Researchers have known for a long time that we develop a preference for our dominant hand very early on; it had been thought to be related to genetic differences between brain hemispheres. Last year, scientists found evidence to indicate it was actually related to asymmetrical gene activity in the spinal cord during development in the womb. It would seem that a growing embryo picks a favorite hand before the brain starts to control the body.
Studies have suggested that as much as 92 percent of the global population is right-handed. There have been many theories, both scientific and social, that have attempted to answer the question of why that is, and many researchers have suggested that we evolved to favor our right hands. Studies have also found that people who are left-handed are not psychologically or socially different from right-handers in any way.