‘Handedness’ theories even draw from world history

Curiosity Corner

by

Dr. Jerry D. Wilson

Emeritus Professor of Physics

Lander University

reprinted with permission

Question: Why are some people right-handed and some left-handed? (Asked by a curious “lefty.”)

Reply: Most animals have a preferred paw or hand to perform tasks, but it appears that only humans have a species preference for the right hand. About 90 percent of the human population is predominantly right-handed. Of the other 10 percent, some are predominantly left-handed (perhaps up to 8 percent), while the others are ambidextrous — capable of using either hand about equally as well.

It is not known why some people are right-handed and others are left-handed. There have been studies and theories concerning association with the right and left parts of the brain, and even that handedness may be partially genetic. However, as far as I know, there is no conclusive scientific answer. The vast majority of right-hand preference may indeed be due to social pressure resulting from historical cultural effects. For example, it has been speculated that the right got the upper hand because the heart lies on the left side of the body. In battle, one would carry a shield with the left hand so as to better protect the heart, while the right hand did the activity of wielding a sword or some other weapon.

The Romans were very right-hand oriented. They adopted the right-hand handshake (to show there was no weapon in the fighting hand), and, of course, giving a breast salute to the heart is easier to do with the right hand with the heart on the left side of the body. The Roman right preference is a bit evident in their words for right and left — “dexter” (right) and “sinister” (left) — from which we derive “dexterous” meaning skillful or artful, and “sinister” meaning threatening evil or harm.

Even in the Judeo-Christian tradition there seems to be a religious right preference. In both the Old and New Testaments there are positions of grace “at the right hand of God.” Also, in Matthew (25:31-42), Jesus talks about separating the sheep from the goats (sheep on the right, goats on the left), and it was a good thing to be with the rightful sheep.

Another theory associates the predominance of right-handedness with tool development. As tools were invented, more complicated ones were better suited for one hand, and were especially fashioned for this hand (presumably the right). Tools became prized possessions and as they were passed down from one generation to another, one hand became predominant in activities. Probably because of such social development, children showing left-hand tendencies were at one time discouraged from being left-handed. Left-handers got down to about 2 percent of the population because of this. (I remember some of my grade-school teachers telling students to quit using their left hands and write with the right.) Fortunately, that’s not done much anymore.

Whatever the case, lefties have had a tough row to hoe. (Well, a hoe’s not much of a problem — works for both right and left hands.) But think about scissors, a bolt-action rifle, or golf clubs. Left-handers do have some special advantages. For example, in baseball, first basemen are usually lefties. They can catch and throw to home and third base outside of the baselines. Southpaw pitchers have various advantages pitching to different batters. (Incidentally, the term “southpaw” was coined by a Chicago sportswriter to describe left-handed pitchers who, on going into the stretch with a runner on first, faced south in an old ballpark.) Also, switch-hitters are sometimes told to bat left-handed, which gives a half-step start in going to first base.

Even we right-handers do some things left-handed. I shuffle cards right-handed, but I deal left-handed. I don’t know why — maybe because the deal is to the left (it’s easier).

But left-handers can hold their heads high. There have been many famous lefties. Try Gerald Ford, Ronald Regan, Bill Clinton, Charlie Chaplin, Lou Gehrig, Babe Ruth, Stan Musial, Lefty Gomez (naturally), Robert Redford, Rex Harrison, Bubba Beauregard, Pablo Picasso, Leonardo da Vinci, Michelangelo (maybe ambidextrous) and Albert Einstein. Left on!

C.P.S. (Curious Postscript): The trouble with retirement is that you never get a day off. ~Abe Lemons

Curious about something? Send your questions to Dr. Jerry D. Wilson, Science Division, Lander University, Greenwood, SC, 29649, or for e-mail, jerry@curiosity-corner.net . Selected questions will appear in the Curiosity Corner. © JDW