Navigation Links
Skin color: Handy tool for teaching evolution
Date:2/20/2011

Variations in skin color provide one of the best examples of evolution by natural selection acting on the human body and should be used to teach evolution in schools, according to a Penn State anthropologist.

"There is an inherent level of interest in skin color and for teachers, that is a great bonus -- kids want to know," said Nina Jablonski, professor and head, Department of Anthropology, Penn State. "The mechanism of evolution can be completely understood from skin color."

Scientists have understood for years that evolutionary selection of skin pigmentation was caused by the sun. As human ancestors gradually lost their pelts to allow evaporative cooling through sweating, their naked skin was directly exposed to sunlight. In the tropics, natural selection created darkly pigmented individuals to protect against the sun.

Ultraviolet B radiation produces vitamin D in human skin, but can destroy folate. Folate is important for the rapid growth of cells, especially during pregnancy, when its deficiency can cause neural tube defects. Destruction of folate and deficiencies in vitamin D are evolutionary factors because folate-deficient mothers produce fewer children who survive, and vitamin D-deficient women are less fertile than healthy women.

Dark skin pigmentation in the tropics protects people from folate destruction, allowing normal reproduction. However, because levels of ultraviolet B are high year round, the body can still produce sufficient vitamin D. As humans moved out of Africa, they moved into the subtropics and eventually inhabited areas up to the Arctic Circle. North or south of 46 degrees latitude -- Canada, Russia, Scandinavia, Western Europe and Mongolia -- dark-skinned people could not produce enough vitamin D, while lighter-skinned people could and thrived. Natural selection of light skin occurred.

The differences between light-skinned and dark-skinned people are more interesting than studying changes in the wing color of moths or, the most commonly used evolutionary example, bacterial colonies, according to Jablonski. Adaptation to the environment through evolutionary change becomes even more interesting when looking at the mechanism of tanning.

"In the middle latitudes tanning evolved multiple times as a mechanism to partly protect humans from harmful effect of the sun," Jablonski told attendees at the annual meeting of the American Association for the Advancement of Science today (Feb. 20) in Washington, D.C.

Tanning evolved for humans so that when ultraviolet B radiation increases in early spring, the skin gradually darkens. As the sun becomes stronger, the tan deepens. During the winter, as ultraviolet B wanes, so does the tan, allowing appropriate protection against folate destruction but sufficient vitamin D production. Tanning evolved in North Africa, South America, the Mediterranean and most of China.

Natural variation in skin color due to natural selection can be seen in nearly every classroom in the U.S. because humans now move around the globe far faster than evolution can adjust for the sun. The idea that variation in skin color is due to where someone's ancestors originated and how strong the sun was in those locations is inherently interesting, Jablonski noted.

"People are really socially aware of skin color, intensely self-conscious about it," she said. "The nice thing about skin color is that we can teach the principles of evolution using an example on our own bodies and relieve a lot of social stress about personal skin color at the same time."

Jablonski noted that the ability to tan developed in a wide variety of peoples and while the outcome, tanablity, is the same, the underlying genetic mechanisms are not necessarily identical. She also noted that depigmentated skin also developed at least three times through different genetic mechanisms. Students who never tan, will also understand why they do not and that they never will.


'/>"/>

Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
Source:Eurekalert

Related biology news :

1. Radiologists play key role in teaching physiology to medical students
2. Simple, ingenious way to create lab-on-a-chip devices could become a model for teaching and research
3. ASPBs Teaching Tools in Plant Biology receives Gold Award
4. Mississauga teacher awarded prize for excellence in teaching genomics
5. McMaster, NVIDIA establish first CUDA Teaching Centre in Canada
6. Teaching communication and information literacy skills
7. Ethical issues ignored in teaching, research of sustainability
8. American Sociological Association launches first-of-its-kind teaching tool
9. Physical education teaching staff play key role in making you like sport
10. UAB professors book promises solution for teaching evolution without conflict
11. K-State plant pathologists develop online teaching modules used globally
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/19/2017)... Calif. , Jan. 19, 2017 ... enhancing user experience and security for consumer electronics, ... next-generation payment processing systems and cybersecurity solutions, today ... banks, enterprises and financial institutions worldwide to bolster ... of the end-to-end secure user authentication platforms they ...
(Date:1/13/2017)... , Jan. 13, 2017 Sandata ... solutions for the homecare industry, including Electronic Visit ... industry expert, Justin Jugs, as Senior Vice President ... than 15 years of homecare experience to Sandata, ... developing strategic plans to align Sandata,s suite of ...
(Date:1/12/2017)... and PUNE, India , January 12, 2017 ... Forecasts, 2015 - 2022," projects that the global biometric technology market is expected to ... 2016 to 2022. Continue Reading ... ...      ...
Breaking Biology News(10 mins):
(Date:1/21/2017)... ... ... Nipro Corporation (Osaka, Japan) and Transonic Systems Inc. (New York, USA) announced ... and sales rights for all non-OEM Transonic products in Japan. As partners for more ... Nipro - Transonic JV is a natural next step to advance best practices and ...
(Date:1/21/2017)... , Jan. 21, 2017   Boston Biomedical , ... designed to target cancer stemness pathways, today presented data ... napabucasin, at the 2017 American Society of Clinical Oncology ... . In a Phase Ib/II ... designed to inhibit cancer stemness pathways by targeting STAT3 ...
(Date:1/20/2017)... MALDEN, MA (PRWEB) , ... ... ... the leader in Less Exposure Surgery (LES®) Technologies, announced today the next ... the PedFuse Pedicle Screw System platform). In contrast to the competition, SpineFrontier ...
(Date:1/19/2017)... 19, 2017 Research and Markets ... has announced the addition of the ... Forecast to 2025" report to their offering. ... The report provides a detailed analysis on current and future market trends ... using estimated market values as the base numbers Key ...
Breaking Biology Technology: