One minute, a person can look around them and think, Hey, this makes a lot of sense. After all, there are plenty of times where everything lines up and all of the pieces fall neatly into place. But while people often like to think they know everything, that couldn’t be further from the truth.

See, for every fact or artifact humanity has uncovered, there are dozens more waiting to be revealed. Case in point: these 10 discoveries were hiding in plain sight for thousands (if not millions) of years, but they were only recently discovered—and they’re turning our view of the world upside down.

1. In 1938, archaeologists reportedly discovered an ancient burial cave deep in the Himalayas. The walls were full of pictures depicting the sky and the stars, suggesting a shocking level of cosmic and scientific awareness. That wasn’t the craziest find, though.

Nat Geo

Using radiocarbon analysis, scientists concluded that humans inhabited the caves as far back as 11 million years ago. They also found 716 stone discs, now called dropa stones, that were each marked with an intricate series of unreadable hieroglyphs.

At the same site, they also found the remains of a race of people with abnormally small bodies and large heads. They resembled no other known humans and their origin remains a mystery to this day. Some speculate they were aliens!

 2. In 1936, a married couple traveling around London, Texas, found this strange piece of rock connected to a smooth wooden handle. It was, in fact, an iron hammer, but scientists were still baffled—and for a good reason.

Glen J. Kuban

Radiocarbon analysis allegedly revealed it was roughly 500 million years old. Incredibly, not only did the object—known today as “The London Hammer”—predate what we thought were the earliest humans, but it showed no traces of rust.

3. In 1513, Ottoman admiral and lover of maps Hadji Muhiddin Piri Ibn Hadji Mehmed, better known as Piri Reis, compiled a map of the world for the purposes of sea travel and military expeditions. Though only a third of it survived, it was amazingly accurate… which raised some questions.

Scientists claim that such a detailed map would be impossible without satellite imagery. So how did Piri Reis manage it? Some speculate he synthesized well over 20 maps into one.

Library of Topkapi Palace Museum, No. H 1824

4. In the 1930s, anthropologists discovered the Dogon tribe, a group of about half a million people located in West Africa’s Burkina Faso. They were almost completely cut off from the rest of the world, but they had a rich culture full of rituals and legends. For example…

The Dogon claimed that, in ancient times, a race of extraterrestrial creatures visited the Earth to tell them that they originated from the star Sirius B, which they called Paul Tolo. How wild is that?

J. Drevet / Wikimedia

5. In 1912, Wilfred Voynich, a dealer of rare books, purchased what became known as the Voynich Manuscript and brought it to the public’s attention. The book covered different scientific topics from herbs to cosmology, but something about it puzzled everyone…

Strangely, despite clear drawings and depictions, the book wasn’t written in any known human language. Those who’ve tried decoding it have suggested everything from forgery to Latin shorthand, but the truth remained a mystery.

6. Discovered in 1900 in a shipwreck off the Greek coast, the Antikythera navigator featured an intricate series of bronze discs that determined astrological cycles and tracked the stars in the sky as well as the Olympic Games cycle. What does that mean, you say?

Well, it means the Antikythera navigator was a sort of analog “computer!” Best estimates say it originated in 100 B.C.E., which was 16 centuries before Galileo’s groundbreaking discoveries—and 1,000 years before other complex devices just like it.

7. A 2012 excavation of Montana’s Dawson County revealed this triceratops horn, which was then given to the University of Georgia for radiocarbon analysis. There, scientists estimated that it was only 35,000 years old—and that made them pause.

Dinosaurs were generally believed to have died 65 million years ago. The discovery of this horn, then, suggested that if this triceratops lived 35,000 years ago, it could have lived among humans!

sabreguy29 / Flickr

8. The aboriginal Zuni tribe lived in what is now New Mexico over 4,000 years ago. Their language stumped linguists, as it didn’t resemble any other local dialect. In fact, it shared similarities with a language based very, very far away…

That language? Japanese! Even more amazingly, modern Japanese people can even understand bits and pieces of the Zuni language. How did the roots of Japanese make it to the Americas—or vice-versa?

9. Archaeologists in the Mexican Toluca Valley discovered this terra cotta head statue—eventually called the Tecaxic-Calixtlahuaca head—in 1933. Evidence suggested it’d been buried in about 1500 A.D. The strange part?

Carbon dating placed the head’s origins between the ninth and thirteenth century B.C.E. Stranger, it’s consistent with Roman architecture, like the terra cotta head of Dionysus seen below—so how did it end up in Mexico City?

Metropolitan Museum of Art

10. The 80-ton boulder known as the Los Lunas Decalogue Stone was found in 1933 on a hillside in Los Lunas, New Mexico. When archeologists wiped away the moss on the boulder, they found Hebrew inscriptions. But that only generated more questions…

Brainardo / Wikimedia

For instance, studies estimated that the stone was anywhere between 500 and 2,000 years old, long before Hebrew found its way to the Americas. So how did a 160,000-pound boulder make it across the Pacific Ocean? And why?

Sarah Heidt / YouTube

Unfortunately, we may never learn the answers to these strange artifacts, but don’t fret. In truth, that only makes these historical mysteries even more fascinating!

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