Why are some People Left-Handed ?
- May 3, 2017
- 3 min read
Of the 7 most recent US presidents, 4 have been left-handed.
Why are some People Left-Handed ? Well, the answer is not certain but there is quite a long history to it. For the left-handed people of the world, life isn’t easy. If you know a Older Left-Handed person, chances are that they had to learn to write or eat with their right hand. And in many parts of the world, its still common practice to force children to use their " proper " hand. Even the word " Right " also means correct or good,not just in English but in many languages too...
But if being left-handed is so wrong, Then why does it happen in the first place? Today, about 1/10 of the world's population are left-handed. Archaeological evidence shows that it's been that way for as long as 5,00,000 years. Despite what many may thing, handedness is not a choice. It can be predicted even before birth -- based on the fetus' position in the womb.
So, if handedness is inborn, does that mean it's genetic? Well, Yes and No. There is a reason that evolution has produced this small portion of lefties and maintained it over the course of millennia. And while there have been several theories attempting to explain why handedness exists in the first place, or why most people are right-handed.
A recent mathematical model suggests the actual ratio reflects a balance between Competitive and Cooperative pressures on human evolution.
The benefits of being left-handed are clearest in activities involving an opponent, like combat or competitive sports. For Example, about 50% of top hitters in cricket have been left-handed. Why? Think of it as a surprise advantage. Because lefties are a minority to began with, both right-handed and left-handed competitors will spend most of their time encountering and practicing against righties. So when the two face each other, the left-hander will be better prepared against this right handed opponent, while the righty will be thrown off.
This fighting hypothesis where an imbalance in population results in an advantage for left-handed fighters or athletes, is an example of negative frequency-dependent selection But according to the principles of evolution,groups that have a relative advantage tend to grow until that advantage disappears. If people were only fighting and competing throughout human evolution, natural selection would lead to more lefties being the ones that made it until there were so many of them, that it was no longer a rare asset.
So in a purely competitive world, 50% of the population would be left-handed. But human evolution has been shaped by cooperation, as well as competition. And cooperative pressure pushes handedness distribution in the opposite direction. In golf, where performance doesn't depend on the opponent, only 4% of top players are left-handed, an example of the wider phenomenon of tool sharing.
Just as young potential golfers can more easily find a set of right-handed clubs, many of the important instruments that have shaped society were designed for the right-handed majority.Because lefties are worse at using these tools, and suffer from higher accident rates, they would be less successful in a purely cooperative world, eventually disappearing from the population.
So by correctly predicting the distribution of left-handed people in the general population,as well as matching data from various sports, the model indicates that the persistence of lefties as a small but stable minority reflects an equilibrium that comes from competitive and cooperative effects playing out simultaneously over time.And the most intriguing thing is what the numbers can tell us about various populations.
From the skewed distribution of pawedness in cooperative animals, to the slightly larger percentage of lefties in competitive hunter-gatherer societies, we may even find that the answers to some puzzles of early human evolution are already in our hands.
Source : Ted Ed
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