The Extinct Ice Age Mammals of North America

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The Extinct Ice Age Mammals of North America

JERRY BALDASTY: Good evening Hi I’m Jerry Baldasty I’m the interim provost and executive vice president Welcome to the 40th annual university faculty lecture Every year, the University of Washington faculty members select one of their peers to present this distinguished lecture Over the past four decades, we’ve seen an impressive list of presenters give this prestigious lecture– historians, doctors, artists, engineers, and many others This is the highest honor the faculty can give to a member of their own ranks, and so this is a very special evening for all of us This year’s recipient, Donald Grayson has been an anthropology professor at the University of Washington since 1975, teaching archeology both in the classroom and in the field He’s a true leader in this profession and has been so for decades He’s researched and written extensively on a variety of sites, time periods, and subjects, but he’s most recognized for his research in southwestern France and the Great Basin of western North America In addition to this academic work, there are many students who can speak to the impact of his teaching and mentorship Some of these would be the undergraduates who enjoyed his classes on the prehistory of the arid west and prehistoric extinction, or they might be among the 22 PhD students he has mentored throughout his career, and he has helped them find fulfilling employment across the country He’s an incisive and thoughtful leader He cares deeply about discipline and the people whose lives it touches Aside from all of this, he is also an engaging, thoughtful speaker who inspires curiosity in students and peers alike We are so lucky to have you here Please join me in welcoming our university faculty lecture professor, Donald Grayson [APPLAUSE] DONALD GRAYSON: I will try to live up to part of that [LAUGHTER] The picture on the bottom of the screen is a picture of a mammoth being excavated in the Black Rock Desert of northwestern Nevada, the same Black Rock Desert where the Burning Man Festival is held Almost everybody who grows up in this country learns about this particular animal, the mammoth, alongside animals that lived with it Saber toothed cat is an obvious example A mastodon is another possibility More recently, if anybody has seen the movie Ice Age, you’ve seen what I actually think is someone knows something about these animals– are really good, perhaps, caricatures of these animals– Manny the mammoth, Diego, the saber toothed cat, Sid, the giant ground sloth Everybody’s heard of these animals to one degree or another if you’ve grown up in North America That may be all you know You may not know when they became extinct You may not know why they became extinct, and I will say now, although we’re going to come to this later, if you have heard that they became extinct because they were hunted to death by human hunters, I would claim that you still don’t know why they became extinct, but I will return to that later These extinctions have been the focus of research for over 200 years In fact, some of these animals, including the mammoth and one of the North American ground sloths, was critical around the year 1800 in establishing the fact that extinction could actually occur in the first place By the 1870s, the great evolutionary biologist Alfred Wallace was able to point this out, what’s up on the screen– that some time in the recent past the earth had lost some of its hugest, fiercest, and strangest animals He marveled at this If he were still alive, today he’d marvel at it even more He’d marvel at an even more because we know so much more about these animals than we did when he was alive, but he’d also marvel about it because we still don’t understand any more than he did why these extinctions occurred

I’m going to focus on North American extinctions here North America lost 37 genera of mammals as the ice age came to an end When Wallace said that these were recent disappearances, in modern terms, he could have said that these were late ice age disappearances The ice age is the period of time that lasted from 2.6 million to 10,000 years ago It was characterized by the alternating advances and retreats of massive glaciers on many parts of the earth’s surface The extinctions that I’m going to talk about were extinctions that occurred– oh, I’ll be general about it now– between roughly 30,000 and 10,000 years ago There’s only one term that I have to define besides ice age, and that’s the term genera that I just used Everybody has run across this term, the term genus The plural is genera Similar species are lumped into, grouped into a genus in biological classification Genera are grouped into families and so on up the hierarchy Once having defined that, I can go back to what I just said– that toward the end of the ice age North America lost 37 genera of mammals It’d be fun to just talk about North America It is fun to just talk about North America, but I also want to point out that it wasn’t only North America where this was happening It was happening in Eurasia, but more important for us it was also happening in South America, where 54 genera of mammals were lost Because some of the North American mammals were also found in the south and some of the South American mammals were also found in the north, if you count up the total number of genera of mammals that were lost, you get 77 That is a huge– that is a huge part of biological diversity to have been lost at the end of the ice age, and as I said before, we’re still trying to figure out why and how that happened In addition to that– and this is going to become really obvious as we go along– one thing that characterized these losses is the fact that the animals were all big Well, all is a bit of an overstatement Three fourths of the animals that were lost weighed 100 pounds or more We’ll see that some small ones also went out of business, but we’re also going to see that the overwhelming majority of these animals were really, really big My goal today is to spend an hour– I’m going to look at my watch and see when that’s going to be up– trying to clarify some of these issues, and I know that I’ve got more to talk about I could talk about this stuff forever I teach a whole course on this stuff I know I’ve got more stuff to talk about tonight than we have time to talk about, and when the hour is up, I’ll just stop [LAUGHTER] As I said, 37 genera of mammals were lost from North America Six of these– and we’ll see what they are Horses are one of them– live on elsewhere, but when they became extinct in North America, they never appeared here again unless they were reintroduced later on I’m going to give you a rundown of all these guys, and I’m going to start with the cingulates Think armadillo Cingulates are animals with external bony armor These are South American animals, some of which, just like armadillos, made it north There are two animals very closely related to armadillos called pampatheres If you saw one, you’d immediately think armadillo, but you’d also think something else that I can’t repeat here because of the size of these animals This is an armadillo that was six feet tall, three feet long, and weighed between 500 and 600 pounds I am not, by the way, making any of this up Northern pampatheres were southern animals They made it to southern North America The southern pampathere about the same size There is its shell, but this is a South American shell Southern pampatheres are not as well known for North America, but they did make it here Then there’s this next guy Glyptodont– glyptodonts are also South American These are armadillo-like in the sense that they also have external body armor, but unlike the armadillos, this external body armor is not flexible These guys had carapaces like tortoises They also were almost literally the size of Volkswagen Bugs, the cars Weighed 2,400 pounds– that carapace was fused to their inner skeleton They hung around water These were absolutely remarkable animals

I don’t know if you can see that picture on the lower left If I start free associating like this, we’ll never get through anything, but if you can see this picture on the lower left, I stuck it in here because I love it This is a picture of a glyptodont that was a reconstruction of a glyptodont that was made in the 1930s for work being done by famous paleontologist George Gaylord Simpson In the 1930s, it was already known that some South American glyptodonts had tails that ended with mace-like projections, but in the 1930s, they had yet to find the end of the tail of the North American glyptodont So they hid it behind a bush because they didn’t know what it looked [LAUGHTER] Once it was found, it was discovered that its tail ends without the mace-like projections It’s simply rounded This is its distribution Sid the sloth– the movie Ice Age amazes me I’ve actually looked on the web to see if I could find out who knew enough about the ice age to do those reconstructions because they’re really good There’s a glyptodont in there There are South American animals in there that North Americans generally have never heard of It’s a great movie Sid, the ground sloth, is meant to reflect the fact that North America during the late ice age had four genera of huge ground sloths When we think of sloths, we think of slow moving, tree hugging animals that, if they’re fat, may weigh 20 pounds That is not the case for the North American ground sloth, and the North American ground sloths as a whole are smaller than the ones that went extinct in South America I’ll start with a megalonyx, Jefferson’s ground sloth Here’s a reconstruction done by a very talented paleoecolgoist friend of mine, Wally Wolfenden We’ll be seeing a bunch of his reconstructions today This is a reconstruction of megalonyx Its name means great claw It was given that name by Thomas Jefferson in 1797, and you can probably see why he called it that He called it that because of these great claws He didn’t recognize it as a sloth Not surprising This is 1797 He thought it was a carnivore He was wrong about that He also didn’t realize that it was extinct He argued that if it had once existed it must still exist, and as I said before, some of these animals, including megalonyx were used to argue that extinction was real When Jefferson was writing, he did not yet believe that that could be the case Megalonyx– widespread in North America, as you can see here, coast to coast This one– in my extinctions class that I teach, I have an election every year Not as fancy as the one I had this year This year’s was really fancy We had a primary election, and then we have the final election to see which of these 37 genera– one, the students– I voted, too– all of us– would most want to see if they could see one alive I voted for glyptodonts My students got it wrong, and they voted for eremotherium [LAUGHTER] Eremotherium had the height of a giraffe and the bulk of an elephant It is eastern in distribution, mostly southeastern, but there’s one curious record from coastal New Jersey that you can see on this map If I had to have a favorite sloth, it would be this one, nothrotheriops It is shown here eating the fruits of the Joshua Tree It’s shown that way because we know that it ate those fruits, and we know that it ate those fruits for something I’ll talk about in a minute This was the smallest of the ground sloths, the smallest of the North American ground sloths It was also western distribution By the way, I’ll point out that that odd shaped blob that you see on the west side of the map is a region called the Great Basin If we have time tonight, if I don’t free associate too much and run over time, I’ll talk about the Great Basin towards the very end That’s the distribution of nothrotheriops, the smallest North American ground sloth We know what it ate because we have its turds, if I can say that Here is one of them Nothrotheriops, the Shasta ground sloth, had the friendly habit of pooping in caves in the dry west, in the arid west, including caves in the Grand Canyon This particular one comes from Rampart Cave in the Grand Canyon You can pull these things apart You can identify– you can radiocarbon date them, and you can identify the plants that are in them As a result, we know a lot about ground sloth diets And just to free associate, there must be men in here–

and I’m saying men because this is more common in men than in women– men in here who get kidney stones Most kidney stones are oxalate kidney stones I get them, so I’m familiar with them Most of them are oxalate kidney stones Yuccas and agaves are loaded with oxalates When these pieces of dung were first analyzed in the 1930s, a botanist and a chemist combined to do it, and they discovered that these things were– they did the chemical analysis and discovered that these things were also full of oxalates, and those oxalates are coming out of the plants that they were eating How ground sloths didn’t get kidney stones is beyond me I’d love to know This is paramylodon This is the fourth of our ground sloths This is the most abundant ground sloth at Rancho La Brea It’s part of a family called the mylodon ground sloths, all of which are characterized by the fact that their skins have little bony pebbles embedded in them In fact, that skin that you see on the lower right was found in the late 1800s in southern Chile, and it led to the possibility of that ground sloths might still exist and to an expedition to find them still on the hoof They didn’t, but every so often that possibility reemerges Perhaps the argument is they still exist in the deep Amazon In North America, they were clearly gone by 10,000 years ago That’s the distribution of paramylodon We even have paramylodon footprints from– and I’m not making this up This is going to sound funny, but it’s true This dot right here is the Nevada State prison, and there were footprints found there in the late 1800s that were thought at first to be human footprints, and within a decade or so were recognized to be mylodon ground sloth footprints They’re the only footprints of a sloth, as far as I know, that are known from North America The carnivores– smilodon, the saber toothed cat, is one of the iconic mammals of North America, along with the mammoth, but there were seven genera of carnivores that were lost The short faced skunk– paleontologists are really good at giving common names to animals The short faced skunk is called that because it’s a skunk with a short face It’s not very well known There are only seven sites of it known from North America Cuon, the dhole, is a hyper carnivore that is doing OK– not great, but OK– in southern Asia today During the ice age, it found from northern Spain all the way across into Northeastern North America– pardon me, northwestern North America And then if you look closely, you’ll see that one site in Mexico way down here– every so often somebody gets it in their mind that that can’t possibly cuon, and they go look at it, and sure enough it is It has to– these were not birds It has to have lived someplace in between All the work I did in the Great Basin– the site’s been known for a long time I always had my eyes open for cuon It’s an animal that I would run across in the paleolithic sites that we worked on in France Nobody’s found one in between It had to have been there Somebody will find it sooner or later Tremarctos, the Florida cave bear Tremarctos still exists It’s called the Andean bear It still exists in the mountains of western South America I believe there’s one in the Seattle zoo It’s also called the spectacle bear This is a South American bear with its closest relatives, and it’s distribution during the late ice age was South American It was closely related to this guy Whoops, wrong button This guy, the giant bear The giant bear is called that for a good reason The giant bear was the longest land carnivore of the late ice age anywhere in the world I put 1,500 pounds on there for its weight, but there are some whose weight has been estimated as high as 2,000 pounds People argued for a long time about what its diet might be Argued is the wrong term– pondered, did research on what its diet might be, and in the end, we’ve learned so much about it that the conclusion is obvious This bear ate whatever the hell it wanted to [LAUGHTER] Widespread– coast to coast, and up into the northwest Although one thing that we know is that these records in the far northwest date to the 20,000s while ones down here date to as late as about 11,000 years ago They seem to have become extinct up here before they became extinct down there

The saber toothed cat– one of animals– Diego in the movie Ice Age Massive, massive animals weighing 500 pounds Larger than an African lion with those long sabers protruding from its mouth The sabers had serrations on both sides like pinking shears on both sides Narrow, powerful cutting tools These animals also had really powerful front limbs built in such a way as to be able to resist twisting motions from while they were killing their prey with their front limbs These animals were probably ambush hunters, lurking for their prey to walk by There are also 2,000 of them roughly at Rancho La Brea That fact suggests that they were probably social, as well– a probably social pack hunting animal There is their distribution I should say with all these this is their known distribution Surprises can always be in store Homotherium was called a scimitar cat It also had those protruding teeth, but they were smaller than the protruding teeth of the saber tooth Homotherium was really widespread in the ice age Africa all the away across down into South America Homotherium was a long legged powerful cat, short tailed– long legged, powerful, short tailed cat Pretty clearly ran its prey down We know that it could hunt animals as big as juvenile manners because in a cave in Texas it’s been found associated with its prey That’s its distribution And then there’s this guy, miracinonyx This is such a cool animal This is a type specimen from a site excavated in northern Nevada not far from Pyramid Lake, Winnemucca Lake basin This is the very skull that led to the definition of this genus, miracinonyx It’s called the American cheetah, and it’s called the American cheetah because this animal is so similar in so many ways to African cheetahs that for a long time it was thought that they were really closely related Some even thought that maybe cheetahs evolved in the Americas, crossed into Eurasia, and ended up in Africa People who live in the northwest, have been in eastern Washington, eastern Oregon, Nevada, the Great Plains have probably seen pronghorn antelope Pronghorn are the largest– pronghorn are the fastest herbivores of North America They can reach bursts of speed of 60 miles an hour There’s nothing that can catch them There’s nothing that can come close Why is this animal, it’s reasonable to wonder, over engineered? Why are you able to run 60 miles an hour when nothing like that is needed to get away from your predators? Well, the guess is– and a guess is all it is– that the pronghorn is over engineered for today, but it wasn’t over engineered for the past, that pronghorns evolved with American cheetahs And their speed is accounted for by the fact that slow pronghorn became dinner to the cheetah Fast ones escaped Here’s the distribution of miracinonyx, American cheetah It’s Western The one thing I meant to say and forgot is the fact that fairly recently DNA has been extracted from its bones, and we know that western cheetahs aren’t closely related to African cheetahs at all They are related to our cougars They are similar to cheetahs because their adaptations are similar, not because they share a recent common ancestor Ah, the giant rodents They’re so cool [LAUGHTER] Giant beavers were the size of black bears This is true They’re the size of black bears Different people reconstruct their weights at different amounts, but these were beavers the size of black bears Mostly eastern in distribution They don’t seem to have been dam builders Their teeth don’t match the dam building habits of modern beavers Mostly eastern in distribution, but a couple of sites in the far northwest And then these guys, capybaras Capybaras today are the world’s largest living rodents Big males can reach 120 pounds They still exist in Central and South America Here’s a family group of them One of my students in my extinctions class pointed out to me– I didn’t know this a couple years ago– that they’re bred to be pets

If you Google capybara plus pet, you’ll come up with totally cool YouTube videos of capybaras living as pets in people’s houses If you do that, look closely, and look at the wood in that house There’s one YouTube– [LAUGHTER] Rodents have ever-growing incisors They need to keep their teeth worn down There’s a door in one of the houses in one of the YouTube videos that’s totally– almost totally– destroyed by chewing capybara, but they are, to their credit, totally cute [LAUGHTER] They hang around water because that’s how they tend to escape predators There were capybaras in the– they are southern animals, South American animals Capybaras made it into southern North America during the ice age, as did another genus of capybara– this one, which was at least 50% bigger than the modern capybara This is a capybara also found in South America that pushed 200 pounds Here’s our second small animal Our first small animal was the short faced skunk Aztlanolagus, the aztlan rabbit, was about the size of a pygmy rabbit Pygmy rabbits are fairly well recognized in Washington State because there was an isolated population in eastern Washington that people are now working hard to reintroduce in the Hanford area Aztlanolagus gets was a western rabbits It was about the size of a pygmy rabbit, but it didn’t behave like pygmy rabbits Its post cranial skeleton– its legs suggested that its behavior was more like a jack rabbit, that it was an efficient runner There is its distribution What doesn’t show on here are records south of South America This animal’ is known deep into Mexico Horses– many people here probably know that horses evolved in North America They crossed into Eurasia over the Bering land bridge They also moved into South America, where two different kinds of horses existed until the end of the ice age They subsequently became zebras in Africa They continued to exist in Eurasia into– obviously they still exist into historic times, but they became extinct in North America about 10,000 years ago only to be reintroduced much later by Europeans They were all over the place Let me point out that, whenever you see a picture like this one, that’s showing an archaeological association This is the archaeological site of Wally’s Beach in southwestern Alberta which has artifacts associated with an extinct horse I’ll come back to that later on Tapirs– tapirs evolved in Eurasia and then moved into North America and into South America Don’t know how many species there were Maybe as few as two, maybe as many as four, but they were found from coast to coast The flat-headed peccary What’s on the screen here is an animal that’s known as catagonus It was discovered by scientists in 1975 When scientists discovered it, it was thought to be platygonus, the flat-headed peccary, because it looks so much like Its skeleton looks so much like it There’s no question that platygonus, were we to see it on the hoof, would’ve looked like this This is the Chocoan peccary from the Argentinian Choco I should’ve said that Flat-headed peccaries would’ve looked very much like this Platygonus was widespread coast to coast There’s that one record in the far Northwest in the American Arctic There’s now a second record– it’s not been published– from the northern Yukon It’s not been published, so it’s not on here, but there’s no reason to doubt it So a widespread peccary– we also know that this peccary was a herd animal, and we know that because, often when you find one skeleton of platygonus, you find a bunch more with it That’s very different from the long-nosed peccary The long-nosed peccary– when you find one long-nosed peccary skeleton, that’s all you find This pretty clearly was a solitary animal It was also an animal that you find primarily in the wooded east Camels– some of this is hard to believe I’ve been working with these animals since graduate school, and I still find some of this hard to believe I’ll start with camelops Here’s a reconstruction by Wally Wolfenden of camelops If you saw one today walking down the street, you’d swear it was a dromedary There are some differences Its head is a little bit longer, a little bit skinnier

Its hump is a little bit further forward It’s a little bit taller, but it looks like a dromedary, and genetic– ancient DNA– the analysis of ancient DNA from its bones, which was just studied, shows that it’s more closely related to Eurasian dromedaries than it is to South American llamas It was a western camel– quite common There have not been many Pleistocene age, ice age sites in the Great Basin that I’ve worked on that didn’t have camels in them This is Wally’s Beach again Wally’s Beach has artifacts associated with both horse and camel The other two extinct camels are both lamas and lama size Hemiauchenia was widespread It was also a herd animal We know that, again, because we have found herds of them dead Palaeolama not as widespread Southeastern in distribution Navohoceros– this was the first reconstruction ever to have been done of navahoceros Wally Wolfenden and I did this together I did the anatomy Wally did the hard part, the part that takes talent He drew this When I saw this, I thought it was remarkable, because this animal is exactly how I would have pictured this This animal is not all that well known It was between a deer and an elk in size, but it had the bulk of an elk– of a very large elk– and very simple antlers It’s called a mountain deer because its skeletons suggest that it was a really nimble climber Its skeleton has been compared to the skeleton of a mountain sheep There’s its distribution Cervalces– this is often called the stag moose Found in two very different places in North America Major distribution obviously in the east around the Great Lakes, and then a very isolated distribution up here in the far northwest These animals are found in habitats that would be identical to the habitats in which you find moose today In fact, their post cranial skeletons are– the skeleton that’s not the skull– are very similar to the skeletons of moose So much so that they can be very hard to tell apart, but the antlers are distinctly different Sooner or later– and sooner is probably closer– the genetics of this animal are going to be known And my guess is it’s going to show that these stag moose are closely related to stag moose, cervalces, that occurred on over here in Eurasia, and that these are genetically distinct Nobody’s done that work So here is a moose-like animal that was not a moose We’ve all– many of us have seen pronghorn I can’t say we’ve all seen them, but many of us have seen pronghorn Pronghorn existed during the late ice age One of the things that makes pronghorn distinctive is this What did I do? One of the things that makes prong– I need three hands– pronghorns distinctive is this prong on their horn That’s why they’re called pronghorn Pronghorns have only two horns– a left one and a right one They existed in the late ice age during the ice age, but they existed alongside three other pronghorns, all of which have four, not two horns Capromeryx was the smallest of them Capromeryx would’ve been about that tall– 18 inches to two feet tall and weighed about 25 pounds The other two were pronghorn in size The difference between the other two is that, in one of them, the horns were of equal height In the other one, the horns were of unequal height, with the front horns shorter than the hind horns Capromeryx– reasonably well known It’s an easy animal to identify, because it is a tiny little pronghorn Western North America– tetrameryx not as well known, though you can see a complete skull on the top right there with those shorter front horns Stockoceros is better known There aren’t that many sites of it, but some of the sites that have provided the remains of stockoceros have provided the remains of dozens and dozens of them– 50 to 60 individuals As a result, the skeleton is really well known, and as a result, we know that these were her animals There’s no way the capromeryx, the tiny one, the diminutive pronghorn, could’ve

been a herd animal for the simple reason that it would have been too inviting a target for a predator Capromeryx was probably– the diminutive pronghorn was probably an animal that saved itself by stealth, and it probably had protective coloring Saiga– saiga are a sad story in the sense of that saiga were doing poorly for a long time in historic times People launched a major, major conservation biological effort to save them It was working, and then just recently they got really slammed by disease It’s an awful story They still exist in southern Asia, but during the ice age their distribution went from northern Spain and southern France– we find them in the sites that I used to work on in southern France– all away across into northwestern North America Euceratherium– the shrub ox It also had the convenient habit of pooping in dry caves in the arid west, so we know a good deal about its diet We know, for instance, that it was a browser It’s also western and distribution, and we know from its genetics that it was really closely related to the modern musk ox Bootherium– bootherium, for reasons I’ll talk about in a minute, is called the helmeted musk ox You can probably maybe even see why up there– that heavy mass of bone on its head Widespread– you find in the far northwest, the Arctic You find it from coast to coast It was found pretty much every place in unglaciated North America, except the far southwest and the far southeast There’s why it’s called the helmeted musk ox For a long time, this animal was divided into two different kinds– the genus symbos and the genus bootherium People began to realize that, gee, when we find one, we often find the other Maybe there’s something going on here, and what’s going on is that one was the girl, and one was the boy [LAUGHTER] The girl has horns like the modern musk ox has horns with a split down the middle The boy has horns that look like that– buttressed horns that are clearly meant to be used in head butting battles for male male dominance If you look at these horns, you can see something else here, and I think this is really cool See how these horns curl outwards– this is the male– while these are curving forwards? These horns are made for head butting These horns are not The head butting was meant to be just head butting You weren’t meant to hurt the other guy You were meant to intimidate the other guy These horns curl outwards so when these guys head butt neither of them is getting stuck by horns The female horns point forward perhaps because that’s a more effective way to ward off predators I won’t talk– we’re doing good for time That’s the kind of thing you’re supposed to say to yourself and not out loud I won’t say much about mixotoxodon The toxodonts are South American animals We know from very recent research that they’re most closely related to horses and rhinos, but they are South American Prior to the year 2013, we had no idea they got this far north In 2013, Ernie [INAUDIBLE], a very famous paleontologist, published the first record for a toxodont in North America from eastern Texas He told me about this two years before it was published, and I thought Ernie, who is quite old, had lost it It just doesn’t seem possible, but there is the tooth This is a toxodont Ernie will never lose it He’s right This is the only specimen we have for this animal in North America The next one down is in southern Mexico Mammoth, mastodon– everybody’s heard of mammoths Many of you– maybe even all of you– have heard of mastodons I’d be surprised if many of you who are not in the business have heard of gompotheres Gompotheres were the South American version of mammoth and mastodon Mammoth and mastodon did not make it south of Panama– the Isthmus of Panama South of there the proboscidean, the elephant-like animal, was the gompothere That’s what its jaw looked like

Gompotheres are characterized by the fact that they have these really complex cheek teeth These are a lot like the cheek teeth of mastodon, but they’re even more complex than their cheek teeth You can see how big they are These were massive, massive animals Gompothere specimens have been known for North America for quite some time, but only recently– and I mean really recently– was it realized how long they lasted in North America We now know that from this site called El Fin de Mundo that gompotheres survived in North America until about 11,550 years ago This is called a Clovis point It’s associated with the two gompotheres from this site Here is the site This site was excavated by Lupita Sanchez– you see her name here– and Vance Holiday Vance Holiday was the one who provided me with these illustrations There it is right there There they are excavating that gompothere mandible that you just saw, and here are what are called Clovis points I’ll show you another picture of these in a minute because I want to talk about Clovis for a minute Clovis is one of the most famous archaeological phenomena in North America It’s probably fair to say that Clovis is one of the most famous archaeological phenomena in the world Clovis dates to between 11,600 and 10,800 years ago It has an artifact that is totally diagnostic When you see it, you know what it is When you see it, you know how old it is When you’re an archaeologist and you find one, you never forget where you were when you found it They are splendid artifacts Like pronghorn, they seem to be over engineered People were importing raw materials– gorgeous raw materials all over the place to make these beautiful specimens Here is a cast of one that I’ll come back to in a minute Clovis sites are primarily the sites of the planes and southwest When people argue that the animals we’ve been talking about were driven to extinction by human hunters, it’s Clovis hunters that they mean One of the things that characterizes Clovis is the fact that they made what are called caches Nobody knows why they did this They’re amazing things They dug holes in the ground, left artifacts in them, and left them there I’m mentioning this one because there’s a famous Clovis cache in eastern Washington near Wenatchee It’s called the Richey Roberts site or the East Wenatchee Clovis cache There are about two dozen of these known from North America The Richey Roberts artifacts are on the second floor in the Burke Museum– not all of them, but enough of them to make it worthwhile to go see them there There’s also a great ground sloth skeleton– megalonyx skeleton– in the Burke Museum right near the Richey Roberts artifacts found when they were digging SETAC airport That one has a radiocarbon date, as I recall, of about 12,000 years ago– the museum one Mastodon– mastodons are quite different from mammoths I will point to that in a minute, but mammoths have these high domed heads Mastodons lack that These are low, long tank-like animals whose tusks jutted out kind of horizontally and whose teeth were much more complex than the teeth of mammoth Here’s their distribution There are two archaeological sites from North America that have both mastodon and either Clovis age artifacts, or Clovis points themselves, or Clovis dates– some combination of those two things I put this up here just to remind me of this amazing fact There’s a mastodon known from the Wasatch range of Utah at 9,800 feet elevation People who are interested in this stuff may notice that I’ve only got two sites here that I’m willing to accept as associated with Clovis age artifacts or Clovis age dates What’s missing is this site, the Manis mastodon site It is a very famous site in Washington State It’s near Sequim, Washington

It’s now on a set aside It’s being preserved The little museum in Sequim– you can go see the mounted skeleton of the mastodon from there Here’s the artifact– wrong thing to say Here’s the specimen that started the big deal about mammoths Many people think that this is also a human associated site, and they think that because of this particular bone This is a head of a rib Here are the articular surfaces where the rib would have joined with a vertebra, the backbone And here is this thing that appears to be sticking out of it Many people think that this is the tip of a bone projectile point This, by the way, is– I took this picture in– I shouldn’t tell you when, but 1977 when this was excavated This is the way looked right after it came out of the ground This is the way it looks today this is what paper published in Science in 2011 This is the location of that rib and this thing sticking out You can see the computerized x-ray, the CAT scan there It looks like a pointy thing The argument is that this is a bone projectile point sticking into a rib I am unconvinced, and here’s why I’m unconvinced, and I’ll just let you read this This is a musth battle, a musth battle between two male elephants Not only do we know that male elephants do this We know that mastodons did it, because there are mastodons known from the Great Lakes area with skeletal damage that only could have been done as part of this kind of battle That skeletal damage includes broken, shattered vertebrae It is fully possible that this piece of bone sticking into the mammoth’s rib is part of that animals own skeleton Until it’s shown otherwise, I’m not willing to accept this as an archaeological object Mammoth– we’re almost done with our tour Mammoths– the second iconic mammal of the North American Pleistocene People talk about two to four species of mammoths It’s now looking from ancient DNA that all these guys could probably interbreed These were massive, massive animals with massive, massive tusks There is that dome on its head that was meant to receive the muscles that ran back towards vertebrae, to an old up this massive, massive tusks It looks very different from a mastodon 11 sites have been found that have associations between Clovis artifacts and mammoths There’s no question that people were hunting mammoth I’ve been talking only about the genus level here so far– genus level extinctions, and I’ve been doing that because often it’s so hard to tell what are properly defined species is with extinct animals For horses, the genetics suggest that there may be as few as two species There may have been as few as two species of horses during the late ice age Paleontologists have defined some of them 10 species, some of them 20 species So nobody disagrees about the genus A horse is a horse, but there were three well defined species of animals that went extinct in North America The dire wolf is one of them The genus canis still exists in North America today– wolves, for instance, and coyotes, and humankind’s best invention, the puppy dog They all belong to the same genus Dire wolves were widespread They had massive, massive muscle attachments for the muscles that operate their killing mechanism, their chewing mechanism They were widespread They were clearly social There are 2,000 specimens of saber tooth cats at Rancho la Brea There are more than that of dire wolves at Rancho la Brea When one got stuck in the tar pits, bunches of them got stuck at once, suggesting they were hunting together These were pretty clearly pack hunters They were pretty clearly able to take down animals as big as bison

Panthera leo– this is still hard to believe, but it’s still true There were lions in North America during the late ice age Lions were extremely widespread at one time The Americas all the way over into Africa– the difference about the extinct American lion is that it was bigger than the modern African lion The genus still exists in North America because jaguars are still found in southern North America And then there’s the mountain goat People here know about mountain goats They were introduced into the Olympic Peninsula, where you can see them today They were mammals of the northern Cascades and northern Rocky Mountains There was a very separate species of mountain goat found in the southwestern US– the Great Basin in the southwestern US– for instance, in the Grand Canyon We know that it had white fur because that material has been found in dry caves in the Grand Canyon It was smaller than the modern mountain goat, but it was also a nimble, agile animal just as is the modern mountain goat Well, that’s my not so quick rundown I have 12 minutes left That’s my not so quick rundown of the players, the late ice age mammals of North America One thing that I have been kind of avoiding so far, except to give you a general notion as to when they became extinct, is the chronology, the timing of their extinction Remember, one of the arguments for the loss of these guys is that the root cause are Clovis hunters, that people entered North America The first people in North America were Clovis hunters– and that they hunted these animals to death That means that all these animals must have existed during Clovis times The problem is that we can only show that 17 of these 37 genera of mammals made it past 12,000 years ago We pretty much know that they were all gone by 10,000 years ago because there is not a single compelling date from any site in North America that has these animals much below 10,000, but less than half of them can be shown to have coexisted with Clovis Some of these animals– the most recent date predates 25,000 years ago What we can be sure of is that all of these animals were around 25,000 or so years ago All of them are gone by roughly 10,000 years ago, and a lot of them, but not necessarily all of them, were going out of existence between 12 and 10,000 years ago when Clovis people were around The age old question is, why? The obvious answer is climate change I have published a ton on this topic People always associate me with the climate change group, but the truth is that nobody has made a coherent compelling argument that climate can explain all of this, and I’m just going to leave it at that There is another explanation that’s quite recent that you may have heard about It made the popular media just as kind of sexy science often does That argument is that a comet exploded above glacial ice in the Great Lakes region of eastern Canada and caused these extinctions That is, the extinctions are due to an extraterrestrial impact In fact, that argument is not only that the extinctions were due to an extraterrestrial impact, but that the end of Clovis is to be explained by an extraterrestrial impact, as are a wide range of other things, including continent-wide burning for which there is no evidence, massive climate change, and a bunch of other things All I want to do is show you one slide This is the chronology of the latest dates for mammoth in the area where Alaska and Eurasia come closest together It’s called Beringia Remember, that comet is said to have exploded 10,900 years ago If that’s the case, their argument is that these extensions all occurred around 10,900 years ago, but as you can see here, our latest date for Alaska is 11, 500 There are probably younger ones Maybe they made it to 10,900, but our youngest date for a mammoth in mainland northern Siberia is 8,700 years ago Saint Paul Island– 5,700 years ago,

and amazingly enough, the youngest data Wrangel Island for a mammoth– and these are really good dates There’s over 100 dates on mammoth from Wrangel– is 3,700 years ago An impact event of 10,900 years ago which caused all these extensions doesn’t work And also remember that this is one of the reasons I mentioned South America when I started 37 genera became extinct in North America 54 genera became extinct in South America, all the way down to the tip of Tierra Del Fuego It’s hard to imagine, even without the slide I just showed you, an impact event explaining all of that Well, then there’s this We may not have time to get to my avocado [LAUGHTER] There is a really intriguing relationship between mammoths and avocados, gompotheres, and ground sloths, and avocados, but I promised I would only go an hour, and I only have about eight minutes left Human predation is clearly the most common argument that you encounter for these extensions, that Clovis people did all of these animals in The argument isn’t that Clovis people hunted the carnivores to death The argument is that Clovis people hunted the herbivores to death and that because of that their predators died, that saber tooth cats, and scimitar cats, and American cheetahs died because people did in their prey I’m no fan of that argument, and I’m no fan of that argument for reasons that I’ve actually kind of already mentioned Reason number one is this We can’t even show that half these animals made it into Clovis times That’s reason number one Reason number two is this There are 37 genera of mammals that became extinct, seven of which are carnivores, 30 of which are herbivores Of those herbivores, we can only show that people were associated with them in such a way that they were probably hunting them We can only show that for five of these animals Here are the sites We have one site with a camel in it and a horse in it We have one site with a gompothere in it We have two sites with mastodon in it, and we have 11 sites with mammoth, and that’s it I’m sure I would be gratified if you remember the distribution of ground sloths in North America, but in case you’ve forgotten, if you add them all up– all four of them– they were all over the place There’s not a single– not a single archaeological association with ground sloths in North America, even though they seem to have been everywhere There are other reasons I don’t like these arguments, but these are the prime ones We can’t show that people were hunting these animals, yet they are said to have hunted them to death We can’t show that all these animals, or even half of them, coexisted with people, yet they’re said to have hunted them to death Well, unfortunately, the conclusion to all this is that we simply don’t know what caused the extinctions The nice thing about this– and this may sound odd– the nice thing about this is the fact that we don’t know what caused the extinctions drives people nuts, and because it drives them nuts, it causes them to learn more, and more, and more about these animals Are you bored yet? [LAUGHTER] It’s 8 o’clock SPEAKER 1: [INAUDIBLE] DONALD GRAYSON: Avocado [LAUGHTER] Avocado, OK We’ve all seen reconstructions like this This is the 1972 reconstruction from the National Geographic It doesn’t matter that it’s, what, 40 years old? There are the animals We’ve talked about all of these, and let me point something out I just said that there’s not a single association between artifacts and ground sloths in North America that is in any way convincing Nobody even argues there is one There wasn’t one in 1972, but so deep is the assumption that people caused these extinctions that, if you look here, those are people hunting a Jefferson’s ground sloth There is absolutely no archaeological associations anywhere between Jefferson’s ground sloths, megalonyx, and people This drives me nuts [LAUGHTER]

But this is the view– I didn’t show this to foam at the mouth This is a common view Here are some more of them These are the reconstructions that you see of the North American ice age landscape It’s got the landscape teeming with animals Until relatively recently, I kind of pictured the American past this way I let myself think by analogy with the African plains, the African Savannah that North America was just covered with animals just like it’s shown here This, by the way, is from the Great Basin, an area that we’re going to talk about in a minute– high elevation Great Basin And so let me quickly talk about this I think five minutes is about right Let me quickly talk about this North America has four botanically defined deserts One of them is the Great Basin Desert right here Three of them are probably better known– the Chihuahuan Desert, the Sonoran Desert I think of these two as Walt Disney deserts This has saguaro cactus This has Joshua trees These are the three warm deserts of North America The cool deserts– warm summers, cold winters The warm deserts– hot summers, warm winters Here’s what the lower elevations of the botanical Great Basin look like– kind like parts of eastern Washington– sagebrush, and before livestock were introduced, grasses Here’s what the Chihuahuan Desert looks like I’m not going to talk about it anymore Loads and loads of creosote bush Here are Joshua trees in the Mojave Desert– kind of an iconic plant of the Mojave desert– and saguaro trees in the Sonoran Desert These are the warm deserts The Great Basin botanical desert has a diverse late ice age fauna 20 genera of animals– all of which we’ve talked about Here are their pictures– are known from there It also has a really well defined archaeological record One of the two earliest sites known from the Americas is from the Great Basin It is from eastern Oregon– called the Paisley Caves It has human fossilized feces I said turds before, but I don’t want to say it again because I shouldn’t have said it [LAUGHTER] Dated to 12,400 years ago from which human DNA has been extracted– Native American human DNA This is one of the two oldest sites known from the Americas The other is a site called Monte Verde in southern Chile that dates to 12,500 years ago The earliest diagnostic obvious artifacts from the Great Basin are also known from the Paisley Caves They’re known from everywhere, but they’re best dated from the Paisley Caves, and date to 11,100 years ago These kinds of artifacts are also associated with this cool thing called a crescent They’re widespread in the desert west We’ve got a really good archaeological record from the Great Basin We know that people were here by 12,400 years ago and that they were using points that looked like this– artifacts that looked like this 11,100 years ago We also have a good radiocarbon record for the extinct mammals, and because of that, we know that people were in the Great Basin at the same time as at least these seven genera of now extinct ice age mammals We know that people were living in the same places where those animals live That is, they overlapped in dates and they overlapped in habitat, and this made me wonder a couple of things There is no association between artifacts and an extinct mammal whatsoever in the Great Basin None None that people even argue about There are no kill sites from the Great Basin That made me wonder about how often people saw these animals Were they as common on the landscape as this reconstruction– this common kind of reconstruction suggests? Or where they rare on the landscape? Well, that made me think about an article that I read a 19– I read it before 1982 Richard Mack and John Thompson were botanists at Washington State I think Richard Mack is still there They sent me a manuscript when I was a young puppy and said, what do you think of this? And I read it, and made some comments on it, and thought it was cool, but I just didn’t get how important it really was What they pointed out was that, unlike the Great Plains– let me put this differently The Great Plains has grasses that are adapted to being eaten by larger herbivores like bison

The Great Basin doesn’t This is what they pointed out– that the Great Basin lacks widespread grasses that do well when they are chewed by large herbivores– when they’re grazed That’s why when you go to the Great Basin today in areas that have cattle on them you see hardly any grasses in the valleys They concluded that large grazers of the sort that we’ve been talking about here, these large herbivores, were never abundant there Well, it only took me 30 years to realize that maybe this is worth thinking about, and what I started thinking about was this– pointy, dangerous things on tall plants, plants that my colleague Connie [? Malark ?] calls ouchy plants Connie is sitting right there Anybody who’s a gardener, when you prune your roses, you come away with stuff that looks like this Well, imagine being a herbivore trying to eat one of these things So I’m talking about plants that have spines, thorns, anything that, if you try to eat it, it’s going to hurt you Their function is clear They’re meant to provide a mechanical defense against large herbivores Well, guess what? The warm deserts– Mojave, and I’m not going to worry about the Chihuahuan The warm deserts of western North America– the Mojave and Sonoran Deserts– have over 100 species of these ouchy plants, these mechanically defended plants spread across 21 different plant families They look like this– catcclaw acacia– there’s its distribution– or this, or this, or this with these very pointy, spiky leaves These are plants that have that armament to keep large mammals from eating them How about the Great Basin? There’s only six species in six families of these things in the Great Basin Here are three of them with their distributions That’s a huge difference Over 100 species in the warm deserts, only six species in the Great Basin cool desert? Somehow you cross a boundary when you go from here to there, from mechanically– from tall plants that are mechanically– pardon me From the lack of tall plants that are mechanically armed to an abundance of them And by tall plants, by the way, I mean plants that are over six feet tall Lots of them down here Hardly any of them up there I am calling that the mechanical defense line, because that’s what this represents– a line that bounds a place where plants are defending themselves with mechanical devices Obvious question to ask is, what created this line? Obvious answer is that it was created by climate After all, we’re going from a cool desert to a warm desert or vice versa, and sure enough, when you look at the history of these plants, that does explain some of it For instance, yellow paloverde, parkinsonia, doesn’t reach its northern edge of its distribution until about 4,000 years ago It had to wait till it warmed up until it could get that far north, but that doesn’t account for all of this Catclaw acacia with those really scary things– catclaw acacia was in the Grand Canyon 22,000 years ago during the late ice age Joshua tree was at the northern edge of its distribution by at least 18,500 years ago Climate can’t account for all of this What I think does account for it is the distribution of huge ice age herbivores, the animals these plants were defending themselves against Here are the heights of a subset of those 100 species There’s no herbivore today that can reach up 50 feet and eat the top of an acacia plant Doesn’t happen Here are the heights of the biggest herbivores in arid western North America today, and just to be as fair as I could, I include bison on there even though bison are looking down to eat and not up These animals are not tall enough to account for these tall mechanically defended plants The animals that can account for this are all now extinct So my guess is that, as we move north from down here up

into this area, the botanical Great Basin, we move from an area where these animals were relatively common to an area where they may well have been quite rare That perfectly matches the argument that Mack and Thompson made in 1982 Well, when I first made this argument, I don’t remember if I was talking to this person or sent him a manuscript that talked about this None of this is published, by the way He asked me– this is Dave Rhodey, a paleobotanist, one of my own students who’s often done this to me He said, don’t extinct herbivores ever look down? By which he meant, why are you only looking at tall plants? Why don’t you look at the short ones, also? That annoyed me, number one, because I hadn’t thought of it, because certainly extinct herbivores would look down, and number two because it meant a lot more work, and I thought I was done [LAUGHTER] So now rather than looking just at the tall mechanically defended plants, I looked at the short mechanically defended plants, and guess what? There is no difference in the distribution of these plants Short plants are mechanically armed as often in the cool Great Basin Desert as they are in the warm southwestern deserts, leading me to wonder why climate would matter to a plant that was seven feet tall, but not to a plant that’s five feet tall The only thing that can explain this is the height of the herbivores and the abundance of the herbivores that existed in this area in the late ice age So this is the argument, and I promise I’m almost done I’ve gone one hour and two minutes, but we’ve reached this [LAUGHTER] I’ve noticed that I walk down the ave holding an avocado, people applaud Now maybe I understand why There’s an avocado Avocados are amazing These obviously are kind of domesticated avocados, but the difference between wild avocados and this guy is the pulp of the fruit It’s not in the seed The seeds of a wild ones are this big This is obviously an avocado seed You see a fruit like this or a seed like this, the obvious question to ask, if you’re smart enough to ask it– and I wasn’t It was Paul Martin and Dan [? Jensen ?] in the 1980s who asked it and answered it– is here’s a big fruit with a huge seed Why? What could have possibly eaten this and distributed the seeds across the landscape? Well, it’s things like gompotheres, ground sloth, mammoths They’re all gone today It’s called a megafaunal fruit Megafaunal fruits are large fruits Here’s lots of characteristics of them– large fruits with large seeds The seeds could pass through the guts of an animal and still be able to germinate In fact, some of the seeds of megafaunal fruits have to pass through the guts of an animal to be able to germinate That’s the avocado story When you buy avocados when you eat guacamole, think to yourself that this plant clearly evolved in the presence of gompotheres, ground sloths, and other large things that were eating it and distributing its seeds Well, there’s at least 10 different species of plants with megafaunal fruits in the warm deserts of the southwest There is not a single one in the Great Basin That matches the distribution of mechanically defended plants and Mack and Thompson’s grasses Sloth poop Shasta ground sloth, sloth poop Many people think– and that includes me– that the dispersal mechanism for the large fruits of Joshua trees– these fruits are characterized by the fact that not only are they large, but they don’t break open on their own They’re called indehiscent They don’t break open and spread their seeds Many people think that one of the prime seed spreaders of yucca trees– of Joshua trees Excuse me– of Joshua trees during the late ice age was the shasta ground sloth It would eat those fruits It would wander across the landscape It would drop this someplace else

Then Joshua trees would emerge That, they argue, is why we have a distribution of Joshua trees that looks like it’s declining That is, that the primary disperser of this planet is now gone, and as a result, the plant is in retreat And sure enough, the late Pleistocene distribution of Joshua trees looks like this So that means to me as we go north in the arid west we go through an area where large mammals may not have been common, but they were common enough to lead to those diverse set of mechanically armed plants and to plants with megafaunal fruits to an area where animals– large mammals may have been quite rare Well, the other question to ask is this, and I’m not going to answer because I’m done, but the other question to ask is this Did any place in America actually look like this? There was recently a reconstruction of biomass, the number of animals on the landscape in Alaska, that determined that Alaska didn’t– not only– how do I put this? That a version of Alaska that looks like this vastly underestimated what Alaska looked like In fact, we don’t know that for any part of North America The next question to ask in this vein is just that– is there any place in North America that looked like this? And as part of that, the other question that’s going to continue to be asked is, what in the world caused the extinction of all these things? And with that and an hour and five minutes after I started, thank you [APPLAUSE] Thank you