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Genetics of Left-Handedness

Genetics of Left-Handedness: Major Breakthroughs


Key pointsAbout 10 in 100 people are left-handed. The reasons for left-handedness are not well understood. A synthesis of recent findings suggests that genes involved in early development of the brain are crucial. Tubulin genes play an especially critical role in left-handedness.

About 10 out of 100 people are left-handed. Understanding the reason why has intrigued scientists for many years. However, despite more than 100 years of scientific research on left-handedness, it is still not well understood why some people are left-handed while most people are right-handed.

One clue comes from the fact that left-handedness runs in families. Two right-handed parents have a lower chance of having a left-handed child than two left-handed parents. Therefore, scientists concluded that handedness is to some extent determined by genetic factors.

The genetics of left-handedness: New data

Using a variety of modern molecular techniques, scientists made a lot of progress in understanding the genetics of left-handedness in the last few years. In a new scientific article, an international author team (of which I was part) now reviewed and synthesized these findings in the scientific journal Trends in Genetics (Ocklenburg and co-workers, 2025).

Mainly, three sources of data have provided new insights into the genetics of left-handedness:Studies on common genetic variants: These genetic variants are present in at least 1% of people (some studies say 5%). Studies on rare genetic variants: These genetic variants are present in less than 1% of the population and can include extremely rare mutations that only occur in a few people, but may have strong effects. Epigenetic studies: Epigenetic factors modulate how the protein product of a gene is produced by the body.

The important role of early brain development in left-handedness

By analyzing the results of these different lines of research, several important insights about the genetic factors influencing left-handedness were discussed in the article. The most striking finding was that across different studies using different techniques, many genes associated with so-called tubulins were shown to be relevant for handedness. Tubulins are a group of proteins that previously did not play a major role in research on left-handedness.

Tubulins play an important role in brain development. Three processes were highlighted:Axon growth: Axons are the long projections of nerve cells that are crucial for transporting information to other cells.
Axon guidance: This process is important so that axons are organized in the intended way when the brain develops.

Building the inner structure of motile cilia: Motile cilia are structures that are crucial for moving gene products from left to right or right to left during development. As such, they are important for all sorts of asymmetries in the body or the brain. Therefore, it makes a lot of sense that they are relevant for left-handedness, too.

Taken together, these findings make it clear that the key to understanding the mystery of left-handedness lies in the early development of the brain.

Genetics of left-handedness, heritability of handedness, genetic variants in handedness, left-handedness and brain asymmetry, handedness and gene expression, genetic influence on motor control, twin studies on handedness, epigenetics of handedness, handedness and neurodevelopment, GWAS on left-handedness, inheritance patterns of handedness, left-handedness and cognitive function, genetic loci linked to handedness, handedness and neurological disorders, handedness and prenatal environment, gene-environment interactions in handedness, handedness and corpus callosum, handedness

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