Left handedness, as the name suggests, refers to people who habitually use their left hand, and the exact cause is still unknown. Many people believe that left handedness has a strong genetic predisposition, but scientists have not found evidence of left handedness being inherited. So, is left handedness hereditary?
This is the current mainstream school of thought, widely recognized at the turn of the 19th and 20th centuries. Visually speaking, the dominant hand is a human nature. In any social form, no matter what forced correction measures are taken, for left-handed individuals, they may be able to use their right hand very proficiently, but their innate preference for using their left hand remains unchanged. In real life, many parents resort to various methods such as corporal punishment, binding, and wearing gloves to restrict left-handed children from using their left hand, often only achieving success in a limited number of hand activities. Once the child moves freely, the left hand becomes dominant again.
There is more obvious evidence in statistics. A medical study aimed at investigating the probability of left-handed children being born in families where both parents are left-handed or both parents are right-handed shows that in families where both parents are left-handed, the probability of a child being left-handed is 50%; In families where both parents are right-handed, the probability of a child being left-handed is only 2%. Another piece of evidence is that the proportion of left-handed individuals is significantly higher in certain families than in the general family, indicating a direct genetic correlation between the preference for using hands. The Scots have a Kerr family that has been known for centuries for its numerous left-handed individuals. The stairs of the castle they built all rotate counterclockwise to meet the defense needs of the Kerr left-handed warriors. In this family, left-handed individuals have become the majority, while right-handed individuals have become the minority. Their public facilities and production tools are all left first.
Some people use dominant and recessive genes to explain the causes of left and right handedness. The right-handed gene is dominant, while the left-handed gene is recessive. Only in special gene pairs can the traits of left-handed recessive genes be displayed, so left-handed individuals become a minority in the total population. There are also research reports that a person's habit of using their left or right hand is determined by a single gene, and the medical community is working hard to identify this gene. A study on 100 left-handed couples and their parents and children found that those who inherit this gene from their parents are naturally right-handed; Those without this gene may be left-handed or right-handed. 82% of people have at least one of these genes, making them right-handed; 18% of people do not have this gene, with half becoming right-handed and the other half either left-handed or proficient in both hands. This study explains why identical twins have different dominant hands.
Some people have studied genes that may control left-handed traits through the rotation of hair. Expert Clare from the American Cancer Institute observed the rotation of human hair in densely populated airports and supermarkets, and found that 95% of right-handed individuals rotate their hair clockwise, while left-handed and left-handed individuals with flexible hands rotate their hair clockwise and counterclockwise equally.
Kral believes that there may be a gene in the human body that has two forms of expression, one with the characteristic information of right-handed hair and the other with the characteristic information of randomly rotated hair. It is this gene that controls the handedness and hair rotation. The former form of expression is explicit, while the latter form of expression is implicit. A person with one or both right-handed information genes is definitely right-handed, with hair rotating clockwise. Individuals with two randomly oriented genes may not necessarily be right-handed, but have a 50% chance of becoming left-handed or right-handed. This theory is somewhat different from the theory of single gene determination, but it can also explain the phenomenon of one egg twin with half left and half right sperm. Because they all carry two random rotation characteristic genes, with a probability of half being left-handed and half being right-handed. What exactly this base is still requires continuous efforts from scientists to finally unravel the mystery.
Through the description in this article, it can be concluded that if parents are left-handed, the likelihood of their children being left-handed will greatly increase. However, scientists have not yet provided conclusive evidence on whether left handedness is hereditary, and further research is needed by the scientific community to discover.
