable activity and this, in turn, makes it a behavioral commodity that can be traded between primates for desirable rewards such as protection against future aggression or opportunities to handle infants. Social touch is essential to normal primate development, and individuals deprived of social touch exhibit high levels of anxiety and lower fertility compared to those receiving regular social touch. Understanding the centrality of social touch to primate health and well-being throughout the lifespan provides the foundation for appreciating the importance of social touch in human life.
Skin color and race Jablonski, Nina G.
American journal of physical anthropology,
June 2021, Letnik:
175, Številka:
2
Journal Article
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Skin color is the primary physical criterion by which people have been classified into groups in the Western scientific tradition. From the earliest classifications of Linnaeus, skin color labels ...were not neutral descriptors, but connoted meanings that influenced the perceptions of described groups. In this article, the history of the use of skin color is reviewed to show how the imprint of history in connection with a single trait influenced subsequent thinking about human diversity. Skin color was the keystone trait to which other physical, behavioral, and culture characteristics were linked. To most naturalists and philosophers of the European Enlightenment, skin color was influenced by the external environment and expressed an inner state of being. It was both the effect and the cause. Early investigations of skin color and human diversity focused on understanding the central polarity between “white” Europeans and nonwhite others, with most attention devoted to explaining the origin and meaning of the blackness of Africans. Consistently negative associations with black and darkness influenced philosophers David Hume and Immanuel Kant to consider Africans as less than fully human and lacking in personal agency. Hume and Kant's views on skin color, the integrity of separate races, and the lower status of Africans provided support to diverse political, economic, and religious constituencies in Europe and the Americas interested in maintaining the transatlantic slave trade and upholding chattel slavery. The mental constructs and stereotypes of color‐based races remained, more strongly in some places than others, after the abolition of the slave trade and of slavery. The concept of color‐based hierarchies of people arranged from the superior light‐colored people to inferior dark‐colored ones hardened during the late seventeenth century and have been reinforced by diverse forces ever since. These ideas manifest themselves as racism, colorism, and in the development of implicit bias. Current knowledge of the evolution of skin color and of the historical development of color‐based race concepts should inform all levels of formal and informal education. Awareness of the influence of color memes and race ideation in general on human behavior and the conduct of science is important.
Special Issue: Race reconciled II: Interpreting and communicating biological variation and race in 2021
Human skin pigmentation is the product of two clines produced by natural selection to adjust levels of constitutive pigmentation to levels of UV radiation (UVR). One cline was generated by high UVR ...near the equator and led to the evolution of dark, photoprotective, eumelanin-rich pigmentation. The other was produced by the requirement for UVB photons to sustain cutaneous photosynthesis of vitamin D₃ in low-UVB environments, and resulted in the evolution of depigmented skin. As hominins dispersed outside of the tropics, they experienced different intensities and seasonal mixtures of UVA and UVB. Extreme UVA throughout the year and two equinoctial peaks of UVB prevail within the tropics. Under these conditions, the primary selective pressure was to protect folate by maintaining dark pigmentation. Photolysis of folate and its main serum form of 5-methylhydrofolate is caused by UVR and by reactive oxygen species generated by UVA. Competition for folate between the needs for cell division, DNA repair, and melanogenesis is severe under stressful, high-UVR conditions and is exacerbated by dietary insufficiency. Outside of tropical latitudes, UVB levels are generally low and peak only once during the year. The populations exhibiting maximally depigmented skin are those inhabiting environments with the lowest annual and summer peak levels of UVB. Development of facultative pigmentation (tanning) was important to populations settling between roughly 23° and 46° , where levels of UVB varied strongly according to season. Depigmented and tannable skin evolved numerous times in hominin evolution via independent genetic pathways under positive selection.
The primary biological role of human skin pigmentation is as a mediator of penetration of ultraviolet radiation (UVR) into the deep layers of skin and the cutaneous circulation. Since the origin of ...Homo sapiens, dark, protective constitutive pigmentation and strong tanning abilities have been favored under conditions of high UVR and represent the baseline condition for modern humans. The evolution of partly depigmented skin and variable tanning abilities has occurred multiple times in prehistory, as populations have dispersed into environments with lower and more seasonal UVR regimes, with unique complements of genes and cultural practices. The evolution of extremes of dark pigmentation and depigmentation has been rare and occurred only under conditions of extremely high or low environmental UVR, promoted by positive selection on variant pigmentation genes followed by limited gene flow. Over time, the evolution of human skin pigmentation has been influenced by the nature and course of human dispersals and modifications of cultural practices, which have modified the nature and actions of skin pigmentation genes. Throughout most of prehistory and history, the evolution of human skin pigmentation has been a contingent and non‐deterministic process.
We expose it, cover it, paint it, tattoo it, scar it, and pierce it. Our intimate connection with the world, skin protects us while advertising our health, our identity, and our individuality. This ...dazzling synthetic overview, written with a poetic touch and taking many intriguing side excursions, is a complete guidebook to the pliable covering that makes us who we are. Skin: A Natural History celebrates the evolution of three unique attributes of human skin: its naked sweatiness, its distinctive sepia rainbow of colors, and its remarkable range of decorations. Jablonski begins with a look at skin's structure and functions and then tours its three-hundred-million-year evolution, delving into such topics as the importance of touch and how the skin reflects and affects emotions. She examines the modern human obsession with age-related changes in skin, especially wrinkles. She then turns to skin as a canvas for self-expression, exploring our use of cosmetics, body paint, tattooing, and scarification. Skin: A Natural History places the rich cultural canvas of skin within its broader biological context for the first time, and the result is a tremendously engaging look at ourselves.
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. Functionally naked skin has ...been the physical interface between the physical environment and the human body for most of the history of the genus Homo, and hence skin coloration has been under intense natural selection. From an original condition of protective, dark, eumelanin-enriched coloration in early tropical-dwelling Homo and Homo sapiens, loss of melanin pigmentation occurred under natural selection as Homo sapiens dispersed into non-tropical latitudes of Africa and Eurasia. Genes responsible for skin, hair and eye coloration appear to have been affected significantly by population bottlenecks in the course of Homo sapiens dispersals. Because specific skin colour phenotypes can be created by different combinations of skin colour–associated genetic markers, loss of genetic variability due to genetic drift appears to have had negligible effects on the highly redundant genetic ‘palette’ for the skin colour. This does not appear to have been the case for hair and eye coloration, however, and these traits appear to have been more strongly influenced by genetic drift and, possibly, sexual selection.
This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
Living Color is the first book to investigate the social history of skin color from prehistory to the present, showing how our body's most visible trait influences our social interactions in profound ...and complex ways. In a fascinating and wide-ranging discussion, Nina G. Jablonski begins with the biology and evolution of skin pigmentation, explaining how skin color changed as humans moved around the globe. She explores the relationship between melanin pigment and sunlight, and examines the consequences of rapid migrations, vacations, and other lifestyle choices that can create mismatches between our skin color and our environment. Richly illustrated, this book explains why skin color has come to be a biological trait with great social meaning— a product of evolution perceived by culture. It considers how we form impressions of others, how we create and use stereotypes, how negative stereotypes about dark skin developed and have played out through history—including being a basis for the transatlantic slave trade. Offering examples of how attitudes about skin color differ in the U.S., Brazil, India, and South Africa, Jablonski suggests that a knowledge of the evolution and social importance of skin color can help eliminate color-based discrimination and racism.
A new study examines anatomy and genetics of skin in whales and hippos and reveals that adaptations to aquatic and semi-aquatic lifestyles evolved convergently in these lineages.
A new study examines ...anatomy and genetics of skin in whales and hippos and reveals that adaptations to aquatic and semi-aquatic lifestyles evolved convergently in these lineages.
The biology of color Cuthill, Innes C.; Allen, William L.; Arbuckle, Kevin ...
Science (American Association for the Advancement of Science),
08/2017, Letnik:
357, Številka:
6350
Journal Article
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Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and ...protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.
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