Why do majority of humans (or possibly other living beings too) have a dominant side of their body?
In: Biology
We have a dominance of the left side or right side of the body, which side that is, depends on whether your brain’s left hemisphere or right hemisphere is dominant. If you’re left-handed your right hemisphere is dominant, if you’re right-handed, the left hemisphere is dominant. As to why one hemisphere is dominant, the current theory is division of labour. There are limited connections between the hemispheres of your brain, dividing a task between both sides would require much more work from the brain as it needs to utilize both hemispheres and the bottleneck that are the limited connections between them. Therefore the brain prioritises all the important functions such as motor skills and cognitive functions to one hemisphere. That side then becomes the dominant hemisphere and dominant side of your body.
Oversimplified, think that you have 2 toolboxes, one has the hammer and nails and the other has screwdrivers and screws. Well you happen to need screwdrivers and hammers often, so you always have to get both toolboxes. Then, however, you get the idea of transferring the most often used stuff to one toolbox. That is how dominant sides came to work.
At a young age it just feels more natural to do tasks with one hand/foot than the other. Over time of using your dominant side, muscle memory builds and this side becomes more skilled and trained as you log in more and more reps with it
Im not sure what the most recent research suggests but this looks to be fairly untrue.
I’ll let Hank explain
I’ve read that brain matter is expensive as far as calories and body resources. Therefore, every part of the brain has a reasonably important job, if we were primitive hunter-gatherers who had very little food in the winter.
Whether you are right-handed of a lefty, one of the main differences between hominids and apes is that apes are ideally suited for climbing in trees to catch food, and to escape predators.
Hominids can throw projectiles like a primitive spear or even just a rock. That can be a crucial skill that allows your “tribe” to prosper. If you are ambi-dextrous (equally skilled at using both hands/arms at difficult tasks), then that uses up a lot of brain. By being “handed”, you can be a skilled spear thrower, which helps you catch more food, and prevents you from becoming someone else’s food.
Just a theory, but it makes sense to me…
Don’t know why (but if I had to guess I’d say it probably just comes down to practice from a young age but don’t quote me on that), but we do see left/right “handedness” in other animals, from cats, to whales, to kangaroos, to rats. In fact left “handed” guide dogs are much more likely to fail training, which is probably more a criticism of the training methods not being universal.
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