For millenia humanity has been haunted by one burning question: What’s the deal with all these lefties? Answers to this question have varied over the years. In the middle ages popular explanations for south paw-ism included demonic possession and witchcraft. In the 19th century left handedness was associated with ignorance and laziness. Even today some sources claim that left handedness is the result of brain damage sustained either in the womb or during delivery, even though that explanation has largely been written off by the majority of researchers.
However, in recent years new light has been shined on the issue and in today’s edition of Beyond Bones I’m going to tell you what scientists think makes a lefty and how you might unknowingly be one yourself.
The weird thing about left handedness is that only around 10% of the world’s population is left handed, while around 90% is right handed. The percentage of lefties to righties has remained in that ballpark for all of recorded history, and that’s strange because if left handedness is the result of genetics, the percentage of lefties to righties should have varied significantly over time and by location. Why are world-wide lefty populations neither growing nor declining significantly over time? If the trait is disadvantageous, should’t it have been selected out by now?
In recent years it has been established that left handedness has a genetic basis and is most likely an inherited trait. However, there are many lefty children with righty parents and grandparents. Also, identical twins sometimes end up with different hand preferences. So leftiness cannot be the result of genetics alone. It seems that leftiness is the result of a complex mixture of genetic disposition and cultural influence.
A study in 2012 revealed that there are disproportionate numbers of lefties among the ranks of certain professional athletes, such as baseball players. The study revealed that more than 50% of top baseball players were lefties, a much larger percentage than what is found in the general population. This got the researchers to thinking: maybe hand preference is related to competitiveness.
A paper written about the study goes on to explain that the strong right hand preference among humans is probably due to the fact that we are highly social animals who exist in highly cooperative societies. In the animal kingdom, where competition for food is the name of the game, hand preference between individuals is split more equally. For example there is a nearly 50/50 split in chimpanzee populations. But complex human society demands an extremely high amount of cooperation between individuals. Even if you consider yourself an iconoclast, you still cooperate with other humans in ways that animals don’t. For example, if you go and beat up your boss, you will not inherit his/her position, you will go to jail. This would seem totally unreasonable to a chimpanzee, but you get it, because you are human and you realize that there are rules.
So because human society requires such a high degree of cooperation, unusual traits like left handedness, which affect an individual’s ability to use certain tools and thus participate in social activities, are suppressed. Predictably, the largest concentrations of lefties are in competitive sports, where punching or throwing from an unexpected angle can give an individual the advantage. In sports being different is often a good thing, but for the vast majority of non-athletic humans, it’s not.
This all leads us to our final answer for the big historic question. The current popular theory for why the left handed population of the world has remained so low yet so stable throughout history is that there are more people genetically predisposed to being left handed than there are actual lefty’s. As exhibited by studies showing identical twins with different hand preferences, genetics isn’t the only thing that makes someone a lefty. Some people are genetically predisposed to be left handed, but they end up as righties anyway due to pressure to conform to societal norms.
So lefty genes may be more widely distributed among humans than actual left hand preference. This means it’s possible that you are a lefty and you don’t even know it. Perhaps your parents switched the crayon to your right hand when you were young, gently nudging you to conform to society’s right preference. It’s hard to say what the percentage of lefties to righties would be without this preference, but it would most likely be much more even than it is now.
Interestingly, the cultural preference for right handedness is exhibited in the word left itself. “Left” comes from the Old English word lyftwhich means weak or foolish. The Latin word for left is sinistera word that has decidedly negative connotations today thanks to biblical references to the left hand of God being the one that smashes and smites everything.
Whether or not you’re left handed, you surely enjoy learning new things about the world and the people who inhabit it. Otherwise you wouldn’t have made it to the end of this article!
If you want to explore more, check out our further readings below and also maybe consider visiting the Houston Museum of Natural Science. Our institution has tons of cool exhibits to explore, including our new special exhibit Biophilia: A Dialogue of Nature, Art and Science. The amazing pieces on display, created by artist Chris Marley, are sure to change your perspective on some of the world’s creepiest crawlies.