As mankind made its evolutionary transition from ape to human, scientists think that there was a time when a flushed cheek and a downcast eye was a key survival instinct. When one species was still evolving into the other, it meant your genetic line wouldn't end in a dismembered pile of limbs. Blushing would have been especially useful, since it's an involuntary reaction. No matter how hard you tried to maintain eye contact, your blushing face broadcasts just how close you were to soiling your loincloth.

GettyOn the other hand, losing bladder control directly on a shark usually has negative repercussions.

Blushing, after all, signals remorse. Since it can't be faked or hidden, researchers think that our ancestors evolved the function as a display of appeasement towards those that we've wronged. Or who could kick our ass. The walk back to the cave might have been shameful, but it was accomplished with fully intact sexual organs -- the only victory that matters when it comes to the gene pool.

The part of the species that averted their eyes and turned beet red no matter how much they wanted to stand up to the big aggressive guy taking their lunch lived to see another day, and breed with the (presumably underwhelmed, but realistic) females of the species. The big guy eating our lunch might have won that battle, but that same unwavering belief in himself was what sent him out in a blaze of monkey-fisted Neanderthal asswhoop. The meek end up inheriting the Earth by default.

Getty"Hmm, it's a choice between that nerd or the chunks of Brad's intestines that were left behind after the ass kicking."

Being called a baby is one of the most stinging insults most of us encounter as kids. Wah-wah. Is little baby gonna cry? they'd chide as we ran home crying for a breast feeding. In the grand sweep of nature, we have good reason to be insecure. Most animals are pretty much able to fend for themselves days after they're born. Anything longer than a week, and they're legally declared dinner. Human babies are completely useless balls of skin, tar poop and weird belly button stumps for years.

GettyWho's an adorable drain on society's resources? You are!

Not only are human babies the failures of the baby world, we stay that way for years, taking longer than any other primate to reach sexual maturity and adulthood. While foals are standing within their first hour of life and lions are banging each other by age four -- humans take their sweet time learning how to do everything that's not crying, farting or being adorable viral video fodder.

GettyOutside the safety of the towns, we're all just fodder for vicious wild animals.

Its Badass Origins

That stupid baby who ruined your flight by crying might actually be the main reason we're sitting on top of the food chain in the first place.

iStockPhotoBabies make terrible pilots.

At some point way up the evolutionary chain, our babies probably hit the ground running and screwing too. But as we evolved our super large brains, we also had to evolve larger skulls which required a birth canal you could go bowling in. This led to a sort of anatomical arms race between mom's cha-cha and junior's head. If the heads got too big, mom would lose the ability to run (No. 2 on our list of the 6 Abilities You Didn't Want to Lose in a World Filled With Man-Eating Animals). To keep women ambulatory without losing any of that big-brained goodness on the back end, the species began naturally selecting women who gave birth earlier. The species got to keep our big, tool-operating brains and female hips that wouldn't get clogged in a hula hoop.

The trade-off was that our babies came out stupid and helpless, and had to be taken care of for years if you didn't want them to find the only sharp rock in the entire jungle and try to do a headstand on it. While this extended ankle biting phase might seem like nothing but downside at first, the mixture of big brains and more time spent hanging around made us even smarter.

GettyBut still vulnerable.

Scientists believe that this delay actually allows us to reach higher cognitive levels, because it prolongs the types of learning that only juveniles are capable of. You can't teach an old dog new tricks, so you keep the dog a puppy longer, thereby allowing him to learn more tricks overall. And considering those "tricks" are language, culture and the ability to solve a Rubik's cube, being born helpless isn't such a bad trade-off.

Getty It also helps that just being around a baby drugs you into a happy stupor.

Early helplessness is the price we pay for later brilliance. Or, at least our later capacity for non-idiocy.

It seems a little pathetic that some of us can't even handle a light touch to certain parts of our body without peeing our pants a little bit. While we wouldn't say being ticklish makes you a wuss per se, it's hard to picture Teddy Roosevelt squirming around while being attacked by the tickle monster, and it's literally impossible to tickle someone without talking like a Muppet.

GettyHe often left himself open to a tickle attack, because he knew no fear.

Its Badass Origins

Ever see dogs play? They tackle and growl at each other, bite and slash at each other's throats, stopping just shy of a playful disembowelment. In fact, in most of the Animal Kingdom, playing looks a lot like two animals trying to murder each other. Now imagine what tickling must look like to them. One person's got their hands on the throat or ribs of another person who is screaming and begging for them to stop. Hell, under the right circumstances, that would look like a murder to just about anyone.

iStockPhotoA wedgie is, at best, provoked manslaughter on the grounds that your victim is an insufferable nerd.

In good news for creepy uncles everywhere, tickling totally evolved as a way to hone our self-defense reflexes. One researcher pointed out that the most ticklish parts of our body (our ribs and neck) also tend to be the most open to attack. So when primates evolved the behavior of tickling our little ones, they were actually training their babies to protect their most vulnerable body parts in a safe (and hilarious!) way.

Getty"Laugh it up! This is where the grizzly will strike, son!"

Not only is the behavior of tickling rooted in our evolutionary history, being ticklish was also once the trait of a survivor. Because ancient humans who were highly sensitive to swishing, creeping stimuli were faster to detect predators and parasites and, thus, lived longer. Individuals who had low sensitivity got eaten or infected. In this respect, ticklishness evolved as a form of self-preservation and was a 100-percent-beneficial trait back when the tickle monster was an actual monster.

Even when we're not talking about physical food allergies, there's something pretty lame about a guy who can't stomach the food on his plate.

Its Badass Origins

Today's pickiest eaters had the bad luck of inheriting a gene that kept the species alive thousands of years ago. There's even an official name for them: Supertasters.

GettyCan't eat certain birds, can't eat on planes ...

And while that name might sound like even science is mocking them, it turns out they actually have extra taste buds and are therefore extra-sensitive to something called phenylthiocarbamide (PTC). For supertasters, PTC is to food as beer is to angry drunk stepfathers; it makes everything bitter.

Getty"Every stem represents a way you've RUINED MY LIFE."

But back before we had the FDA and award-winning documentaries telling us what was what in our food, they were our first and only line of defense. Because toxins are bitter, supertasters could pick out the poisonous stuff and scoot us on our way before we gorged ourselves on deathberries. With literally no other mechanism for detecting poison, our picky-eating friends would have been like superheroes to their communities.

GettyCommunities that separated everything on their plate and were terrible in sushi restaurants.

They were so useful that while all the guys who hear sounds 20 times louder than everyone all died off years ago, the supertaster gene was useful enough to hang around in the mouths of certain unfortunate members of the species. Spinach and Brussels sprouts just taste bad to most of us, supertasters are experiencing every note of the horrible sensation that just crapped in your mouth in hi-def with Dolby digital surround sound.

Getty "It's got a hint of nutmeg with a used condom finish."

So while eating with a supertaster can be as fun as eating with a colicky baby while nursing a raging canker sore in one cheek and mouth cancer in the other ... at the Golden Corral ... on Mexican night ... we should let them complain, and stop calling them that clearly sarcastic name.

... they also confine you to a life indoors. And what could be wussier than that?

Their Badass Origins

People tend to think of allergies as a weakness, but the big irony is that they're the exact opposite. Allergies are actually caused by an extra active immune system, or the immunosuppressant equivalent of Steven Seagal in the early 90s: kicking so much ass that a few innocent bystanders are going to catch an arm snap once in a while.

GettyHe always sends flowers to the hospital bed, which just makes things so much worse.

Normally, dangerous foreign substances that get inside our body are recognized by antibodies, which then bind to white blood cells to tell the immune response it's "go time." Think of white blood cells and antibodies as the Batman and Robin of disease fighting. Coughing, sneezing, fevers -- these are just the tactics our dynamic duo initiates to take out the trash. One of their favorite crime-fighting techniques is to drown the bad guys with phlegm, and then literally explode them out of your body via sneeze.

Holy snot-bomb, Batman! Honestly though, that's disgusting.

Sometimes, though, the dynamic duo decide to also go for the occasional litterbug or the overly nosy neighbor down the street. Or, in the case of the bodies of allergic people, dust and pollen. And the body attacks them with the same ferocity it would attack a cold. If successfully fighting off disease were scoring a touchdown, then an allergy is like Forrest Gump barreling through the end zone, mowing down the marching band and sprinting halfway across town while still clutching the football.

GettySTOP, IMMUNE SYSTEM! STOP!

Recently, the discovery of an ancient antibody has shed some light on why our immune system is prone to overreaction. According to this study, way back when humans were little more than nomadic tribes of lice-picking, loincloth-sporting fruit and nut herders, there was a particularly nasty pathogen floating around. In order to survive, primitive humans started producing an antibody that would latch on more tightly to white blood cells, thereby initiating an unusually ferocious immune response.

This worked out great for those primitive humans who were actually infected, and we survived to this day. Unfortunately, the antibody stuck around inside us long after the deadly pathogen was eradicated. Nobody told this obsolete bastard his job is done, so he spends his time waging imaginary battles, reliving the glory days by pretending like he's saving lives.

The similarities really are startling.

Its Badass Origins

Tears aren't just eye-lube and Oscar magnets. Scientists think they actually started out as a signaling system. More specifically, a sneaky, sophisticated signaling system that provided the crier a strategic advantage in no-holds-barred Neanderthal warfare.

GettyBecause there's only so much secrecy, "I WANT MY MOOOOMMMM," can provide.

Imagine you're an early man and you're compromised in some way. Maybe you've impaled yourself on a mammoth tusk or got a really bad foot cramp. You need help, but you want to keep your impairment on the down low, so your enemies don't pounce. You need a signal that tells your allies that something is wrong that doesn't involve shrieking like a little bitch, which is Neanderthal for "finish me." You could stay silent and bear it like a man, at which point no one will hear you and you're still impaled on the tusk of the mammoth that guy was riding when you killed him. But tears -- dramatic, glistening tears quietly streaming down your ashen, pain-wrought visage -- will tell the people close enough to see the shininess of your cheeks that something is wrong and you need a hand.

In other words, early man's ability to survive actually depended on his ability to cry like a baby.

Getty"I am the warrior king. You will bow before me."

Oh, and we should also mention the guy who could summon up some eye water would also be the guy more likely to get laid later. Even today, scientists point out that tears are a strategic weapon in getting empathy from the opposite sex. But back when the first humans were becoming what we are today, emotional tears were an evolutionary breakthrough. No other animal cries in sadness, after all, and crying would have been one of the first behaviors that separated us from the beasts.

That and our ability to beatbox.

Check out more of Dennis's musings on life and love here. Kristi can be found on Twitter.

Learn more about bullies in, 5 Douchebag Behaviors Explained by Science and 6 Reasons Assholes Are Healthier (According to Science).

And stop by Linkstorm to discover why the average man only last 27 seconds in bed.

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