Mysterious Fossils Science Still Can't Explain

Countless science fiction stories revolve around life on Mars, and more than a few pseudo-scientists have found "proof" of life in odd Martian rock formations and camera glitches. But scientists take possible life on Mars seriously, and actually might have proof in the mysterious meteorite known as ALH84001.

The little meteor fell to Earth in 1984 and seemed like an interesting, albeit normal, meteor sample. With more study, scientists came to a shocking conclusion: The meteor was from Mars and was 4.1 billion years old. It was blown off the planet during a collision and traveled space since then, finally coming down to Earth. Even more shockingly, it had what looked like features of fossilized bacteria in it. Overnight, ALH84001 became the most famous meteor on Earth.

Since then, scientists have debated the nature of the rock. Sure, it looks like there are bacteria embedded in it, but further study has proven inconclusive. It could just be remnants of mineral structures found on Mars all those years ago, or a fluke of geologic formation. What makes ALH84001 so amazing is that, even after 30 years of study, it's still a mystery. Scientists still take it very seriously, with groups even proposing that ALH84001 provides evidence that the moon and other worlds could be "littered with fossils" knocked away from Earth by asteroid collisions. Possibly, the planets are constantly trading rocks through this mechanism, and maybe even trading life as well.

Discovered in 1955 by collector Francis Tully, the first Tully Monster fossil completely defied explanation. Paleontologists eagerly attempted to place the fossil within well-known classifications, but nobody could figure out what the "monster" was actually related to.

Looking at reproductions of the monster show why it was so confusing. The main part of the creature had a body like a cuttlefish, with vertical fins sticking off the top. It had no bones in its body, but could keep a rigid shape like mollusks or worms do. Eye pods stuck out from the sides of the body. Most unusually, the monster had a long, segmented proboscis with a "head" on the end. Unlike the proboscis found on animals like butterflies, the Tully Monster's proboscis ended in a set of jaws with teeth. Adding it all up, the Tully Monster looked like something a child would draw.

When trying to set it into classification, researchers were completely stumped about where it fit. They thought it might be related to a worm, mollusk, arthropod, or a conodont. Unfortunately, all those classifications are unrelated to each other. Finally, some samples showed up with a rudimentary spinal cord, letting researchers know that they could at least classify it as an early vertebrate. Aside from that, the Tully Monster remains a baffling evolutionary turn in our planet's history. Researchers are still trying to decide how it evolved and what place it held in the prehistoric ecosystem.

The Klerksdorp Spheres were first discovered in Ottosdal, South Africa, during mineral deposit excavations. The spheres became an intense curiosity among the miners and geologists as more cropped up during the dig. As the name suggests, they're spherical in shape and made out of an extremely hard mixture of metals. Most of the spheres have a groove running around their equator. These spheres' grooves date back to 3 million B.C., which quickly led to conspiracy theories about ancient aliens or highly advanced prehistoric civilizations. The spheres just seemed too perfect for any natural process. Ancient-astronaut theorists quickly latched on to the story and speculated that these were out-of-place artifacts left by aliens.

Of course, party-pooper geologists were quick to shoot down the idea. They pointed out that the fossils could have occurred due to natural volcanic activity. Certain types of volcanic metals are apt to form spherical shapes, and weather could have created the equatorial groves. Geologists point out that spherical rocks are not uncommon, but conspiracy theorists hold onto the idea that the spheres are part of the fossil record of ancient alien contact with the Earth.

Honestly, neither group has an airtight theory about the spheres' origin. Geologists have remained skeptical but have not yet come up with a solid explanation, and ancient-alien conspiracists still cannot explain why aliens would come down to Earth just to scatter metal spheres all over South Africa. That's an awful long route to travel just to relieve boredom.

Discovering new ancestors of modern humans is always fascinating, but sometimes completely baffling. When an Australian-Indonesian team discovered the fossils of a small hominid in 2003, they realized they would open new mysteries and questions about the human family. Indeed, their discovery, named Homo floresiensis, has forced researchers to rethink the human family history and the place of modern humans in it.

The hominid was diminutive, with samples averaging only a little over 3 feet tall, with big feet. Researchers began calling them Hobbits, which caused the Tolkien estate to threaten legal proceedings. Still, the nickname persisted, because what else are you going to call them?

So far, Homo floresiensis has only been found on one island in Indonesia, and records indicate they lived as recently as 50,000 years ago. Since the Hobbits are so close in the timeline to our own species, researchers are utterly baffled by them. Some contend that it's a totally separate species from humans, meaning Homo sapiens were not the only hominid species inhabiting the planet back in ancient times. This completely flies in the face of the old consensus that Homo sapiens were the only hominid species remaining when they took over the world. Others believe that the Hobbits were actually Homo sapiens who settled on Indonesia and, over centuries of inbreeding, developed dwarfism. Oddly, it seems like the second option has captured more steam among researchers, though if anybody digs up a shiny gold ring and dubs it their precious, all bets are off.

Most people don't think of Idaho as a hotspot for archaeological mysteries, but it's actually the home of a mysterious figure that remains unexplained. The figure was dug up in 1889 when workers were digging a well in Nampa, right outside Boise. Resembling a human doll but made of stone and clay, the figure was buried 320 feet below the surface of the Earth. Finding a stone doll is weird enough — finding it that deep is a spine-tingling mystery.

The rock around the doll dated to 2 million years ago, far before any hominid made it to Idaho. This was also millions of years before Homo sapiens or comparable species walked the Earth, period. Paleontologists believe only Homo sapiens have the ability for this sort of workmanship, but they only appeared 200,000 years ago. Here is a stone doll that was at least a million and a half years older, with ornate designs that were clearly carved by hand. The right arm is even cemented to the doll, showing clear signs of artistic workmanship. This was certainly created by ancient humans who should not have existed at the time.

So, how did it get in the rock? Of course, skeptics have proposed a variety of mechanisms, including that it's fake. If it is evidence of ancient humans in Idaho, it would completely rewrite the evolutionary timeline of humanity, showing that Homo sapiens — or a currently unknown, comparable species — existed way before we expected it. (It could also just be a fake.)

Everyone knows that the dinosaurs died out from a giant asteroid collision, but few people know that the dinosaur extinction was not the only — or even the worst — mass extinction that our planet faced. There have been five, with the largest being the end-Permian event, which happened 252 million years ago. It is also the most mysterious. Fossil records show that 95% of all marine species and 75% of all terrestrial species went extinct during the event. The biodiversity loss was catastrophic, and it took millions of years to get back to pre-extinction levels.

But here's the weirdest part: Nobody knows why it happened. You'd think that such a traumatic event in the Earth's history would leave pretty definitive clues about what caused it, but that's not the case. For years, scientists have struggled to figure out why so many species died, seemingly out of nowhere. One leading theory is that intense global warming caused the extinction, leading to wide-scale ocean acidification that was absolutely deadly to marine life.

But other theories are much more exciting. Geologist Gregory Retallack has discovered microscopic fractures in quartz crystals that date from the time of the extinction, implying that some sort of massive force shook the Earth. According to Retallack, it could have been an asteroid collision, just like with the dinosaurs. An even more exotic theory held by many scientists is that coal in Canada and basalt in Siberia might have blown up out of nowhere, causing a huge ash cloud and making almost all life on Earth go extinct.

The late 1800s is known within paleontology as the time of the Bone Wars, when rival scientists Othniel Charles Marsh and Edward Drinker Cope engaged in a fierce and bitter contest to find and classify as many new fossils as possible. The two men spent fortunes on expeditions to the American West — expeditions prepared to sabotage the other side.

Out of the Bone Wars came the discovery of what Cope named Amphicoelias fragillimus, a long-necked dinosaur related to the genus Diplodocus. Cope described A. fragillimus from a single, incomplete vertebra found somewhere near Cañon City, Colorado. The fragment was measured at almost 5 feet tall, which would make the complete bone 8.5 feet and belonging to an animal 190 feet long (per FiveThirtyEight). Based on that, A. fragillimus has been proposed as not only the largest dinosaur, but the largest known animal to have ever lived next to the blue whale, according to Annals of Carnegie Museum.

But that's assuming the bone was that big, and A. fragillimus really was a diplodocid. Some paleontologists suspect Cope invented the find to get one up on Marsh, though Marsh, never shy on such matters, never challenged it. Others think Cope made a mistake in his measurements. It's recently been reclassified and renamed Maraapunisaurus, with a smaller size estimate. But with the only known bone lost since Cope's time, and no others discovered since, nothing can be said for certain. What even happened to the vertebra is a mystery itself, though it may have simply crumbled away.

Paleontology has a large number of what are known as "problematica", fossils that cannot be confidently identified or placed on the tree of life. Whether it's on account of incomplete remains or unusual features that defy easy classification, these plants and animals fill the drawers of museums, awaiting answers.

Many problematica come from very early in the history of life, when a large number of organisms unlike anything alive today existed. There's an entire category designed for such fossils: acritarchs. According to the geosciences department of the University College London, the term "acritarch" was first coined in 1963. Literally translated as "of uncertain origin," acritarch is a catch-all for microscopic fossils that don't fit anywhere else in the evolutionary chain.

It's been suggested that acritarchs represent stages of growth, or organic material discarded from single-cell plants and animals. Whatever they are, the oldest of them date back to 1900 million years ago. Their fossils are some of the earliest records of life.

[Featured image by John A. Cunningham, Kelly Vargas, Zongjun Yin, Stefan Bengtson and Philip C. J. Donoghue via Wikimedia Commons | Cropped and scaled | CC BY 3.0 ]

Among the most prized sources of fossils in the world, particularly from the Cambrian period, is the Burgess Shale of British Columbia. First observed scientifically by paleontologist Charles Walcott in 1907, it's the place where many microfossils have been found and described, including a large number of problematica.

Among the organisms found in the Burgess Shale is Dinomischus, first described in 1977 from a fossil Walcott found decades earlier. To look at it, Dinomischus seems like a flower. But it is an animal, though what kind has been an open question since it was named. We know that it was a species that attached itself to the seafloor and filtered food from the water through the ring around its mouth. Linking to a specific group is frustrated by its superficial similarities to a number of still-living species.

The closest known relative of Dinomischus may not be an extant animal, but another fossil. In 2012, PLOS One (via PubMed Central) published findings from a Canadian team on another stalked filter feeder, Siphusauctum gregarium. Its best match in the known fossil record was Dinomischus. But the two animals' resemblance to one another doesn't help place either one of them confidently in the evolutionary chain. Even the traits they share aren't enough to conclusively prove that they're related.

[Featured image by Lorna J. O'Brien, Jean-Bernard Caron via Wikimedia Commons | Cropped and scaled | CC BY 4.0]

Some fossil sites hold more than one specimen in their rocks. One such site gave its name to a preserve, the Berlin-Ichthyosaur State Park in Nevada. There, multiple skeletons of Shonisaurus, Triassic marine reptiles that somewhat resemble modern-day dolphins, have been found together in one of the park's quarries. The first collection of Shonisaurus at the site was found in the 1950s, and later research in 2014 found repeat gatherings at the same location spanning thousands of years.

Since the first mass find, paleontologists have wondered why so many Shonisaurus died together. Adding to the mystery was the seeming absence of any juvenile animals; all the known fossils were adults, and Shonisaurus was the only species found in the area. Theories have ranged from toxic algae blooms to the reptiles becoming stranded on land en masse. What is now Berlin-Ichthyosaur was then a shallow area of the ocean, and the Shonisaurus could have ended up beached like modern whales.

A study published in Current Biology in 2022 (via The New York Times) examined the rocks the fossils were found in and seemed to rule both causes out. Looking through the bones, the research team found the remains of embryos and newborn Shonisaurus. Based on this, the team suggested the spot was a birthing site. But while this study seemed to explain why the Shonisaurus were there en masse, it still doesn't explain why multiple gatherings died together over millennia.

[Featured image by Kenneth Carpenter via Wikimedia Commons | Cropped and scaled | CC BY-SA 4.0] 

Bats have an unearned sinister reputation. They're handy pollinators and good at pest control. But they are nocturnal animals, often unseen by humans, and that can attract an air of fear and mystery. For paleontologists, bats are mysterious for another reason: They don't know where they came from.

The oldest bat fossils date to around 50 million years ago. Extinct bat species have been uncovered in the Americas, Europe, Asia, and Australia. These fossils have helped scientists track the evolution of bats over time and observe how they developed echolocation and lost the claws on their wings. But every bat fossil known is unmistakably a fully formed bat. The fossils that would represent their immediate predecessor species have never been found.

Bats aren't the only species for which the fossil record has long hidden their ancestry. Whales, birds, and turtles all seemed to turn up without explanation. But fossil discoveries in the 1990s and early 2000s filled in the evolutionary gaps for all three families. Many bats live in forests, which rarely provide ideal conditions for fossilization; if bat ancestors lived in the same environments, that might explain the gap in the fossil record. Professor Emily Brown told the Smithsonian that the hunt for bat ancestors would best be conducted at sites that were once lake beds around the time the dinosaurs went extinct. There, stray animals might have been trapped in mud and been properly preserved.