Left-handers have always been looked at with a certain sense of suspicion. They have long been discriminated against because they seem to go against the natural human disposition to favour the right hand, but nowadays certain pseudo-scientific theories sustain that that very same group of people is more creative and intelligent. Left-handedness has its roots in an inversion of the role of the two cerebral hemispheres, a feature that is constant across biological populations, not only in human beings.

This was explained to the audience in Piazza Mantegna by Giorgio Vallortigara, neuroscientist.

(caricamento...)

It is well known that the human brain is divided in two halves, or hemispheres, and each one controls the movement of one half of our body and specialises in different tasks. This feature of our brain is known as brain asymmetry and it is found in a great number of different species, independently from their level of mental sophistication. Brain asymmetry can be explained, on an evolutionary level, in a number of different ways.

It allows for the optimisation of cerebral material, relegating some functions to more restricted areas of the brain. This avoids conflict between the two hemispheres, ensuring that the individual can contemporaneously carry out two activities, each one controlled by due separate hemispheres (and this what we know as multi-tasking, which has even been observed in chicks).

The fact that one section of a species, a figure more or less fixed at around 10%, has the reversal of the function of the two hemispheres is a phenomenon that has its origins in evolution. To understand how natural selection maintains this fixed quota of 'eccentric' individuals, we have to consider certain examples of left-handedness that are different to those that we see each day: people who write or use their fork with the opposite hand to most. We must consider that, in nature, behaving in an opposite way to the rest of the group can bring significant advantages. But this advantage would soon disappear if the number of individuals behaving in this way grew too large, as they would no longer be a minority. And nature therefore that governs the fluctuations in the number of left-handers, always keeping it below 50% of the total population.

It has nothing to with the devil then, nor does it indicate some sort of brain damage at birth. Left-handers (the Italian term, mancino, derives from the Latin mancus, meaning mutilated or crippled) are generated through Darwinian selection and statistical calculation.