Blue eyes and evolution

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Science stories are well-read but they don’t often bring as many questions and comments as the one that ran Dec. 11. That story reported on a study that found, ‘The pace of human evolution has been increasing at a stunning rate since our ancestors began spreading through Europe, Asia and Africa 40,000 years ago.’ Not only was evolution a spark for some readers to write, but so was the last line, which quoted University of Wisconsin-Madison anthropologist John Hawks, who led the study: ‘Nobody 10,000 years ago had blue eyes. Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea.’

Science writer Karen Kaplan responds to the readers.

Bill Baerg, from Costa Mesa living now in Kumamoto, Japan, gives his own response to Hawks’ question about blue eyes: ‘It’s because we’re more handsome, silly!’ He adds, ‘Enjoyed your article. Thanks.’

Not privy to Baerg’s note, the question came again from Maureen Schoenky, of Santa Susana: ‘What caught my (blue) eyes was the last paragraph -- ‘Nobody 10,000 years ago had blue eyes.’ Oh! Nobody had pale skin or blonde hair then either? Nobody lived up north to soak up more sun in the cold places? How was this discovered, please? How would one KNOW about eyes - skin and hair, maybe, but eyes? Different genes? Just raised the level of curiosity! Thank you.’

The way we know is, indeed, in the genes, says Kaplan. Her response, based on an explanation from Hawks: ‘Each person’s genome is a unique mixture of DNA from mom and dad. But sometimes researchers find a long stretch of DNA -- called a linkage disequilibrium -- that is still identical in a large number of people. That tells them that the particular gene it encodes is relatively recent, because it hasn’t had time to change through the normal shuffling of genes that happens when sperm and egg cells meet. In fact, the longer the region of linkage disequilibrium, the younger the gene. By measuring the length of the linkage disequilibrium involved in the ‘blue eyes’ gene, the researchers were able to estimate that it is less than 10,000 years old.’

Roger Bonilla of Sunnyvale wrote: ‘Interesting article about the accelerating changes in the human genome. It is unfortunate that many people will stop reading in the first paragraph, because the time span of 40,000 years conflicts with their interpretation of the Book of Genesis.’

And in fact, that was the point made by Joe Hudson of Carthage, TX: ‘You were absolutely right about no one having blue eyes 10,000 years ago. There was no one here 10,000 years ago. You are probably right again, I am a Christian and I believe what God said in Genesis.’ And Victor Schoessler of East Helena, MT wrote, ‘Does your story on the subject matter mean that the longer we wait, the more likely ‘scientists’ will make another ‘discovery’ that will more closely match the Bible’s history as recorded in Genesis 1 through 11? When are people going to realize that these guesses are not facts. True facts can only be observed.’

Far more readers, though, say that the story struck a chord given the increasing role the issue has played in politics. JW Collins from Atlanta wrote, ‘Excellent article....most enlightening.’ Collins said that his appreciation for The Times’ reporting the study was in part because of the politicians who ‘have declared that they do not believe in evolution. At all. They don’t understand that the theory to explain the fact of evolution is the discussion. They just say they don’t believe in it.’ And Laura Museo of Denver wrote, ‘In the contentious national debate about evolution, well-written science articles are critical to the public discussion. Nice job. Perhaps the next thing we’ll see is selection for a capable ‘Blackberry thumb.’ Keep the science coming.’

In response to the several readers writing to express doubt in the study, the science reporter noted that scientists consider that these are observable facts, and they are observing them by looking at DNA. Wrote Kaplan, ‘You don’t have to have been there 10,000 years ago to ‘observe’ it. There is currently observable evidence of things that occurred 10,000 years ago, and more.’

One reader focused on the order in which continents were listed in that opening line (‘spreading through Europe, Asia and Africa’). Walter Peguise of Raleigh, N.C. wrote: ‘Very interesting article. You mentioned in the first paragraph about the spread of our ancestors throughout, Europe, Asia and Africa. Are you sure it wasn’t, Africa, Asia and Europe? Regardless of what happens in history, accurate or not, if written about by whites, [they] always come first.’

Kaplan wrote it in that order, she told Peguise, ‘because that’s how the lead author of the study (who is Caucasian) said it. The turning point 40,000 years ago came as the Neanderthals were dying out in Europe, and humans who were in Southern Europe spread into the rest of Europe, east to Asia and back south into Africa. You raise a good point.’