Why does handedness exist

Some argue that this division of neurological labour has been a feature of animals for half a billion years. Perhaps it evolved because it is more efficient to allow the two hemispheres to carry out different computations at the same time. The left side of the brain, for instance, might have evolved to carry out routine operations — things like foraging for food — while the right side was kept free to detect and react rapidly to unexpected challenges in the environment — an approaching predator, for instance.

This can be seen in various fish, toads and birds, which are all more likely to attack prey seen in the right eye. So it is possible though hard to prove that as our hominin ancestors began walking on two legs rather than four, freeing up their hands to perform new tasks like making tools, they were predisposed to begin using those hands differently.

Or, as cognitive scientist Stephanie Braccini and colleagues put it in a Journal of Human Evolution study, " a strengthening of individual asymmetry [may have] started as soon as early hominins assumed a habitual upright posture during tool use or foraging ". It was only when forced to assume an upright stance that a lateral preference emerged — although individual chimps in the study were equally likely to be left-handed as right-handed.

Evidently, then, something else was needed to push early humans from a lateral preference in general to the extremely high levels of right-handedness we see today. We know roughly when that change occurred from experiments in which researchers made their own versions of ancient stone tools using either their left or right hands to chip — or knap — the tool into shape, before comparing them with the tools made by early hominins.

This may cause coordination difficulties. However, some sports such as gymnastics benefit from the distribution of brain dominance. Research into cross laterality is ongoing. Since 90 per cent of the population is right-handed, left-handed people do experience some practical problems, including:. This page has been produced in consultation with and approved by:.

The abdominal muscles support the trunk, allow movement and hold organs in place by regulating internal abdominal pressure. People who run regularly seem to be susceptible to Achilles tendonitis. Acromegaly is caused by an excess of growth hormone in adults, which causes the overgrowth of bones in the face, hands, feet and internal organs. Exercise can prevent age-related changes to muscles, bones and joints and can reverse these changes too.

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Skip to main content. Babies and toddlers Contact a health care provider if you have questions about your health. Is handedness determined by genetics? From Genetics Home Reference. Topics in the Genetics and Human Traits chapter Are fingerprints determined by genetics? Is eye color determined by genetics? Is intelligence determined by genetics? Is the probability of having twins determined by genetics?

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Is longevity determined by genetics? Scientists can even look at the direction of diagonal scratches on fossilized teeth to see which hand people were using to tear off meat or animal hides in their mouths. Righties have dominated for as far back in the archaeological record as researchers can see, about , years , Uomini said. Neanderthals, our now-extinct human cousins, were also strongly right-handed. That makes humans pretty strange among animals.

Several nonhuman species, such as the other great apes, are individually handed, but the split between righties and lefties is typically closer to What caused our extreme bias toward right-handedness to evolve and persist? From an evolutionary perspective, if right-handedness evolved because it had some kind of advantage, then you might expect left-handers to disappear completely, Uomini told Live Science.