Genetic secrets of left-handedness revealed as part of huge study

James Marshall
September 5, 2019

"Many researchers have studied the biological basis of handedness, but using large datasets from UK Biobank has allowed us to shed considerably more light on the processes leading to left-handedness". The result? Left-handed male players performed more shots overall, more shots per minute, and most importantly, scored more goals than right-handed players.

Moreover, left-handedness was influenced by birthweight, being part of a multiple birth, season of birth, breastfeeding, and sex.

What does this tell us?

Dr Akira Wiberg, a Medical Research Council fellow at the University of Oxford, who carried out the analyses, said: "Around 90% of people are right-handed, and this has been the case for at least 10,000 years".

Studies on twins have already revealed genetics - the DNA inherited from parents - has some role to play.

Image copyright Getty Images Image caption President Barack Obama signing a bill, with his left hand.

The new study, published in the journal Brain, identified some of the genetic variants associated with left-handedness by analysing the genomes of about 400,000 people from UK Biobank, which included 38,332 left-handers.

And unlike being a Saggitarius, being left-handed has had a concrete effect on my life.

They found that a small number of genes played a role for the development of left-handedness, among them MAP2 (microtubule-associated protein 2), a gene that is crucial for the development of nerve cells in the brain.

But how does it work?

In particular, these proteins were related to microtubules important to cell scaffolding - called the cytoskeleton - guiding the construction and functioning of the cells in the body.

Similar mutations that change the cytoskeleton in snails have been shown to lead to the molluscs having an anticlockwise or "lefty" shell.

After taking detailed brain images of 10,000 of the study's participants, the researchers found that genetic effects were associated with differences in brain structure in white matter tracts.

What's more, Douaud told CNN, the research indicated that in left-handed people, "the left and right sides of the brain communicate in a more coordinated way".

The language brain regions were more coordinated in left-handers between the two sides of the brain (green and orange) and were also connected by the white matter tracts influenced by one genetic region related to handedness (blue).

However, they did find lefties have a slightly high risk of schizophrenia, but a lower risk of Parkinson's disease.

Did you know that humans are not the only species that shows left-handedness?

It is thought that this effect is due to the fact that opponents expect a throw or a hit with the right hand, and are surprised if someone uses their left.

Professor Dominic Furniss, joint senior author on the study, from the Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Science at the University of Oxford, said: "Throughout history, left-handedness has been considered unlucky, or even malicious".

In French, "gauche" can mean "left" or "clumsy".

"What this study shows is that being left-handed is just a outcome of the developmental biology of the brain, it has nothing to do with luck or maliciousness", Prof Furniss said. In English, "right" also means "to be right".

A series of genetic variants can influence handedness, according to a new paper. "Therefore, beginning to understand what is responsible for this distribution in humans helps us start along the road to understanding the question 'what makes us human?'"

Is this the end of the story?

The best guess is handedness is 25% genetic and 75% down to the environment (anything that's not in the genes).

Yet this study has found only the first 1% of that genetic component and only in a British population.

Four areas in the DNA structure of the left-handed people were identified as having mutations to those that are right-handed.

Other reports by Click Lancashire

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