1. While digging a new subway station, something caught Francisco’s eye

Under a city block mere feet away from a busy Los Angeles intersection, Francisco Palacios stood in a large underground cavern. The ceiling was made up of a series of pipes while the artificial bright white lights attempted to illuminate the mounds of dirt all around him.

Los Angeles Purple Line excavation station
Image by Steve Hymon/LA Metro

Huge earthmoving machines (bulldozers, excavators, and the like) moved around the cavern, carting dirt from one place to another. As Palacios was watching the machines dig, something intriguing caught his eye. He waved to the excavator’s operator, gesturing from his eyes to the wall. The operator lifted his own hands over his head; it was now safe for Palacios to get a closer look.

2. This find was big, much bigger than the usual fossil

In the cavern, the machines were so loud that people were shouting just to be heard. And to be seen, Palacios was dressed in neon yellow and orange with a white hard hat. Once the machine operator had his hands in the air, Palacios knew it was safe to get a closer look to where it was digging.

Purple Line construction LA Metro
Image by Steve Hymon/LA Metro

On his knees, he brushed some dirt off the object and got a shovel to uncover it further. This was a big find. He may not have known exactly what the thing was, but he knew it was important enough to call in the lead paleontologist.

3. In most other states, this would never have been found

If this dig were happening in any other state, the monitors and paleontologists may have never found what was lost thousands of years ago. Unlike many other states, California has strict environmental laws that require scientists to be involved in construction like this.

Purple line los angeles metro fossil find expansion
Image by Visitor7/Wikimedia Commons

So what were these construction workers doing digging under the city? They were carving out a new subway station. Los Angeles is known for its car-heavy culture and monstrous traffic, but the City Council is aiming to change that by 2035. They already have several rail lines, but this dig was part of an effort to expand their underground Purple Line.

4. The excavation was part of LA’s work to expand their subway system

Los Angeles is one of the largest cities in the country; its population is second only to New York City but it sprawls out 150 square miles more than NYC. As such, it’s a huge task to build a subway system comprehensive enough for everyone to be able to get where they need to go.

Los Angeles subway system map extension
Image by Shannon1/Wikipedia — cropped from original

The county is working to expand its existing subway system. For the Purple Line, the plan is to extend it out of downtown and west toward Beverly Hills. But while digging out new stations, the construction crew and monitors found something very unexpected. Of course, this was exactly why they had paleontologists on staff.

5. California’s laws required a paleontologist be present to look for fossils

Due to California’s environmental laws, fossils and artifacts must be preserved when possible. Before beginning the ambitious subway expansion, the Los Angeles Metro knew there was a chance they might find fossils during their digs; the excavation’s location and depth were just right for it. Finding small fossils isn’t a big surprise with these projects, but something much larger and menacing? Absolutely.

Image by LA Metro

To abide by this rule, the LA Metro hired Cogstone Resource Management to accompany them on the Purple Line project. Cogstone employs experts in paleontology, archaeology, and history. They can be hired to make sure any project meets California’s requirements. It was a Cogstone employee who truly felt the importance of what workers were about to discover under Los Angeles.

6. Francisco called in paleontologist Ashley Leger to identify the big find

After monitor Francisco Palacios found what he thought was a fossil, he called paleontologist Dr. Ashley Leger to the scene. She had been working with Cogstone on the Purple Line project for several months at this point, but this was when things got really interesting.

LA Metro fossil excavation discovery
Image by LA Metro

Earlier in the year and very shortly after earning her Ph.D, an old acquaintance of Leger’s had called her and offered her the position. Soon after, she packed up and moved from South Dakota all the way to Los Angeles. After many years of looking in South Dakota, Leger had no idea she was going to find exactly what she wanted in California.

7. The fossil was most likely from the last Ice Age

Ashley Leger was perfect for this job because she got her degree in Pleistocene megafauna, which was the large animals that lived between 2.6 million years ago and 11,700 years ago (think the last Ice Age). Los Angeles, in particular, is a treasure trove for Pleistocene fossils.

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The shallower ground under Los Angeles, at about 20 feet below the surface, is from this time period. So because of that, the scientists expected that many of the fossils found during the Purple Line project would be from the last Ice Age, aka during the Pleistocene Epoch. Leger had spent the past ten years or so preparing for this dig.

8. L.A. didn’t look how you would think during the last Ice Age…

In order to understand what they might find, paleontologists like to know about the location’s past environment and climate. While the term “Ice Age” normally brings up mental images of glaciers, snow, and animals covered in thick fur, Los Angeles is southern enough that the land was lush and green some 11,000 years ago.

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As a result, Los Angeles didn’t have woolly mammoths roaming its lands. Instead of a metropolis, grasses, trees, and streams covered the land back then. And while life flourished in this Southern California haven, something in the middle of it all continuously killed animals, plants, and other living things.

9. Unexpectedly, this fossil was not discovered in the Tar Pits

Los Angeles is home to the most extensive Pleistocene fossil site in the world because of the black, sticky tar pits in the middle of it. Countless animals and plants found themselves stuck in the unforgiving asphalt over the last 50,000 years. While it was an unlucky end for those trapped in the viscous goop, it was lucky for today’s scientists.

La Brea tar pits ice age fossils
Image by atlantic-kid/iStock

Excavating the pits has taught paleontologists a whole lot about the Ice Age because it’s almost like an entire ecosystem was preserved in the asphalt. So when LA Metro began excavating for the Purple Line, Leger imagined they would find the most fossils near the Tar Pits. That turned out to not be the case at all.

10. The excavators are finding fossils in the subway stations, but not tunnels

In accordance with California’s laws, the Los Angeles Metro is making sure to keep a lookout for any fossils buried in their excavation sites. However, this isn’t really possible in the newly renovated subway tunnels because the digging machines completely carve up everything in their path.

Los Angeles purple line extension fossil discovery
Image by Mark Boster/Los Angeles Times via Getty Images

Luckily, the tunnels are deep enough that there are few fossils to find in them. At that point in geologic time, Los Angeles was completely under water. So where is LA Metro discovering remnants of the past? In the subway stations, which they are digging out a little closer to the surface. It’s here that they found something spectacular.

11. Francisco was a monitor trained to spot fossils

Francisco Palacios and the other monitors were trained to spot fossils. A monitor will stand by and watch as someone else works the earthmoving machine. Often, they find fossils when the machine hits the bone or rock cast, which is much harder than the sediment around it.

Los Angeles metro station extension
Image by LA Metro

The fossils have a distinct color and texture to them, which helps people distinguish them from their surroundings. Sometimes, the fossils are entirely contained in a scoop of dirt, so the monitors have to check the discarded piles as well. Palacios was watching the excavation closely the day they made the big discovery.

12. Ashley tried to not get her hopes up too much as she went to the site

Late one night, Ashley Leger got the message: “I’ve got fossils and they’re big. I’m going to need help.” Without getting her hopes up too much, Leger got to the excavation site early the next morning, curious about what she’d find.

Purple line LA Metro extension fossil discovery
Image by Mark Boster/Los Angeles Times via Getty Images

She donned her hard hat and neon vest, then walked into the cavernous station. Once she got to the fossil discovery site, Leger looked at the exposed portion to get a better understanding of what they found. Based on the texture and flat areas of the bone, Leger had a pretty good idea of what she was looking at.

13. Ashley was pretty certain she knew what it was as they continued to uncover the fossil

“My first thought was: Oh my gosh, this looks like skull material,” Leger said. While she couldn’t be 100 percent sure about what kind of bone it was until it was completely uncovered, Leger had a feeling she knew. She had spent the last 10 years studying this and she had a Ph.D. on this particular animal.

Image by LA Metro

They started digging and uncovered more of the bone. Pausing for a moment, Leger looked at the fossil in front of her and then at the surrounding dirt. She pointed to a different spot nearby and directed the monitor working with her to dig there. If this fossil was what she thought it was, they’d find something special there.

14. The fossil find was a dream come true for Ashley

As Leger and the team dug, they soon uncovered the pointed tip of a fossil. Leger was extremely excited by this point. She knew what this was; she’d spent many years studying this very animal bone. So she pointed to another spot and said, dig over there.

Excavating mammoth skull Los Angeles subway
Image by LA Metro

After a little bit of dirt and grime, the team uncovered another pointed fossil tip. This was it. The big find. “It’s a dream come true for a paleontologist,” Leger later said to CBS News. “This is the bucket list you always want to find at some point in your career and then it’s one of the first things we found here.”

15. They found a nearly completely intact mammoth skull

After about 15 hours, Ashley Leger and her team finally dug out the almost completely intact skull of a juvenile Columbian mammoth. “That was the most exciting day I have ever had,” Leger said. She may have had dirt on her face, but she was the happiest she could be.

Mammoth skull Los Angeles subway Metro
Image by LA Metro

Leger’s degree was specifically in Columbian mammoths, so finding such a rare, complete skull was a total dream come true. And while most fossils are actually natural rock casts, this one was the real bone. It was the skull of a young mammoth, somewhere between six and 12 years old (they normally lived about 65 years).

16. Columbian mammoths were larger than woolly mammoths

Columbian mammoths are related to the equally extinct woolly mammoths. But while the woolly species lived in the frozen plains of the Eurasian Arctic, the Columbian mammoths lived in warmer climates of North America. As such, the Columbian mammoths didn’t have thick fur, but instead looked like very large elephants.

Columbian mammoth los angeles fossil discovery
Image by National Park Service

Contrary to most people’s perceptions, woolly mammoths were about the same size as today’s African elephants. Columbian mammoths, on the other hand, were huge. You’d have to be on the second floor of a building to touch its head. A woolly mammoth could walk under an average male Columbian mammoth’s chin.

17. They named the young mammoth Hayden

The young Columbian mammoth was named Hayden, after the actress Hayden Panettiere (from Nashville and Heroes); she’d been on TV shortly before they found the mammoth skull. The mammoth was found face up. The top part of her skull was crushed and rest of her skeleton was nowhere to be found.

Columbian mammoth skeleton cast pleistocene epoch
Image by James St. John/Flickr

It’s very common to find mammoth skulls with the top portion broken because the area below is actually hollow. The larger skull allows for more muscle attachment, but to compensate for the tusks’ weight, the top section is hollow. This adaptation keeps the mammoth’s skull from being too heavy to hold up.

18. It’s unclear how Hayden died thousands of years ago

It’s unclear how Hayden the Columbian mammoth died, especially since the rest of her skeleton was not found in the dig. While the skull itself showed no indication of a predator killing her, it’s still possible that a sabertooth cat or dire wolf took her down. Skulls don’t have much meat on them, so a predator may have ignored it.

La brea tar pits mammoth sculpture
Image by stevezmina1/iStock

It’s also possible that Hayden was sick or stuck in a mud pit. “For animals to preserve, they have to die somewhere where they’re buried fast and exposed to low oxygen conditions,” Leger said. So the least we know is that Hayden’s skull was quickly buried in water and sediment while the rest of her body was not. Perhaps a predator carried it off.

19. The team put plaster on the skull and took it to their lab

Once the team found the mammoth skull, they had a lot of work left to do. Whenever they find fossils, they take notes on where it was found and its condition. With the mammoth skull, they put a plaster jacket on it to keep it from breaking in transit.

Los angeles natural history museum
Image by David Leigh Ellis/Flickr

Hayden was taken to a nearby lab. The skull will be cleaned off and then eventually it’ll be given to the Los Angeles Natural History Museum. All the fossils found in this excavation (that weren’t in asphalt) will be donated to that museum. There, the people of Los Angeles will be able to see the animals that used to live in their very own city.

20. Hayden wasn’t the only fossil they found during the excavation

While Hayden the mammoth was perhaps the best fossil discovery in the Purple Line project (so far), the team found hundreds of other fossils. They’re finding pieces of just about every animal from the Ice Age: mastodons, bison, horses, camelops (an extinct type of camel), giant ground sloths, dire wolves, and sabertooth cats.

Camelops bone fossil discovery los angeles
Image by LA Metro

The tricky part is remembering how rare it is for something to fossilize — it’s estimated that less than one percent of life on Earth has been fossilized — so these fossils are only a small sample of the sheer number of animals that once lived in the Los Angeles area. But the scientists are using these samples to infer what it was like in the past.

21. Over 11,000 years ago, humans and mammoths lived in LA

All these animals that lived during the Ice Age were similar to animals we can see today, but a little different. However, to put it in perspective, these fossils are all at least 11,000 years old. At that point, humans were living in North America alongside the mammoths, giant ground sloths, and dire wolves.

Pleistocene ice age epoch
Image by National Park Service

When the construction workers dug deeper, to about 80 feet down, they found a whale fossil. At that point, hundreds of thousands of years ago, Los Angeles was underwater. Each fossil the team finds provides another glimpse into the past, which together form a more well-rounded understanding of the area’s natural history.

22. Mammoths and mastodons lived in different environments

Elephants, mammoths, and mastodons are all related to each other with some differences. Compared to elephants, mammoth ears are fairly small. To contrast with mastodons, mammoths generally lived in open grassy areas, where they ate grass for a living. Mastodons, on the other hand, lived in wooded areas among the trees.

Mastodon tooth los angeles fossil discovery
Image by LA Metro

Mastodons, which were smaller than Columbian mammoths, ate twigs, branches, and shrubs. They also had very flat backs. Mammoth backs were angled; their shoulders were higher than their rear end. The two animals also had very different teeth to accommodate their different diets. Mammoths and mastodons all went extinct, but elephants endured.

23. In 2009, paleontologists found Ice Age fossils under an LA parking lot

This wasn’t the first time construction in Los Angeles resulted in Ice Age fossil finds. In 2009, excavators found many fossils under a parking lot near the La Brea Tar Pits. In contrast to the Purple Line finds, however, these animals were covered in asphalt.

Los angeles fossil discovery
Image by David McNew/Getty Images

On top of the typical large Ice Age fauna, the paleontologists found fish, turtles, rodents, millipedes, and trees, too. This helps give scientists a more well-rounded understanding of the past ecosystem. The La Brea Tar Pit museum has so many different fossils that scientists can compare their findings with the collection to help identify fossils.

24. The LA Metro subway expansion is supposed to open in 2022

As for the LA Metro subway expansion, the new stations may not open until 2022. It was originally supposed to open next year, but it’s an ambitious undertaking and has thus been delayed. Finding fossils doesn’t delay the progress, though, as the construction workers momentarily divert their efforts to a different area. They let the paleontology team carefully dig out the bones.

LA Metro subway extension station
Image by LA Metro

But even while Los Angeles is working to expand their current rail lines, they’re also adding several new ones. And it turns out they’ve run out of colors to name them. So LA is renaming all the lines after letters instead. The Purple Line will be the D Line.

25. The fossils will all go to the local natural history museum

For Ashley Leger, this fossil was a once in a lifetime find and she’s excited for the public to see it. “We’re really bringing the past to life. It’s one thing to go to a museum and look at specimens of fossils and say, oh, this dinosaur was found in China and this dinosaur was found in Mongolia and this dinosaur was found in Colorado,” Leger said.

Los Angeles Natural history museum
Image by Allie_Caulfield/Wikimedia Commons

“It’s different when you would look at that sign and say, this fossil was found literally in our backyard,” she said. “Now, of course, they’re not dinosaurs. They’re mammals. They lived long after the dinosaurs. But to a small child looking at that big mountain skeleton in a museum, it’s just as impressive.”