By IANS
Toronto : Is sexual orientation something people are born with or a matter of choice? In findings that are bound to re-ignite the debate, a new study weighs in on the side of genetics.
Researchers at McMaster University and Sunnybrook Health Sciences Centre here have found new evidence that shows that your genes are what make you straight or gay.
Led by neuroscientist Sandra Witelson, the study scanned the brains of healthy, right-handed homosexual and heterosexual men using magnetic resonance imaging (MRI).
A decade back, Witelson had demonstrated there are more left-handers in the homosexual population.
Handedness is a sign of how the brain is organized to represent different aspects of intelligence. Language, for example, is usually on the left- music on the right.
In other research, Witelson had also found that left-handers have a larger posterior corpus callosum – the band of nerve fibres connecting the two hemispheres of the brain – than right handers.
This raised the hypothesis for the current study: whether the anatomy of the brain of the sub-group of right-handed homosexual men is similar to that of left-handers.
The researchers found that the posterior part of the corpus callosum is larger in homosexual than heterosexual men.
As the size of the corpus callosum is largely inherited, it suggested a genetic factor in sexual orientation, said Witelson.
“Our results do not mean that heredity is destiny, but they do indicate that environment is not the only player in the field,” she said.
Witelson said the finding may be one additional piece of information for individuals trying to determine their sexual orientation.
“Sometimes people aren’t sure of their sexual orientation.”