Right-handedness or left-handedness may be determined at the embryonic stage before the fetus develops
The right and left hands are linearly symmetrical, so it would seem that the probability of being right-handed and the probability of being left-handed would be exactly half and half. However, in reality, the rate of left-handed people is about 10%, and right-handedness is the overwhelming majority. A research team at the Max Planck Institute for Psycholinguistics has shown in a paper that whether one is dominant or left-handed may be related to 'mutations in specific genes.'
Exome-wide analysis implicates rare protein-altering variants in human handedness | Nature Communications
Right- or left-handed? Protein in embryo cells might help decide
https://www.nature.com/articles/d41586-024-00977-x
Previous studies have consistently shown that right-handedness is overwhelmingly more prevalent than left-handedness across continents, and a 2009 study of twins found that left-handedness is inherited with about a quarter probability, suggesting that handedness may be a genetic trait.
In 2019, a research team from Oxford University published a study that examined the personal records of approximately 400,000 people. The results of the study found four genetic regions that appear to be associated with left-handedness.
Gene mutation responsible for left-handedness identified - GIGAZINE
Additionally, in 2020, a genetic analysis of 1.7 million people identified 41 genetic mutations that affect left-handedness.
Genetic analysis of 1.7 million people identifies 41 new genes related to 'left-handedness' - GIGAZINE
So a research team led by geneticist Clyde Franks of the Max Planck Institute for Psycholinguistics looked at the genetic data of more than 350,000 people registered in the UK Biobank, including 313,271 right-handed people and 38,043 left-handed people.
They looked at the specific genetic region associated with left-handedness and investigated the extent to which mutations in this genetic region affect handedness, and found that the heritability of the mutation for left-handedness was about 1%.
Furthermore, left-handed people were found to be 2.7 times more likely to have a mutation in the gene TUBB4B, which expresses microtubules, tube-like structures inside cells made of a protein called tubulin .
These microtubules form part of the cytoskeleton that gives cells their shape and play an important role in neuronal development and plasticity. They also form the cilia that create asymmetric currents in the cell membrane during embryonic development, which may influence handedness.
'Although it is unclear how microtubules affect individual differences in handedness, our findings suggest that they may contribute to cellular handedness during early brain development, thereby contributing to the organ-specific formation of the left-right axis of the brain,' the team wrote.
The research team further stated, 'This study sheds light on the role of rare genetic variants in left-handedness and further supports the involvement of microtubules and disease-related genes,' and argued that larger studies are likely to reveal more genes associated with left-handedness.
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