Left- or right-handed bath water? This seems a silly question, but it was the subject of a serious scientific investigation sponsored by the Daily Mail in 1965. The investigation showed that the direction water swirls down the plug-hole vortex depends on which side of the Equator you are.
As for homo sapiens, between 5 and 30% of the population are estimated to be left-handed, with more males than females / although in one test, 95% of foetuses were found to suck their right thumb in.the womb. The general consensus of opinion is that left-handedness is determined by a dominant right cerebral hemisphere controlling the left side of the body, and vice versa. Hereditary factors have been ruled out. So too have earlier theories concerning the need for soldiers to shield their hearts, and the desirability of learning to use Stone Age tools and implements with the hand they were designed for, as well as Plato's idea that it all boiled down to which arm a baby was cradled with. However, the almost universal human preference for dextrality, or right-handedness, remains a mystery.
Prejudice against the left hand dates back to ancient times and is so entwined with religious beliefs and superstitions that it still exists today in everyday speech. Sinister, the Latin for left hand, means 'suggestive of evil' in English, while the French gauche is awkward, or clumsy. Left itself derives from Anglo Saxon lef (weak and fragile). The non- judgmental term southpaw, by contrast, originates from the Chicago baseball stadium where pitchers faced west, so the pitching arm of a lefthander is to the South.
Other negative terms include pen pushers, while a left-handed compliment is actually an insult. Thomas Carlyle, who described right-handedness as the oldest institution in the world, introduced the political concept of ‘left' in his work on the French Revolution in the 1789 Paris Assembly the nobles sat on the right, opposite the radicals.
Associations with luck also go back to early history. The ancient Greek and Roman augurs foretold the future from bird-flight. While the former faced North, with the propitious sunrise side to their right, the latter, before changing later, when sinister took on its ominous meaning, looked southward, so the left was for good omens.
Superstitions world-wide reflect this bias. In Morocco, as in many countries, an itchy left palm means losing money, and a twitching left eyelid denotes the death of a relative or sorrow, whereas the right side has felicitous indications. We throw salt over our left shoulder to thwart the demons creeping up on us, but bless with the right hand. One pours wine with this hand and passes it round the table clockwise, the direction of the sun.
Our relatives, the primates, appear to be ambidextrous, or able to use both hands, although gorillas have heavier left arms seemingly due to greater utilization. Aristotle observed that crabs and lobsters had larger right claws. Rats are 80% dextral, yet polar bears are believed to be left-pawed. Flat fish provide interesting data: in northern seas plaice and sole have their eyes and colour on the right side, but tropical halibut are the other way round. If this is to do with light and sun rotation, it may explain why Indian Ocean sole are reversed, but not why northern halibut are just as sinistral as their southern cousins. In the plant kingdom, honeysuckle is a rare example of a left-handed climber that twines anti-clockwise, or widdershins!
Although we live in a more tolerant age, not so long ago in the UK youngsters were forced to use their right hand, 'to learn the value of conformity' (A. N. Palmer), often resulting in the stuttering speech defects common in 'switched sinistrals' like George VI. In the 1950s the American psychiatrist Abram Blau accused left-handed children of infantile perversity and a stubborn refusal to accept dextrality.
Not all experts were so anti- sinistral, however. The 17th century Norfolk scholar Sir Thomas Browne wrote of the prejudices against left-handedness, but accepted that a small proportion of people would always be so and saw no reason to prevent them. Apart from being considered difficult, anti-social troublemakers, left-handers have also been thought to be artistic, creative and gifted.
Famous lefties include Leonardo da Vinci, Michelangelo, Benjamin Franklin, Bill Clinton, Joan of Arc, Lewis Carroll, Paul McCartney, Jimi Hendrix, Jean Genet, Beethoven and many others.
Finally, in defence of all sinistrals, if the left side of the body is really controlled by the right hemisphere of the brain, then left-handers are the only people in their right minds!