Why Do Left-Handers Exist?

March 27, 2016 / Humans / 0 Comments /
Why do left handed people exist?

I’ve got nothing against left handed people – I am one. But the existence of left handed people defies the evolutionary logic that if a trait is favourable, it will become persistent throughout the entire population. Unfavourable traits get lost pretty quickly, and even neutral traits can fade out in the gene pool. A great example of this is a giraffe. The long neck trait is very desirable because it allows you to reach food that is harder to get. This meant that the longer necked giraffes are more likely to survive and bread/ pass on the long neck genes, and before you know it, all giraffes will have long necks. There is no small population of giraffes with short necks.

Being right handed is clearly be the most favourable trait, with about 90% of the population being right handed. You would expect the left handed genes to fade away many thousands of years ago, but it hasn’t. In fact, left handers have consistently made up around 10% of the population for as long as we know, right back to the earliest humans, so there must be a reason for left handed people to exist.

 

What makes a person left handed?

There are 2 reasons why people can become left handed. The first is genetic. You can see from the table below that left handed parents are more likely to have left handed off spring, and right handed parents are more likely to have right handed off spring.  The genetics are not particularly straightforward because there are thought to be a number of genes involved in making someone left handed, and no one really knows which.

Graph showing that being left handed is linked to genes.

The second reason is that trauma or stress at birth such as oxygen deprivation to the brain can cause damage to the left hemisphere of the brain and cause dominance to shift. Research has shown that birth complications like this result in an increased number of left handers.

There is no way of determining the cause for an individuals left handedness, but the fact that there is a genetic link is very interesting, and suggests that there is so advantage to being left handed.

 

Left VS Right

lets look at the key differences between left handed people and right handed people:

They think differentlyEvidence published in the American Journal of Psychology showed that left handed people were much better at tasks which required divergent thinking, which requires creative thinking and exploring different solutions. This shows that left handed people are often better at problem solving than right handed people, and this is supported by the fact that left handed people tend to pursue careers in science, art and technology. All of which require a large amount of creativity and problem solving. The study showed that there was no difference in convergent thinking (required no creativity), suggesting that left handers may be better thinkers. However, other research has shown that left-handers are not so good with language and communication skills.

 

Better at sports – It is a well acknowledged fact that the left handed people are over represented in professional sports, particularly ones where you are in direct competition with another player like boxing or tennis. In 2015 left handed tennis players made up 40% of the top players, which is 4 times more than the proportion of lefties in the general population. The advantage is so well known that some top tennis were taught from a young age to play left handed even though it wasn’t their dominant hand, and this is something Rafael Nadal is famous for.

This is thought to be because left handed people are so uncommon, most players will practice against a right handed player. Right handed players practice against right handed players, and left handed players practice against right handed player. Everyone knows how to read and play against a right handed opponent, but everyone has very little experience playing against a left handed opponent. This is supported by research published in the British Journal of Psychology which showed that novices and experts alike find right handed shots much easier to predict than left handed ones.

 

Increased risk of mental disorders – It has been observed that the risk of developing mental disorders such as schizophrenia and autism increases with left handedness. This could very well be due to the mental trauma at birth that causes some people to become left handed.

Other differences of note include left handed people are often shorter in height, live slightly shorter lives but earn about 4% more than their right handed counterparts.

 

Why Do Left-Handers Exist?

We have ascertained that there are some significant differences between left handed people and right handed people, and that being left handed is at least in part an inherited trait. Despite being apparently the lesser of the 2 traits, it has remained throughout the gene pool – why?

Despite the potential health risks (shorter lives and association with metal disorders) being left handed is an advantage in a population which is right handed dominant, and this is why it has not become an extinct trait.

Historically left handed people would have had the upper hand in a fight, which would increase their chance of survival, and are able to ‘think outside the box’, which would allow them to tackle problems that their tribe would otherwise struggle with.

 

Why is left handedness not dominant?

On the surface, the pros of being left handed seem to outweigh the cons (after all, not all lefties suffer from autism), but left handed people only have an advantage in a right handed population. A right handed person would enjoy all the same benefits in a left handed population, and more. They would not only be better at fighting, but bigger too, making them formidable and make the right handed trait much more favourable. Right handed people would dominate left handers to the point that the left handed trait is rare, at which point it become an advantage. This is the state we find ourselves in today- a working equilibrium of handedness.

 

Summary

Left handed people differ from right handed people in a number of ways, but the most notable is their creativity and dominance in sport.These advantages only exist because the population is predominantly right handed, and this is why the left handed trait has remained a minority trait, but not become extinct. The fewer the left handed people there are, the more advantage they have, but if the trait becomes too abundant, the have less of an advantage, and the trait declines in the population.


 

Image courtesy of beezart

This Youtube video will give an overview of the information found on the article tab. If you want to know more about the topic, or want to see where the information came from, have a read of the article after you watch the video.

Left handed people exist as a minority because their only advantage is as a minority. They are smaller, and think differently, to right handed people, which makes them difficult to fight (or play against in sports) and approach problems differently. 

If left handed people were the majority of the population, these benefits would vanish, because they would be common.