North American Proboscideans and Dr. Chris Widga – Part 1

“Most zooarchaeologists are interested in the people, and they use the animals as kind of a tool for understanding butchering patterns or food ways or something like that.”

Dr. Chris Widga and I were in the midst of a great conversation about three recent papers he co-authored, paleontology, proboscideans, and the state of science today.

“I was always interested in the animals themselves,” he continued, “so when I got the position as a vertebrate paleontologist at the [Illinois State Museum], all of my friends who’d known me for years said, ‘well, that was a no-brainer for us. You were doing vertebrate paleontology all the time on Holocene bison. You never cared much about the people!’”

That beginning in zooarchaeology and the subsequent immersion in paleontology are what give him a unique perspective of the two sciences.  Or, as he himself explained: “I guess I kind of have this foot in both worlds.”

The two occasionally overlap.  In the paper published this past February in Boreas, “Late Pleistocene proboscidean population dynamics in the North American Midcontinent,” he and his colleagues take a closer look at what might have caused the extinction of mammoths and mastodons in what is now the middle of North America. Possible culprits include climate change, shifts in available vegetation, and predators (including humans).

Of the 627 localities included in this study, only 3 offer any kind of human association.  The authors state that these sites were “re-visited to ensure consistent taphonomic and zooarchaeological data,” and that, despite this, whether or not these specific humans and proboscideans interacted remains unclear.

“That’s a distinction I like to make as a paleontologist and a zooarchaeologist,” Dr. Widga offered. “Just because we have a couple of the sites with humans associated [doesn’t necessarily indicate that] humans actually hunted, killed and butchered those animals.  [Humans] may have scavenged them.  They may just simply be associated in these sites. And very few of those sites have been analyzed to the degree of detail that we really need to start teasing apart those issues.”

What he and co-authors Stacey N. Lengyel, Jeff Saunders, Gregory Hodgins, J. Douglas Walker, and Alan D. Wanamaker try to do, however, is take a deeper look at the late Pleistocene environment in which these proboscideans lived.  It’s exciting research: Rather than simply describing fossils discovered in the various US states and one Canadian province, they are trying to put them into context.  In other words, they are trying to understand the ecology of that time period and how that may have affected the megafauna living within it.

But it’s not an easy task.

“Ecologists can look at modern ecosystems and say, ‘Ok. This is what’s going on, and this is why we think that, and this is how we’re measuring it’ in great detail.  But extrapolating those same processes back into the paleontological record is often really, really difficult even with the best data set.

For example, “[w]e can observe boom-and-bust cycles in deer populations, in caribou populations, in musk ox and things like that. But when you try and translate that into the paleontological record, most of the time it’s really difficult because you simply don’t have the samples and you don’t have the time resolution.

“Even in our case, where we have really good samples and we have really good dates on our samples and we’re creating this chronological structure to kind of fit them in, it’s really difficult to translate those patterns into ecology.

“We can’t date a single mastodon any more precisely than about a hundred-year window.”

The fact that some of the ecological constructs used today in extant populations are controversial makes trying to apply such constructs to extinct animals that much more of a challenge.

“When even the ecologists can’t truly [agree upon] what’s going on, you have to navigate things very, very carefully.”

The amount of work put into this paper (work that has produced previous, subsequent and yet-to-be-published papers) is staggering.  Thanks to a National Science Foundation grant, Dr. Widga and Dr. Jeff Saunders—both previously at the Illinois State Museum—were able to visit an astounding number of museum collections in the Midwest and review their proboscidean fossils.

“We’ve [basically] spent the last 5 years in other people’s collections,” he explained. “It was fun because we visited a lot of collections that people don’t usually go to. About half of the data set comes from repositories that have fewer than five mammoths and mastodons.”

 

 

An inside look at the extensive fossil collection at the Indiana State Museum collection–one of the many collections visited by Dr. Widga.  In our conversation, he said, “The Indiana State Museum is a big dot on the map in terms of mammoths and mastodons, in part because of [paleobiologist Ron Richards’] work!”   This image was taken in 2005, picturing then Collections Manager Michele Gretna (currently Director of Archaeology); image courtesy Indiana State Museum and Historic Sites.

Another inside look at the Indiana State Museum collection; Preparator Elizabeth Scott after the reconstruction of the Kolarik locality mastodon tusks, 2014; image courtesy Indiana State Museum and Historic Sites

 

 

Their work involved the review of over 1600 fossils that currently reside in collections in Ontario, Canada, as well as in Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Michigan, Nevada, Ohio, South Dakota and Wisconsin.

“We doubled the number of known published sites for mammoths and mastodons in the Midwest.”

Information that they are willing to share with other scientists, as evidenced by the number of papers they continue to co-author.  Following the Boreas paper, Dr. Widga was part of another two papers published in March in Quaternary International and then in Scientific Reports.

Mammoth teeth take a leading role in the paper, “Reconciling phylogenetic and morphological trends in North American Mammuthus,” published in Quaternary International and co-written with Jeff Saunders and Jacob Enk.

“We’re starting to put out some of these ideas that actually put data onto these [traditional] species boxes that we like to put specimens into.  So that was one of the first steps into thinking about these things: more as morphologically variable populations rather than just trying to assign them to a particular species.

“A lot of times these studies kind of happen in isolation.  So the people that think about morphology, they’ll publish on the morphology and then post-hoc, they’ll say, ‘oh but this doesn’t agree with the genetics at all.’ Or the geneticists will publish on the genetics, but they don’t integrate any morphology.  So our point was to try and integrate both of them and see what they say. Can you use the genetics to kind of structure your interpretations of what the morphology means?”

The authors studied “M3s”—the permanent upper 3^rd molar—of both female and male mammoths of various ages from museum collections and from previously published work.

Per Dr. Widga, this is the upper 3rd mammoth molar from Clear Lake Sand and Gravel Pit, Sangamon County, IL. One of his favorites from the ISM collection. It dates to the Last Glacial Maximum and had preserved DNA so is included in the Enk dataset; image and caption courtesy Chris Widga.

 

“Jeff [Saunders] and I would say, ‘this genetic information actually fits perfectly with our morphological information which suggests that there’s a lot of population overlap in between these normally well-defined populations.’ So in between Columbian mammoths in the Great Plains and woolly mammoths from the Great Lakes you have Iowa mammoths that show characteristics of both. And also they show characteristics of both in the same animal!

“That was kind of the impetus for the [Quaternary International paper]: to get that out there, show that you do get a lot of overlap in the morphology. It’s not just clean boxes of Columbian mammoths and woolly mammoths. And even pygmy mammoths overlap with Western Columbian mammoths! So that was kind of the point of the paper: to get the conversation going and make a first pass–a first attempt–to reconcile the two data sets.”

Following soon after the paper in Quaternary International, he was part of a remarkable group of proboscidean and genetic scientists whose paper The evolutionary and phylogeographic history of woolly mammoths: a comprehensive mitogenomic analysis analyzed 143 woolly mammoth mitochondrial genomes.

As Dr. Widga said with characteristic enthusiasm about his work in paleontology, “It’s always fun! There’s always a mountain to climb and a vista to see!”

*****

A Mammuthus columbi-sized THANK YOU to Dr. Chris Widga, who was remarkably generous with his time, with images to use and with answering my many, many questions (both for this blog and for my own proboscidean curiosity).  Speaking with him was delightful; he is an incredible ambassador for science in general!

Another sincere THANK YOU to Ron Richards for providing the great images of the Indiana State Museum collection. 

References:

1. Widga, C., Lengyel, S. N., Saunders, J., Hodgins, G., Walker, J. D. & Wanamaker, A. D.: Late Pleistocene proboscidean population dynamics in the North American Midcontinent. Boreas. 10.1111/bor.12235. ISSN 0300- 9483.
2. Widga, C., et al., Reconciling phylogenetic and morphological trends in North American Mammuthus, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.01.034
3. Chang, D. et al. The evolutionary and phylogeographic history of woolly mammoths: a comprehensive mitogenomic analysis. Sci. Rep. 7, 44585; doi: 10.1038/srep44585 (2017).

Mastodon fossil at the Illinois State Museum; image courtesy of Chris Widga.

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Eliann Stoffel – Unlocking the Secrets of a Forgotten Mammoth

A rather large bone, revealed by his bulldozer, prompted William McEvoy and his crew to cease work on the road and call the police. The police then called the local archaeological society, who, in turn, called an archaeologist at the local Natural History Museum.

When word got out that a mammoth had been discovered, visitors began pouring in to see the site.  Just a few miles outside of the town of Kyle in Saskatchewan, Canada, the excavation of these fragile bones from the hard clay was witnessed by an ever-growing number of people.  It is estimated that 20,000 visitors came to see the site that autumn in 1964.

Embed from Getty Images

 

Eventually, the plaster casts protecting the bones were taken to the Natural History Museum (now known as the Royal Saskatchewan Museum); radiocarbon dating was conducted.  Possible museum displays and skeletal reconstructions were discussed.

And then?

Nothing.

Once the cause of great local excitement, the bones of the Kyle Mammoth faded from view.

The references above to archaeology are not errors.  Although the bones found were paleontological in nature, the focus on the find—and, indeed, the very reason they were recently resurrected—was to determine whether there was any evidence of human-proboscidean interaction.  When no stone tools were recovered in the surrounding sediment and with no obvious signs of butchering on the bones, interest in the fossil seems to have collectively disappeared.  For over 50 years, the various bones found on that stretch of road have been shelved in the Museum’s collections.

“I had always planned on doing my thesis at the University of Saskatchewan and I knew I wanted to do my thesis on hunting and butchering strategies utilized by Paleoindian people,” explained Eliann Stoffel, a recent graduate, in an email.

Her interest was not specific to any one species of megafauna. She hoped to study any and all large animals ancient people may have hunted: camels, bison, horse, proboscidea.

“I had approached my supervisor, Dr. Ernie Walker, with this topic and he had spoken with a member of the Saskatchewan Archaeological Society, Frank McDougal, who had suggested taking a look at the Kyle Mammoth.”

Which is how the long-forgotten fossil came back into view in 2015.

“We knew that the mammoth belonged to a time when people were in North America and actively hunting mammoths so we had the possibility of finding some sort of evidence of humans on the Kyle mammoth.”

This evidence is rare in the area known as the Northern Great Plains, an area that encompasses Saskatchewan (as well as another Canadian province and five U.S. states).

“It was one of those projects,” she said later by phone, “that, as soon as it came up, I couldn’t turn it down.  It needed to be done.”

Travelling between Saskatoon and Regina (where the Royal Saskatchewan Museum and the fossil are located), Eliann spent many hours studying and analyzing the bones from the 1964 excavation.  This included five boxes of bone fragments as well as 56 complete or near-complete bones, such as vertebrae, mandible, a partial tusk, and ribs.  Also included were ungulate bones, which—like the mammoth—did not comprise a full skeleton and did not present any clear association with its proboscidean fossil companion.

 

About 20% of the mammoth skeleton survived; image courtesy of Eliann Stoffel, University of Saskatchewan

 

Eliann’s thesis presents a comprehensive taphonomic analysis of the mammoth bones, and this was done because she and her advisors “knew that we needed to keep in mind that we might not find any evidence of human involvement.”

The idea of determining who or what made any kind of marks on a fossil seems like an overwhelming challenge.  This was not an animal that died the other day.  In this case, it died roughly 12,000 years ago. That is a considerable amount of time in which—after an animal is butchered, killed or otherwise dies of natural causes–it can be scavenged after death, it can be moved and scraped by natural elements, it can be affected by its fossilization, and then possibly affected by the process of discovery (in this case, by a bulldozer). How is anyone able to read the marks on fossil bones and know what they represent?

“[T]he first giveaway is the colour,” she wrote. “Bone, when it has been buried for a long time, tends to become stained from the surrounding sediment but only the outer surface. So when someone (an excavator) knicks the bone, the unstained inner portion of the bone is exposed and tends to be a lighter colour.

“The other indicator can be the clustering of marks. [With] butchering, there tends to be more than one cut mark on the bone in the same general area, usually at muscle attachment sites, and they tend to be orientated in the same direction. Rarely do you find cut marks that intersect each other. They are usually parallel. In accidental knick marks there is usually just the single mark and it tends to be located in a spot that you wouldn’t generally find cut marks (i.e. on joint surfaces or midshaft of a long bone).”

 

 

Photo of the Kyle Mammoth right mandible from her thesis; courtesy of Eliann Stoffel, University of Saskatchewan

 

Contrary to initial review in the 1960s, Eliann discovered a few tantalizing signs that this mammoth may have, indeed, suffered from trauma induced by ancient humans.  From a suspicious-looking lesion to a possible puncture wound on vertebrae to a puzzling set of lines in a bone fragment, there was reason to wonder whether humans had been responsible for these scars.

Ultimately, however, the first two were determined to be pathological. The lesions conform to known understanding of malnutrition in the form of osteolytic lesions.

Knowing her hope to find evidence of human interaction, I asked if this was a bit of a disappointment.

“[I]t was a bit of a kick in the knees,” she admitted, “but still a super interesting avenue of study in terms of pathology. I am more than thrilled with my findings though!”

 

Images courtesy of Eliann Stoffel, University of Saskatchewan

 

Another startling discovery appeared in what she describes as a “spongy” bone fragment, shown above, which contain traces of blood vessels.

“I remember bringing it to my supervisor and we both scratched our heads over it…So we called on our resident bioarchaeologist Dr. [Angela] Lieverse to take a look and she wasn’t sure but suggested possibly something vascular. Sure enough, when I searched for studies fitting that criteria, a couple articles turned up. So it seems that it is an occurring phenomena but possibly not that common,” Eliann wrote.

Ultimately, Eliann determined that this was a young male woolly mammoth (between 28 – 35 years old) that was still growing at the time of its death.  She estimates it was 328.66 cm (approximately 10.8 feet) tall.  While the large open wound on one of the vertebra points to a possible puncture wound from Clovis weaponry, other pathological features point to a mammoth suffering from malnutrition.

Eliann’s enthusiasm for those who helped her in her research was apparent.

“[T]he folks at the [Royal Saskatchewan M]useum were more than happy to help in any way possible,” she expressed, “and it is something that I have always appreciated! Also my major funders [were] the Saskatchewan Heritage Foundation, the Saskatchewan Archaeological Society, and, of course, the Department of Archaeology and Anthropology at the [University of Saskatchewan].”

More than just a strenuous academic endeavor, Eliann’s research has painted a picture that has been missing for decades on a significant local paleontological find.

“The [people in the] town of Kyle identify with this mammoth.  As you come into Kyle, there’s this statue of a mammoth.  Their sign that says ‘Welcome to Kyle’ has a picture of a mammoth on it.  It’s clear that they identify with it.”

 

 

A Mammuthus primigenius-sized THANK YOU to Eliann Stoffel—not only for her time in emails and by phone–but also for her gracious permission to use a number of pictures from her work!  Her thesis is fascinating and well written.  I recommend it to all!  Eliann, may you find many mammoths with evidence of human association in the future!

Another enormous thank you to Dr. Angela Lieverse, head of the Department of Archaeology and Anthropology at the University of Saskatchewan, who was also responsible for the generous use of images from Eliann’s thesis!

And I am very grateful to Dr. Emily Bamforth at the Royal Saskatchewan Museum for connecting me to Eliann! I could not have written this otherwise. THANK YOU!!

*****

References:

1. The Kyle Mammoth: An Archaeological, Palaeoecological and Taphonomic Analysis, Eliann W. Stoffel, July 2016, University of Saskatchewan
2. Shedding Some Light on the Kyle Mammoth, David Zammit, Swift Current Online, Nov. 13, 2016; the article that brought Eliann Stoffel and the Kyle Mammoth to my attention!
3. PDF about the Kyle Mammoth from the Royal Saskatchewan Museum

Screenshot from the aforementioned PDF of the Kyle Mammoth, Royal Saskatchewan Museum

Meet Dr. Katy Smith – Mastodon Detective

If you imagine the Great Lakes region over 10,000 years ago, you might see large, hairy beasts with relatively straight tusks grazing around boggy areas or moving within dense forests.  Their fur and overall appearance might cause you to confuse them with woolly mammoths, but these are the mammoths’ shorter, stockier cousins.  And if any of them would let you get close enough to inspect their mouths, you’d see in an instant that their teeth are completely different than those of mammoths.

 

[image of contemporary boggy area in Alaska, courtesy Getty Images]

 

Whereas mammoths are believed to have eaten grasses and even flowers, mastodons needed teeth suited to the mastication of hardier stuff: shrubs, parts of trees, perhaps pinecones?   Mastodon teeth, with the bumps and ridges one might associate with carnivores, are easily recognizable as ‘teeth.’  Mammoths, in contrast, needed to grind food, producing teeth with spherical lengths of ridges across each tooth.

 

[image courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 1.  Can you tell which tooth belongs to which species?]

 

 

[image courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 1.]

And while woolly mammoths pervade popular culture and interest, there are some, like Dr. Katy Smith, Associate Professor of Geology at Georgia Southern University and Curator of the Georgia Southern Museum, who prefer their lesser-known cousins and have made fascinating contributions to our understanding of them.

Mastodon discoveries usually produce the fossils of a single animal, and rarely a complete skeleton. Rarer still, finding skeletal remains of multiple mastodons at the same site.

Such a unique discovery occurred in 2005, when more than 300 fossils were found in Hebron, Indiana.  Now known as the “Bothwell site,” it was originally going to be the location of the landowner’s pond.  Instead, Indiana State Museum paleobiologist Ron Richards and his crew uncovered bones that included numerous mastodons (Mammut americanum), giant beaver (Castoroides) and hoofed animals with even-toes (artiodactyls).

 

[images of the Bothwell site dig, courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 2.]

 

Four years later, the Bothwell site became the focus of Katy Smith, her dissertation, and two subsequent papers she co-wrote with Dr. Daniel Fisher at the University of Michigan.

But let’s take a moment to consider what paleontologists uncover. However rudimentary this may seem, it is important to note that bones are generally not discovered in neat order, intact and with each skeletal component attached where it would have been in the life of the animal.

Consider, too, that not all bones survive.  And those that do are often broken or in terrible condition.

So even at a site such as Bothwell, which produced lots of fossils, a paleontologist’s job is no less challenging.  The pieces of information are incomplete, mere clues to the animals that died there.

The questions, however, are profuse.

Why were so many animals found in that one spot?

If, as it is currently debated, mastodons shared behavioral traits with modern-day elephants, was this a family unit?

If so, was this group—like elephants–comprised largely of female and juvenile mastodons?

And why were other unrelated animals discovered among them?

Did a sudden disaster kill them all?  Were humans involved?

 

Embed from Getty Images

 

Sexual dimorphism is another way of referring to the traits that make an animal either female or male.  Some of us would assume, since mastodon pelvic bones were not among the Bothwell fossil assemblage, that the sex of these animals would remain unknown.

There were 13 mastodon tusks, only four of which were complete. And this, remarkably, is what prompted Katy Smith’s research.

“I wanted to know if I just had tusks, what can I do to figure out if I’m looking at a male or a female,” she explained by phone.

 

[image of Dr. Katy Smith measuring an African elephant tusk in (what this author believes must be one of the greatest places on earth) the basement and fossil collection of the University of Michigan; courtesy of Dr. Katy Smith]

 

“Other people have looked at [sexual dimorphism], but I wanted to look at it specifically with the Bothwell mastodons, because they were inferred to be female, and female mastodons are less common in the fossil record than males.

“When I presented preliminary results from my research in a paleontology class, the professor said, ‘Why don’t you try multivariate analysis?’ And it just kind of spiraled from there.”

‘Multivariate analysis,’ as the name implies, means using more than one type of measurement or observation towards a hypothesis.  In other words, rather than simply using size as a determination of sexual dimorphism, applying numerous methods and statistics that support or disprove it.

Already, the amount of information scientists have pulled from tusks alone is fascinating.

Tusks are teeth.  They are described, in Dr. Smith’s dissertation as “hypertrophic incisors.” And, unlike human teeth, they continue to grow the entire life of the animal. So where we can simply look at a human tooth and know immediately whether it is from an adult or a child, the same cannot be done with tusks.

What their hardy structure records includes the age of the animal, growth in winter or summer months each year, their overall diet, and periods of nutritional stress.  (As described in an earlier post, Proboscidean molars can even provide details regarding where they roamed during life.)

But much of this information can only be gleaned from well-preserved, intact tusks, as well as from cutting into and examining their chemical composition.

“If you don’t know what the sex of the animal is before you look at tusk microstructure,” she said, “it can be hard to interpret what you’re looking at.”

Part of what Dr. Smith hoped to discover were similarities in the tusks where sex and age had already been determined.  If certain structural elements were the same across female mastodon tusks, such that they tended to differ from male mastodon tusks, this might help determine sexual dimorphism in future tusk discoveries.

She also hoped to discover any similarities between the tusks of extant elephants and mastodons.

 

[image of longitudinally bisected tusk, courtesy of Dr. Katy Smith] 

 

Thus, she studied and measured tusks of both species from numerous museum collections. (Asian elephant tusks were not used, as female elephants of this species tend to have either tiny tusks or no tusks at all.)  She rather amusingly refers to the approximate amount of tusks involved as “5,000 pounds of tusk.”

Her dissertation and the two papers describe the type of analysis performed in detail.  Among them were canonical variates analysis (CVA) and discriminant function analysis (DFA).

“Fortunately, we didn’t have to cut into the tusks to do those measurements. You just insert a stiff wire into the pulp cavity.”

“We think about tusks sometimes as stacks of sugar cones, because they actually grow in a kind of [layered] cone structure. So you think about one sugar cone, and then you put another one inside that one and then another one inside that one and so on and so forth. And the last sugar cone is empty. There’s nothing in it. That represents the pulp cavity.”

“[Analyzing the] pulp cavity is probably one of the best single measurements that you can use to distinguish between male and females. [I]n females, that pulp cavity will terminate before the gum line, and in males, it will terminate after the gum line, closer to the tip.

“This is something that we saw in almost every mastodon. So it was kind of cool.”

 

 

[image of female mastodon skull and tusks, courtesy of Dr. Katy Smith]

 

“If we could have cut every tusk, I would have,” she admitted, and laughed. “But it was a matter of collecting these measurements at different museums. And so I would just go there and collect all of them, and that was how we’d get the pulp cavity depth.”

“I’ve always been interested in paleontology,” she said when I asked her how she got started.

“I’m one of those kids who just never grew out of it. My parents used to take me to the museum all the time, and I used to spend hours and hours staring at the dinosaur dioramas there, just loving it.  I told my kindergarten teacher I wanted to be a paleontologist. I never changed! My 5-year-old self grew up and became a paleontologist.”

But her interests moved away from dinosaurs when she realized that their fossil record in Wisconsin, her home state, was rare to nonexistent.

After all, she said, “I started just wanting to explore what was underneath my feet.”

It wasn’t until grad school at Michigan State, where she met the late Dr. Alan Holman, that she realized her passion for mastodons.  His own interest in the species was infectious, and it was through him that she learned of the numerous mastodon (Mammut americanum) fossil discoveries in the area.

“Wow!” she said, recalling her initial reaction. “There are over 300 mastodons in Michigan. This is exciting!”

[image of male mastodon skull and tusks, courtesy of Dr. Katy Smith]

Not surprisingly, she did her PhD work at the University of Michigan, home to Proboscidean expert Dr. Daniel Fisher, who was her advisor.

“I wanted to work with him,” she explained, “because I wanted to continue working on mastodons, and he had a couple of ideas for projects. One of them included this assemblage of mastodons from Indiana, which were—supposedly—all female.”

What she discovered regarding the Bothwell site is both thought-provoking and fascinating:

• 8 tusks were determined to be female; the other 5 are unknown
• the ages of the mastodons range between 19 and 31 years old
• there is evidence that at least one juvenile might have been among them (a “juvenile tooth crown” was found)
• given that two mastodons died in winter, and another two died either in late summer or early autumn, this indicates that the collective deaths of these animals didn’t happen at the same time (hence, not a single event)
• none of the mastodons appeared to be under nutritional stress when they died
• members of a family unit would be expected to have the same “isotope profiles”–chemical signatures in their teeth–but these do not

Based on the evidence provided, Dr. Smith wonders whether these animals were part of a meat cache for humans (members of the Clovis culture) that co-existed at that time.

But perhaps the single most remarkable result of her research is helping other paleontologists–who often have nothing more than a single tusk–determine the sex of that animal using her different types of analysis.

Prior to her dissertation, only one female mastodon tusk had been analyzed for growth rate.  To date, I am unaware of any other publication (paper or book) that helps detail the sexual dimorphism in mastodons by tusks alone.

When I remarked upon this, I asked her if others had cited her work.  Her response, after stating that others had, was equally fascinating to me.

“It’s always the hope as a scientist that you’re contributing in some way,” she said, “and you know that you’re contributing if somebody else is using what you’ve done.”

 

An enormous and sincere THANK YOU to Dr. Katy Smith for her generous and fascinating answers to my many questions, her gracious help when I had trouble understanding certain points, and for being so much fun with whom to connect! I cannot express how much I wish I could attend her classes, nor how fascinating I found her dissertation. I am profoundly grateful that she shared it with me!

A sincere thank you to my Dad, as well, for helping me understand tooth components (i.e.: dentin, cementum)!

**A quick reminder that I am neither a scientist nor a paleontologist, so any errors in this post are my own.

Bothwell Mastodont Dig, courtesy of Indiana State Museum; many thanks to Bruce Williams and Leslie Lorance!

—————

References:

• Life histories of female American mastodons (Mammut americanum): Evidence from tusk morphology, stable isotope records, and growth increments, Kathlyn Mai Smith, Dissertation, University of Michigan, 2010
• Sexual dimorphism of structures showing indeterminate growth: tusks of American mastodons (Mammut americanum), Kathlyn M. Smith and Daniel C. Fisher, Paleobiology, 2011
• Sexual Dimorphism and Inter-Generic Variation in Proboscidean Tusks: Multivariate Assessment of American Mastodons (Mammut americanum) and Extant African Elephants, Kathlyn M. Smith and Daniel C. Fisher, Journal of Mammalian Evolution, 2013

 

Other references:

• Woolly Mammoths’ Taste for Flowers May Have Been Their Undoing, NPR
• Fifty thousands years of Arctic vegetation and megafaunal diet, Nature, Eske Willerslev et al.
• Ancient Life of the Great Lakes Basin, J. Alan Holman, 1995, University of Michigan Press
• Mammoths & Mastodons of the Ice Age, Adrian Lister, 2014, Firefly Books Ltd.

 

[image of sign in the NY State Museum illustrating the size difference between an extant elephant, a woolly mammoth and the Cohoes mastodon; picture taken by the author]