Why Am I Left-Handed?

11 insights saved from this article by @science

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Fetal arm-movement asymmetry appears around 10 weeks after conception, before the brain connects to the limbs.
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A 2026 review found that people are stabbed more often on the left, and left-sided stabbings are more often fatal.
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The biggest genetic surprise: most handedness-associated variants are tubulin genes, which build cellular structures and transport components.
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Only about 10% of humans are left-handed, yet left-handers are overrepresented among presidents, artists, musicians, and elite athletes.
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Microtubules may transport signaling molecules asymmetrically inside spinal-cord progenitor cells, amplifying tiny imbalances into neural differences.
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Tubulin variants might weaken the initial rightward bias, letting random fluctuations occasionally give the left side an advantage.
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Large-scale genetic studies identified about 40 variants that each slightly increase left-handedness likelihood. No single gene explains it.
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Some genes linked to left-handedness are also linked to schizophrenia, dyslexia, and autism, where left-handedness is more common.
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A plausible developmental model must explain handedness’s partial heritability, strong rightward bias, and substantial randomness.
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In traditional Ghanaian etiquette, the left hand is for dirty tasks, while the right handles eating, paying, and social interactions.
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Combat advantages alone may not explain why humans preserve such a stable 10–90 split between left- and right-handers.

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