Level 2 Reading 9B

Ch.18 Reading 9B

SEEING DOUBLE Many scientists once believed that physical similarities between identical twins are genetic, while their personalities, intelligence, and other differences between them are an effect of their environment. But scientists are now discovering that the boundaries between genetics and environment are not so clear after all. The Jim Twins Identical twins Jim Springer and jim Lewis were adopted as babies and raised by different couples. When the two Jims finally met at age 39, they discovered they had plenty in common. Both were 182 centimeters tall and weighed 82 kilograms. They had the same smile and the same voice. When psychologist Thomas Bouchard Jr. invited the Jim twins to his lab, his colleagues found it very hard to tell them apart. But the similarities didn't stop at the physical. They had both had dogs named Toy. They had both married women named Linda, and then divorced them. They had both been sheriffs, enjoyed making things with wood, suffered severe headaches, and admitted to leaving love notes around the house for their wives. They had so much in common that it seemed unlikely these were just coincidences. Genetics and Intelligence The jim twins were just one of 137 sets of separated twins Bouchard tested. When they compared the twins' IQ scores, Bouchard and his team reached a surprising conclusion. They concluded that intelligence was mostly connected to genetics rather than to training or education. It seemed the differences in family and environment had little effect. However, genes can't control everything, argues geneticist Danielle Reed, who also studies twins. Reed's research shows that, though nothing can truly change our DNA, environmental differences that a child experiences before birth and in their first year can sometimes affect the way the DNA behaves. This can make even identical twins into vastly different people. "What I like to say is that Mother Nature writes some things in pencil and some things in pen," she explains. "Things written in pen you can't change. That's DNA. But things written in pencil you can."

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