Anything Left-Handed > Blog Posts > Research > Is left-handedness genetic?

Is left-handedness genetic?

Genetics and left-handednessA 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.”

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.

Left ahd right handsA 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.

If you have any views on this or more information to share, please add a comment below.

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45 comments on “Is left-handedness genetic?
  1. Dr Billy Levin says:

    Roger Sperry was awarded the Nobel prize for his split brain research. His comments explain all . This knowledge and insight has been well re research and documented for the last 46 years.

  2. Dr Billy Levin says:

    The two hemispheres of brain each have their own talents. We mostly become left brain dominant due to the all important language ability only known to “MAN”. Occasionally due to genetic inheritance we are right brain dominant making us left handed. Each hemisphere looks after the opposite side of the body. Thus damage to left brain might result in paralysis of right side of body and speech might also be affected. Severe damage to right brain results in paralysis of left side of body and speech is not affected.

  3. Dr Billy Levin says:

    Medical science has certainly explained why some are lefties. An Inherited right brain dominance instead of left brain dominance. The brain looks after the opposite side of our bodies. So right brain dominance causes left handedness. QED.

  4. Bob says:

    My paternal grandfather was left handed.

    parents: both right
    older brother: right
    Me: left
    younger sis: right
    younger brother: left

    not sure about my father’s siblings or my cousins on that side. I think at least some of them are lefty.

  5. Stu Lloyd says:

    In my family, only myself and my maternal grandmother are left handed. Since I didn’t see her much as an infant, there would have been no way in which I could have been influenced by her handed ness – quite the opposite in fact, since the rest of my family are right handed.
    It did have the advantage though, once my preference was recognised, in that my mother knew how to teach me to do various tasks with my left hand, having been taught herself, as a right hander, by a left handed mother herself.
    My other grandmother, however, didn’t understand at all, so she would buy me girls blouses as they did up the other way. Needless to say, I rarely wore those garments!

  6. Roddy Turlington says:

    Geschwind-Galaburda says maternal hormones determine handedness.

    The propensity to have high Testosterone during pregnancy could be genetic I suppose. But handedness is more hormonal than genetic.

    GG Hypothesis says Testosterone slows development of the left hemisphere, so the right develops to be the dominant hemisphere. R dom hemisphere = L handed child. The left hemisphere catches up later in childhood.

    • Dr Billy Levin says:

      If we are born left handed as a result of right brain dominance there is every likely of ADHD. There is a tendency to mature but not always but left handedness remains.

  7. polly says:

    I’m curious to know if anyone else who is left handed is a middle child. I am a middle, so is one daughter and so is one grandson. Other people I’ve asked are also “the middles.”
    Would love to hear from any others. ~Polly~

    • Rachel Bach says:

      My daughter is the only leftie in the family and she is a second child, she might well have been a middle child if I had had any more.

  8. Margaret says:

    I am left handed so is my 4 year old daughter. My mum Is left handed. I have 3 older sisters and 2 are left handed leaving the other to be right handed and so is my dad. I eat right handed and hold spoon in my left. I can use scissors left or right handed depending on what I am doing, stir either left or right and can write right handed though shaky, so if anything ever happened to my left hand I could still write. I don’t like using gadgets designed for left handed people.

    I do a lot of crafts. Knitting mainly. I knit right handed. Just learnt to Crochet but can only crochet left handed.

  9. Ann says:

    Left handedness seems to run in my family, mainly on my mums side, but as stated it’s a bit like having a red head in the family it seems to have skipped my mums generation where as in my generation and the next there is at least one left hander in each of my aunties families and I think it is mainly girls.

    My mum, dad, brother and sister all righties.

    My daughter is left handed as is her aunt on her father’s.

    I am a complete leftie. Left hand, left eye, left foot.

    Daughter is left handed, left eyed, but right footed and plays the bagpipes with her right hand.

    I think I knew from the start that she was a leftie, because as soon as I put something in front of her from the day that she recognized things it was the left hand that was out stretched.

    My baby great niece is left handed, but neither of her parents are.-

  10. Andrew says:

    I am the only left hander in my immediate family(both parents and brother all RH). I married a fellow leftie and we have three children who are all left handed. They are now all married with children who are mostly left handed.

  11. Jennifer Bright says:

    I am the only one in my family line other than my maternal grandmother & maternal grandfather. There were no further lefties noted on my grandfathers side and my grandmother was adopted and has no history of her biological family. Both my parents and sister are righties. I married a leftie. We have two right-handed children.

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