Are you left-handed? A recent study of the causes of human left-handedness shows that genes that control body asymmetry help determine a person's hand preference.
William Brandler of Oxford University and his colleagues conducted a behavioral test on the tendency to use the left and right hands and carefully studied the data from 3,300 volunteers. The researchers also analyzed more than 100,000 common variants in the volunteer's genes, and finally found that a gene called PCSK6 had the strongest association with the left or right hand.
"When we figure out what the role of this gene is, it's a moment of a flash of light," Brandler said. "When the body develops, PCSK6 plays a key role in controlling the left and right asymmetrical structure of the body. If it stops The expression of this gene in mice causes their organs to grow to the other side of the body."
In fact, the most common mutations associated with left-handed or right-handed are concentrated in genes that control body asymmetry.
Language association
This result indicates that human hand habits are a complex trait controlled by the combined activities of countless genes. This may help explain why there is still left-handedness in a world dominated by right-handers: too many genes contribute to this trait, and it is impossible to silence them all.
Other animals will also show the characteristics of the left or right limbs, but usually, they are equal in left or right scorpions. The reason why human beings are more likely to become right-handers is not clear, but there is a view that it is related to language processing. We know that the areas of language processing are asymmetrically distributed in the brain.
"Most people show that the left hemisphere is leading the language," Brandler explained. The idea is that as language becomes more and more important to human ancestors, the left hemisphere that controls the right side of the body gains a dominant position. This makes people more inclined to use the right hand. In other words, the right-handed dominant phenomenon throughout all cultures is a by-product of the development of human language.
There may be deeper connections between language and hand habits. Michael Corballis of the University of Auckland in New Zealand believes that language is developed from a series of gestures. For example, we know that chimpanzees and bonobos use a set of gestures to communicate – and chimpanzees seem to be more likely to be right-handers than people.
"I think there is a lot of evidence that chimpanzees are generally used to the right hand, and the chimpanzee's brain shows a tendency to expand to the left, corresponding to the region of the human language center," he said.
However, experts still have differences on this issue. Brandler pointed out that a comprehensive analysis of anthropoid hand-habits published a few years ago showed that the proportion of left-handed and right-handed scorpions in wild chimpanzees was roughly 50:50.
For many centuries, man refused to recognize the existence of left-handedness, and left-handed people were considered the embodiment of the devil or sick. Which, of course, is not so. Nowadays, they no longer retrain them on the "how-to".
A study conducted by scientists from Holland, Great Britain, and China included monitoring the development of fetuses in the womb. The result was interesting:
“The motor cortex of the brain sends signals to the spinal cord, which commands arms and legs. But when studying the development of the child before birth, it became clear that the decision on the greater use of the right or left hand is made before the cerebral cortex connects to the spinal cord. ”
So, left-handedness (or ambidextrous, that is, the use of both hands) is due to genetic and environmental factors, and not development or upbringing after birth. In the coming years, monitoring of the choice of the leading arm in the early stages of fetal development will continue.