Why is there more right than left? What's more, why that specialization?

2000/10/18 Elhuyar Zientzia

• Anatomia/Fisiologia

In the last 160 years much has been investigated about the reason that human beings have a right or left, but so far this trend has not been fully explained.

It is a mystery why we use one hand more than the other and in most cases why that hand is right. It has been observed that the existence of right or left depends on genetic factors, although these specific genetic mechanisms are not known. At the same time, society and culture have a great influence. Who does not know those who being left have to write with the right?

In general, very restrictive societies have less left. Some studies have concluded that some of the left are pathological, that is, they are due to brain trauma suffered at birth. It is believed that the tendency to be left or right occurs in the fetal era, that is, at the moment when the cerebral hemispheres are developing.

In 1860, the French physician Paul Broca discovered the relationship between being the right and being the left hemisphere of the brain specialized in speech capacity. But the research carried out in the 1970s brought down this theory, as it was seen that most of the left people had the same degree of specialization. That is, that most human beings, whether left-handed or right-handed, use the two cerebral hemispheres equally.

At the moment, with certainty it can only be said that 70-95% of human beings are right-handed, 5-30% are left-handed and a small indeterminate amount uses both hands to the same extent. These percentages seem to be fulfilled in any human population in the world, but no one has been able to explain why the trend instead of the left is right.