Joe Frazier had one of the greatest left hooks in combat sports history. ‘Smoke’ was a converted Southpaw – no one wants to box left-handed prizefighters, so in order to get bouts, his trainer Yank Durham trained Frazier to box orthodox. In addition to making a fighter awkward, left-handedness is linked with a variety of disorders including an increased risk for dyslexia and ADHD, and a possible risk factor for autoimmune disorders, with a 2001 British study finding that lefties are twice as likely to suffer from bowel problems such as Crohn’s disease and ulcerative colitis.

So why does left-handedness exist? Why hasn’t the trait disappeared during human evolution? One answer is the “fighting hypothesis,” an argument that the increased health risks are offset by the advantage in hand to hand fighting that being a Southpaw imparts. Imagine a US driver suddenly dropped in the UK, where driving is on the other side of the road. The result is disorienting and similar to what happens in the ring – everything is backward. During more violent periods of human existence, this trait might not just be awkward, it might determine whether you reproduce, or not.

Thomas Richardson and R. Tucker Gilman from the University of Manchester’s School of Earth and Environmental Sciences recently published a study looking at 9,800 athletes; it demonstrating that Southpaws do indeed do better in boxing and MMA. “Left-handed fighters are overrepresented in combat sports and are better fighters” was published in the online journal BioRxiv where it can be read in full.

Author Richardson, an evolutionary biologist, Ph.D. candidate, and leftie, definitively tells Jack Guy for CNN that, “The reason left-handers exist is because our left-handed ancestors won more fights.”