A new study has concluded that there is no single, major gene which accounts for why people are right- or left-handed. About 10 percent of people worldwide are left-handed, but the mechanisms by which people favour one hand over the other remain unclear. In an effort to learn more, researchers from Nottingham University conducted detailed genetic analyses of nearly 4,000 twins who had been studied by the London Twin Research Unit in the United Kingdom. There is little doubt that left-handedness runs in families and that identical twins are more similar in their handedness than non-identical twins. They had hoped to see a difference in the gene variants of twins who were left and right handed but did not find any single gene which could account for the differences in a statistically significant way. Crucially they also calculated the statistical power of their data, and were confident that had there been a single major gene then they could have found it.
The study was published recently in the journal Heredity. Even though they didn't find a strong genetic influence on handedness, the researchers noted that it is widely believed that handedness is not just the result of choice or learning. Therefore, it is still likely that genetic factors play at least a minor role in determining handedness and the probability is that there are many genes, all with small effect.
Professor Armour said: It is likely that there are many relatively weak genetic factors in handedness, rather than any strong factors, and much bigger studies than our own will be needed to identify such genes unambiguously. As a consequence, even if these genes are identified in the future, it is very unlikely that handedness could be usefully predicted by analysis of human DNA.â€
This situation is very similar to many other complex characteristics which are being studied genetically at present, including height, weight, cognitive abilities, and even whether the heart is on the left side or the right side.
A previous study done at Oxford University did find some links between handedness and a particular gene that controls left and right side development in embryos. However the authors warned that their results did not completely explain the variation of left- and right-handedness within the human population. William Brandler, of Oxford University's MRC Functional Genomics Unit, said “As with all aspects of human behavior, nature and nurture go hand-in-hand. The development of handedness derives from a mixture of genes, environment and cultural pressure to conform to right-handedness.”
The interesting thing about this study is that it might have found a gene which is related to how strongly handed people are, be it that they are right or left handed. The same gene has also been implicated in a separate study from Germany.
Left Handers Club comment:
Well, not much change there then and we still do not have any definitive link between genetics and left-handedness. What we do know from our own experience and from surveys and member feedback is that people ARE BORN left-handed and do not just learn it from their parents and others. We also know that left-handedness DOES run in families, though not in a predictable way. These facts would seem to indicate that there IS a strong genetic link, but it clearly does not show up in an easily identified way!
Note from Keith – Professor Chris McManus, author of the excellent book Right Hand Left Hand was involved in the Nottingham study and I am grateful to him for reviewing my article and making valuable clarifications and improvements. he also kindly said “Your LHC comment at the end strikes me as entirely fair and accurate!”
For those of you that want to know more, Chris also sent me another far more detailed paper he has written on this subject and you can see it as a pdf document here.
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