Tongue Rolling and 5 Other Oversimplified Genetic Traits


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.”

15 Scientific Reasons Spring Is the Most Delightful Season

Summer, winter, and fall may have their fans, but spring is clearly the most lovable of the four seasons. Not convinced? Here are 15 scientific reasons why spring is great:


road and field on a sunny day

Spring marks the end of blistering winter and the transitional period to scorching summer. In many places, the season brings mild temperatures in the 60s and 70s. People tend to be most comfortable at temperatures of about 72°F, research shows, so the arrival of spring means you can finally ditch the heavy winter layers and still be comfortable.


sunny sky

Following the spring equinox, days begin lasting longer and nights get shorter. Daylight Saving Time, which moves the clock forward starting in March, gives you even more light hours to get things done. Those extra hours of sun can be a major mood-booster, according to some research. A 2016 study of students in counseling at Brigham Young University found that the longer the sun was up during the day, the less mental distress people experienced.


blue bird on branch

Many animals migrate south during the winter, then head north as temperatures rise. For relatively northern regions, there is no better indicator of spring than birds chirping outside your window. Their northward migration can start as early as mid-February and last into June, meaning that throughout the spring, you can expect to see a major avian influx. In addition to the satisfaction of marking species off your bird-watching checklist, seeing more of our feathered friends can make you happy. In 2017, a UK study found that the more birds people could see in their neighborhoods, the better their mental health.


Baby squirrels

Many animals reproduce in the spring, when temperatures are warmer and food is plentiful. Baby bunnies, ducklings, chipmunks, and other adorable animals abound come spring. Studies have found that seeing cute animals can have positive effects on humans. For instance, one small study in 2012 found that when college students looked at cute images of baby animals, they were better at focusing on a task in the lab. Being able to watch fluffy baby squirrels frolic outside your office window might make spring your most productive season of the year.


flowers hanging outside of a house

In 2015, a pair of public policy researchers discovered a hidden upside to "springing forward" for Daylight Saving Time. It reduced crime. When the sun set later in the evening, the study published in the Review of Economics and Statistics found, robbery rates fell. After Daylight Saving Time started in the spring, there was a 27 percent drop in robberies during that extra hour of evening sunlight, and a 7 percent drop over the course of the whole day.


child with rainbow umbrella jumping in puddle

Warmer temperatures mean you can spend more time outside without freezing your feet off, which is great for mental health. Across the seasons, research has found that taking walks in nature slows your heart rate and makes you more relaxed, but some research indicates that there is something special about spring's effect on your brain. A 2005 study from the University of Michigan linked spending 30 minutes or more outside in warm, sunny spring weather to higher mood and better memory. But the effect reverses when spring ends, since being outside in the warmest days of summer is usually pretty uncomfortable.


woman writing in a park

That same University of Michigan study found that spending time outside in the sunny spring weather isn't just a mood booster, it actually can change the way people think. The researchers found that being outdoors broadened participants' minds, leaving them more open to new information and creative thoughts.


leaves budding in spring

Spring brings green growth back to plants and trees. Depending on where you live, trees may begin sporting new leaves as early as mid-March. That successful spring leaf growth ensures a cool canopy to relax under during the hot summer—a hugely important factor in keeping cities comfortable. According to researchers, vegetation plays a big role in mitigating the urban heat island effect. When trees release water back into the air through evapotranspiration, it can cool down the areas around them by up to 9°F, according to the EPA.


tulip bulbs

It's amazing what a little sun can do for plants and grass. Through photosynthesis, plants convert sunlight, carbon dioxide, and water into food, releasing oxygen in the process. That means as plants start to grow in the spring, they pull carbon out of the atmosphere, providing an important environmental service. Plants take in roughly 25 percent of the carbon emissions humans produce, absorbing more than 100 gigatons of carbon through photosynthesis each growing season. Because of this, the amount of carbon dioxide in the atmosphere drops each spring and summer. (Unfortunately, it rises in the winter, when most plants aren't growing.)


wooden box full of fresh produce

Many vegetables and some fruits are harvested in the spring. 'Tis the season to get your local asparagus, greens, peas, rhubarb, and other fresh produce. Getting more fruits and vegetables into your diet isn't just good for the body; it's good for the soul. A 2016 study of more than 12,000 Australians found that when people increased the amount of fruits and vegetables in their diet, they felt happier and had higher rates of life satisfaction. If they increased their intake by eight portions a day (a tall order, we know) the psychological gains were equivalent to the change in well-being people experience when they go from being unemployed to having a job, the researchers found.


Flowers in a vase

After months spent conserving energy, flowers bloom in the spring, once they sense that the days have grown longer and the weather has turned warmer. That's good for humans, because several studies have shown that looking at flowers can make you happy. A 2008 study of hospital patients found that having flowers in the room made people feel more positive and reduced their pain and anxiety [PDF]. Another study from Rutgers University found that when participants were presented with a bouquet of flowers, it resulted in what scientists call a "true smile" a full 100 percent of the time. Seeing flowers had both "immediate and long-term effects" that resulted in elevated moods for days afterward, according to the researchers [PDF].


woman tying shoes in flower field

While it's important to keep moving no matter what the weather, research shows that working out can be more beneficial if you do it outside. A 2011 study found that, compared with an indoor workout, exercising outdoors in nature increased energy levels, made people feel revitalized, and decreased tension, among other positive effects. People who worked out in the fresh air also tended to say they enjoyed the experience more and would be likely to repeat it, suggesting that using nature as your gym might help you stick with your exercise regimen. While those benefits probably extend to winter, too, it's a whole lot easier to stomach the idea of a run once the weather warms up.


dew on grass and a daisy

Flu season in the U.S. typically lasts through the fall and winter, usually peaking between December and February and tapering off during the spring. The seasonal change is in part because of dry air. Cold temperatures mean a drop in humidity, and indoor heating only makes the air drier. This lack of moisture in the air can dry out your skin and the nasal cavities, leading to nose bleeds, irritated sinuses, and a greater risk of getting sick. Since the mucus in your nose is designed to trap viruses, when it dries up, you're more likely to catch something nasty, like the flu. As the weather warms up and becomes more humid throughout the spring, that mucus comes back. As the season wears on, not only can you lay off the body lotion, but you can probably put away the tissues—if you don't have spring allergies, that is.


windows open on a red house

Temperate weather makes it easier to get the fresh air you need. Opening your windows and allowing the breeze in serves as an important way to ventilate indoor spaces, according to the EPA. A lack of ventilation can lead to an unhealthy concentration of indoor pollutants from sources like cleaning product fumes, certain furniture and building materials, and stoves (especially gas ones), posing a threat to your health and comfort. Winter brings the highest rates of indoor pollutants like nitrogen oxide, a 2016 study of unventilated stove use in homes found. Spring brings the perfect opportunity to throw open those windows and doors and get the air moving again.


woman enjoying sitting in the sun

Sunlight triggers your body to produce vitamin D, which keeps your bones strong. At northern latitudes, it's extremely difficult to get enough sun exposure naturally to maintain healthy vitamin D levels during the winter—even if you did want to expose your skin to the elements—but that starts to change during the spring. One Spanish study found that in Valencia (which shares a latitude with Philadelphia, Denver, Baltimore, Kansas City, and several other major U.S. cities), people only need 10 minutes outside with a quarter of their bodies exposed to the spring sunshine to get an adequate daily dose of vitamin D.

A version of this story originally ran in 2014.

High-Speed Railway Project Uncovers a Prehistoric Coastline Near London

UK engineers have discovered evidence of a prehistoric coastline just outside London while preparing for a new high-speed railway, The Guardian reports.

The UK government has been analyzing the ground at the proposed locations for the railway, HS2, since 2015. Engineers are using radar, taking core samples, and digging pits before Phase 1 of construction. While evaluating the site of a future tunnel, geologists found signs that the site in the West London area of Ruislip was once a coastal marsh. Almost 110 feet under the ground, they discovered black clay they believe was formed from wooded swampland on the coast of a subtropical sea.

soil specimens from 56 million years ago

The unusually well-preserved layer of clay, which features traces of vegetation, dates back to around 56 million years ago, when Great Britain was partially covered by a warm sea. Less than 200 feet away from where the black clay was discovered, the layer of earth at the same depth is made of sand and gravel, likely deposited by the sea.

"Although ground investigations regularly take place across the country, it's really exciting and very unusual to come across a material that no one has ever seen before," geological expert Jacqueline Skipper said in a press release from HS2. "The 'Ruislip Bed' discovery is particularly fascinating, as it is a window into our geological history." While researchers knew that much of England was underwater during this period, this evidence helps them pinpoint exactly where that sea began.

[h/t The Guardian]


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