A new study found leftties have an evolutionary advantage when it comes to hand-to-hand combat, because righties aren't used to fighting them.
Which also means lefties have an advantage in boxing.
Around 10% of the population is left-handed, and research has linked the preference to higher rates of breast cancer, bowel problems such as Crohn's disease, and schizophrenia.
Given the costs of left-handedness you might expect the trait to have disappeared as humans evolved, but there is an interesting explanation.
According to the "fighting hypothesis," right-handed people are more used to fighting fellow right-handers due to the relative rarity of left-handed people.
As a result, left-handed people, also known as southpaws, have a competitive advantage in combat because their opponents are likely to be disoriented by their fighting stance.
Rocky was a lefty in the movies. But in the second one, he fought Apollo right-handed to keep him guessing, and to protect his bad eye.
Here's the end of the fight, where Mickey tells him to fight southpaw again.