What Causes Left-Handedness?

Written by on March 27, 2014 in Left-Handed Basic Information with 3 Comments

The most common question we hear is what causes left-handness? Our most typical answer is that we are born this way. That’s how we got our left-handed orientation. While that is actually the truth, it’s not the whole answer.

Talking Theories Only

When we talk about the whole answer, we can only talk theories. Nothing is proved conclusively, even in this modern day and age. But several rather prominent theories are worth talking about here.

First, hand orientation can be seen while a baby is still a fetus. There is a natural tendency of babies to hold their dominant hand closest to their mouth. An interesting fact to discover, especially for pregnant women.

Researchers discovered a gene that tends to link to left-handed orientation. In 2007, one of three single-nucleotide polymorphisms located just downstream from the infamous LRRTM1 gene may cause left-handed tendencies. The LRRTM1 was the first gene to be linked to increased tendency toward left-handedness. It’s a gene that is inherited only from the father. This does sound like left-handed orientation comes from the father, but this is still just a theory. It still hasn’t been proved, even after all this time.

The Failed Theories

Another theory comes from twins. There is a high occurrence of identical twins being one right-handed and one left-handed. The twin theory says that left-handed people were originally an identical twin, but that the right-handed embyro failed to develop. Australian researchers believe they have debunked this, but the theory persists because of the twin sets that are born, one with each-handed-ness.

A final theory worth noting is one that blames prenatal hormone levels for left-handed orientation. Again, this is a highly debated and potentially proven-wrong theory. The theory also doesn’t explain women who are left-handed, only men who were exposed to a synthetic prenatal estrogen had a higher instance of left-handedness.

So What Causes Left-handedness

The end result is that no one really knows for sure what causes one to have a dominant left hand. We do know it’s not so unusual in our population. Call it a gift from above, call it an intelligent Mother Nature, call it whatever good connotation you want. The result is the same. Left-handed people are born this way. That’s what causes left-handedness.

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