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left handedness
left hemisphere
human evolution
global population
language functions
external factors
genetics
accidents
brain
Why Are Some People Left - Handed?
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Why Are Some People Left  -  handed?

This question seems difficult to answer, even by experts and scientists who have performed tons of researches on this subject. They have tried to explain why are some people left-handed and so far they have agreed that those causes are biological and, most likely, genetic.

It seems this fact has something to do with the evolution: most individuals have their speech and language functions controlled by the left hemisphere of their brain, which also controls the movements of the right hand. So, as humans evolve, their left-hemisphere/right-hand preference tends to establish.

Apart from the evolution theory, left-handedness might also be an outcome of an accident. If a right-handed human injures (or, even worse, misses) their right hand, they have no other choice than starting to use their left. Of course, this also may happen to lefties, so that they eventually switch to righties.

These facts and theories, though, cannot explain another fact: through the ages of human evolution, a significantly large majority of right-handed people has been observed: about 90% of the global population, over only 10% of the lefties.

So another question arises:

Why are left-handed people outnumbered?

There is another theory, on genetic basis, according to which there are two forms of a gene, at the same genetic location, related to handedness. There seem to be two forms of one particular gene which are related to handedness: the D gene and the C gene. The first is responsible for the right-handness, gets herited more often, so appears most of the times. On the other hand (literally!), the C appears less and inherits randomly the handness, so there is more or less an equal chance that the individuals is either righty or lefty.

Apart from genetics and accidents, some scientists state that the handness of those who have the C gene may be determined by external factors (such as environmental, cultural, even societal ones). These researchers may as well explain how right-handed parents are possible to have left-handed children and vice versa.

“How much” left-handed are you?

Some people believe that handedness is something measurable, due to our natural tendency to oversimplify our thoughts: if you write with your left hand, you are a lefty; if not, you are a righty.

Simple, isn’t it?

No, it isn’t!

The (simple, as well) explanation is that left-handed people aren’t “tagged” so exclusively because of their preference on which hand they use to write. It also involves every other activity in their life, every function they perform, every action they take besides writing. For example, everyone of us knows people who write with their right hand and perform other important actions with their left hand. Or write with their left hand and any other activity is made with their right hand. “How much” can we say they are left- or right- handed?

There comes science again!

After a number of researches, experts seem to agree that there are individuals who perform most of everyday functions only with their preferred hand, known as “strongly” left- or right-handed, while there are others that can use both of their hands -the one for certain actions, the other for some other actions-, known as “weakly” left- or right-handed. The percentages are about 10% for the strongly left-handed and 35% for the weakly left-handed over the global population.

Last, but not least, we should also think of those people who favor a specific side of their body: those who prefer to use most not only their left hand, but also their left foot, eye or ear. As you can imagine, researches about the preferred side are more complicated than those about left- or right- handness. The variation on percentages in those cases are so wide, that any correlation and conclusion would be extremely unsafe to talk about.


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