Let's talk about lefties.

08/02/2017

Let's talk about lefties.

Many studies show that approximately 10% of the world's population preferentially use their left hand for the practical activities of everyday life, or more simply, millions upon millions of people on planet earth are lefties in A radius of one in ten.

Those figures, we know, are a common place that almost everyone drives, but ... Why are not lefties 50% and right-handers the other 50% of the world's population? Or, what differentiates lefties, if there are differences, except for the use of the left hand, of course, the other 90% that are rights?

And is it true that there are more men left-handed than women? Or, more striking and important for those interested in this matter of the hands: Are they more intelligent, or, to put it another way, are the socially, scientifically and artistically more prominent people of the sinister preferential hand?

Let us cite some of these famous "sinister" ones: Aristotle, Leonardo da Vinci, Michelangelo Buonarroti, Napoleon Bonaparte, Wolfgang Amadeus Mozart, Paul McCartney and Ringo Starr, Mark Twain, David and Nelson Rockefeller, Henry Ford, Benjamin Franklin, Bill Gates, Winston Churchill, Cole Porter, David Letterman, Prince Charles of England and his son William, Paul Simon, Simon Bolivar, HG Wells and Albert Einstein, to mention a few Famous lefties as examples at random.

More illustrative and easier to define yet. At least eleven American presidents were, or are, lefties: Thomas Jefferson, Abraham Lincoln, James A. Garfield, Herbert Hoover, Harry S. Truman, John F. Kennedy, Gerald Ford, Ronald Reagan (ambidextrous but born left- George HW Bush, Bill Clinton and Barak Obama.

Only the last elected president, Donald Trump (who is right-handed), has been 45 US presidents in the two and a half centuries (approximate) life as an independent nation of this country, and if we understand that being left-handed was considered a disability before (Jefferson and Lincoln did not seem to disturb them), it is reasonable to think that there were some others of this handful of powerful men with predominance of the left hand, although they hid it to their electors and collaborators or the history did not properly collect the fact. Therefore, we have here a statistical figure that is possible to approach 25-30% of the total, if not more, which would triple the above mentioned average number.

Ah, and although they were not - and they are not - luckily - American presidents, let's not forget the left-handers (of course, yes) Adolf Hitler, Osama Bin Laden, Hugo Chavez and Vladimir Putin.

Interesting theme. Let us explore with more depth then the matter.

Why are so few, is it to say, left-handed, when it would be expected that they would be half the people living on the planet?

Well, left-handers are so few because ... let's face it, the reality is that we do not know for sure.

Possible theoretical explanations do have a few:

    First, as in almost everything, genes: Some forty related genes have been detected, direct (the least) or indirectly with body asymmetry and the predominant hand; The two most studied are the LRRTM1 gene and the PCSK6 gene (by modifying it it has provoked "inverse situs" in mouse embryos). Among the great apes, with relatively related genetics, there are also lefties and rights, but in different proportions to humans.
    Relationship to language mediated by the cerebral hemispheres (hypothesis of left hemisphere predominance). This aspect, very complicated from the neurophysiological point of view, is, along with genetics, the most studied and debated at the moment. And it is because all human brains do not behave in the same way nor do they distribute their functions in an identical anatomical framework.
    A placental increase, during the formative period of the fetus, of certain hormones, especially testosterone. This, although not scientifically proven, would explain, among other things, the male predominance among left-handed people.
    Darwinian evolution and its avatars. The evolutionary imbalance between cooperation and competition may, in the long run, modify certain bodily abilities, including, of course, the predominance of one hand or another. The issue of evolutionary changes has complicated derivations that go beyond the limits of this work, but it should be clear that, although there are various theories, there are no certainties here either.
    Other causes, none of them definitively proven: Culture, climatological geography, demography, microlesiones cerebral (stress of the birth) followed by alterations of the cortical functions, incapacities of the right hand (left handed by obligation or contradicted) and several more until arriving, in The last t