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# 6.5: Human Variation- An Adaptive Significance Approach

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Leslie E. Fitzpatrick, Ph.D., Mercyhurst University

##### Learning Objectives
• Describe how specific patterns of human adaptation are correlated to natural selection processes.
• Summarize the role of solar radiation in variations of human skin tone. In your explanation, include information as to why reduced pigmentation leading to lighter skin colors is advantageous for populations indigenous to northern latitudes.
• Compare and contrast the various genetic mutations present in Tibetan, Andean, and Ethiopian populations that allow them to survive at high altitudes.
• Define the relationship between specific genetic mutations in some human populations and certain infectious diseases, such as the sickle-cell trait mutation and malarial infection.

In the previous chapters of this text, we explored the role of evolutionary forces in human evolution as well as the basics of genetic variation. Within this framework, we now shift our focus toward examining the numerous challenges our species has faced throughout its evolutionary odyssey as well as how we have met those trials. Genetic variability within and between modern populations of humans has been influenced by years of evolutionary forces, most notably natural selection and genetic drift. As early humans left Africa and spread across the globe, they faced numerous challenges related to their new environments. Beyond genetically influenced changes in physiology as a result of evolution, humans have developed lifestyle strategies to cope with and even thrive in a wide range of habitats. The ways populations of humans met such challenges, coupled with their geographic separation throughout the majority of the last two centamillenia, have led to the many forms of adaptation in our species. This chapter focuses on the complexities of modern human variation through the lens of human evolutionary history.

## About the Author

### Leslie Fitzpatrick, Ph.D.

Mercyhurst University, Lfitzpatrick@mercyhurst.edu

Leslie Fitzpatrick

Leslie Fitzpatrick is an Assistant Professor in the Department of Biological Anthropology and Applied Forensic Sciences at Mercyhurst University in Erie, Pennsylvania. She earned a Ph.D. in Anthropology from the University of Wyoming (2017), an M.A. in Anthropology from Georgia State (2012), and a B.S. in Mechanical Engineering from Georgia Tech (2000). Her primary research focus is the stable-isotope analysis of human remains as a means of interpreting past mobility and diet profiles for both modern and archaeological populations. In addition to her work in the classroom and laboratory, she has worked as a bioarchaeologist at field sites in Germany, Spain, Croatia, Mexico, Peru, and throughout the United States.

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## Figure Attributions

Figure 14.1 Deep water diver by Leslie E. Fitzpatrick is under a CC BY-NC 4.0 License.

Figure 14.2 Mechanisms of heat transfer original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.3 Body heat maintenance in cold and warm original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.4 Vasoconstriction and vasodilation original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.5 Atmospheric pressure original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.6 Premature infant by Leslie E. Fitzpatrick is under a CC BY-NC 4.0 License.

Figure 14.7 Quechua Woman in Peru by Alexander Fiebrandt (Alecconnell at de.Wikipedia) is under a CC BY-SA 2.0 DE License.

Figure 14.8 Плагиоцефалия (Plagiocephaly) by Medical advises at larece.ru/?p=27115 is under a CC BY-SA 3.0 License.

Figure 14.9 World Map of HVR adaptation in high altitude populations by Chkuu is used under a CC BY-SA 4.0 License.

Figure 14.10 Skin Pigmentation (Anatomy and Physiology, Figure 5.8) by OpenStax is used under a CC BY 4.0 License.

Figure 14.11 Penetration of skin layers by UVA and UVB rays a derivative work original to Explorations: An Open Invitation to Biological Anthropology by Katie Nelson is under a CC BY-NC 4.0 License. [Includes Skin Anatomy by NIH National Cancer Institute, public domain].

Figure 14.12 Evolutionary basis for human skin color variation original to Explorations: An Open Invitation to Biological Anthropology by Katie Nelson is under a CC BY-NC 4.0 License.

Figure 14.13 Rachitis, stages of development for children (slide numbers 7181 and 7182; photo number: M0003399) by Wellcome Collection is under a CC BY 4.0 license.

Figure 14.14 Eskimo Family NGM-v31-p564 by George R. King [original from National Geographic Magazine, Volume 31 (1917)] is in the public domain.

Figure 14.15a COLLECTIE TROPENMUSEUM Fulani vrouwen en kinderen putten water uit de waterput van Santaba TMnr 20010199 (Fulani women and children draw water from the Santaba water well) by Tropenmuseum, part of the National Museum of World Cultures is used under a CC BY-SA 3.0 License.

Figure 14.15b Greenland 1999 (01) by vadeve has been designated to the public domain (CC0).

Figure 14.16a Bergmann’s Rule original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.16b Allen’s Rule original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.17 Human nasal morphological variation original to Explorations: An Open Invitation to Biological Anthropology by Mary Nelson is under a CC BY-NC 4.0 License.

Figure 14.18 Malaria parasite life cycle-NIAID by NIH National Institute of Allergy and Infectious Diseases is in the public domain.

Figure 14.19 Sickle cell 01 by The National Heart, Lung, and Blood Institute (NHLBI) is in the public domain.

Figure 14.20 Red Blood Cell abnormalities by Armando Moreno Vranich has been designated to the public domain (CC0).

Figure 14.21 Sickle cell disease a derivative work original to Explorations: An Open Invitation to Biological Anthropology by Katie Nelson is under a CC BY-NC 4.0 License. [Includes two illustrations by Mary Nelson; Sickle cell anemia by Pkleong at English Wikibooks, public domain (CC0), modified (labels removed background erased).]

Figure 14.22 Lactose tolerance in the Old World by Joe Roe is used under a CC BY 4.0 License.

6.5: Human Variation- An Adaptive Significance Approach is shared under a CC BY-NC license and was authored, remixed, and/or curated by LibreTexts.

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