That's right -- subjects were unable to anticipate a fake smile. Also, when one subject gave a genuine smile, they got a genuine one in return. When their smile was fake, so was the responding smile. In other words, a genuine smile and a fake smile -- though identical on the surface -- are treated as completely different expressions by the brain. Likewise, a separate study found that we're not actually fooled by fake laughter, either -- on some level your uncle knows his racist jokes are only getting polite fake laughs, but he just doesn't care.

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"We've never showed genuine emotion at Thanksgiving so far. I figured, why start now?"

You might find yourself wondering why we bother faking smiles at all. Why maintain this fiction that pleasant feelings can be faked? Why not just be up front and let our expressions reflect what we're feeling inside? It's because once you start asking questions like that, all of the rules of polite society will come crashing down. A sudden wave of total honesty would be the one disaster our civilization could not endure.

Researchers then measured the testosterone levels of the shirt snufflers and found that these women reacted exactly the way the men did -- smelling ovulation kicked up testosterone levels, smelling low fertility shirts made them drop. And as anyone who's ever watched a professional football player brutally annihilate someone from the opposing team (or a middle school boy vigorously dry hump an anime pillow) can tell you, testosterone is a powerful thing. In women, just like men, testosterone drives up the desire to compete and/or fight, depending on the circumstances.

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"Does it smell like a bitch about to get stabbed in here, or is it just you?"

Now put a bunch of men and women together in close quarters, and the guys start showing off for the ovulating women and get aggressive with each other, and the other women start trying to compete ... yeah we're thinking the deodorant industry was all a secret project intended to prevent wars.

For example, researchers at the University of Western Australia did an experiment where they polled some subjects about how faithful they were in their last relationship. Once they had a group of faithful and non-faithful partners, they took their photos and showed them to a different group and asked them to play a game of "spot the cheater." Remember, they knew nothing else about the person in the photo -- they couldn't talk to them, or smell them, or observe their mannerisms to see if they were walking funny or something. The result: From a photo alone, women could correctly guess whether a man was a cheater 62 percent of the time. You might think that's just slightly better than flipping a coin, but note that the males could only do it with a 23 percent success rate. And while it was just one small study, this falls in line with what we already know about how many snap judgments we make based on things like the shape of someone's face. It kind of makes you wonder how often we get an accurate subconscious feeling about someone, but then talk ourselves out of it.

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"Nah, he probably just works for Cutco."

Wait, it gets weirder!

Russian researchers collected the armpit sweat from 34 men, some of whom had gonorrhea, some of whom didn't, and some who'd had gonorrhea in the past but had recovered. They then asked healthy women to sniff the different vials of sweat, and to rate them on a 10-point scale, along with descriptors like "putrid" and "floral." The gonorrhea sufferers, sure enough, consistently smelled worse to the women. Again, this was one small study, but it would make sense -- the species would have needed a way to try to steer clear of sexually transmitted diseases long before anyone invented condoms or high school health classes.

This would also explain why, despite the fact that evolution has created all sorts of natural scents intended to attract the opposite sex, we still prefer artificial colognes, deodorants, and Axe Body Sprays: It's because our natural scents contain all sorts of other information we don't want getting out there. Better cover that shit up!

There's no denying that fatty food is goddamn near irresistible. And while today this might be largely seen as a weakness that's causing humans to gradually evolve into a race of helpless rolling blob-monsters, for much of the human timeline it made perfect sense: When food is scarce, fattier food means more calories, and more calories means a better chance of preventing nature from starving your hunting, gathering ass to death.

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You've come a long way, baby!

While the obvious way to detect whether or not a food has a high fat content is to taste it and then wait patiently in front of a mirror for its waist-embiggening effects to kick in, scientists have recently discovered that we possess another, much more subtle ability to detect which foods have a higher calorie count. Researchers at the Monell Chemical Senses Center conducted several experiments in which they had participants -- some from Philadelphia, others from the Netherlands -- smell glasses of milk, each of which had a small variance in its fat content. Sure enough, participants were able to detect which milk was fattier just by its smell.

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We typically just go by color.

To make sure this was an innate ability, researchers compared the results of the Americans versus the Dutch (whose diets contain way more milk than ours) and also analyzed the results against the BMIs of the participants to see if the fatter participants (read "the Americans") were better equipped to smell the fattiness of their foods. What they found was that, regardless of national dietary preferences or waist size, participants were equally equipped to smell fat content across the board.

Researchers are hopeful that this discovery will lead to further study into how people can use their built-in fat-sensing sixth sense to improve their diet by regulating their fat intake. Unfortunately, that will presumably also require the invention of some type of A Clockwork Orange-style brainwashing device to rewire that pesky "fat = delicious" connection that evolution has soldered somewhere deep within our grey matter.