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Drew J, Philipp C, Westneat MW (2013)

How Ancient Shark-Tooth Swords Uncovered Two Long-Lost Species

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Drew J, Philipp C, Westneat MW (2013)

By Chris Gayomali

Biologist Joshua Drew's surprise discovery began as many do: "I just wanted to... look at really cool stuff," he tells The Los Angeles Times. Drew, now a postdoctoral researcher at Columbia University, was with a few colleagues at the Field Museum of Natural History in Chicago scoping out a new exhibit — a collection of "badass" swords, knives, and lances once used by the inhabitants of the Central Pacific's Gilbert Islands 130 years ago to rip their enemies to shreds.

This particular arsenal wasn't pounded out of iron or steel, though. The 124 flesh-tearing weapons on display had a more biological origin, and were carved out of wood, with each blade edge carefully outfitted with rows of dagger-like shark teeth. 

Drew was admiring the pieces when he noticed something strange: A few of the teeth appeared to belong to dusky and spottail sharks, which, oddly, aren't typically found near the Gilbert Isles. How could he tell, you might ask? Well, he was in a natural history museum, and could easily look up fossil records to confirm his suspicions.

"Shape, serration patterns, and other features of shark teeth were enough for researchers to identify the species," says LiveScience.

Using field guides and the museum's collections of shark jaws, the researchers identified teeth from eight species of shark on 122 weapons and teeth collections from the Gilbert Islands. The most common of those species was the silvertip shark (C. albimarginatus), whose teeth graced 34 weapons. Gilbert Islands weapon-makers also used teeth from silky sharks, oceanic whitetip sharks, tiger sharks, blue sharks, and hammerheads. [Live Science]

Yet, a deep-dive through history revealed no evidence that the dusky and spottail sharks had ever lived in Gilbert Island's reefs. While trading with other far-away cultures could explain how the teeth got there, the likelier answer is one we've already heard before:

"Probably, they were fished out," says Drew. Although it's not clear why the sharks disappeared,says Ed Yong at National Geographic — "people were hacking off shark fins in the Gilbert Islands as far back as 1910 and by the 1950s, around 3,000 kilograms of fins were being shipped from the islands every year." It's become so bad that some conservationists estimate that 100 million sharks are killed worldwide every year

After publishing their findings this month in the journal PLoS One, Drew and his team hope that the discovery of a "shadow biodiversity" along the Gilbert Islands' waters will aid conservation efforts for marine animals that have been over-fished for decades:

Given the importance of these species to the ecology of the Gilbert Island reefs and to the culture of the Gilbertese people, documenting these shifts in baseline fauna represents an important step toward restoring the vivid splendor of both ecological and cultural diversity. [PLoS One]

That's something worth sinking your teeth into.

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Animals
Owning a Dog May Add Years to Your Life, Study Shows
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We've said that having a furry friend can reduce depression, promote better sleep, and encourage more exercise. Now, research has indicated that caring for a canine might actually extend your lifespan.

Previous studies have shown that dog owners have an innate sense of comfort and increased well-being. A new paper published in Scientific Reports and conducted by Uppsala University in Sweden looked at the health records of 3.4 million of the country's residents. These records typically include personal data like marital status and whether the individual owns a pet. Researchers got additional insight from a national dog registry providing ownership information. According to the study, those with a dog for a housemate were less likely to die from cardiovascular disease or any other cause during the study's 12-year duration.

The study included adults 40 to 80 years old, with a mean age of 57. Researchers found that dogs were a positive predictor in health, particularly among singles. Those who had one were 33 percent less likely to die early than those who did not. Authors didn't conclude the exact reason behind the correlation: It could be active people are more likely to own dogs, that dogs promoted more activity, or that psychological factors like lowered incidences of depression might bolster overall well-being. Either way, having a pooch in your life could mean living a longer one.

[h/t Bloomberg]

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Big Questions
Why Don't We Eat Turkey Tails?
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Turkey sandwiches. Turkey soup. Roasted turkey. This year, Americans will consume roughly 245 million birds, with 46 million being prepared and presented on Thanksgiving. What we don’t eat will be repurposed into leftovers.

But there’s one part of the turkey that virtually no family will have on their table: the tail.

Despite our country’s obsession with fattening, dissecting, and searing turkeys, we almost inevitably pass up the fat-infused rear portion. According to Michael Carolan, professor of sociology and associate dean for research at the College for Liberal Arts at Colorado State University, that may have something to do with how Americans have traditionally perceived turkeys. Consumption was rare prior to World War II. When the birds were readily available, there was no demand for the tail because it had never been offered in the first place.

"Tails did and do not fit into what has become our culinary fascination with white meat," Carolan tells Mental Floss. "But also from a marketing [and] processor standpoint, if the consumer was just going to throw the tail away, or will not miss it if it was omitted, [suppliers] saw an opportunity to make additional money."

Indeed, the fact that Americans didn't have a taste for tail didn't prevent the poultry industry from moving on. Tails were being routed to Pacific Island consumers in the 1950s. Rich in protein and fat—a turkey tail is really a gland that produces oil used for grooming—suppliers were able to make use of the unwanted portion. And once consumers were exposed to it, they couldn't get enough.

“By 2007,” according to Carolan, “the average Samoan was consuming more than 44 pounds of turkey tails every year.” Perhaps not coincidentally, Samoans also have alarmingly high obesity rates of 75 percent. In an effort to stave off contributing factors, importing tails to the Islands was banned from 2007 until 2013, when it was argued that doing so violated World Trade Organization rules.

With tradition going hand-in-hand with commerce, poultry suppliers don’t really have a reason to try and change domestic consumer appetites for the tails. In preparing his research into the missing treat, Carolan says he had to search high and low before finally finding a source of tails at a Whole Foods that was about to discard them. "[You] can't expect the food to be accepted if people can't even find the piece!"

Unless the meat industry mounts a major campaign to shift American tastes, Thanksgiving will once again be filled with turkeys missing one of their juicier body parts.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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