mutation found that accounts for white skin

Rick Weiss, a staff writer at the Washington Post, recently wrote an article titled Scientists Find A DNA Change That Accounts For White Skin. Here's the beginning of the article. If it interests, you follow the link to read the whole thing.

Scientists said yesterday that they have discovered a tiny genetic mutation that largely explains the first appearance of white skin in humans tens of thousands of years ago, a finding that helps solve one of biology's most enduring mysteries and illuminates one of humanity's greatest sources of strife.

The work suggests that the skin-whitening mutation occurred by chance in a single individual after the first human exodus from Africa, when all people were brown-skinned. That person's offspring apparently thrived as humans moved northward into what is now Europe, helping to give rise to the lightest of the world's races.

Leaders of the study, at Penn State University, warned against interpreting the finding as a discovery of "the race gene." Race is a vaguely defined biological, social and political concept, they noted, and skin color is only part of what race is -- and is not.

In fact, several scientists said, the new work shows just how small a biological difference is reflected by skin color. The newly found mutation involves a change of just one letter of DNA code out of the 3.1 billion letters in the human genome -- the complete instructions for making a human being.

I find this article interesting for two reasons. First it illustrates just how little change in our DNA is required for a big difference in our appearance. In case you want the technical language for that, genotype is the DNA sequence and phenotype is what we look like.

In the case of this study, published today in Science, a change of only one nucleic acid in a total of over 3 billion helps cause a change in skin color. They figure this one mutation accounts for about a third of the color difference between the original phenotype and the "European white" phenotype.

The second thing I find amazing about the article is how badly it skews the study. The reporter really doesn't get some of the science and makes some really silly "politically correct" statements as a result. For example:

Several sociologists and others said they feared that such revelations might wrongly overshadow the prevailing finding of genetics over the past 10 years: that the number of DNA differences between races is tiny compared with the range of genetic diversity found within any single racial group.

Even study leader Keith Cheng said he was at first uncomfortable talking about the new work, fearing that the finding of such a clear genetic difference between people of African and European ancestries might reawaken discredited assertions of other purported inborn differences between races -- the most long-standing and inflammatory of those being intelligence.

He emphasizes how genetics doesn't really matter and that across the races there's 99.9% correspondence of genotype (homology). That strikes me as missing the point since the article is showing how much of a change one nucleic acid makes. That 0.1% difference across the various groups of people equals over 3 MILLION nucleic acid changes in our DNA. Imagine how much difference that can make!

I think he'd have done better to emphasize how much simpler genetic coding is in phenotypical areas such as the color of skin, eyes, hair et cetera versus the much more complicated coding involved in intelligence or behavior.

This tendency for journalists to create news out of routine scientific papers is worrisome to me. Often the results being reported in the science journals are "tarted up" by the media and become controversial as a result. Most scientists don't encourage media attention and can get caught blindsided when obscure papers are sensationalized by reporters that usually don't understand the experimental results in the first place.

On the other hand, there are scientists that court media exposure--often as a way to receive greater notice and more funding. The mind springs quickly to the Korean scientist, Hwang Woo-suk, and the cloning controversy he's mired in.

In any case, the article that started me down this line of thought is a good illustration of how one successful mutation can change history. Our species originated in Africa where having dark skin was needed to protect us against ultraviolet light. This resulted in a lower efficiency in producing vitamin K but with plenty of sunlight available, that didn't matter.

Once some of our ancestors left Africa for some sightseeing in Europe and Asia this dark skin became an issue. Not having enough vitamin K results in weak bones and improper blood clotting. Having light skin would allow more vitamin K to be produced but wouldn't protect against high exposure to the sun.

This light skin mutation probably occurred a number of times in Africa but there it would be harmful and the child would have probably died of excessive sunburn. But once the location is changed to Europe with it's northern latitude and cloudy skies--skin fit with location. Hello ski vacations! Please excuse me if I make light of this. Ha-ha. Anyway, once the location fit the mutation the child survived and prospered which allowed the mutated gene to spread throughout the population over time. Ta-da.