Nothing in the study indicates why this may be true. It's a term that apparently originated in sports. The most common explanation is that it had to do with the typical layout of a major league baseball field. A left-handed pitcher would end up facing south as he finished throwing the ball. However, some experts believe the term was actually in use as a wrestling term before there was such a thing a major league baseball, so the true origin is uncertain.
Many researchers claim that all polar bears are left-handed.