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How Many Mammoths?

Hebior Mammoth

Hebior Mammoth (Mammuthus primigenius) on display at the Kenosha Public Museum. Collections housed at the Milwaukee Public Museum. Image by Chris Widga and Stacey Lengyel. Used with permission from the KPM.

To paraphrase Larry Agenbroad, the former director of the Mammoth Site in Hot Springs, SD, Mammoth taxonomy is confused, and confusing. And it has been this way for a long while. Henry Fairfield Osborn, a giant of North American vertebrate paleontology dedicated decades of his life (and that of his assistants) to the production of a 1600-page, 2-volume, tome describing the Proboscidea, published posthumously in 1942.  Through a specimen-by-specimen analysis, he described 16 species of North American mammoths across 3 genera. Since that time, North American mammoth species have undergone significant pruning, with most paleontologists recognizing 4-5 species across North America: M. meridionalis (Southern Mammoth), M. columbi (Columbian Mammoth), M. primigenius (Woolly Mammoth), and M. exilis (Channel Island Pygmy Mammoth). A fifth species, M. jeffersonii (Jeffersonian Mammoth) was considered an intermediate form showing characteristics of both Columbian and Woolly mammoths.

The story went something like this…Around 1.5 million years ago, the Southern Mammoth (M. meridionalis) emigrated to North America, settling along the west coast. Shortly after, the Eurasian Steppe Mammoth (M. trogontherii) joined its trunked brethren. Both were found in early deposits in the Anza Borrego Desert of southern California (and potentially the Great Plains and Florida). The Southern Mammoth died out or was swallowed up by the more successful Columbian forms, which radiated throughout most of North America. The BIG mammoths that fill western museums, like Archie at the University of Nebraska and the Angus Mammoth at Denver were initially considered to be too big to be run-of-the-mill Columbian mammoths and were anointed “Imperial” mammoths. Woollies migrated down the front of the continental ice sheets late in the game, during the Wisconsin glaciation sometime in the last 100 thousand years. Jeffersonian mammoths were the love-children of Woolly and Columbian mammoths. And the Island Pygmies were early Columbian mammoths that swam the channel or wandered across a land bridge.

This was a great story. It had action and explanation. And it was the framework that most museums used to explain their monstrous Mammuthus mounts (or miniscule mounts, in the case of the Pygmy Mammoth on display at the Santa Barbara Museum of Natural History). But two papers in the last 6 months have shown that the reality is actually much more complicated…and interesting.

The first paper was a study by Adrian Lister and Andrei Sher. There are few scientists who have seen as many mammoths as Lister (who literally wrote the book on the subject). In a project that spanned decades, Lister and Sher visited many North American collections housing early mammoths. From California to Florida and everywhere in between. They concluded that the earliest mammoths on the continent were, in fact, not M. meridionalis. Rather they were an odd assortment of poorly prepared/reconstructed material, individuals with heavily worn teeth, or simply Columbian mammoths from an early context. The clincher was that they had an excellent sample of Old World Southern Mammoths that didn’t overlap with any of the North American specimens. Any-of-them…

The second paper (Poinar et al. in press) came out this week. A few years ago, we hosted a sharp graduate student from McMaster University (Ontario) who was interested in our midwestern mammoths, Jake Enk. I bought him lunch. We talked at length about messed up mammoth taxonomy. Normal stuff. Ultimately, Jake sampled ~30 teeth for genetic studies (like this one), then moved on to major collections of Mammuthus in Nebraska, Denver, UC-Berkeley, and Santa Barbara. Given the success rate of previous aDNA studies, we expected that one or two of these specimens might actually give us some decent data. To my surprise, Jake was able to extract complete mitochondrial genomes from 67 mammoths from south of the Laurentide ice. An even bigger surprise, was that they were all chips off of the same block. They weren’t even different species.

Well…this was a surprise/not surprise. We had been looking at this issue through the morphology of midwestern mammoth teeth and found that there was a significant amount of overlap between different “species” and shared our data with Jake. The conventional wisdom that Columbian mammoth teeth were distinct from woolly and Jeffersonian mammoth teeth just wasn’t holding up. You could see multiple morphs within a small geographic area–and we had the dates to prove that we weren’t seeing the influx of “new populations” through time. Things seemed to get really complicated in ecotonal areas, like Iowa. During the Last Glacial Maximum Iowa was a transitional landscape between the more open steppic grasslands to the west (“Columbian” mammoth territory) and the forest steppe (think Taiga) of the east (“Jeffersonian” and “Woolly” Mammoth territory). We hit collections at the University of Iowa, Iowa State Historical Society, Putnam Museum (Davenport) and the Sanford Museum (Cherokee) hard, hoping to figure out where one species left off and the other began. We ended up scratching our heads over animals that had jaws that looked like Woolly mammoths, but teeth that were Columbian…or jaws that were Jeffersonian on one side, but Woolly on the other. We found localities like the mammoth bonebed in Mahaska County, that had one jaw that looked like a Columbian mammoth, but two more that were dead ringers for big Woollies. These were exactly the morphological patterns that we might expect if a) Mammoths were a single biological population capable of inter-breeding and producing viable offspring, and 2) the midwestern mammoths were in the middle of the mess, showing characters of both populations.

So do these different “species” of mammoths mean anything? Why bother measuring teeth if all mammoths are the same? After the initial shock wore off I had plenty of time to think about this. As a morphologist, the idea that we are dealing with a single, morphologically variable population is actually…well…kind of liberating. Now we can explore how certain characters may have been selected for in different environments. We can think about functional morphology, broad-scale impacts of landscape/diet on body-size, or the morphological effects of introgressing populations. Before…the pygmy mammoths of California’s Channel Islands were an unrelated off-shoot of my midwestern behemouths, perhaps responding to nutritional stress and landscape changes in very different ways than their mainland cousins. Now, they are just another mammoth population that is using the same set of morphological and genetic tools to deal with the situation at hand. And we can learn from that.

Mammoths are fun to think about, even when we don’t know all of the answers. These papers (and a third that Jeff Saunders and I are hoping to finish up this week) illustrate the importance of retaining natural history collections in museums. A decade ago, there would have been no chance of getting this degree of genetic recovery out of fossil mammoths south of the ice. Even for “traditional” studies of morphology the only way to get sample sizes large enough to say meaningful things about the biogeography of a creature is to rely on the materials collected and accumulated through many generations.

 

 

Excuses, excuses, excuses…

This blog has been *sleeping* for a few months. Why, you might ask dear reader? Well…the last few months could best be described as schizophrenic. The projects that we’ve been working on are pretty diverse, and they’ve all been progressing, more or less, synchronously. So stay tuned for more details. In the meantime, here’s a rundown of what’s in the hopper.

1. Mammoths and mastodons. Our extinction project is in its last year. The dates are rolling in and we have some very interesting results. We’ve narrowed down the error estimate around the actual time of mastodon extinction to ~250 years. They blip out in the Midwest just as the Younger Dryas, a return to glacial conditions, is getting underway ~12.9 ka. Although mammoths are probably extirpated at about the same time (the last mammoth dates are just a few hundred years earlier than the last mastodon dates), their pattern of extinction is much different. Mastodons go out with a bang. In the last few hundred years prior to extinctions, mastodons are still distributed widely throughout the Midwest. In fact, many sites dating to this time period have multiple animals in them (including Boney Spring, MO, with ~31 mastodons). Mammoths however, are fewer and farther between by the time the terminal Pleistocene rolls around. Although they are here, shoulder to shoulder with mastodons, they are not present in high numbers.

2. MORE Mammoths and Mastodons. Although our project is focused on the extinction of these beasts, we’ve also been able to document quite a bit of morphological diversity in mammoths and mastodons. What do these patterns mean? Are they due to a complex evolutionary history? Or to local environmental pressures? Are there chronoclines (shape and size changes through time) that might give us insight into adaptive strategies?

3. Even MORE Mammoths and Mastodons…and isotopes. We’ve been tweaking our new micromill technique to drill very tiny holes in mammoth teeth. The importance of this research is that it gives us a seasonal-scale picture of the life of a mammoth over the course of a few years. We can see what it was eating and where it was moving (IF it was moving).

4. 3D scanning and printing. In June we received our first 3D printer. In August we received our second. We’ve been working to test the dozens of 3D scans we’ve done over the last year or so. We’re hoping to post them to a gallery soon.

5. Going to the dogs. Illinois is home to one of the most complete records of early dogs in North America. A few years back, we started re-analyzing dog remains from the Koster and Stilwell sites in western Illinois for insight into the lives of these early dogs. I’ll definitely be talking more about them in the next few months.

6. Just batty. Finally, no blog post would be complete without some mention of the bat paleontology that we’ve been working on. Bat guano. Bat bones. Bat ecology.

From mega to micro. Stay tuned for more updates.

C

Midwestern Mastodon Bonebeds: Death Traps and Salt Licks

Big mastodon sites have been getting a lot of press lately. In particular, the Snowmass site high up in the Colorado Rockies has produced over 30 mastodons over the course of two field seasons. This site–making national news on a regular basis over the last year–was a pond where the bones of mastodons, mammoths, bison, and ground sloths (to name a few) were found by the dozens. The Snowmastodon site (as it has been called) was featured on Nova a few weeks ago. Kirk Johnson (Denver Museum of Nature and Science) and Dan Fisher (University of Michigan) suggest that the high number of mastodon bones in debris flows are the result animals trapped on the sandy shores of the pond during earthquake liquefaction, and that humans may be partly responsible for a partially articulated mammoth in the upper levels. This is a fascinating site, and we’re looking forward to seeing what comes from the scientific investigations…which have only begun.

However, the Snowmastodon site puts in my mind a few other big mastodon bonebeds. The Boney Spring site in the western Ozarks was excavated by crews from the Universities of Arizona and Missouri, and the Illinois State Museum in the 1970s. The Ozark project explored a number of important paleontological and archaeological localities. Boney Spring itself was the latest of three major paleontological sites spanning the last ~150,000 years. In all, 31 mastodons were excavated from a single component of the site, dating to ~16,000 years ago. This assemblage includes animals of all ages and sexes, including a very large bull, who remains the largest North American mastodon on record. Although dominated by mastodons, the Boney Spring assemblage includes a minor number of other critters, including: 4 Paramylodon harlani (Ground Sloth), 2 giant beavers (Castoroides), horse, and tapir.  Although small mammals are well represented, no large carnivores were present in the assemblage. Long-time ISM curator Jeff Saunders suggested that this concentration of mastodons was the result of environmental conditions–specifically, a severe drought which caused dying mastodons to congregate around the only source of permanent water, Boney Spring.

Another big Midwestern mastodon site is the “Birthplace of American Vertebrate Paleontology” itself, Big Bone Lick, Kentucky. Located in north-central Kentucky near the Ohio River, BBL has been the site of paleontological investigations since the 1730s. By the early 19th century, Thomas Jefferson became interested in the locality, tasking William Clark (of Lewis and Clark fame) to collect fossils for him. Mastodons figured prominently in early collections from BBL. The locality was investigated periodically throughout the 19th century by paleontological notables, but became a research backwater by the early 1900s. In 1962, University of Nebraska paleontologist C. Bertrand Schultz returned to BBL for five field seasons, the first modern paleontological excavations to occur at the site. Schultz and his collaborators discovered that the BBL locality had a complex geological history. Mastodons and other Pleistocene fauna were recovered cheek-to-jowl with bison. But these bison were not the large-horned animals contemporaneous with Pleistocene megafauna, but rather short-horned late Holocene forms. Today, the locality is a state park with an on-site visitor center and full-sized Pleistocene dioramas.  Bones still erode out of the creek banks…

Welcome!

Welcome to my world! This is a research blog about what we do every day at the Illinois State Museum. I am a vertebrate paleontologist who specializes in Ice Age mammals. My research, and much of our museum outreach focuses on the rich record of Quaternary vertebrates in the Midwest and Great Lakes area. Why do we need another blog about giant extinct animals you ask? Doesn’t Switek already take care of that? Believe it or not, modern paleontology is a field whose breadth is huge! Here at the Illinois State Museum, many of the natural history curators are part of the Landscape History program. This describes what we do fairly well. The botanists look at vegetation change and the immediate impact of climate changes on the landscape. Paleontologists and zoologists work with ancient and modern critters, respectively. Archaeologists and historians look at how people used the landscape. Most importantly, we all work together to piece together how past ecosystems work. Just like we can’t understand the dynamics of human populations without understanding their physical environment, it is increasingly evident that we can’t understand vegetation or faunal communities in isolation either.

But why a blog? And why “Backyard Paleo?” Well, I work at the Illinois State Museum. That means that my research and activities are geographically focused on the Midwest. I don’t head west every summer to dig dinosaurs. I don’t travel to Africa to look for human ancestors. It is my job to explore the nooks and crannies of midwestern creekbanks, road-cuts, gravel quarries, and yes, backyards. In reality, there is really cool paleo almost anywhere–you just need to slow down and look closely. This blog allows me to show you (oh loyal reader) what we do, and why it’s important.

At least for the next few months I’ll probably be blogging about Quaternary mammals–with a particular affinity for mammoths and mastodons. This is because we’re in the middle of a big project to understand how and why these massive creatures went extinct at the end of the Ice Age, and frankly, there are a lot of stories to tell about elephants. So stay tuned, and maybe you’ll learn something about YOUR backyard.

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