Tongue Rolling and 5 Other Oversimplified Genetic Traits
By jessica hullinger | mar 18, 2015.
Can you roll your tongue? If so, you’re part of the majority. Between 65 and 81 percent of people on Earth have this strange and seemingly arbitrary talent. But why can some do it while others can’t? The most common answer, the one often taught in elementary schools and museums, is that it’s all about genetics. The story goes that, if you inherited a dominant variation of the “tongue rolling gene” from one of your parents, you too will inherit this party trick. In other words, if you can’t do it, blame mom and dad.
But John H. McDonald , a professor in the University of Delaware department of biological sciences, calls B.S. “If that were true, you could never have two non-rolling parents that having a tongue-rolling kid,” he says. “Yet people have looked at families and find you do see that.”
According to McDonald, teachers and textbooks have been over-simplifying this story for decades. The genetic theory of tongue-rolling can be traced back to a 1940 study by a scientist called Alfred Sturtevant that was quickly debunked. “By the early 1950s, people knew pairs of twins where one could roll and one couldn’t,” McDonald says. “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.”
The truth is a bit more complicated. McDonald says that in some cases, the environment plays a part. It's “nature vs. nurture” in action—many people can break genetic bounds and teach themselves the sacred art of tongue rolling. In other cases, it could just come down to a developmental quirk, like your position in the womb, he says.
So why has this rumor persisted? “It would be really nice to have a biology experiment you can do just by looking around the room,” McDonald says. But spreading these kinds of inaccuracies can be really dangerous. “It is an embarrassment to the field of biology education that textbooks and lab manuals continue to perpetuate these myths,” he writes . “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.”
Tongue-rolling isn’t the only genetic trait we’ve oversimplified. Here, a few other examples McDonald says he's debunked.
1. Hand-clasping
The myth: Whether you put your left thumb on top or your right thumb on top when you clasp your hands is determined by a single gene.
The reality: Even identical twins have different preferences for how to clasp their hands, indicating that there isn’t a “left thumb on top” gene.
2. Eye color
The myth: Blue eyes are determined by a single recessive gene. A brown-eyed kid cannot have two blue-eyed parents.
The reality: “Eye color is determined by variation at several different genes and the interactions between them,” McDonald says. “This makes it possible for two blue-eyed parents to have brown-eyed children.”
3. Hair color
The myth: Red hair is determined by a single gene that yields to other colors. Two red-headed parents cannot have a non-red-haired kid.
The reality: There are many variations in the gene that controls red hair pigment, and this gene can be influenced strongly by genes that control brown hair. Indeed, two parents with red hair can have kids with brown or blonde hair.
4. Attached earlobes
The myth: Everyone has one of two kinds of earlobes: attached (connecting directly to the side of the head) or unattached (a slight separation causing the lobe to dangle). A single gene decides the fate of your earlobes.
The reality: Our earlobes don’t fall into two categories . Instead, there’s a sliding scale between attached and free. Two of the early studies on attached versus unattached earlobes disagreed on which was the dominant trait, showing that the genetics involved aren't as simple as many have been taught.
5. Hitchhiker’s thumb
The myth: Your thumb is either straight or bent at the knuckle. The latter is called hitchhiker’s thumb, and whether or not you have it comes down to a variation in a single gene. “If the myth were true,” McDonald writes, “two parents with hitchhiker's thumb could not have a child with a straight thumb.”
The reality: There can be no clear-cut definition of a hitchhiker’s thumb because thumb flexibility ranges dramatically from person to person. “It’s completely arbitrary where you draw the line between straight and angled,” McDonald says. Parents with bent thumbs can produce kids with straight thumbs.
The moral of the story? Genetics are complicated. If you really want to see basic genetic traits in action, McDonald suggests looking at cats instead of humans. “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 says. “Everyone either has a cat or knows someone else’s cat.”
Genetics of tongue twisting: Why some people do it while others can’t
The term tongue twisting comprises rolling, folding, rotating, adjusting, and turning of the tongue…All aspects of a person are in some way influenced by genetics. Likewise, the tongue structure or its movement is controlled by one’s respective gene pattern…Tongue twisting is not a genetic disease or disorder, but a unique activity by a person using his tongue.
The early history of tongue genetics stated that the ability of tongue twisting is due to the influence of traits…The tongue rolling ability occurs due to the influence of a dominant allele of the gene. A person who has either one or two copies of the dominant allele will be able to twist their tongue. In the case that a person is born with two recessive alleles, they cannot twist their tongue. In most cases, parents with a twisting-tongue ability can give birth to non-tongue twisters, and vice versa.
After a long-drawn out struggle, geneticists and researchers have finally proved that tongue twisting does not occur by genetic transformation. Genetic inheritance has only a minimal role to play in tongue twisting skills.
The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion, and analysis. Read full, original post: Genetics of Tongue Twisting
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On-line version issn 0717-9502, int. j. morphol. vol.26 no.3 temuco sept. 2008, http://dx.doi.org/10.4067/s0717-95022008000300004 .
If You Can't Do This, Genetics Aren't to Blame
Have trouble rolling your tongue? It isn't your parent's fault.
For years, it had been thought that heredity was to blame if you couldn't fold one of your body's strongest muscles into a tube shape , but scientists have recently debunked that theory, saying no one really knows why we have or lack this ability.
"If tongue rolling were purely genetic, identical twins would be identical. So we absolutely, positively know that tongue rolling is not a purely genetic trait," John McDonald, associate professor of biological sciences at the University of Delaware, told The Huffington Post . "In reality, just about everything in human anatomy and behavior is determined by a complicated mix of multiple genes and the environment."
He also noted that while genes may have some influence, there is not a single tongue-roll ability gene . But there is small-study evidence that people can actually learn to do it.
So there you have it. Maybe it's time to stop pointing fingers and start practicing.
[via The Huffington Post
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Tongue-rolling phenotypes and geographical variation in the United Kingdom
Affiliation.
- 1 Department of Medical Biochemistry and Genetics, Tehran University of Medical Sciences, Iran.
- PMID: 2629620
The distribution of tongue-rolling phenotypes in a sample (n = 477) of undergraduate students of the University College of Swansea (U.K.) was studied. The birthplaces of these students were also recorded. England was divided into six areas, and Wales was left as an area on its own. The data suggest that those students who come from north-east are more non-rollers, which may be due to mixture with Scandinavians.
- Gene Frequency
- Genetics, Population*
- Tongue / anatomy & histology*
- Tongue Habits*
IMAGES
VIDEO
COMMENTS
For example, for the boys who can roll their tongue, 8/15 = .53 = 53%. Table 4.4.6 Row of the Boys' Data from the Two-Way Table Yes - Can Roll Tongue No - Can't Roll Tongue Total Boy 8 7 15 10. Using Table 4.4.7, ask your students to fi nd the percentage of girls who can and cannot roll their tongue.
A rolled tongue. Tongue rolling is the ability to roll the lateral edges of the tongue upwards into a tube. The tongue's intrinsic muscles allow some people to form their tongues into specific shapes. Rolling the tongue into a tube shape is often described as a dominant trait with simple Mendelian inheritance, and it is commonly referenced in introductory and genetic biology courses, although ...
Tongue-rolling isn't the only genetic trait we've oversimplified. Here, a few other examples McDonald says he's debunked. 1. Hand-clasping. The myth: Whether you put your left thumb on top or ...
characters such as tongue rolling or earlobe attachment, characters that are inherited with greater variation than can be described by Mendelian inheritance. [21] Achondroplasia, the most common form of human dwarfism is known to be inherited in a Mendelian autosomal dominant manner. Remember autosomes are a chromosome not directly
Six specific tongue movements have been described thus far, being: rolling, folding, twisting (2 sides), cloverleaf, and a pointing tongue [ 7 ]. The percentage of people who can roll the tongue varies from 60 to 80% [ 8 - 15] and the average percentage of tongue folding lies between 1.5 and 3% [ 10, 16, 17 ].
determine if this X-linked recessive hypothesis holds true for our class population. 1. Place one of your hands on the line. The fourth (ring) finger should just touch the line. 2. Make a pencil mark at the uppermost tip of the second (index) finger. A short index finger would show the mark below the line. A mark on or above the line would show
Many investigators hypothesize a common aetiology for left-handedness and tongue rolling ability, but the particular mechanism involved - genetic, environmental, or hormonal continues to be a topic of discussion.20, 21, 22 It can be hypothesized that person with the natural ability to roll the tongue may perform tongue-training better at ...
Hypothesis: Tongue rolling ability is affected by genes that we inherit from our parents ¥If I can/cannot roll my tongue ¥Then one or both of my parents can/cannot roll their tongue. TodayÕs Black Box stimulus physiology gene product behavior gene. Part 1 - Termite Behavior ¥Divide into groups
Abstract. Tongue rolling is widely used in elementary biology education to illustrate simple genetics despite doubts about its validity. A survey was carried out to determine the extent to which apparent non-rollers can learn to roll their tongues and to discover what advantage the ability to roll the tongue or not might confer and thus offer an explanation for this apparent polymorphism.
The results revealed that the frequencies of tongue rolling, tongue folding, tongue twisting, pointed tongue and clover-leaf tongue were 63.6, ... [Show full abstract] 14.0, 12.6, 54.8 and 0 % ...
The early history of tongue genetics stated that the ability of tongue twisting is due to the influence of traits…The tongue rolling ability occurs due to the influence of a dominant allele of ...
investigated variations in cerumen type, tongue rolling and tongue folding abilities of pre-service teachers. One hundred and thirty-two students took part in the study. The tongue and ear wax ...
For many years, textbooks have suggested that the ability to roll the tongue easily into a tube was a simple dominant Mendelian trait. However, studies of identical twins have provided convincing evidence against this type of inheritance pattern. Identical twins are no more likely than other siblings to display the same tongue-rolling behav-ior.
Six specific tongue movements have been described thus far, being: rolling, folding, twisting (2 sides), cloverleaf, and a pointing tongue [7]. The percentage of people who can roll the tongue varies from 60 to 80% [8-15] and the average percentage of tongue folding lies between 1.5 and 3% [10, 16, 17].
Garakani and colleagues reported a greater incidence of tongue rolling ability amongst undergraduate students majoring in the physical or life sciences than amongst those majoring in the arts. 26 If differences in tongue-training performance and learning had been demonstrated in this study, it would have led us to form a hypothesis that the ...
Gandhi, P. Tongue rolling and tongue folding among five endogenous groups of Jains. Paper presented at 3rd Annual General Conference of Ethnographic and Culture Society, Luchnow, 1976. Hernandez, M. La movilidad del pabellon auditivo. Trab. Anthropol., XVIII:199-203, 1980.
RESULTS. Tables I and II, show the frequency distribution of tongue rollers and tongue folders amongst Urhobo people of Nigeria. The frequency of folders, Fig. 1 (120) and rollers, Fig. 2 (87) were more common than non-folders (23) and non-rollers (56). The incidence of tongue rolling was higher in females than in their male counterparts.
Like colorblindness or the color of your skin, there are endless traits we can turn to mom and dad and label as "inherited." But despite the common lore, rolling your tongue isn't one of them. For ...
Tongue / anatomy & histology*. Tongue Habits*. Wales. The distribution of tongue-rolling phenotypes in a sample (n = 477) of undergraduate students of the University College of Swansea (U.K.) was studied. The birthplaces of these students were also recorded. England was divided into six areas, and Wales was left as an area on its own.
Tongue rolling is the tendency to turn up the lateral edges of the tongue and it is due to the single dominant gene (Liu and Hsu, 1949). However, according to Tahir et al. (2014), tongue rolling ...
This study was conducted amongst. years and over to determine their ability to roll or fold the tongues. The frequency of folders (120) and rollers (87) were more common. than non-folders (23) and ...
The present pilot study was conducted to screen a random population of 194 female Indian graduate students for 13 different morphogenetic traits i.e., tongue rolling, tongue folding, polydactyly ...