I am a faithful listener of National Public Radio (NPR) in the United States. Every morning, I tune in to hear the latest news and commentary. Recently, I was pleasantly surprised to hear Ayesha Rascoe, the host of NPR Weekend Morning Edition Sunday, interview Clyde Francks. Clyde Francks is one of the world’s leading researchers investigating the genetics of handedness. It was not surprising to learn that Ayesha Rascoe is left-handed. In my experience with journalists, it is often the left-handed ones among them who seek out the latest scientific news about the topic. Ayesha Rascoe revealed that she had a mixture of left- and right-handers in her family and “…thought that being left-handed must have something to do with genes…”.
During the interview Clyde Francks stated that “The heritability of left-handedness is actually quite low.” He further explained that there is not a simple genetic explanation for the trait of left-handedness. His research has focused on sites in the genome that code for the proteins that make up our bodies. His team is specifically interested in variants at these sites that are very rare in the human population.
Francks and his team used genetic data from 38,000 left-handers and over 300,000 right-handers listed in the UK Biobank, a massive database of biomedical information. They analyzed a gene, TUBB4B, that codes for proteins called tubulins. Tubulins make up microtubules that are crucial for cell structure. If an individual has a rare variant of this gene, they are likely to be left-handed. However, the variant is so rare, even among left-handers, that its presence would account for only about 1 in 1000 left-handers. When pressed about the causes of left-handedness, Francks explained his view that “…most of the left-handedness in the population is not caused by genetic variants.” He speculated that the cause of left-handedness might reside in “…random fluctuations of chemicals in the very early developing brain…”. You can listen to the full conversation by accessing the NPR site with this link. Francks interview
Clyde Francks’s research exemplifies the emerging pattern of 21st century investigations into the genetics of human handedness. The search for a handedness gene that dominated research in the 19th and 20th centuries has been abandoned in favor of explorations of gene variants involved in the microprocesses of brain development. These variants may eventually be linked to the formation of handedness types. As Clyde Francks stated in the interview “So in most people who are left-handed, there will not be a simple genetic explanation…”.