Friday, March 25, 2011

Is There Something in the Water?

 I know about four sets of twins, and I can guess that everyone else knows about that many, too. But what if you lived in a town where about 20% of the people you knew had a twin? According to a report in The New York Times, in the small village of São Pedro this is the case.

For years, so many twins have been born in the small southern Brazilian town of Cândido Godói that residents wonder whether something mysterious lurks in the water, or even if Josef Mengele, the Nazi physician known as the Angel of Death, conducted experiments on the women there.

But a group of scientists now says it can rule out such long-rumored possibilities. Ursula Matte, a geneticist in Porto Alegre, Brazil, said a series of DNA tests conducted on about 30 families since 2009 found that a specific gene in the population of Cândido Godói appears more frequently in mothers of twins than in those without.

The phenomenon is compounded by a high level of inbreeding among the population, which is composed almost entirely of German-speaking immigrants, she said. “We analyzed six genes and found one gene that confirms, in this population, a predisposition to the birth of twins,” Dr. Matte said.

In biology class, you learn that genes control everything from hair color to diseases you may have. They also control your offspring, including if you are prone to having twins or not. But to find this gene in so many women in a small community raises the question of whether it was inbreeding or maybe a dominant or linked gene that caused this spike in twins? The scientists in this article credit the increased twin birth rate with inbreeding, but this has been going on for almost a hundred years. I feel like this gene would have died out or mutated by now; which would lead me to believe that the gene may be dominant or link to a dominate trait.

It was especially high in São Pedro, a village of about 350 residents that is part of Cândido Godói. Dr. Matte found that from 1990 to 1994, 10 percent of the births in São Pedro were twins, compared with less than 1 percent for Brazil as a whole.

The high concentration of twins has stirred outlandish theories.  An Argentine journalist suggested in a 2008 book that Mengele conducted experiments on women in Cândido Godói that resulted in a baby boom of twins, many of whom have blond hair and light-colored eyes. But the study led by Dr. Matte analyzed 6,615 baptism certificates dating back 80 years in the predominantly Roman Catholic town and found that the twins phenomenon existed in the 1930s, “long before Mengele’s period,” she said.

Her team of 20 researchers also analyzed the town’s water supply — residents believe a mysterious mineral may be responsible for the high rate of twin births — and uncovered no abnormalities.

While studying the baptism certificates, the scientists confirmed that the highest concentration of twins has been in São Pedro, with 33 pairs out of 436 births from 1959 to 2008, all living in a one-and-a-half-square-mile area. “With a small population of about 80 families, it was a challenge to find women that did not have twins within a first-degree relation,” Dr. Matte said. The scientists believe that a small number of immigrant families living in São Pedro may have brought the variant gene to the region. 

Even though this village now has this information, I do not think it will change their way of life. The twin population in São Pedro will most likely continue to grow. Maybe one day the village of São Pedro will be in the record books for village with the greatest population of twins.

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