Where It Actually Comes From:

Handshakes are a relic of an era when everyone was a paranoid wreck expecting to be murdered to death by anyone and everyone they saw ... maybe even more so than nowadays.

You see, in the distant past, extending an empty hand was more than a friendly gesture -- it was an indication that a person wasn't holding some sort of sharp rock/knife/wrist-mounted miniature catapult about to be used against you. As history progressed, the practice became more and more complicated to address increasing fears: When ancient Romans got together, for example, they latched onto each other's arms clear up to the elbow to feel for daggers hidden up sleeves.

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It's like Wolverine, but way, way weirder and more inconvenient.

And have you ever noticed that handshakes always involve the right hand? Obviously that's because it's the one most likely to be brandishing a surprise abdomen aerator. At least, that's why some cultures favored the right over the left -- others used the right hand because, in those pre-toilet paper days, your left hand was your ass-wipin' hand.

Medieval Europeans built on the tradition passed down by the Romans, following up the simple arm clasp with a vigorous shake intended to dislodge any particularly well-tucked armaments, which presumably often resulted in a cartoonish pile of impossibly large weapons around the feet of the shakee. Thus what we today know as the handshake was truly born, to remain pretty much unimproved upon until the 20th century invention of hand sanitizer.

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"Shit, that was the last of it. Don't introduce anyone to me until after I get back from the store."

The Tradition You Know:

Unless you're British, Australian, or a free-wheeling, high-spirited maniac, you probably drive on the right-hand side of the road. It's one of those things we never really question because it just works, but the truth is that traffic didn't always follow this rule of the road -- in fact, it used to be the exact opposite.

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"Aaaaaand SWITCH!"

Where It Actually Comes From:

Going all the way back to ancient Rome, inventor of everything, traffic generally stayed to the left. The reason? You never knew what type of sketchy passersby you might run into along the way, and since people lacking mutant superpowers tend to be right-handed, traveling to the left allowed them ample head-cleaving room.

Think about it: If you were passing on the right and went to swing your sword at your newly made acquaintance/enemy on your left, you'd end up stranded in the breakdown lane with a headless horse. So instead you'd stay to the left in order to be better prepared should a fight ensue or if, conversely, friendly fist bumps were offered. The habit of traveling to the left eventually became so ensconced that it was officially codified into law in 1300 by Pope Boniface.

Via Wikipedia
That's an interesting fashion choice for a guy whose name sounds like "boner face."

So how did we end up switching sides? Well, popular legend has it that Napoleon mandated the change because ... he was short, or something? But while it's true that Napoleon (and, um, Hitler) helped spread right-hand road travel, the switch had already in large part taken place before the 19th century -- and once again, it was directly linked to our species' nascent road rage tendencies.

You see, with the introduction of firearms, it no longer made sense for right-handed people to stay to the left, because you'd have to pull some seriously sexy contortions to aim your even sexier arquebus at someone passing you. So instead, travelers kept their guns tucked into their left arms and traveled to the right, thereby being better prepared to fire at someone passing on their left. Take into account that another reason was the poorly designed Conestoga wagon, which forced the driver to sit on the left-rear horse in order to properly yield his whip in his right hand, and it turns out that our tradition of driving on the right came about through a combination of our desires to more easily cap some asses and more efficiently beat our animals.

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"When I evolve thumbs, you're all going to pay."

Where They Actually Come From:

Early Islamic cultures viewed yawning as an open invitation for Satan to slither his scaly way into your body, presumably to do really evil stuff like use your uvula as a punching bag while tickling your pancreas with his bifurcated tail. Meanwhile, in India, yawning was more of a two-way street: Not only did it allow bhuts (spirits) to enter your body and run amok with their spiritual shenanigans, but it also allowed a little bit of your own soul to escape. Luckily, we humans come equipped with a handy Satan/spirit/soul blocker at the end of each arm. That didn't do much good for infants with their little Jell-O hands, though, which is why early physicians instructed mothers to be constantly attentive to the task of covering their babies' yawns in order to prevent all their soul-stuff from leaking out.

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Which explains why hippos have no souls.

Now let's take an Indiana Jones-style plane jaunt over to medieval Europe, where covering yawns was less spiritual and more of an actual physical necessity. You see, with bubonic plague running rampant across the continent, unlatching your jaw and gulping in a heaping dose of your fellow man's filth was seen as a surefire way to become the next contestant on Watch Your Own Groin Rot Off. During this period, it became common to not only cover your gaping maw during a yawn, but also make the sign of the cross in front of it to ward off the invisible disease gremlins.

Similarly, the custom of saying "God bless you" after someone sneezes also finds its origins in the plague. That's because those who were infected could be identified by a few telltale symptoms, one of which was sneezing -- and since catching the plague was basically an inescapable death sentence, Pope Gregory instructed the populace to start blessing anyone who sneezed. Thus "God bless you" promptly replaced the previous refrain of "Good luck in the afterlife, motherfucker" and, incidentally, anyone with allergies suddenly found themselves with far fewer friends.

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That's sign language for "Get the fuck out of my office."

The Tradition You Know:

For many Americans, becoming an adult means a night of regret-filled debauchery on their 21st birthday. Sure, they may have already been allowed to vote, fight a war, and star in porn prior to that, but goddammit, 21 is the age when Americans can drink alcohol and proudly strut down the street waving their official Adult Card all up in the face of every person they meet.

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In six years, you'll finally be able to have your first ... oh, wait.

Where It Actually Comes From:

But why 21? Is it because that's when your body suddenly transmogrifies from a Lord of the Flies-style savage into an alcohol-metabolizing responsibility machine? Nope, the reason you're finally allowed to order a beer is because, a thousand years ago, that was the age at which you could finally become a maiden-savin' knight.

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You get to shit in it and everything!

Back in the Middle Ages, warfare pretty much followed an "I stronger, you deader" philosophy, so the most elite units were heavily armored knights. And since clothes made entirely of metal tend to weigh a dragon-sized shit-ton, it was believed that only someone who had reached their 21st birthday could effectively carry that weight. Plus, the age of 21 was extra special because, based on some Aristotelian Greek bullshit, they thought that 7 was a divine number. Therefore, according to the Official Knight Users Manual, boys could become pages at 7, squires at 14, and knights at 21.

fotokostic/Photos.com
Age 25: Dragon friend!

As you may or may not have heard, we 'mericans were once British colonials, so this perceived importance of the age of 21 eventually filtered on down to us. So the next time someone you know turns 21, don't buy them a beer. Instead, slap some armor on them, strap them onto a horse, and send them off to fight some Lannisters ... or, seeing as how that's probably illegal wherever you live, just tell them that they had to wait until they turned 21 to consume alcohol because a medieval English common law said they were too much of a pussy to wear a suit of armor before that.

The Traditions You Know:

If there's one thing that's chock-full of seemingly cliche and mind-numbingly pointless traditions, it's your average wedding. From appointing a best man, to tossing the bride's wedding garter to a horde of salivating men, to bridesmaids (which seem to exist mainly as living mannequins for horrid dresses), the entire ordeal seems somewhat unnecessary but, ultimately, harmless.

Digital Vision./Digital Vision/Getty Images
Well, depending upon the freaks getting hitched.

Where They Actually Come From:

Today, a best man's main purpose is to help the groom through his pre-wedding cold feet (by way of strippers). But during the Dark Ages, he would have been more concerned with the bride's cold feet -- because back then the best man was less about fumbling through toasts and more about helping to kidnap the bride.

The Germanic Goths had a custom dictating that a man should marry a woman who lived in his own community, which inevitably led to bachelors dealing with a shortage of acceptable prospects. Since we're talking the Dark Ages, this of course resulted in pillaging neighboring communities -- and since everyone knows that kidnapping is sort of a two-man job, the best man stepped in to help out. Over time, the best man evolved from partner-in-kidnapping to the more bride-friendly role of bodyguard: To protect the happy couple (which became a thing once all the kidnapping died down), the best man would stay nearby to defend them from disapproving family or other suitors hoping for one last shot (we're picturing a dude in a tux wielding a massive battleaxe).

Digital Vision./Digital Vision/Getty Images
And of course, there's the modern version.

Moving to the other side of the aisle, bridesmaids also find themselves with sinister origins. In ancient Rome, it was required by law for the wedding party to consist of 10 witnesses. Unlike today, these girls would commit the ultimate faux-pas and dress the same as the bride in order to confuse evil spirits, as the Romans believed that these spirits would otherwise ruin the wedding and plague the couple with bad luck. So, in what was perhaps the birth of the grand wedding tradition of being cruel to your girlfriends, the bride would use her best friends as evil spirit bait.

Jupiterimages/Photos.com
Not her problem anymore.

Throwing the garter also originated as a way to protect the bride, proving once and for all that today's weddings are goddamned boring compared to their 14th century counterparts (the tradeoff being that they're much less likely to result in serious bodily injury). Back then, the wedding guests would jostle the new couple to the bedroom directly after the ceremony for a sort of crowdsourced consummation. Snatching part of the bride's dress on the way to this live porn show was considered good luck, so naturally the gown would be reduced to rags. As a result, brides eventually began tossing the garter for the guests to fight over while she and her new husband escaped to the bedroom. You know, sort of like how a movie burglar might toss a T-bone to some guard dogs, except instead of stealing a TV, you're protecting yourself from your friends' and family's rapey tendencies. And now, it's time for the Chicken Dance!

Auriane has an incredibly pointless Tumblr, and you can contact her at auriane.desombre@gmail.com. If you can wear a suit of armor, Steve recommends that you clank on over to his blog, then head over to the Princeton Tiger for another crescent kick to your giggle glands.

Did you know that the kids who graduate from high school in your town this year will be, on average, 30 IQ points smarter than the average student who graduated in 1923? To put that in prospective, the average student in the class of '23 would be considered legally retarded by modern standards. In this month's Cracked Podcast, Michael Swaim and Jack O'Brien look at the mysterious reason science thinks humans are getting smarter every year. Go here to subscribe on iTunes or download it here. Getting your Cracked fix while driving has never been this unlikely to kill you.

Related Reading: Traditions have a way of shocking us. You'll be surprised to learn that the ancient bushido code of honor only dates back to 1905. You might also be surprised to learn that those ridiculous old prohibitions against pork and beef saved a shitload of lives. Still haven't had enough laughs at the expense of our ancestors? Click this link and read away.