Why are there more Lefthanded Males than Females?
Recent research has looked at the amount of Testosterone present in the fetus and amniotic fluid during pregnancy. Scientists have speculated that an excessive level of testosterone slows the development of the left side of the brain, which allows the right side of the brain to achieve and maintain dominance. Adult females normally produce a small amount of testosterone which will find its way into the amniotic fluid during pregnancy. A male fetus produces some testosterone in the uterus during development while a female fetus will produce no testosterone. Therefore, the chances of testosterone reaching excessive levels are much higher in a male fetus than in a female fetus simply because the normal levels of testosterone for a male fetus are higher in the first place. Males are about one and one half times more likely to be lefthanded than are females.
