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Tongue Rolling and 5 Other Oversimplified Genetic Traits

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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.”

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Department Of Classics, University Of Cincinnati
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Stones, Bones, and Wrecks
Ancient Poop Contains First Evidence of Parasites Described by Hippocrates
Department Of Classics, University Of Cincinnati
Department Of Classics, University Of Cincinnati

The long-held mystery of Hippocrates and the parasitic worms has finally been solved, and it’s all thanks to a few samples of ancient poop.

Researchers don’t know much about the parasites that plagued the Greeks thousands of years ago, and what they do know is largely from the Hippocratic Corpus, the medical texts that the father of medicine and his students put together between the 4th and 3rd centuries BCE. Modern historians have spent years trying to figure out which diseases and parasites Hippocrates and his followers were referring to in their writing, relying solely on their descriptions to guess at what ailments the ancient Greeks might have suffered from. Now, they finally have concrete evidence of the existence of some of the intestinal worms Hippocrates mentioned, Helmins strongyle and Ascaris.

As part of a study in the Journal of Archaeological Science: Reports, an international group of researchers analyzed the ancient remains of feces in 25 prehistoric burials on the Greek island of Kea to determine what parasites the people were carrying when they died. Using microscopes, they looked at the soil (formed by the decomposed poop) found on the pelvic bones of skeletons dating back to the Neolithic, Bronze, and Roman periods.

A roundworm egg under the microscope
A roundworm egg
Elsevier

Around 16 percent of the burials they studied contained evidence of parasites. In these ancient fecal samples, they found the eggs of two different parasitic species. In the soil taken from the skeletons dating back to the Neolithic period, they found whipworm eggs, and in the soil taken from the Bronze Age skeletons, roundworm.

With this information, researchers deduced that what Hippocrates called the Helmins strongyle worm was probably what modern doctors would call roundworm. The Ascaris worm probably referred to two different parasites, they conclude, known today as pinworm (which was not found in this analysis) and whipworm (pictured below).

Whipworm under a microscope
A whipworm egg
Elsevier

Though historians already hypothesized that Hippocrates's patients on Kea had roundworm, the Ascaris finding comes as a particular surprise. Previous research based solely on Hippocrates’s writing rather than physical evidence suggested that what he called Ascaris was probably a pinworm, and another worm he mentioned, Helmins plateia, was probably a tapeworm. But the current research didn’t turn up any evidence of either of those two worms. Instead of pinworm eggs, the researchers found whipworm, another worm that’s similarly small and round. (Pinworms may very well have existed in ancient Greece, the researchers caution, since evidence of their fragile eggs could easily have been lost to time.) The soil analysis has already changed what we know about the intestinal woes of the ancient Greeks of Kea.

More importantly, this study provides the earliest evidence of ancient Greece’s parasitic worm population, proving yet again that ancient poop is one of the world’s most important scientific resources.

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Arctic Temperatures are Rising So Fast, They're Confusing the Hell Out of Computers
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This past year was a brutal one for northern Alaska, which saw temperatures that soared above what was normal month after month. But you wouldn't know that by looking at the numbers from the weather station at Utqiaġvik, Alaska. That's because the recent heat was so unusual for the area that computers marked the data as incorrect and failed to report it for the entirety of 2017, leaving a hole in the records of the Climate Monitoring group at the National Centers for Environmental Information (NCEI), according to the Huffington Post.

The weather station in the northernmost tip of Alaska has been measuring temperatures for nearly a century. A computer system there is programed to recognize if the data has been influenced by artificial forces: Perhaps one of the instruments isn't working correctly, or something is making the immediate area unnaturally hot or cold. In these cases, the computer edits out the anomalies so they don't affect the rest of the data.

But climate change has complicated this failsafe. Temperatures have been so abnormally high that the Utqiaġvik station erroneously removed all its data for 2017 and part of 2016. A look at the region's weather history explains why the computers might have sensed a mistake: The average yearly temperature for the era between 2000 and 2017 has gone up by 1.9°F from that of the era between 1979 and 1999. Break it down by month and the numbers are even more alarming: The average temperature increase is 7.8°F for October, 6.9°F for November, and 4.7°F for December.

"In the context of a changing climate, the Arctic is changing more rapidly than the rest of the planet," Deke Arndt, chief of NOAA's Climate Monitoring Branch, wrote for climate.gov. The higher temperatures rise, the faster Arctic sea ice melts. Arctic sea ice acts as a mirror that reflects the Sun's rays back into space, and without that barrier, the sea absorbs more heat from the Sun and speeds up the warming process. “Utqiaġvik, as one of a precious few fairly long-term observing sites in the American Arctic, is often referenced as an embodiment of rapid Arctic change,” Arndt wrote.

As temperatures continue to grow faster than computers are used to, scientists will have to adjust their algorithms in response. The team at NCEI plans to have the Utqiaġvik station ready to record our changing climate once again within the next few months.

[h/t Huffington Post]

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