Posted on 02/28/2011 12:05:32 PM PST by SeekAndFind
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.
Provided by Pennsylvania State University
Dark skin was the curse set upon Ham
Dark skin is a blessing for people who live near the equator.
What would have happened to the descendants of Ham had they moved north?
Natural selection of genetic variation would favor his lighter skin descendants - of course.
Everyone who pays the slightest attention to science knows that humans are extremely close genetically. Much less diverse than say chimps.
Every evo knows that blacks are millions of years behind on evolution
This is hogwash. They are trying to use apples to prove oranges.
No one denies that existing physical traits will become dominat or recessive based on environmental conditions.
If a famine comes along, the people that naturally carry more fat tend to survive the famine (and reproduce). The people that naturally didn’t store much fat die (and don’t reproduce). Humans as a group become “fatter”.
But it doesn’t explain where the fat cells came from to begin with. That’s the big question evolution can’t answer.
What this article describes is nothing more than selective breeding. Anyone adept at breeding animals can produce these kind of changes. A great example is the dog.
The dog is an animal breed 100% created by mankind. Wolves took up with humans. By selectively breeding wolves, we produced dogs (a lot of differnt kinds of dogs). But the truth is, a dog is (in every way that matters) exactly like a wolf. Everything about a dog—from hair to organs—is just a variation on a wolf.
Evoluntion talks about jumps. New species developing from existing species. There isn’t any evidence for that at all.
IF they did the groups, based upon DNA difference, would be...
Islanders/Thai/New Guinea/Australian
European/MiddleEastern/NorthAsian/Indian/Amerindian
African.
re: “Dark skin was the curse set upon Ham”
It never says this in scripture. The curse is as follows from Genesis 9:24 -
“When Noah awoke from his wine and found out what his youngest son had done to him, he said, ‘Cursed be Canaan!The lowest of slaves will he be to his brothers.’”
There is no indication whatsoever that skin color was a part of the curse. Slavery has existed since man has been on earth and blacks are not the only ones to experience it.
When I was growing up I heard about the “mark” of Cain being black skin, but again, no where is this implied or described in the Scriptures. I think it was a “justification” made up by slave oweners to excuse their subjugation of blacks in the antebellum south. They tried to use the Bible in an attempt to “elevate” slavery to obedience to God - in other words - the blacks being slaves was “dictated” by God through this “mark of Cain” or “curse of Ham”, so promoted the idea that they were just “following God’s command” when they enslaved these poor Africans.
MICRO-evolution, that is, which isn't what evolution is really about. I want to know what skin color has to do with evolving from an amoeba.
ML/NJ
Professors in universities can teach whatever nonsense they wish, but teachers in public schools should not waste class time with discussions on origins.
Windburn is from wind and cold.
If you’ve chafed your face, I really don’t want to know how you did it.
Actually, it’s a good example of genetic selection.
None of these people have evolved into another species, have they? That is what evolution teaches. That one species mutates over time into a better, more highly evolved and complex, species.
If which case, which of the directions we are headed (black, white, or Asian) is the “better” one? I know black people are more susceptible to diabetes, sickle cell anemia, and high blood pressure.
Are they on the “old species” side? Are whites the new and improved? We are more susceptible to skin cancer, right?
Are we speciating now? Is that what is going on?
(insert eyeroll)
Yes, that was supposed to be followed by a “?”. I don’t believe it for a second that any human population bears a curse, or that dark skin would be a curse.
Dark skin, is indeed a blessing, if you were an early human living in Africa.
If you embrace evolution, get ready to be connected with racism. It's just a fact of life. Evolution inherently infers that some mammals are progressing at different speeds, ergo, some humans must be behind others on the evolution scale. Haven't you heard this is why blacks run faster and jump higher?
To have a "scientific" discussion about pigment only invites the old discussions to emerge again. If you embrace evolution, you can't divorce yourself from it's teachings. All these things have been discussed to death for a hundred years. If you believe all races are the same, then you must reject the theory that "proves" they aren't.
New Guineans and Australian natives are as dark as anyone out of Africa, and yet they are more closely related to Polynesians than they are to any other group.
So how did we get a “black” population out of the presumably ‘yellow’ son of Noah?
No sir. You are stuck on the idea that evolution is moving a species towards some destination. No such thing. Any individual is either more or less fit to survive compared to any other individual. The word progress simply does not apply.
Racists have used evo "science" from the beginning to discriminate against certain races.
MIS-used evo science. Evil people have MIS-used the Bible for similarly evil purposes.
Has anyone else noticed a change in the vocabulary of the evolution faithful???
Just like the climate faithful had to change their rhetoric when global warming was debunked, so, too, have the evolutionists had to change their rhetoric with more and more evidence of intelligent design, and, therefore, a Designer.
The sly change: Instead of evolution being the origination of all species from a single cell (as was the previous montra), they now speak of adaption as evolution.
For the uninitiated (or willingly ignorant):
- Adaption (species adapting to their environment, even when that environment changes) is undisputed - it’s part of the design.
- Evolution (all species originating from a single cell) continues to be an unproven theory, while the proof of intelligent design and creation continues to grow.
RE: Professors in universities can teach whatever nonsense they wish, but teachers in public schools should not waste class time with discussions on origins.
What about professors in PUBLIC universities?
Finally, someone who can point me to some peer reviewed journals that prove intelligent design. Send me the links, please!
The Aztecs (Mexica) were relatively recent immigrants from further north—their language is related to some of the Indian languages of the Southwestern US. They seem to have been in the Valley of Mexico less than 300 years when Cortez showed up.
Noahs sons looked like Noah and his wife. The story of the Ark does not say that the only humans on the boat were Noah and his kin. It says he took two of every flesh. I would assume that means he took two of every race. On another related topic, the people of Adam were created on the 8th day. The other humans on Earth were created on the 6th day. That is why Cain had another place to go to when he was chased from the sight of his family. Adam was to be the “father” of the Messiah, the head of a peculiar clan of people through which he would be born. That is why the “Jews” are called the chosen ones. That is all it is, they were chose to be Gods messengers to the world, and to be the line of humans through which God presented his Son to the world.
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