Nov. 17, 2022
La Brea Tar Pits (Ice Age California!) with Sean Campbell
Have you ever wondered what was going on in California, oh, ten or fifty thousand years ago? About, perhaps, the social lives of saber-toothed cats, just how big giant ground sloths actually were, or the difference between a mammoth and a mastodon? Join me and Sean Campbell, Senior Paleontological Preparator at the La Brea Tar Pits in Los Angeles, California, as we explore what California and the world were like at the last glacial maximum.
La Brea Tar Pits: https://tarpits.org/
Island Living Can Shrink Humans: https://www.science.org/content/article/island-living-can-shrink-humans
Saber-toothed animals: https://www.livescience.com/54130-saber-toothed-animals.html
Extremophile Microbes: https://www.sciencedaily.com/releases/2007/05/070510151916.htm
You can find me on Instagram or Tiktok @goldenstatenaturalist
My website is www.goldenstatenaturalist.com
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The theme song is called "i dunno" by grapes, and it can be found here.
tar, deposit, fossils, extinct, asphalt, species, la brea, tar pits, animals, mammoths, pleistocene, excavate, saber toothed cats, tar pits, remains, area, ice age, teeth, paleontology, nature podcast
Note: This transcription was made by robots and may be a little wonky.
Hello and welcome to Golden State naturalist, a podcast for anyone who has ever just sort of looked around and wondered what was this place like at the height of the last ice age. I'm Michelle Fullner. And today we're going back in time because today is all about the La Brea Tar Pits, which has more Ice Age fossils than any other institution in the world. In this episode, you'll hear my conversation with Sean Campbell about saber toothed cats mammoths, mastodons what makes an ice age and Ice Age The fact that dire wolves are not fictional fossil excavation, ancient camels that roamed North America how I got lost repeatedly in a building that is literally one big circle how humans have used the tar pits across the millennia de extinction the difference between tar and asphalt what happens when a bunch of mammoths hang out on an island for a long time human remains in the Tirpitz 10 foot tall slobs what might have caused a bunch of species to go extinct around the same time, pop culture references deep time and how much still remains to be discovered and understood about the La Brea Tar Pits. We'll get to all of that ice age goodness in just a second. But first, a couple of quick things. On previous episodes of Golden State naturalist you've learned about things like Giant Sequoias, vernal pools, fire ecology, Monarch butterflies, how California was formed, and even how beavers help out in the face of historic droughts and wildfires and more great content is on the way to episodes on urban nature, amphibians, native plants, nature journaling, and a bunch more are coming out this season. So if you're interested in California ecology or really any of those topics, make sure you're following the podcast wherever you listen so that you get notified as soon as a new episode is released. In Apple podcasts you can follow by hitting the little plus sign at the top right hand corner of your screen it will look like a checkmark. If you've already done this on Spotify and audible just tap the word follow. And if you want to help Golden State naturalist get made while also getting some lovely perks and community you might consider becoming a patron. I make this show completely independently, including researching and scheduling guests traveling for interviews, editing audio and promoting episodes. So every contribution helps fund things like audio equipment travel for interviews necessary subscriptions for making the show. Plus patrons get exclusive access to audio and video extras from the show and they get to submit questions to be included in interviews. You can join for as little as $4 a month at www.patreon.com/michelle Fullner. That's Michelle with two L's and Fullner is fu ll en er it also helps a ton to leave a rating or review wherever you listen or just to share your favorite episode with a friend, family member or colleague or anyone who has ever pointed out a sunset to you if you want to see what outdoorsy things they've been up to. You can follow me on Instagram or Tiktok at Golden State naturalist. My website is www dot Golden State naturalist.com. But now let's get to the episode. Sean Campbell is a senior paleontological prepared hitter at the La Brea Tar Pits. He graduated from San Diego State in 2011, with a major in anthropology and minor in geology, focusing on forensics and human osteology. And then he did so much he volunteered at libreria interned at the Milwaukee Public Museum volunteered with a Forest Service on passport and time or pet projects. And on several of those projects. He's been involved in excavations on historic prehistoric and paleontological sites in California, Wisconsin, Illinois, and North Dakota. He's also been on dinosaur digs in places like Utah, New Mexico, and Patagonia. And he goes to Mexico twice a year to collect Pleistocene terrestrial fossils. Basically, dude is living out all of our wildest childhood dreams. So without further ado, let's hear from Sean Campbell on Golden State naturalist.
We just did a whole loop of the museum and that was supposed to help me narrow down what I wanted to talk about. And it didn't work at all.
Too much, right? Oh, I just wanted.
That's what the collections manager say all the time too much.
So the museum, the tar pits where Shawn and I met up is called the page museum. And there is in fact, so much to see there. And so much more is regularly pulled out of the ground that Shawn told me they're actually running out of room to store it all. Now, you might hear that and ask, why don't they just slow down and we'll leave some of these things in the ground. But Lebra is located in Los Angeles and in such an urban setting, the second largest city in the country. In fact, businesses that come in and build in the area frequently find fossils, while digging foundations and the folks from libreria have to excavate, measure, prepare and store all of those fossils. You realize what an incredible feat that is when you look around the museum and then remember that only a tiny percentage of the fossils stored there are actually on display in the midst of this incredible richness of fossils of the museum shown and I stopped next to an American lion Panthera a trucks which went extinct about 11 to 13,000 years ago, around the same time as a bunch of other species that we'll talk about later in the episode, so hang on to that when it was alive though the American lion was about 25% larger than modern lions would, you may recall are not tiny. These American lions are not thought to have been very social animals. In contrast with another cat found at the Tirpitz.
Funny enough the saber toothed cats, they're thought to actually be probably more social than the American lion or Panther a trucks. So saber toothed cat, smilodon, fatalis, the specific species that we find that libreria, there's been so many specimens found in these deposits, as well as so many pathologies or injuries that are evident on the remains and bones that we find that it's very clear that some of these individuals who have been so damaged and hurt and unable to tend to themselves that others were tending to them, or at least they were allowed to accompany the pride or social structure, whatever exactly it was, and then, you know, eat to go to the kill site, and maybe get the last remains, but something to keep them going. Wow. So the separative cat is speculated to be a fairly social creature.
So I don't know about you, but I love humans, and I'm aware of our many imperfections. But I love that humans will do this kind of thing where we won't necessarily get anything back. But we will still give to somebody who needs something to make sure that they can be okay. And I just think it's really cool. Every time I learned about another species that exhibits or exhibited this type of behavior and just real talk, I don't know a whole lot about saber toothed cats, but like,
how do they it doesn't seem possible for them to kill something. Right? Like their their mouth, their teeth get in the way, right, like how do they kill something?
They so there, this has been argued by scientists throughout the like the discovery of saber toothed cats.
Do you think there's any chance that they could just be like showing off to each other? Like, it's like some kind of a meeting arms race where it's like, yeah, big teeth are so impressive, right?
So that's probably part of it. But not the only part because males and females, they both have really large canines, there is a very small amount of sexual dimorphism. That's been analyzed in specimens found at libreria. And so they are somewhat distinguishable. Oh, this is most likely a male This is most likely a female, but they're pretty close. And when it comes to their canines that are about the same length interesting, and they all have serrations. So it definitely is not only mating display, it's there's definitely functionality to their prey capture and dispatching,
right like I'm not going to turn down those cool teeth. But like that's not the only reason.
Right? Yeah. But this specific species smiling on fe, tallis and the smile it on genus, it's thought that they are ambush predators. And so they might be in a slightly more forested environment or some sort of place where they of cover, they're hiding out until a prey item walks along, and then they ambush and pounce on it directly.
What you're about to hear is in contrast to all those nice, warm, fuzzy things we learned about smilodon, fatalis a minute ago. So if you think he might be sensitive to hearing the details of how these cats made their kills, maybe just skip forward like 30 seconds, okay, good,
hold it down and then use their canines in a very particular way, because they are definitely liable to break if they hit bone or if the animal struggles too much. So the current idea is that the extremely powerful four limbs of the smile add on, we're capable of wrestling an animal down and holding it still so that it could use its canines in probably the throat area, and either slice out the trachea and the jugular and it would either suffocate or bleed out extremely quickly. So we know that the saber tooth morphology or the shape of the canines, and how long they are, has evolved multiple times in geologic history and multiple different types of lineages.
I'm sorry, did he just say that these giant sword teeth evolved multiple times over the eons? He did. According to live science.com More than a dozen kinds of animals, many of them now extinct had saber teeth, including saber toothed salmon and the marsupial. FileInfo smilers which please go look at the Wikipedia page for Lycos fileless immediately because it has the most amazing chin I have ever seen. The article goes on to say that today, Sabretooth animals include the walrus, muskdeer, and warthog, all of which grow incredibly long in sharp canines the hallmark of a saber tooth. elephant tusks are long incisor teeth and thus are not sabers. One of the things I think is interesting about the saber tooth animals living today is that they aren't using those saber teeth for hunting like the saber toothed cats were walruses, for example use their tusks to pull themselves out of the water onto the ice and muskdeer the males they look like little things is on the Musketeer. And they use those to fight with each other to prove how cool they are for the females. So while Saber Tooth cats use their teeth for hunting, not every type of animal ever to have saber teeth uses them in that way.
But these canines that are super elongated keep evolving multiple times. And so many paleontologist postulate that given enough time, eventually we'll see Saber Tooth cat morphology arise again, in some, some sort of fashion. So obviously, it's not going to be tomorrow, we're probably not gonna be alive to see it on time. But eventually, deep time going into the future, we're most likely going to see the saber toothed cat morphology. Again,
one of the many things that I learned while visiting the page Museum is that you can in fact, take a wrong turn while traveling in a circle. Okay, so I tried to get lost, and then we turned around with the right way. And then we came to the massive mammoth like, I've never actually stood by a mammoth skeleton, and I had no idea that it was this much bigger than an elephant.
Yeah, they're very large depends on what mammoth you're exactly talking about. So a very common misconception that Libre is that everyone thinks the woolly mammoth is here. Oh, so the woolly mammoth is not here, the woolly mammoth is farther north, it would have been closer to the essentially the ice sheets, the major ice sheets up in North America. So the last glacial called the Wisconsin ice sheets came as far south as like the Wisconsin area, which is what it's called, that can actually walk a trail in Wisconsin where there was a terminal moraine of the ice sheet is really cool. So the Ice Age has been going on the Quaternary Ice Age since the beginning of the Pleistocene. So like over 2 million years, the Earth was cooling down starting around like 35 million years ago, but you have permanent ice sheets, both in the north and southern hemispheres, starting around two and a half million years ago. And that the technical definition of an ice age is that you have those permanent ice sheets and both hemispheres and they oscillate. So global average temperatures are oscillating depending on a bunch of different factors. But when it warms up, and it's an interglacial, the ice sheets are melting and receding away. And then when it cools down, it's a glacial period, and more water is being trapped in the ice sheets and the ice sheets are expanding and going in different directions, including in North America, going farther south, as far as Wisconsin, the last major glacial.
What Shawn is saying here is that we are still in an ice age, just not the really cool part of an ice age, which is called the glacial period. Instead, we're in an interglacial period, the last glacial period hit a maximum around 20,000 years ago, and then ended around 11 and a half 1000 years ago, a timeframe that coincides with the age of many fossils found at libreria. And although some of the fossils are much older, they're still on the scale of 10s of 1000s of years old, not millions of years old, so there are no dinosaurs being pulled out of the tar pits. Also, this feels like a good moment to mention that LA was actually underwater when the dinosaurs were alive. So definitely no dinosaurs. But even though it was colder during the Pleistocene, when these fossils date back to there weren't these major ice sheets here in California? Okay, I promised that this was all important. And we didn't forget about the mammoths.
So the woolly mammoths would have been closer to the areas that were much colder because they were adapted to colder environments, Southern California, specifically LA, it might have been a little bit cooler and a little bit wetter. But it wasn't snowing every day. There wasn't ice everywhere. So it wasn't like that at all during the 1000s of years that represent the La Brea Tar Pits. So the Columbian Mammoth is actually a larger mammoth than woolly mammoth. Okay. And my mother's Columbia is the species of mammoth that we find here at this specific locality. It was really across a lot of North America all the way down into like Mexico, and maybe even a little bit farther south than that, but it most likely preferred warmer local climates like Southern California would
there have been more for it to eat in those climates? And that's like, get bigger, yeah,
but it's more about not being adapted to certain environments. So like the woolly mammoth was very Shaggy and had hair its ears were severely reduced to prevent frostbite. So it was its tail. The tusks are oriented maybe slightly different directions and the woolly mammoths were probably shoveling snow out of the way to get get to grass and other things that were underneath. Whereas the Columbian mammoth was not adapted for exactly those types of environments. It's more adapted to mostly grazing because that's what the teeth are based on.
Okay, so that's the difference between woolly mammoths and Columbian mammoths. But aren't there also mastodons somewhere in this picture that are another big elephant type of creature? How are those different from mammoths?
The easiest way to tell mammoths, mastodons apart from each other is based on the teeth, you can actually see physically those teeth right there. Each one of those is just one big tooth and it's a bunch of plates that are all fused together and it's dentin and enamel and cement them and they all grind down at different times. So it creates these little rings and ridges. And when those two occlusal surfaces grind past each other, there are perfect surface for grinding up silica rich vegetation such as like grasses and things like that. So mammoths didn't only eat grass but they are adapted to eat grasses. That's the main difference, whereas mastodons we can look at their teeth later, they have these huge loafs and cusps and they're better for breaking up larger bits of vegetation, foliage, branches, all that sort of stuff. So again, they can eat a little bit of grass as well, but they're not adapted to take on that abrasive sort of vegetation.
So the day after I recorded this interview with Sean, I went to the Natural History Museum of LA and from across this giant exhibit hall, I saw this massive skeleton of a large animal with tusks, and I looked at the teeth and I was like Mastodon, and when I got closer, I read the sign and it wasn't Mastodon and I could tell because the teeth look super different. So on a mastodon, like Sean is describing there, these very big pronounced molar looking things with many more sort of hills and valleys within them. Whereas a mammoths teeth almost look like a flat grinding surface. I was so proud of myself that I texted Sean to tell him about it. So that's the most obvious way to tell them apart. Yeah. But what other kinds of differences did they have
the overall size so like this Columbian Mammoth is roughly like 12 feet at the shoulder and it's a huge animal weighing many 1000s of pounds many times. The mastodons are much shorter. They're probably like eight to nine feet at the shoulder usually, and they weigh 1000s of pounds. Less
mastodons, mammoths and elephants are all part of a group of animals called proba, Citians. And just like humans, they evolved in Africa and then spread out across many parts of the globe. Unlike humans, who only have one remaining species in the world, though proba Citians have three, two in Africa and one in Asia. Maybe you already knew this, but I was shocked when Sean told me that there are two species of African elephants. I thought there were just African elephants and Asian elephants and that was it. But apparently there's a bush elephant and a forest elephant in Africa. I had no idea. Okay, but back two minutes. Do you ever learn something and it just sticks in your head and rattles around in there and sort of pops up randomly when you're spacing out what Shawn is about to say here is like that, for me. It's been months and I still think about this all the time.
So another really quick thing about pro sedans I need to show you this over here. Not many people know this story. But dwarfism in Provo Citians is extremely common. So essentially every major lineage Gompa theories, mastodons, mammoths, elephants, they all have pygmy versions at some point in the past on different islands around the world, along the west coast in North America. In this case, right here, we can actually show you real specimens of the difference between a Columbian mammoth. So this is Ed's mandible that we found in 2006. And then this is a mandible of a pygmy mammoth that was found on the Channel Islands. So the sea level change has fluctuated and oscillated with the average global temperatures. And at different points in time, the Channel Islands, the sea level was lower and some of the islands formed one big island called Santa Rosae. The Columbian mammoth swam over there, and then had no predators, but they needed to get smaller in order to stay there for a long period of time. So over many, many generations, they adapted and evolved to become as small as possible. These are like roughly a quarter of the size of Colombian mammoths. And they speciated and became their own species and lives specifically on the Channel Islands.
It's like a purse sized one. Yeah, it's I have to go
there was definitely still a few 100 pounds. Maybe you would still be riding on it. But uh, yeah, first sizes, for sure. A personalized one. Or the Columbia. Yeah, the Columbia mounts would have been carrying around, I guess.