Sunday, February 20, 2011

The best way to eliminate racism from the world -- teach evolution.

It's interesting that Christians used to invoke their Bible to justify slavery. Even today Christians in Idiot America's Bible Belt are likely to be racist assholes. Meanwhile they stupidly equate evolution with racism, showing that they know nothing about biology.

When two cows have different skin colors, does that make one cow superior to the other? Of course not. The same is true about any species, including human apes. Biologists can explain the reason for the evolution of human skin color. Of course it has nothing to do with intelligence. Every human race has evolved to adapt to their different environments. In tropical climates a darker skin protects against skin cancer. In northern climates a lighter skin allows for more absorption of vitamin D from a limited amount of sunlight. If students learn about evolution (they would never learn anything about it if cowardly Christians had their way) they will be much less likely to be the racist pigs their parents are.

The previous paragraph was written by me and so of course it's not necessarily completely accurate. This PBS website has a better explanation for the evolution of skin color.

The Biology of Skin Color: Black and White

Humans have spent most of their history moving around. To do that, they've had to adapt their tools, clothes, housing, and eating habits to each new climate and landscape. But Jablonski's work indicates that our adaptations go much further. People in the tropics have developed dark skin to block out the sun and protect their body's folate reserves. People far from the equator have developed fair skin to drink in the sun and produce adequate amounts of vitamin D during the long winter months.

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I wish I could attend this AAAS meeting:

"Penn State anthropologist Nina Jablonski will talk about how the range of human skin colors came to be. Find out how our skin adapted to changing light conditions as our ancestors migrated from the equator to northern reaches of the globe."


February 20th, 2011

How did early humans adapt to different climates and diets as they split off from other primates and spread across the globe? And what does that mean for humans living today?

A panel of scholars from the fields of genetics and anthropology will present their findings on Sunday February 20th at the AAAS meeting in Washington, DC, as part of a session titled "Humans Without Borders: Evolutionary Processes at Work In Humans and Their Relatives."

The speakers in this session will plumb human and nonhuman primate DNA for clues to our evolutionary past, and what this means for our present. What do we know about our ancestors' movements in and out of Africa, what challenges they met while on the move, and how those challenges leave their mark on us today? Find out answers to these and other questions during the following presentations:

Building bigger brains

Duke University biologist Gregory Wray will talk about some of the genetic and dietary factors underlying brain size differences between humans and our closest living relatives, the chimpanzees.

Skin deep

Penn State anthropologist Nina Jablonski will talk about how the range of human skin colors came to be. Find out how our skin adapted to changing light conditions as our ancestors migrated from the equator to northern reaches of the globe.

Got milk?

University of Pennsylvania geneticist Sarah Tishkoff will talk about how in the past 10,000 yrs, several different populations - all raising cattle or camels in Northern Europe, East Africa and the Middle East - gained the ability to digest milk past infancy into adulthood.

The panel, organized by the National Evolutionary Synthesis Center (NESCent), will take place Sunday, February 20th, from 8:00 AM-9:30 AM (EST) in room 207A of the Washington Convention Center, 801 Mount Vernon Place NW, Washington, DC.

NESCent Director Allen Rodrigo will moderate the symposium. Science journalist Carl Zimmer will serve as the discussant.

Humans Without Borders: Evolutionary Processes at Work In Humans and Their Relatives

Sunday, 20 February 8:00AM-9:30AM

SPEAKERS

Greg Wray, Duke University

Genetic Links Between Human Diet and Brain Evolution, 8:00 AM

Nina Jablonski, Pennsylvania State University

Human Skin Pigmentation as an Example of the Action of Natural Selection, 8:30 AM

Sarah Tishkoff, University of Pennsylvania

Evolution of Lactose Tolerance in Human Populations in Africa, 9:00 AM

Provided by National Evolutionary Synthesis Center (NESCent)

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Skin color: Handy tool for teaching evolution

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.

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From Jerry Coyne's blog: Are there human races?

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