Kevin Mitchell in Wiring the Brain:
It seems an innocent enough question: why are males more frequently left-handed than females? But the answer is far from simple, and it reveals fundamental principles of how our psychological and behavioural traits are encoded in our genomes, how variability in those traits arise, and how development is channelled towards specific outcomes. It turns out that the explanation rests on an underlying difference between males and females that has far-reaching consequences for all kinds of traits, including neurodevelopmental disorders.
A recent tweet from Abdel Abdellaoui showed data on rates of left-handedness obtained from the UK Biobank, and asked two questions: why is left-handedness more common in males and why are rates of reported left-handedness increasing over time?
I don’t think the answer to the second question is known but I presume it has to do with the declining practice of forcing left-handers to write right-handed. This once common practice reflects a long history of prejudice against lefties, illustrated by the derivation of the word “sinister”, which in Latin means “left”, as opposed to “dexter” meaning “right” which is the root of the positive words “dexterity” and “dextrous”.
The first question – why is left-handedness more common in males? – is the one I want to explore here, as it opens up some fascinating questions about robustness, variability, and developmental attractors.