Why was tongue rolling taught as a dominant gene?

A 1940 paper by geneticist Alfred Sturtevant suggested tongue rolling followed a simple dominant-recessive pattern, and it became a favourite classroom example because it's quick to demonstrate and easy to score. Sturtevant himself later retracted the idea after a 1952 twin study contradicted it. Unfortunately, the catchy version stuck in textbooks long after the science moved on, which is why so many people still believe it's a one-gene trait.

What do twin studies actually show about tongue rolling?

The landmark 1952 study by Philip Matlock found that some identical twins differed in their ability to roll the tongue. If a single gene fully controlled the trait, identical twins — sharing 100% of their DNA — should always match. They don't. That mismatch is strong evidence that tongue rolling is influenced by a mix of factors, possibly including practice and development, not one inherited gene switching the ability on or off.

Are other 'classic' genetic traits also myths?

Yes. Tongue rolling sits alongside earlobe attachment, widow's peak, dimples, and hitchhiker's thumb as traits long taught as simple single-gene Mendelian examples. None of them follows clean dominant-recessive ratios. Earlobe shape is linked to dozens of genes, while dimples and widow's peak have barely been studied at all. They're fun to look at, but they're not reliable evidence of how genes are passed down.

Is tongue rolling genetic?

Curling the sides of your tongue into a U-shape is the most famous “genetics” party trick — and one of the most misleading. For generations it was taught as a clean dominant-recessive trait controlled by a single gene. It isn’t. Some identical twins, who share every strand of DNA, disagree on whether they can roll, and some non-rollers learn to do it later on. This page walks through the classic classroom claim, where it came from, and why scientists now call it a textbook myth rather than real, predictable inheritance.

The short answer

Tongue rolling is not a simple inherited trait. Genes seem to play a real part, but it isn’t controlled by one dominant gene, and you can’t reliably predict it from parents to children.

The classic classroom claim

Here’s the version most of us learned in school. Tongue rolling was said to be controlled by a single gene with two versions (“alleles”): a dominant “roller” allele and a recessive “non-roller” allele. If you inherited at least one roller allele you could roll; if you inherited two non-roller alleles you couldn’t. It was the perfect teaching tool — fast to test in a classroom, easy to tally, and it seemed to produce the neat ratios a Punnett square predicts.

The trouble is that none of those tidy ratios hold up when you look closely. Real families don’t split cleanly into rollers and non-rollers the way a single-gene trait should, and the ability turns out to be far more slippery than a simple yes/no switch.

Where the myth came from

The idea traces back to a 1940 paper by the well-known geneticist Alfred Sturtevant, who proposed that tongue rolling followed a simple dominant-recessive pattern. It was an attractive, teachable claim and it spread quickly into biology textbooks.

The twist most textbooks never mention: Sturtevant himself walked it back. After a 1952 twin study found identical twins who differed in their tongue-rolling ability, he acknowledged the simple model didn’t fit and reportedly said he was embarrassed it kept being taught as fact. The science was corrected within roughly a decade — but the catchy classroom version had already taken on a life of its own.

What twin studies actually show

Identical twins are the cleanest natural experiment in genetics. They share 100% of their DNA, so any trait controlled entirely by a single gene should always match between them. If one identical twin could roll their tongue, the other should too — every single time.

That’s not what researchers found. In the 1952 study by Philip Matlock, a notable share of identical twin pairs disagreed: one twin could roll, the other couldn’t. A single “roller gene” simply cannot explain twins with identical DNA landing on opposite sides of the trait. Something else must play a part too — maybe more complex genetics, maybe development or learning. Scientists don’t yet know which.

One gene controlling it → identical twins should always match.
Some real identical twins differ.
So tongue rolling is not a one-gene trait.

Some people learn it later

Here’s the final nail. A true inherited on/off trait shouldn’t change with effort — you either have the gene or you don’t. Yet studies have found that some people, especially children, who start out as non-rollers learn to roll their tongue later. In one large study of Japanese schoolchildren, the share who could roll rose from 54% at ages 6–7 to 76% at age 12.

If people can gain the ability after first being unable to do it, it isn’t a fixed, single-gene readout of your DNA. That doesn’t mean genes play no role — family studies suggest they matter a lot — but it does mean the neat “you inherited it or you didn’t” story is wrong.

The honest verdict

So, is tongue rolling genetic? The most accurate answer is “not in any simple, predictable way.” Genes seem to matter, but tongue rolling is a complex trait. It’s shaped by genes plus other things scientists don’t fully understand — not a clean Mendelian switch you can chart on a Punnett square. It’s a fun thing to test at the dinner table. It’s a terrible way to teach how inheritance really works.

Tongue rolling is in good company. Earlobe attachment, widow’s peak, dimples, and hitchhiker’s thumb were all once taught as simple dominant-recessive traits. None of them fits that tidy pattern. Earlobe shape is linked to dozens of genes, while dimples and widow’s peak have barely been studied at all.

Frequently asked questions

Is tongue rolling genetic?: Not in the simple way textbooks once claimed. For decades, rolling the sides of your tongue into a U-shape was taught as a clean dominant-recessive trait controlled by one gene. Modern evidence has overturned that. Twin studies show that some pairs of identical twins — who share all their DNA — disagree, with one able to roll and the other not. And some people, especially children, can't roll their tongue at first but learn to later. Genes likely have some influence, but tongue rolling is not a tidy single-gene inherited trait.
Why was tongue rolling taught as a dominant gene?: A 1940 paper by geneticist Alfred Sturtevant suggested tongue rolling followed a simple dominant-recessive pattern, and it became a favourite classroom example because it's quick to demonstrate and easy to score. Sturtevant himself later retracted the idea after a 1952 twin study contradicted it. Unfortunately, the catchy version stuck in textbooks long after the science moved on, which is why so many people still believe it's a one-gene trait.
What do twin studies actually show about tongue rolling?: The landmark 1952 study by Philip Matlock found that some identical twins differed in their ability to roll the tongue. If a single gene fully controlled the trait, identical twins — sharing 100% of their DNA — should always match. They don't. That mismatch is strong evidence that tongue rolling is influenced by a mix of factors, possibly including practice and development, not one inherited gene switching the ability on or off.
Can you learn to roll your tongue?: Many children can. Some people can't roll their tongue when first asked but learn to later. In one large study of Japanese schoolchildren, the share who could roll rose from 54% at ages 6–7 to 76% at age 12. The fact that people can gain the ability after first being unable to is another reason it doesn't fit the simple genetic story.
Are other 'classic' genetic traits also myths?: Yes. Tongue rolling sits alongside earlobe attachment, widow's peak, dimples, and hitchhiker's thumb as traits long taught as simple single-gene Mendelian examples. None of them follows clean dominant-recessive ratios. Earlobe shape is linked to dozens of genes, while dimples and widow's peak have barely been studied at all. They're fun to look at, but they're not reliable evidence of how genes are passed down.

Sources

Checked against the following public guidance on October 2, 2026. Advice can differ between countries; your doctor, nurse or midwife can apply it to you.

— The Period Tools Team