Tongue Rolling And 5 Other Oversimplified Genetic Traits

Think rolling your tongue is all in the genes? Think again—it’s actually a little more complicated than you might think.

June 2, 2017
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Eye color, hair color, whether someone can roll their tongue or not—they’re all traits that are often said to come down to genetics. As it turns out, though, we’ve been oversimplifying the reasons behind these traits for decades.

For anyone who can roll their tongue, it seems almost unfathomable that someone couldn’t do this simple trick. It’s actually something that up to 81 percent of all people on this planet are able to do, after all. If it’s so easy, though, why are there still so many people who aren’t able to do it?

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The answer that’s been passed around for decades is that it’s genetic, but as it turns out, that explanation isn’t exactly correct. And the truth is more complicated than you might realize.

Way More Complicated, Actually

The story usually goes something like this: People who can roll their tongues were lucky enough to have inherited an awesome (but ultimately pretty useless) tongue-rolling gene from their parents. Those who can’t, of course, are then free to bother their parents about it forever, wondering why they were destined for such a cruel fate.

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However, according to John H. McDonald, a University of Delaware professor in the department of biological sciences, there’s more to it. “If that were true, you could never have two non-rolling parents that having a tongue-rolling kid,” he explained. “Yet people have looked at families and find you do see that.”

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McDonald says this common explanation is grossly oversimplified. It originated with a study that took place in 1940, but its findings were debunked pretty quickly. “By the early 1950s, people knew pairs of twins where one could roll and one couldn’t,” he said.

“That pretty clearly tells you it’s not all genetic. Yet I ask even today my students, ‘how many of you have been told that tongue rolling is a simple genetic characteristic?’ and most raise their hands.”

So, what’s the truth?

Ever heard of nature vs. nurture? You know, how as you move through life, certain things are said to be influenced by your heredity and genes and others are influenced by your environment?

McDonald says it’s the true driving force behind why some people can roll their tongues with ease and others find it impossible. In some cases, he says something as simple as your positioning as a fetus in the womb could prevent the trait from developing, whereas others are able to overcome the odds and teach themselves how to do it.

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Why has this inaccurate reasoning persisted, then? It’s not really clear, but McDonald wants to put an end to it. “It is an embarrassment to the field of biology education that textbooks and lab manuals continue to perpetuate these myths,” he said. “If students took it seriously, a large proportion of students would look at mom and dad and conclude that the mom was sleeping around and dad wasn’t really their dad.”

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Believe it or not, it’s not just tongue rolling, either. As it turns out, this type of oversimplified explanation applies to a lot of things we’ve learned about throughout our lives.

Eye Color

Does anyone else have vivid memories of going over the Punnett square in high school while learning about genetics?

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Eye color is one of those things that’s talked about a lot when it comes to making genetic predictions, and there are certain things we all think are true when it comes to this type of science. For example, it’s long been said that it’s impossible for two parents with blue eyes to end up with a kid whose eyes are brown.

The Truth?

It’s actually very possible, because something like is eye color isn’t determined by just one single dominant or recessive gene.

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“Eye color is determined by variation at several different genes and the interactions between them,” McDonald said. “This makes it possible for two blue-eyed parents to have brown-eyed children.”

Hair Color

Hair color is usually another popular topic when it comes to discussing genes. Teenagers studying biology often try to figure out how they got the hair color they did or the color hair their kids would have if they ended up marrying their crush of the moment.

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When it comes to red hair in particular, most people are under the assumption that red hair will always be a trait that runs in the family, and any baby with at least one redheaded parent will end up with it.

The Truth?

Although there is one main gene that controls whether someone will end up with red hair, it actually has quite a few different variations. Not only that, but it can be easily influenced by other genes, particularly the ones that would give someone brown hair.

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Despite what you’ve heard, parents who both have red hair can definitely produce a child that’s either blonde or brunette.

Attached vs. Detached Earlobes

Most of us have probably heard that there are two main types of earlobes we can have—attached and detached.

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An attached earlobe will be one that’s actually connected to the side of your head, whereas one that’s detatched will be separated, causing it to dangle slightly. Like many other traits, it is said that one gene determines which you end up with.

The Truth?

There really aren’t just two categories of earlobes at all. Instead, there’s actually a wide range of how attached or detached a person’s earlobes can be.

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Not only that, but it’s still not even completely clear which trait is considered to be more dominant than the other.

Hitchhiker’s Thumb

Yes, even something as simple as your thumb shape has been a topic of debate. Anyone who has a thumb that bends backward at the knuckle is said to have a hitchhiker’s thumb and everyone else is just…normal?

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If you’ve got them, it’s frequently said that it’s because of a single variation within just one gene.

The Truth?

“If the myth were true, two parents with hitchhiker’s thumb could not have a child with a straight thumb,” McDonald said. Not only that, but there’s also no clearly defined line or angle that dictates what is a hitchhiker’s thumb and what isn’t. Everyone is different when it comes to flexibility, including their fingers, so it can be difficult to determine if someone even has the trait.

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“It’s completely arbitrary where you draw the line between straight and angled,” McDonald added.

Hand Clasping

Yes, even the way you clasp your hands is often believed to come down to biology.

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Apparently a single gene is responsible for whether you clasp your hands with your right or left thumb on top.

The Truth?

That’s really not the case. It’s been determined that even twins seem to have their own preferences when it comes to the position of their hands when they’re clasped. Not to mention that your preferences might change throughout life, and another position may feel more natural and comfortable at some point in time.

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So, what’s the bottom line here? Although there are certain ways we can predict genetic traits, genes are actually way more complicated than we’ve been led to believe in our high school biology classes. For anyone interesting in learning more, McDonald actually suggests studying cats instead of other humans.

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“Cats do have a number of traits—long versus short hair, orange versus black hair, white boots or not that—that are nice, simple, one gene-traits,” he said. Oh, and: “Everyone either has a cat or knows someone else’s cat,” he added.

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