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quote:Originally posted by Carol-AMelanin protects us, to some degree from the damaging effects of the sun, and so people livingclose to the equator will have dark skin and eyes, to prevent too much uv damage. The downside of a lot of melanin is that it reduces the amount of vitamin d you can make. Near to the equator, where sun is not a problem, vitamin d is not a problem, but closer to the poles, where sun is limited, a dark skin could result in ricketts, so closer to the poles, there has been an advantage to reducing the level of melanin. Melanin is what causes hair and eye colour too. Skin and hair pigment is made up of different types of melanin. There are two broad groups of melanin, eumelanin, which is brown, and phaeomelanin, which is red. If you have high levels of melanin, the hair and eyes will basically look black, but as the total level of melanin falls, differences in hair and eye colour will show. It is not fully understood why there are some people with very dark hair but fair skin, but people are working on it!
quote:Originally posted by neilepThis is all very interesting....I am one of those very fair skinned people with dark hair and blue eyes, I only have to be in the sun for a few minutes before turning pink !!.
quote:THE Rh-NEGATIVE POPULATIONThe first mesolithic people from the Basque peninsula were without doubt the most experienced sailors of the Atlantic. These people who populated the northwest coast of Europe have a very special blood peculiarty which thier descendants are still living today. Dr.Luigi Cavalli-Sforza published a map of the populations with the highest percentage of thier members with Rh-negative blood. He wrote:"Rh-negative genes are frequent in Europe, infrequent in Africa and West Asia, and virtually absent in East Asia and among the aboriginal populations of America and Australia. One can estimate degrees of relatedness by subtracting the percentage of Rh-negative individuals among, say, the English (16%) from that of the Basques (25%) to find a difference of nine percentage points.The highest percentage of people with rh- blood is found in the Atlas mountains of Morocco(40%). The next highest are the Basques, reported in different publications as having 25 and 32%, depending on location. The people of northwest Ireland, the Highland Scots and the western islanders of Norway all have between 16 and 25%, while the Lapps of Norway and Finland have between 5 and 7%
quote:2002 October 10 ThursdayMutation for redheads is of recent origin In evolutionary terms a mutation that arose only 20,000 years ago is pretty recent. If this is correct then the pheomelanin variation of melanin that produces red hair is pretty new.quote:According to the most recent estimates, the first red hair sprouted just 20,000 years ago, long after the advent of modern homo sapiens.
quote:According to the most recent estimates, the first red hair sprouted just 20,000 years ago, long after the advent of modern homo sapiens.
quote:Originally posted by geckoif this is true, why arent dark haired and dark eyed people dying from vitamin D depletion all through russia and northern europe? is it because nutrition is more adequate?
quote:Another complicating factor for folate may be sunlight. A recent article in Scientific American cited evidence that ultra-violet radiation can actually penetrate the skin and destroy folate in the bloodstream, especially in fair-skinned people. This is another reason to avoid sunbathing.