5 Mar 2021

Why Are Some People Left Handed

Why are some people left-handed? Which hand would be the dominant hand is decided in the womb or after our birth? Does it has anything to do with our brain or the environment?
Do you know that around 10% of the people all over the world are left-handed and August 13 is celebrated as International Left Handers Day.

Why Are Some People Born Left Handed Video

Left-handed people are unique in themselves and there are some advantages and disadvantages of being left-handed. So let's now come to our main question, why some people are born left-handed.

Why Are Some People Left Handed 

The dominant hand-left or right hand has, in the past years, been a characteristic believed to be determined by a particular hemisphere of the brain. This was even before birth, but new research done in 2017 showed that hand dominance is instead associated with the spinal cord.

The study found that a baby's left- or right-handed tendency is already present and set in the womb, long before the baby's brain gains mastery over all movements in the body. The motor cortex in the brain controls all the hand and arm movements by sending signals down to the spinal cord, which interprets them into motion. However, at this time, the motor cortex in the brain and the spinal cord aren't yet connected until the 15th week of pregnancy. Interestingly, babies show hand preferences starting 13 weeks, sucking either the right or left thumb. This early behavior shows that the brain does not determine handedness since it is not connected to the spinal cord, at least not yet. It is in weeks 8 to 12 of pregnancy that scientists find variations in gene expression in the spinal cord between the arm-moving and leg-moving segments. These differences in expression make a person left-handed or right-handed. So, it is our spinal cord, not our brains!

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