A new Canadian study has added new fuel to the nature vs nurture debate over the origins of sexual orientation. The study looked at the brains of healthy, right-handed, 18- to 35-year-old homosexual and heterosexual men using structural Magnetic Resonance Imaging (MRI) and follows up on a ten year study that shows a higher percentage of left-handed people in the LGBT community than in the general populace.
From Psych Central News:
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 and research associate Debra Kigar, had found that left-handers have a larger region of the posterior corpus callosum – the thick 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.
They found that the posterior part of the corpus callosum is larger in homosexual than heterosexual men.
The size of the corpus callosum is largely inherited suggesting 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.