The only thing we don't know is who they were.

That is, we have no idea what race they were, or what they actually looked like. Mummies of any screed tend to revert to a racially homogenous shade of dirt brown after a few thousand years baking in the desert heat.

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Most people probably imagine the ancient Egyptians as being vaguely Middle Eastern in appearance, because that's how they're portrayed in the movies (you know, when they aren't being played by straight-up white dudes). However, that's just how they've looked since the Persian conquest of Egypt ... which was thousands of years after the people who actually built the pyramids died. Before that, it's anyone's guess.

You see, in the mid-1800s (when Egypt-mania really took off in the Western world), white people who marveled at these giant ancient constructs applied their strongest racist science and assumed the Egyptians were pasty Aryan Europeans, specifically because only white people could have the technical ability to build the pyramids. Others theorized that they were black, due to the fact that Egypt is, you know, in Africa.

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"But what about the thousands of ancient Egyptian paintings we've found?" you might be thinking. "Surely we can look at those and know the skin tone of the mighty Pharaohs!" Well, if you were thinking that, you're wrong again. Egyptian paintings were heavily stylized, with men often portrayed as red and women as bright yellow, which, discounting severe sunburn and/or jaundice, aren't really shades that human beings come in.

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Greek sources refer to the Egyptians as being "dark-skinned" and "curly-haired," which is sort of helpful in the sense that it lets us know that they probably didn't look like Jackie Chan, but otherwise could mean they were anything from black to Semitic to Italian.

The closest thing that science has to a conclusion is that the Egyptians probably emerged from northern Africa, which, as you may have noticed, is where Egypt is located. So we've got a rough idea, but only in the sense that Dwayne "The Rock" Johnson and Arnold Vosloo are equally believable as ancient Egyptian princes.

People were surprisingly good at moving giant stones around in ancient times, mostly because living in the Stone Age gave you little other choice. And despite the History Channel's dogged insistence that Stonehenge and the Great Pyramid could only have been built by extraterrestrials, the truth is that science actually has some pretty good ideas about how regular human beings were able to put those awe-inspiring structures together.

But then there are the Olmec colossal heads, and we're not talking about the magical storytelling dome on Legends of the Hidden Temple.

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That's one of the giant stone heads carved by the Olmec civilization in Central America, and archaeologists don't know what the hell their deal is.

The Olmecs are thought to be the oldest civilization in the Americas, predating the better-known trinity of the Incas, the Mayas, and the Aztecs by hundreds of years. Daily life in the Olmec civilization was presumably pretty boring, as they came to the same conclusion as the folks half a world away on Easter Island did and decided that they might as well dedicate all of their idle time to carving giant stone heads.

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Cutting a person's face into a giant piece of rock isn't exactly beyond the realm of possibility, but check this out -- the Olmec heads are carved from volcanic basalt, which was located 80 miles from where the Olmec ultimately settled. Each head weighs close to 20 tons, and the Olmecs never got around to inventing the wheel. So the question is, how in the hell did they get those immense rocks through 80 miles of sweltering, hostile jungle?

Before you say "Well, obviously the same way the Egyptians did it," consider this -- dragging slabs of impossible weight across a desert is an entirely different word problem than figuring out how to carry a bunch of stones each weighing approximately the same amount as Optimus Prime across 80 miles of dense foliage, spiders, snakes, and the occasional 150-foot plateau. The same techniques just wouldn't work.

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Modern science still doesn't know how or why the Olmecs dedicated such a huge amount of effort into dragging these massive heads through such impassable terrain, outside of maybe some ancient, oversized game of long-distance bowling.

We'd like to tell you more about them, but the modern world's knowledge of the subterranean caves of Chinese mystery begins and ends with that single fact. We literally know nothing else about them.

There are no documents whatsoever, at least none that have been discovered, that record the construction or purpose of the Longyou Caves, although the excavation would have been an immense, government-contracted project involving the movement of 900,000 cubic meters of rock. This is especially odd considering the ancient Chinese were meticulous record-keepers. That's one of the reasons why the Great Wall is about as much of a mystery as the Chrysler Building -- there are documents telling us exactly who built it and for what purpose. However, nothing like that exists for the three dozen caves buried beneath the area on the outskirts of Shanghai. For all we know, a wizard put them there one year to heighten the suspense of an Easter egg hunt.

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We know that they're not natural formations, because the interior of the caves are covered in chisel marks, and it contains stairs, support columns, and paintings, which generally aren't the result of tectonic shifts. But for whatever reason, this huge and very expensive project had been kept top secret until its accidental rediscovery in the early-1990s. They could be a clandestine series of burial chambers for an elite Chinese family, or they could be strategically placed man caves dug for the wealthiest man in Shanghai to hide from his family and play the ancient Chinese equivalent of NFL Blitz. There is precisely the same amount of evidence to support either scenario.

Anyway, the Etruscans were a small civilization from modern-day Tuscany who basically invented aqueducts, city planning, sewers, bridges, and metallurgy. Basically, all the things that we mistakenly attribute to Rome, because the Romans took everything and slapped their own watermark on it like an ancient eBaum's World. But although modern scholars might look to the Etruscans as one of the most influential and important civilizations in history, there's one major roadblock to finding out their secrets (doubly ironic because roads are another thing the Etruscans invented): We have never been able to completely decipher their language.

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The big problem with decoding ancient extinct languages is that, well, nobody speaks them anymore. You can't exactly hire a translator. In most cases, the translation has already been done for us by people who lived at the time -- most famously, modern researchers were able to translate Egyptian hieroglyphs thanks to the discovery of the Rosetta Stone, a convenient Egyptian-to-Greek travel dictionary created because King Ptolemy V wanted to simulcast one of his decrees in three different languages. No such luck with the Etruscans -- although they wrote prolifically, none of those writings were ever translated by any other civilization in any way that has survived. The closest we have is the Pyrgi Tablets, which only contained a handful of Etruscan words translated into Phoenician. Again, we have the Romans to thank -- when the Roman Empire sprang up and absorbed the Etruscans, they didn't bother to preserve their language.

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As a result, we have about a thousand inscriptions from the Etruscan civilization, but only about a hundred words have ever been deciphered. Dothraki has more words than that, and that is a language we invented for a television show.

The first place to face the wrath of the mysterious invaders was Anatolia, in what is now modern-day Turkey. By all accounts, Anatolia was one of the most powerful areas in the Mediterranean, which is why the king of the Anatolian city Ugarit was understandably taken aback and more than a little spooked when emissaries from a neighboring king, Suppiluliuma, arrived with a desperate plea for assistance against a band of unknown attackers.

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Ugarit sent their own military to help ward off the mysterious aggressors, but even that wasn't enough. The Sea Peoples burned Suppiluliuma's city to the ground, then pulled up their sea-sleeves and marched to Ugarit to burn it to the ground as well, all before disappearing back into their undersea kingdom.

A few years later, the same thing happened to Kadesh, a major trading center in modern-day Syria. After that, they continued to burn their way through the cradle of civilization to such a violent extent that they wound up reshaping the landscape of the ancient world. Eventually, though, they got cocky and attacked Egypt, which went about as well for them as the Nazi invasion of Russia. The Egyptians were the only nation powerful enough to stand up to the Sea Peoples, but that's not to say the mysterious ocean ravagers didn't put up one hell of a fight -- after two massive invasion attempts with heavy losses on both sides, the Sea Peoples finally decided to eat some crow and slinked away (again, presumably back to Atlantis).

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But who were these invaders who managed to walk over the most powerful civilizations on Earth like the aliens in Independence Day? Well, scholars think they might have come from Europe, or the Balkans, or Asia Minor, or f*****g New Jersey for all anyone knows. The problem is that the only human beings to ever meet the Sea Peoples were too busy being stabbed and set on fire to ask them where they came from and what the hell they were after.

The whole thing seems eerily like "The Doom That Came to Sarnath," a story by H.P. Lovecraft about an underwater civilization of lizard people who tear down the most powerful city in the world on the eve of its 1,000th anniversary. Considering the fact that nobody knows who the Sea People were or any land they could have come from, and their sole motive seemed to be the destruction of all the greatest cities of mankind, the "Lovecraftian horror beasts" theory is as good an explanation as any.

For more things science is clueless about, check out 6 Things Your Body Does Every Day That Science Can't Explain and 6 Insane Discoveries That Science Can't Explain.

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