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Woolly Mammoths Had Humps Like Camels, and Genes Made For Cold

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What makes a mammoth different from an elephant? The Asian elephant is the closest living relative of the prehistoric woolly mammoth, but mammoths lived under vastly different circumstances from their cousins—in the freezing tundra versus the tropics. 

In a new study in the journal Cell Reports, geneticists and anthropologists from the University of Chicago and Penn State University sequenced the genomes of three Asian elephants and two woolly mammoths to discover what genetic changes would have allowed mammoths to live in such different climates from their modern relatives. 

In order to live in climates where average winter temperatures ranged from -22 degrees Fahrenheit to -58 degrees Fahrenheit, mammoths had small ears and tails and large sebaceous glands, which secrete oil to waterproof and insulate mammals. They also had thick layers of fat to protect them from the elements, including a hump of fat much like those seen in modern-day camels. This hump would have helped them store energy during long Arctic winters without sunlight. 

And they had a genetically coded preference for the cold. An amino acid change specific to woolly mammoth DNA played a major role in the animals' sensitivity to temperature, according to the study. The TRPV3 gene is involved in exterior temperature sensation, cellular differentiation, and hair growth, and mice without it are more sensitive to heat, and prefer colder temperatures. In the lab, the researchers found that the woolly mammoth's genetic tweak turned down the activity of the protein produced by TRPV3. 

The mammoth DNA in the study came from individuals that died 20,000 to 60,000 years ago. Some came from mammoth fur bought on eBay for a mere $100, the researchers told NPR

[h/t: NPR]

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

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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Animals
Listen to the Impossibly Adorable Sounds of a Baby Sloth
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Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]

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