All over the world, right-handers make up the bulk of the population. But why did it happen and what is hidden in this mystery of evolution? What can you say to right-handers and left-handers?
We humans rarely agree, but at least one question the majority will give the same answer - which hand is more convenient to use. If you write with one hand, then you probably eat with it, and for most people - about 85% - this is the right hand. In addition, "there is no history of lefties predominating anywhere," says archaeologist Natalie Uomini of the University of Liverpool.
Lateralization in the use of the limbs - that is, the preference for the left or right arm or leg - is most often attributed to the characteristics of the brain. It is known that the left hemisphere is responsible for some tasks, while others are controlled by the right. This is complicated by the fact that the nerves connecting the brain to the body intersect, so that the left hemisphere is more in control of the right side of the body and vice versa. In other words, with the help of the left hemisphere of the brain, we use the right hand, eye, leg, and so on.
Some scientists believe that this neurological "division of labor" has existed in the animal kingdom for half a billion years. Perhaps it arose during evolution because the brain processes information more efficiently when the hemispheres do different jobs. For example, it can be assumed that the left half of the brain was solving everyday tasks, say, finding food, while the right one was always alert to notice and quickly respond to an unexpected change in the environment, in particular the approach of a predator. This is confirmed by various species of fish, toads and birds, which more often grab prey visible with the right eye.
It turns out (although it is not so easy to prove it) that when our hominini ancestors (the so-called tribe of hominini traditionally include humans, chimpanzees and their extinct ancestors - ed.) Began to walk on two limbs instead of four and they had free hands for new work, such as making tools, they were prone to using their hands differently. Or, as Stephanie Braccini and her colleagues put it in an article in the Journal of Human Evolution, "the development of individual asymmetry may have already begun at the stage when early homininis routinely transitioned to upright posture when using tools or searching for food."
In an effort to confirm their theory, Braccini and her colleagues observed chimpanzees and found that, standing on four limbs, monkeys used both hands equally. The asymmetry in hand preference only appears when they have to straighten up to do something - however, there are equally left-handed and right-handed monkeys among monkeys.
In this case, there must be some other explanation for the fact that the early people, who equally often preferred this or that hand, were replaced by modern man - almost always right-handed.
We roughly know the era when this happened: as part of the experiment, scientists tried to independently make ancient stone tools, chipping the stone with their left or right hand and then comparing the resulting objects with those that remained from the early hominini. As a result, we still have few arguments in favor of the right-handedness of our ancestors, who created tools two million years ago or more.
However, stone tools found at the Koobi Fora site in Kenya, made one and a half million years ago by representatives of two species that preceded man - Homo habilis ("skillful man") and Homo erectus ("upright man"), already suggest a tendency towards right-handedness in scale of the whole species. By the time of the appearance of the species Homo heidelbergensis ("Heidelberg man"), about 600 thousand years ago, right-handers already clearly dominated prehistoric society. For example, the wear pattern of the preserved teeth of Homo heidelbergensis shows that food was usually brought to the mouth with the right hand.
So, we found out when the skew to the right began, but did not find out why. There is a version that this is due to the language. Just as most of us are right-handed - and the left side of the brain, as we remember, is responsible for the right side of the body - so in most people, the left hemisphere is responsible for speech. This type of asymmetry is even more common than right-handedness; it can be assumed that as the language specialization of the left hemisphere developed, the right hand began to dominate simply as a side effect. This is the so-called Homo loquens hypothesis: the lateralization of brain functions as a whole manifested itself under the influence of a person's ability to walk on two legs and maintain an upright posture, and the preference for the right hand arose later, as the ability to language developed.
Thus, universal right-handedness can only be an accidental side effect of the structure of the brain in most of us. But proving this hypothesis is difficult, if not impossible, since ideally it would be necessary to conduct a series of neurological tests on our ancestors who have long been dead. It turns out that we will never know for sure what sequence of events led to the fact that our species relies so heavily on the right side of the body and, accordingly, the left half of the brain.
What can you say to lefties? Cheer up! As the authors of a 1977 study published in the Psychological Bulletin note, there is "very little evidence for a hypothesized link between left-handedness and any deficiency." What's more, a number of studies have shown that left-handers recover faster from head injuries. And in a fight on the side of the one who has a good command of the left hand, the effect of surprise - which means that left-handers have an advantage in combat sports.
All this suggests that you can always find your advantages in deviation from the norm.