Science

The La Brea Tar Pits are full of mysteries. Here are three of the most puzzling

The La Brea Tar Pits are full of mysteries. Here are three of the most puzzling

The lake pit in front of the La Brea Tar Pit Museum is left over from nineteenth-century asphalt mining. (Gina Ferazzi / Los Angeles Times)

Last year we started inviting readers send us their urgent questions about Los Angeles and California.

Every few weeks we ask questions votingasking readers to decide which question they would like to see answered in story form.

This question, asked by Ricky Fulton, was included in one of our most recent reader polls: What are the La Brea Tar Pits? Is it a pile of bubbling tar with dinosaur bones sticking out of it?

You can vote in our next reader poll here. Follow previous stories written as part of this project here.

There’s more to the La Brea tar pits than meets the eye – and a nose.

For those who don’t know, La Brea Tar Pits is internationally recognized geological heritage site, located in downtown Los Angeles. The site is known for its numerous fossil quarries (called “pits”), where animals, plants and insects have become stuck and preserved in the asphalt over the past 50,000 years.

For scientists, they are an invaluable, unique treasure trove of information that allows us to better understand what ancient life was like in present-day Los Angeles.

“The science you can do in the La Brea Tar Pits is something you can’t do at any other paleontological site in the world, just because we have so many fossils, and they’re so well preserved,” said Emily Lindsey, assistant curator and director of excavations. .

Inside the scent gland — a curiosity for locals, tourists and schoolchildren on field trips — more than 3.5 million fossils were discovered.

To answer Fulton’s question right away, here’s one thing they didn’t find in the pits: dinosaurs.

That’s right – this is an Ice Age fossil site, and experts haven’t discovered any remains T. rexestriceratops or other non-avian dinosaurs.

While the La Brea Tar Pits are short on dinosaur fossils, they are full of fossils of legendary Ice Age animals. The two most commonly found large mammals? Dire Wolves (Calling All “Game of Thronesfans) and saber-toothed cats.

A woman looks at a fossil exhibit at The La Brea Tar Pits in Los Angeles

Columbian mammoths and mastodons once called Los Angeles home. Today, their remains can be seen at the La Brea Tar Pits and Museum. (Mel Melcon/Los Angeles Times)

Despite the scientists revolutionary discoveriesmysteries continue to swirl in the leaking pits.

Sometimes, Lindsay said, the things that scientists don’t found in the tar pits are as fascinating as the bones and other objects they uncover.

Lindsey described the puzzles posed by the tar pits that have yet to be solved.

Here are three of the most interesting:

Why are the remains of some indigenous species — such as mountain lions — mostly missing from tar pits?

Something strange: scientists have discovered relatively few remains of mountain lions in tar pits.

Hollywood celebrity status P-22 aside, it might seem odd to worry about the absence of some mountain lion fossils when tar pits have uncovered the remains of extinct mammoths, dire wolves, and giant ground sloths.

Still, it’s strange that mountain lions—which existed in the Los Angeles area during the Ice Age—account for such a small percentage of scientific discoveries in the tar pits. The Tar Pits have the remains of at least seven different mountain lions, while its saber-toothed cats number between 2,500 and 3,000.

And not only mountain lions from the tar pits are missing.

“We have very few mountain lions, very few deer…and only one raccoon,” she said. Except coyotesscientists found “very few of these [large mammal] ‘survivors of the ice age’, which is an interesting thing.”

Why would mountain lions disappear from tar pits?

The answer could help scientists piece together a more detailed picture of what life was like in prehistoric Los Angeles.

Lindsey and her colleagues have a few ideas. Among other potential explanations, it’s possible that—true to their name—mountain lions have always preferred to be in the highlands rather than the flatter areas of present-day Los Angeles near the tar pits.

Or it could be that mountain lions were afraid to hunt in the same areas as saber-toothed cats. “A mountain lion looks like a house cat next to a saber-toothed cat – [it’s possible] they wanted to stay away and not be around all these big scary things.”

Where is the evidence of human life?

Mountain lions, raccoons and deer aren’t the only mammals missing from tar pits. The lack of human remains is also striking.

People were here, but why don’t we find any evidence of them in the La Brea Tar Pits?” Lindsey asked. “We have one human skeleton, and then we have some artifacts that are probably all from the Holocene (our current geologic epoch), but we have no evidence of humans overlapping or interacting with the megafauna” through hunting.

This is puzzling, because “many—perhaps even most—scientists think that the main cause of megafauna extinction is human activity,” Lindsay explains.

Similar to mountain lions, Lindsey notes that the absence of ancient humans could indicate their restraint in hunting nearby saber-toothed cats and other dangerous animals.

A group of adults and children watch a demonstration in the Fossil Laboratory

People watch a demonstration at the Fossil Lab at the La Brea Tar Pits and Museum. (Kent Nishimura / Los Angeles Times)

“It could be that the culture that was here was adapted to the coast and didn’t have to brave, for example, a pack of dire wolves to go hunting for a horse or a camel,” she said. “They could have stayed close to the coast and collected shells .”

Why did large mammals begin to disappear – and what does this tell us about our future?

Once upon a time, giant mammals roamed large parts of the earth.

“There were giant wombats in Australia, giant lemurs in Madagascar, giant sloths and armadillos in South America,” Lindsey said.

So, Lindsay asks, why don’t we have saber-toothed cats and mammoths and giant ground sloths roaming Wilshire Boulevard today?

A dramatic change has taken place. “At the end of the Ice Age, something happened that wiped out the top of the body size distribution everywhere except Africa,” she said. “It’s the biggest extinction event since the extinction of the dinosaurs 66 million years ago.”

Even worse, the loss of giant mammals is being recognized as “the first pulse of the biodiversity crisis we’re in today,” she said.

Why did this extinction occur? “Most scientists think that humans must have played a fairly significant role in this extinction. But the other thing that was happening was that we were coming out of an ice age – the last big episode of global warming,” she said.

“Understanding the kind of interplay between climate change and human activities, how that affects ecosystems and how those two processes can intersect and lead to extinction is incredibly important.”

The La Brea Tar Pits are positioned to help solve the mystery of why exactly the giant mammals went extinct, because of the size and scope of the finds, which can be radiocarbon dated and compared to known changes that occurred simultaneously with humans and the climate. .

Two men are kneeling on the ground carefully digging up fossils

Two volunteers dig for fossils in the La Brea tar pits. (Gina Ferazzi / Los Angeles Times)

On the other side of the coin, 90% of species found in tar pits did not become extinct. “We have tons of rabbits, rodents, lizards, insects and songbirds in our records that still live in the LA area today,” Lindsey said via email.

“We are a record of survival and resilience,” she said, which raises several questions. “What made mountain lions successful? What made coyotes so successful? What made the oaks succeed?”

As climate crisis is worsening today, the answers to these mysteries could pave the way for the future.

“The next few decades to several centuries are going to be one of really extreme global change,” Lindsey said. “How can we use that information to help life thrive going forward?”

This existential question should give you something to think about the next time you pass the Tar Pits’ iconic (and heartbreaking) mammoth statues off Wilshire Boulevard.

This story was written directly in response to a reader’s question about the La Brea Tar Pits. Have a question about living in Los Angeles or California? Ask us!

This story originally appeared in Los Angeles Times.



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