Why Are Some People Left-Handed?

A group of researchers have identified a network of genes that might have connection to the preference of the progress of asymmetry in the body and the brain. And that network of genes relate to handedness in humans.


4 min read
Why Are Some People Left-Handed?

Throughout history, there are many rumors and fallacy about left-handed people. For example, if the issue of left-handedness was seen in someone, they would assume that the person is showing signs of becoming a dingy person to a witch. Again, in medieval times those who wrote with their left hand were accused of being possessed by Satan (devil). Because they knew that Satan was lefty. However, the matter wasn’t accustomed on everywhere and every folks in a same belief. Rather different people thought this in a different angle.

But there is no denying that people must have thought a lot of nonsense about it. However, gradually people from all over the world started taking this matter for granted. Anyway, experts say, only about 10% of people worldwide are left handed. Whereas probably it can be up to 15%. But still there are some undeniable bummers associated with a left-handed tendency. You might also have noticed how rare they are.

To be honest, yet there is no clear explanation or result around it that can decidedly be answered. But there are plenty of hypotheses that have been building for more than a century. A paper published in PLOS Genetics, a group of researchers have identified a network of genes that might have connection to the preference of the progress of asymmetry in the body and the brain. And that network of genes relate to handedness in humans. Moreover, scientists have speculated for many years that a single gene may be responsible for controlling left-right preference. Unfortunately, no one was able to pinpoint where that gene actually was and not yet. [1]

The two most widely published genetic theories of human hand preference proposed after arguing on the left hemisphere of the brain that there are two “alleles”.They thought of two manifestations of a gene at the same genetic location that might be associated with handedness. One of these alleles is a D gene (for Dextral which means Right) and another allele is a C gene (Sinistral, probably a chance of being the cause of left-handedness). The D gene which promotes that right-hand preference in the majority of people. [2] Interestingly, it’s nothing but also a hypothesis.

Credit: Business Insider

Since the 1980s, research has found that the preference for left and right hand is most likely determined before we are born. Greatly, ultrasound screening suggests as early as the eight week of pregnancy. And miraculously, from the 13th week in the womb, babies tend to suck their either right or left thumb. Earlier, we thought the genetic differences between the left and right hemispheres of the brain determine whether someone would be left or right-handed. But a recent study shows something different. It is published in the journal eLife mentioned that the answer of what causes a person to be left-or right-handed could lie in the spinal cord. Motor cortex in the brain sends a signal to the spinal cord that’s translated into a motion.

The researchers analyzed gene expression in the spinal cord in the eight through the 12th week of pregnancy. And this asymmetrical nature of the spinal cord could be down to something called epigenetics. There could be environmental influences or how organisms are affected by the change of gene expression than in the genes themselves. And these gene-expression differences in the spinal cord could affect the right and left parts of the spinal cord differently. And turning out the result being by the righty or lefty. [3]

But still the question arises why are left-handed people so rare? The several researches are showing several results and hypothetical thoughts. Most of the study think the right or left-handedness may be genetic. Or there could be social factors, environmental influences or something that is yet not to be answered confidently. Studies are going on and on. Nevertheless, it is something mysterious because we don’t know the exact answer to where and what is the actual reason for this issue.

Anyway, this is all about for today. Thanks for reading us OUT.

References:

  1. Smilthsonia Magazine, Retrieved From: https://www.smithsonianmag.com/science-nature/why-are-some-people-left-handed-6556937/ On September 12, 2013.
  2. Scientific American, Retrieved From: https://www.scientificamerican.com/article/what-causes-some-people-t/#:~:text=Researchers%20who%20study%20human%20hand,%2C%20most%20likely%2C%20genetic%20causes.&text=The%20D%20gene%20is%20more,genetic%20heritage%20of%20an%20individual. On June 21, 2014.
  3. eLife Sciences, Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetrics. Retrieved From: https://elifesciences.org/articles/22784 On February 1, 2017.



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