They say that those who ignore history are doomed to repeat it, so pay attention for Christ's sake. It turns out that many of our ancestors achieved levels of violence that take them right out of the realm of "badass" and into the less cool area of ball-shriveling atrocity.
These are the civilizations you don't want to face during, say, your next time travel adventure. And yes, the Spartans are down there.
History is kind of spotty on the Celts (they never wrote anything down, and many of the witnesses died brutally) but what facts survived confirm one thing: They had gigantic Celtic balls.
First of all, they had a thing for severed heads. After a long and trying battle they'd all unwind at the end of the day by collecting a few souvenir heads. Then they'd bring them home and decorate the house with them. So the average Celt home probably looked like a hunter's trophy room, crossed with the scene at the end of Halloween when all the mutilated bodies start popping up around every corner. Sweet dreams kids!
If they felt that yours was a head of particular importance, they'd embalm it and whip it out at parties to brag about how awesome they were. When they were alone they'd probably wiggle your jaw around and pretend you were complimenting them.
The reason for all of these head-chopping-good-times was that the Celts believed that the head held the soul, and so if you cut a dead guy's head off before all of that juicy soul leaked out of it, it was yours. A finders-keepers sort of deal, you might say.
A modern Celt.
So, Were They Really So Bad?
Hey, remember Braveheart? And how batshit insane Wallace's army looked with their faces painted blue?
Well, the Celts would sometimes paint themselves blue and fight completely naked. Just because. One would assume that fighting in the nude would present some rather sensitive targets to one's enemies (we're talking about their nuts), but it seems that the Celts were so frigging manly that they just didn't care. It was the ultimate insult: "I am not afraid of you, and to prove it, I have just laid my dong on your sword."
You remember Temple of Doom, and how that unfortunate gentleman had his heart ripped out right before they dropped him down the lava hole? Well, picture lots of that, only this time mom isn't around to turn off the VCR and stop your crying. That's the Aztecs.
The Aztecs believed that for every 52 years that passed, the world would end unless the gods were strong enough. And, as is common knowledge, the best way to toughen up a god is with a steady stream of constant human sacrifice (along with a dash of cannibalism, just for good measure).
Most of the sacrificing went towards keeping their Sun god happy, and it took place on top of giant pyramid, so at least the view was probably pretty good. Then they'd hold you down, saw through your ribs and take out your heart (which was likely still beating). Then, as if things couldn't get any worse, they'd throw you down the staircase.
So, Were They Really So Bad?
Yes. Yes they were. Did we mention the cannibalism? After they removed your heart and threw you down the stairs, they'd eat your arms and thighs, and whatever other bits looked tasty (the nuts? We do not know).
Some historians think that nourishment was the main reason behind all of this willy-nilly human sacrifice, as the Aztecs had no domesticated animals to slaughter, and as such their diet was low in fat and animal-stuff. You know how it is if you've ever had a roommate try a vegetarian diet. It's just a matter of time until you start waking up with teeth marks on your extremities.
And that's not even the bad part. The Aztecs held themselves to a high standard and for every situation they asked, "Could we make this more gut-wrenchingly gruesome?" So, for instance, during the sacrifice to the fire god, a newly-wed couple would be tossed into, you guessed it, a fire. Then, right before they finally died (from their horrendous burns), they'd drag them out, flesh still smoking, and dig out their hearts.
Wait, it gets better! There was the offering to the earth goddess, which involved a young woman's skin being removed and worn around like a Silence of the Lambs-style serial killer flesh suit.
On one hand you might ask why none of the Aztecs thought this was odd. On the other hand, if somebody had an objection to the ceremonies we're guessing they kept that shit to themselves.