Why are most people right-handed? What is the cause of left-handedness?

Beijing time on November 13, according to foreign media reports, when you are a child, the first time you pick up crayons, you may feel that one hand than the other hand to draw more comfortable, more natural.

Why are most people right-handed? What is the cause of left-handedness?

With the exception of a few people who are both hands-on (or double-handed, i.e. both left and right are good at daily activities), the vast majority of people usually have a habitual hand, as well as the body side. So why is this happening?

Most people (about 85 to 90 percent) are right-handed, and no group in the world is left-handed. This imbalance has historically had some negative effects on left-handed people. They had to use scissors, tables, knives and notebooks designed for right-handed people. Many left-handed people are forced to write with their right hand, which goes against their nature, including famous examples such as King George VI of England. Left-handed people have also been discriminated against and suspected, as evidenced by the language used to describe them. “right” (right) also means “right” in English, while the etymology of the word “sinister” (insidious, evil) can be traced back to the Latin word for “left”.

Although in most places the bias against left-handedhands has faded, scientists are still confused about the difference between the right hand and the left-hander. Researchers are still trying to understand why people prefer one hand to the other, and why most people are right-handed.

At the individual level, handyness may be determined at the earliest stages of development. A 2005 study published in the journal Neuropsychologia found that fetuses exhibit a preference for a hand in the womb (sucking the thumb of a hand) and continue after they are born.

Although scientists have not found the right-handed or left-handed genes, DNA does seem to play a role in handyness. In a recent study published in the journal Brain, researchers at Oxford University analyzed the DNA of about 400,000 people in the UK and found that four regions of the genome were widely associated with left-hand. Three of these four regions are associated with brain development and structure. Some researchers hope that by studying the biological differences between the left and right hands, it will reveal how the brain develops its left and right hemispheres.

Trying to answer the question of handyness from the perspective of human evolution is also complicated. Researchers can discover beneficial hand-in-hand phenomena in archaeological records by studying certain anatomical features of prehistoric bones, such as asymmetry in the size and density of the arm bones, and by the study of prehistoric tools.

Natalie Uomini, a senior scientist at the Max Planck Institute for Human History in Germany, said that if you can know how and how the tool is used, you can tell if left-handed or right-handed people are using the tool by looking at the signs of wear and tear. Scientists can even tell which hand people use to tear the flesh or skin off their mouths by looking at the direction of the twill on the fossils of the teeth.

Umini said researchers had long found in archaeological records that right hands dominated about 500,000 years ago. Neanderthals, the extinct close relatives of humans, were also mostly right-hand men. This phenomenon makes humans seem strange in animals. Some non-human primate species, such as other apes, are also handy, but the ratio of left and right hands is usually close to 50 to 50.

What caused humans to evolve the characteristics that leaned in favor of the right hand and remained so far? From an evolutionary point of view, mr Umini says, if the right hand evolves because they have an advantage, you might think that the left hand will eventually disappear altogether. She adds that there are some drawbacks to zolusing, such as the higher frequency of work accidents. A 2013 study published in the journal Brain also showed a link between lefthand and learning disabilities.

At present, there is a mainstream theory that may explain why the left hand is always in the minority, which is the combat hypothesis. “The idea is that the left-hander, who is a minority in the population, has an evolutionary advantage in a battle with a physical or weapon, ” Umini said. ” In a 2010 study published in the journal Laterality, scientists reported that the advantage of the left hand has been demonstrated in one-on-one sports such as fencing.

If this hypothesis is confirmed, it would mean that even if the left-handed’s shortcomings were enough to make them a minority, the advantage in battle would at least give them a chance to avoid eventual extinction. (Any day)

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