After a couple hundred thousand years of loping around this big blue ball in our dopey old meat-mechs, we've got this whole "being human" thing pretty well figured out. We know which end the food goes in and which end the poop comes out, and that's pretty much all that matters. No? You want more? You figured we'd know everything about the human body by now, what with all our awesome science and shameless nude selfies? Well, we've nailed a whole lot down, sure, but there are some shockingly simple questions we don't have very solid answers to yet. We have guesses, theories, and hypotheses, but when it really comes down to it, we're still asking ...

#5. Why Does Pain Hurt?

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Pain is an uncomfortable, but universal, human experience. It's one of the very first things we encounter in life, when the doctor abruptly yanks us away from our wombly apartment, spanks our ass, and calls us income. It will also be one of the last, when we inevitably go out flailing and wailing in the fiery aftermath of a tragic (but glorious) school bus ramping incident.

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It's the only end we consider dying, since flaming bus ramping is the only life we consider living.

But what, exactly, is pain? How does it work? Does it feel the same for you as it does for your asshole neighbor, Gary? If you both hurt the same, isn't that unfair, because he deserves way worse? If you have trouble coming up with answers to those questions, don't feel bad -- science can't answer them either. From the eggheads who study pain to the researchers who design the drugs to treat it and the doctors who prescribe them to you, none of them can even agree on a single definition of what the hell pain is.

Perhaps the best way to demonstrate this is to look at fibromyalgia, a medical condition best described as "MY EVERYTHING HURTS." There are no physical tests to confirm whether you have it -- no brain scan or blood test or spirit medium can confirm your condition. So how do they diagnose it? Well, you fill out a questionnaire. Do you have lots of unexplained pain in various parts of your body that doctors can't figure out? Yes? Boom: fibromyalgia. Or possibly demonic possession. Maaaybe aliens.

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"Oh, sure. Just assume it's the guy with an anal probe."

The FDA has approved drugs to treat Fibby G because they seem to help, but no one really knows why or even if it's actually a thing. But this is the era of science fiction come to life: Surely there's some kind of high-tech brain scan doctors can use to determine when you're in pain. Indeed, doctors say there are differences in the brain scans of people with fibromyalgia, but there's nothing consistent from patient to patient -- no doctor can peek inside your skull theater and definitively say that you have the condition. Actually, no doctor can tell how much pain you're in at all, because we've only just recently taken the first baby steps toward figuring out how to detect pain in a person's brain activity. According to Tor Wager, associate professor of psychology and neuroscience at CU-Boulder and probable Star Wars character: "Right now, there's no clinically acceptable way to measure pain and other emotions other than to ask a person how they feel."

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"Somewhere between 'oxycodone' and 'shit-tons of oxycodone.'"

So ... how're you feeling today? Aside from some general annoyance at the inherent uncertainty of medical science, your body, and all of the universe, we mean.

#4. Why Does Anesthesia Work?

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Anesthesiology is truly a miracle of modern science, but it's more than a little scary when you think about it: With a few random chemicals, anesthesiologists effectively shut down chunks of your brain. Too much, and you'll never wake up. Not enough, and you're reliving a past life as a Civil War soldier on the receiving end of hacksaw surgery. But why do these chemicals work? How do they interact with your body in just such a way as to achieve that delicate balance? Well, here's the scariest part: Science doesn't fucking know.

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In fact, reading that sentence counts as six anesthesiology credit hours.

Basically, anesthesia has evolved over the past couple hundred years by way of medical professionals saying, "Here, pump some of this into that guy and see what happens. Still screaming? OK, try some of this." All that trial and error has given us a pretty clear picture of what we can use to achieve the desired effects -- namely, anything from complex steroids to straight lungfuls of xenon gas -- but as to why these substances dim your consciousness without flipping it off altogether and appending "deceased" to your name, there's no good answer. Hell, they don't even all affect the same areas of the brain.

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"We need to stimulate each area of the brain individually to get a better understanding. Go find a fondue fork."

The main reason it's so hard to figure out how anesthesia alters our consciousness is that science doesn't really know what "consciousness" is, or how it works. There's no definitive test to show whether someone is conscious -- the best anesthesiologists can do is look at a number of things like the presence of certain brain waves, physical responses, and ... wait for it ... sensitivity to pain. But as we've already discussed, science doesn't have a way to determine if you're in pain, so it's completely up to you to tell them if you're not quite anes ... thesed(?) enough. And if you get it wrong, don't worry: You'll have a few hours to think about how else you could have answered while you're locked inside your body, mentally screaming as masked strangers cut you apart. No pressure, though.

#3. Why Do We Laugh?

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Some theorize it's to signal that a suspected threat doesn't actually pose a real danger, some suppose that it's a reaction to a result being different from what we expected, while still others believe it's because Jim Carrey is talking with his butt, and that's not normally how one talks.

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Truly, our society has entered a golden age.

They're all at least sort of correct, because no one knows for certain why we laugh. We do know, however, that more than any other emotional response, laughter affects all kinds of areas of your brain -- even the motor sections. More surprising, though, is the fact that most of our laughter isn't related to comedy at all. Studies have shown that less than 20 percent of laughter happens as a result of something being funny. Far more often, we're laughing to punctuate innocuous statements, to fill pauses in conversation, or because our elaborate evil plan is finally coming to fruition.

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We imagine mistimed farts take a pretty generous slice of that pie as well.

One thing we do (probably) know is where laughing originated: It evolved from the panting that primates do during hardcore tickle sessions. This, of course, leads to the inevitable question of "But why are we ticklish in the first place?" which leads to the inevitable answer: "Fucked if we know."