Q. I just heard that apes are left-handed! What do you know about that or about left-handedness in humans?
A. A decade of research by primatologist Bill Hopkins has shown that apes, like humans, have hand preferences, but apparently handedness differs by type of ‘apes.’ For example, at the Yerkes Regional Primate Research Center in Atlanta, Georgia, a third of the chimpanzees are lefties and the rest have a right-handed preference. In another study, ten out of twelve gorillas used their right hand as the dominant one, all six gibbons used their left, while orangutans used either hand equally. In yet another study, gorillas, chimpanzees, and bonobos showed a right-handed preference, while orangutans evidenced left-handedness. My guess is that it may be a combination of genetics along with epigenetics, including how the parents taught their offspring and what was role modeled to them, whether the studies were done in the wild or in captivity, and perhaps even birth order.
Regarding handedness in humans, most people fall along a continuum depending on the type of task or activity involved. Worldwide, some estimates are that left-handers account for about five to twenty percent (typically ten to twelve percent) of the population, with more males than females evidencing a left-handed preference. Perhaps one percent is definitely ambidextrous, and the majority are right-handed for most tasks. Genetics can play a part; so can epigenetics. For example, identical twins often have differing dominant hand preference. This may be especially true if they are ‘mirror twins’.
Some studies have linked left-handedness with an increased risk for auto-immune diseases and schizophrenia as well as a higher risk for being a genius. Left-handers tend to have an especially fine use of the right cerebral hemisphere and are more likely to excel in architecture and fine arts. They may also be more impacted by fear since the protective emotions of fear, anger, and sadness, tend to be more aligned with the right hemisphere. This means they may also find it easier to ‘get angry,’ Right-handers tend to use the left cerebral hemisphere more efficiently and may excel in math and science and verbal fluency. These are examples of research generalizations, however, and may say little about a specific individual.
A report on research by Professor Daniel M. Abrams and graduate student Mark J. Panaggio of Northwestern University was published in the Journal of the Royal Society Interface (2012). Their mathematical model showed that handedness may reflect the balance between cooperation and competition: cooperation favors same-handedness while competition favors the unusual. Indeed, the model they developed accurately predicted a greater than fifty percent left-handedness among top baseball players and well above the general population rate of ten percent for other sports (e.g., boxing, hockey, fencing, and table tennis).
By the way, did you know that August 13 is International Left-Hander’s Day?