Microkhan by Brendan I. Koerner

Let the Right One In

August 28th, 2009 · 3 Comments

HeartPositionFor all of mankind’s scientific advances in recent centuries, many elemental mysteries still persist. Among the most puzzling is the reason that right-handers far outnumber their southpaw peers. There’s a bevy of theories as to why this is the case, but no single one seems ironclad. So in the absence of a definitive explanation for why this is a right-hander’s world, we prefer to cast our lot with the theory we deem to be the most entertaining—the one that traces the handedness schism back to mankind’s zeal for hand-to-hand combat:

If it is accepted that social habits have as their goal the survival of the group, warfare may have played an important role in the differentiation between the two hands. Pye-Smith (1871) suggested the primitive fighting with club or spear led man to the selection of the right hand. Carlyle, in the same year, after the paralysis of his right arm, wrote in his diary that right-handedness probably arose in fighting and that the left was used in carrying the shield to protect the heart. Sawyer (1900), Harmon (1905), Gould (1908), Woodruff (1909) and others have added their support to this idea, ascribing the selection to the greater survival of right-handed fighters who protected the heart region. Then followed the gradual learning by experience of the advantages of this selection, and finally the propagation of this preference through custom, imitation, and precept.

The big hole in this theory, of course, is that the shield is a relatively novel development in martial history. Have enough centuries elapsed for natural selection to change our species from predominately ambidextrous to mostly right-handed? Especially since, given the heart’s very minor off-centeredness, the advantage of being right-handed doesn’t seem all that spectacular? Probably not, but at least the warfare theory is slightly more convincing than the one about ultrasound.


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3 Comments so far ↓

  • Brian Moore

    I would think that the effects of the features of the brain that affect handedness would swamp any effects from being better with a shield, especially at the time when these traits were being selected for. Right-handedness being a symptom that tends to associate with those brain features, but of course not always.

  • Russ Mitchell

    Although I doubt the theory: Perhaps the left arm had been used as a shield to protect the heart, thousands of years before shields were invented.

  • dmsouthasia

    Dude, I totally believe the ultrasound/synestrism thing. Studies in Norway (or Finland) showed an increase in left handedness among males after ultrasound was introduced to hospitals. Researchers were able to track it because a) all the hospitals are state hospitals and b) all males must do compulsory army service, and military records include what hand the grunt favors.

    There was a tiny, but statistically notable, increase in left-handed males right after ultrasound became standard equipment.

    But that doesn’t all of us pre-Doppler southpaws.