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Hot, Humid Weather May Have Helped Shape Human Noses

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Noses may be the unsung heroes of the face. We tend to think of them as mere scent collectors, but noses do so much more, including make it possible for humans to survive in different climates all over the world. A study published in the American Journal of Physical Anthropology explores how that may have come about.

Your nose acts like a portable, personal HVAC system, treating the air you inhale to make it easier for your body to process. In the winter, your nose warms the air so that it’s nice and toasty by the time it reaches your lungs. In arid climates, our noses add humidity to our inhalations to keep our respiratory tracts from drying out.

Human nose shape, like skin color, generally varies by latitude. Scientists have suggested that northern Europeans’ thin, pointy noses evolved to help their ancestors process their homelands’ cold, dry air, since narrow nasal passages mean that a greater percentage of inhaled air has to come into contact with heat- and moisture-adding mucous membranes. This, the researchers believed, was the only way the nose has evolved: away from the flatter, wider noses of people living closer to the Equator. The air in those regions is typically hot and humid already, requiring no special treatment. So if the winter nose is a custom job, they said, the summer nose must be the base model.

But "we don't really think that that's true," said biological anthropologist Scott Maddux of the University of North Texas Health Science Center. Maddux and his team used global climate data from 1901 to 2013 to construct maps of average annual temperature and humidity. Then, they compared those with the results of a study from 1923, which measured the noses of more than 15,000 people from 147 countries.

Their results suggest that, rather than a starting point, wider, flatter noses have themselves evolved to help their owners cope in those hot, muggy climates. Humidity is rough on the human body. It makes it much harder for us to shed heat by sweating, so we have to find other ways to cope. One way to do that might be allowing more heat to escape through the two holes in the middle of our face. The wider the nose, the more heat it can funnel out of the body. 

More questions remain. Nearly all the work our noses do takes place inside in a part called the nasal cavity. If it’s the cavity that’s doing the heating and humidifying, Maddux says, why would the outside of our noses need to change at all? To find out, scientists will need to go deeper inside, all the way to our skulls.

Nicholas Holton, a biological anthropologist at the University of Iowa, was not involved in the study but praised the team’s work. "A big part of any face, not just the human face, is the nose," he told Inside Science. "Literally, it's a central component of the skull, so understanding what's happening with the nose may tell us a lot about what's happening with the rest of the face."

[h/t Inside Science]

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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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Animals
The Science Behind the Urge to Cuddle Cute Babies
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You don’t have to be a cat person to feel your heart warm up at the sight of a big-eyed, tiny-nosed kitten stumbling across the floor. When confronted with a baby kitty, you may feel the urge to scoop it up and cuddle with it for the rest of the day. This reaction isn’t limited to felines—puppies and even some adult animals trigger these same snuggle instincts. If this feeling sounds familiar, that means your brain is just doing what it evolved to do to preserve the human species.

This episode of the National Geographic video series We’re Wired That Way lays out what's going on in your head when you see something cute. The facial features of most young mammals fall into the same configuration: large round eyes, and small noses, mouths, and chins. This is called kinderschema, and humans are engineered to find it adorable because it can be found in our own babies. When we see a typical baby face, it activates our instincts to nurture and protect while also releasing the feel-good chemical dopamine to reward us for doing so. That way we feel driven to keep babies safe even if they’re not our own, thus boosting their chances of survival and the survival of our species.

Because kinderschema isn’t limited to the human race, we feel this response when looking at non-human baby animals as well. Some mammals, like cats and guinea pigs, retain their kinderschema into adulthood. So next time you let out an involuntary squee at the sight of your pet, remember that you have biology to blame.

[h/t National Geographic]

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