An Ice Age Wonderland – Yukon Paleontology, Part 3

In 2004, scientists in the Yukon discovered a rare and surprising remnant of the Pleistocene: an Ice Age meadow. And some of the grass, although at least 30,000 years old, was STILL GREEN.

[Fossil grass below layer of tephra at Gold Bottom Creek, part of a 30,000-year-old grassy meadow discovered in 2004, from Ice Age Klondike, courtesy of the Government of Yukon. To see a picture of some of the green grass, please see page 33.]

 

In Ice Age Klondike, Dr. Grant Zazula and Dr. Duane Froese explain that this layer—at least 40 meters long–was buried by volcanic ash, or ‘tephra’.

 

[The layer of tephra is the whitish colored portion toward the bottom; 30,000-year-old tephra, image courtesy of the Government of Yukon.]

 

Few places in the world offer us such a concentrated wealth of information about the Pleistocene, and the Yukon is one of them.

“There are a lot of common animals like woolly mammoths and bison and horses that we find all the time,” Dr. Zazula said. “But it’s really exciting when we find the bones or the fossils of the rare species, things like camels, or short-faced bears, or lions. Probably for every 500 bones we find, we might find one bone of a carnivore.”

[Susan Hewitson holding an Ice Age lion humerus, courtesy of the Government of Yukon.]

[Ice Age lion mandible, courtesy of the Government of Yukon.]

“I think that one of the things that has really been exciting for me,” he offered, “is that, in the last 10 years, the field of ancient genetics has really taken off in terms of being able to extract DNA from Ice Age bones, then study the details of evolution and how these animals are related to one another.”

[Geneticist Beth Shapiro examines a partial upper jaw bone of a Yukon horse emerging from the frozen mud at Quartz Creek, from Ice Age Klondike, courtesy of the Government of Yukon.]

 

[Yukon horse jaw uncovered by placer miners on Quartz Creek near Dawson City, from Ice Age Mammals of Yukon, courtesy of the Government of Yukon.]

 

“[The Yukon is] one of the best places in the world to do that because of the bones being found in permafrost. [There are] so many Ice Age bones that are being found, and they’re really accessible.

“So we work really closely with the geneticists all the time; we’re working on all kinds of different projects together. It’s nice to be able to collaborate with a field like that and make fossils from the Yukon available for study.”

[Geneticist Mathias Stiller with tusk found in the muck at Quartz Creek, courtesy of the Government of Yukon.]

This author writes from an area within the United States that is fossil-poor (finding one mastodon tooth is an enormous deal, and most years pass without a single reported fossil). In comparison, the amount of fossil bones found in the Yukon staggers the imagination. But that is not all that the Yukon has to offer.

Even those not generally interested in paleontology get excited when they see or hear about mummified Ice Age animals. There is something so much more dramatic, that much more intriguing, about seeing an extinct animal in the flesh.

Dr. Zazula was frank about being slightly envious of Siberia’s wealth in that domain. Outside of Blue Babe, a steppe bison carcass found in Alaska, the most spectacular mummified animals have been found on the other side of the world.

And yet, one cannot ignore that mummified remains—partial or otherwise—are also an exciting part of Yukon paleontology.

[40,000-year-old mummified black-footed ferret discovered by the McDougall family’s dog, Molly, at their placer gold mine on the Sixtymile River, from Ice Age Klondike, courtesy of the Government of Yukon.]

 

One of the more remarkable finds was a partially mummified horse, discovered by Lee Olynyk and Ron Toews in a gold mine.

 

[26,000-year-old mummified horse (Equus lambeii) foreleg showing preserved hair, hide and muscle tissue, recovered at Last Chance Creek, Yukon, from Ice Age Mammals of Yukon, courtesy of the Canadian Museum of Nature.]

 

[Image of mummified horse tail, courtesy of the Government of Yukon.]

 

Internal organs as well as a significant portion of the hide (with mane and hair!) were recovered. One can see this at the Yukon Beringia Interpretive Centre, the museum in the capital city of Whitehorse.

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Also exciting, but from the neighboring Canadian Territory, was a discovery in the village of Tsiigehtchic. Dr. Zazula participated in uncovering this animal.

“[We excavated] a good portion of a carcass and a skeleton of a steppe bison, which turned out to be about 12,000 years old. There was still a bunch of hair and stomach and intestines and some of the limb bones were still articulated with muscle.”

He wrote about this in more depth with Dr. Beth Shapiro (image above) and several other colleagues in 2009. Not only remarkable for its level of preservation, this was also the first reported mammal soft tissue from the Pleistocene in “the glaciated regions of Northern Canada.”

[Large fossil steppe bison skull found Quartz Creek, from Ice Age Klondike, courtesy of the Government of Yukon. Not the same bison fossil mentioned above.]

Then in 2010, Derek Turner and Brent Ward found the “oldest reliably dated” Western camel fossil found in what was once Eastern Beringia. As mentioned in previous posts, Beringia was the area that covered most of Siberia, Alaska and Yukon when the land was connected in the Pleistocene.

Derek Turner, Brent Ward and Dr. Zazula explain, in their paper about this discovery, that North America was once home to possibly six different species of camel. (There appears to be some dispute about whether six distinctly separate species existed.) And, contrary to what one might expect, Camelops—the camel genus—originated in Central Mexico.

[Ice Age camel metatarsal (foot bone), courtesy of the Government of Yukon.]

For someone who has never participated in the excavation of either a mummified animal or fossils from permafrost, it was interesting to learn that there is a distinct smell when working with the muck.

[Placer gold mining monitor, Dominion Creek, courtesy of the Government of Yukon.]

“The only thing that’s kind of similar is the smell of a barnyard. But this is a barnyard from 30,000 years ago, and it’s from mammoths and horses and camels. All this rotten stuff that was [once] animals and plants that died a long, long time ago, frozen in the ground, and it’s now starting to thaw.”

The ever-growing research and discoveries from the Yukon paint a vivid picture of a by-gone era. It is, perhaps, the closest thing to a window into the Ice Age that we have.

When asked if there was anything that had not yet been found that he would be thrilled to find, Dr. Zazula didn’t hesitate: a woolly rhinoceros.

“We know that woolly rhinoceros are, so far, only found in Siberia,” he said, explaining why this would be so significant. “They extended all the way to the Bering Sea essentially, but they seem to never have crossed Beringia into North America. There is no fossil record of Ice Age rhinos here. But if they did [cross Beringia], that would be pretty amazing to find one of their fossils.”

Dinosaur enthusiasts, however, may be disappointed.

“In the Yukon, there’s almost no record of dinosaurs or Mesozoic fossils at all. I’ve been working with colleagues over the past handful of years, trying to find dinosaur deposits. But there’s no record of dinosaurs here except for a few handful of things. So, it’s not really [the place to be] if you’re interested in dinosaur paleontology. And that’s fine for me because then I don’t have to get involved in dinosaur work.”

“The Ice Age,” he continued, “is definitely what I’m interested in.”

[Paleontologist Grant Zazula with Ice Age horse skull, discovered this past summer, courtesy of the Government of Yukon.]

Dr. Zazula began grad school in Alberta studying anthropology. Initially, he wanted to become an archaeologist. His undergrad studies focused on Arctic people and research. A strong theme, he explained, centered on the first humans to cross the land bridge into what is now North America.

“I found myself becoming more interested in the environments that those first peoples in North America were encountering,” he mused. “Instead of just trying to study the people themselves, [I wanted to understand] them in more of a wider geographic or environmental context. So, I switched gears during my grad school days from anthropology into biological sciences.”

After doing paleoecological work in the Old Crow region of the Yukon, Dr. Zazula was invited to join a group of researchers working in the Klondike.

“We started doing fieldwork at these gold mines, and we kept on running into these strange balls of hay frozen in the frozen mud, in the Ice Age sediments. And we didn’t really know what they were at first.”

So he contacted Dick Harington—a well-known paleontologist within Canada for his decades of work with fossils and gold miners in the Yukon. Dr. Harington thought they might be Arctic ground squirrel nests, and in further conversation, explained that they had not yet been a topic of study. In other words, not much was known about them.

[Fossil nest of an Arctic ground squirrel, 30,000 years old, found at Quartz Creek in summer 2005, from Ice Age Klondike, courtesy of the Government of Yukon.]

“Over the first summer of fieldwork, I think I collected almost a hundred of these ground squirrel nests. And what was really cool about it is that the group that I was working with specialized in glacial stratigraphy [and] using volcanic ash beds to date sediments.

“Because they knew the age of these different volcanic ash layers that are found in the sediment, we could actually place these ground squirrel nests in different points in time in the past. We were able to develop sort of a time series of these Arctic ground squirrel nests.

“[Over] the next four years, I picked apart Arctic ground squirrel nests that [dated] between 20,000 and 80,000 years old or so.”

 

[Arctic ground squirrel nest, courtesy of the Government of Yukon.]

These nests are also known as “middens.” In his paper on the topic, Dr. Zazula and his colleagues describe these underground Ice Age homes. What these middens revealed, not just about these specific Ice Age animals, but about the Pleistocene environment at the time, is incredible.

Contained within these middens were ‘caches’ of food—seeds and plants from the area. These tiny plants give scientists a much better understanding of the climate and environment thousands of years ago.

[Arctic ground squirrel nest, courtesy of the Government of Yukon.]

 

 

[Arctic ground squirrel nest, cache highlighted by author, per the paper on this subject.]

 

“I think we’ve identified over 60 different plant species in them, and I wasn’t expecting that at all.”

In addition—and much to this author’s surprise–they found fossil insects, including beetles.

“Fossil Pleistocene beetle remains are actually quite common in sediments,” he said. “And they’re actually pretty useful for climatic reconstructions, because most beetles have a very narrow temperature or climatic envelope that they can live within.”

 

[Arctic ground squirrel nest, courtesy of the Government of Yukon. Can you find the squirrel skull?]

 

[Extant Arctic Ground Squirrel (Spermophilus parryii) hibernating in burrow, Fairbanks, Alaska; Getty Images]

 

In all of Dr. Zazula’s papers, one can see scientists from a variety of fields as co-authors or in the acknowledgements for their help with research. This was reiterated in our phone conversation: he is uniquely positioned as Yukon paleontologist to provide Ice Age material for a wide-range of study to a wide-range of fields.

“Especially with the Pleistocene,” he explained, “there are so many interconnected aspects of research. You need to have a geologist around. And then, in terms of putting the big picture together, you want to have someone that can reconstruct plant fossils. If you’re just doing it alone, you wouldn’t get much of the [big] picture anyway.

“So we’ve really kind of developed this way of doing things as a team.”

[Archaeologist Jana Morehouse, Paleontologist Grant Zazula and Geneticist Mathias Stiller, image courtesy of the Government of Yukon.]

“To me, it’s all so interconnected: the geology, the ecology and the mammals and then the archaeology. You might as well work together to try to accomplish goals, and that’s how we’ve done it. It’s been pretty successful.”

“And,” he added, “it’s a lot more fun that way anyway.”

[Geneticist Beth Shapiro with Ice Age horse jaw, image courtesy of the Government of Yukon.]

“Prior to the Yukon government establishing the paleontology program, all of the fossils that were being collected went back to Ottawa for the National collection and the National Museum. So most of the material that has ever been collected from the Yukon is actually not here. It’s in Ottawa.

“The Yukon government decided in the mid ‘90’s that they would like to establish its own program in Arctic archaeology and paleontology. Since that time, fossils collected here, stay here. And the position [of Yukon paleontologist] was created to oversee that.”

It’s a position he’s held for the past eight years, and one can hear his genuine enthusiasm for it in his voice.

“It’s a great job,” he stated. “Sometimes I’m shocked that I get paid to do this. It’s pretty exciting.”

Over the years, Dr. Zazula has been featured in some of the most prominent global media. Some of those include NPR, the CBC, the NY Times, and the National Post. This past summer, he was filmed with paleontologist Dick Mol from the Netherlands by a German documentary team. That documentary has been aired in Europe since this past December.

[Paleontologists Grant Zazula and Dick Mol, photographed by Florian Breier, the director of the German documentary; image courtesy of Dick Mol.]

Not everyone, regardless of their profession, is as comfortable with media or journalists.

“I think there are a lot of people that stay in labs and put their heads down and don’t really interact with the media, but I think it’s really important,” he said.

“[I]t’s one thing that’s never taught: how to conduct interviews or how to take your scientific work and present it or make it relevant to the public. And I think that’s a real problem, because if you are a practicing scientist after graduate school, you’re undoubtedly going to do research that attracts interest, and if you don’t have the ability to speak about it or to present it, you lose a lot of traction. In a lot of regards, science is kind of a big competition. It’s like a big science fair. If you don’t produce results and attract attention, you won’t continue to be funded. You can be an excellent scientist and sort of fade away if you don’t have the ability to attract people’s attention.

“I work for [the] government, where we’re publically funded by tax dollars. [F]or some people, [paleontology] might not seem very relevant for society. Still, I think it’s pretty important whenever we have something new to talk about, in terms of new results or new and interesting things, we should make sure it gets out to the public through media.

“Politicians are the people that decide if these programs continue to be funded. And if they see that there’s a lot of media interest and a lot of people learning because of it, then they’ll definitely keep funding these kinds of programs. And I’m grateful that they continue to do so.”

[Paleoecologist Rolf Mathewes from Simon Fraser University,courtesy of the Government of Yukon. Can you pick out the mammoth tooth?]

Explaining the reasons for his fascination with the Ice Age, Dr. Zazula said, “Dinosaur paleontology doesn’t really tell us much about the modern environment. If we’re interested in what we have today and how it’s changing because of, say, climate change, or environmental change, we’re not going to get much information about environmental processes by studying dinosaurs.

“The study of the Ice Age, [however], is how the modern world came to be.

“When you think of tens or hundreds of thousands of years ago, it may seem like a long time ago, [but] it’s just a geological instant. And in that short time period–in that geological instant–the changes that have happened to result in what we have here today are amazing!

“To think of giant elephants and lions running around North America: it’s such a different world. And yet so many aspects of that world can inform us of what we’re dealing with today.”

[Image of mammoth skull found by Hawk Mining along the Sixtymile River, courtesy of the Government of Yukon.]

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——————–

This trilogy of posts on the Yukon–with all of the beautiful images and the fascinating information they contain–could not have been possible without the generosity of Dr. Grant Zazula.  He is an adept and engaging speaker; the Yukon is incredibly lucky to have him at the helm of the paleontology program!  Once again, and with great sincerity, a Mammuthus columbi-sized THANK YOU to him.

This trilogy would not have occurred without the great generosity and wonderful thoughtfulness of Dick Mol, who is a wonderful, wonderful person.  With great sincerity, I wish him, too, a Mammuthus columbi-sized THANK YOU!

——————–

If you haven’t already checked out these publications by Grant Zazula, Duane Frose and Tyler Kuhn, please do! They are available online:

• Ice Age Old Crow
• Ice Age Klondike
• Ice Age Mammals of Yukon

Other articles referenced:

•  Arctic ground squirrels of the mammoth-steppe: paleoecology of Late Pleistocene middens (∼24 000–29 450 14C yr BP), Yukon Territory, Canada, Grant Zazula et al
• Last interglacial western camel (Camelops hesternus) from eastern Beringia, Grant Zazula et al
• A late Pleistocene steppe bison(Bison priscus) partial carcass from Tsiigehtchic, Northwest Territories, Canada, Grant Zazula et al

 

Yukon Paleontology Program: http://www.tc.gov.yk.ca/palaeontology.html

Yukon Beringia Interpretive Centre: http://www.beringia.com/index.html

Terra X – German Documentary: Mammuts – Stars der Eiszeit, http://www.zdf.de/terra-x/mammuts-ikonen-der-eiszeit-35507636.html

The Treasure in Gold Mines: Fossils! – Yukon Paleontology, Part 2

I admit to having preconceived notions of what it means to find fossils and to mine for gold.  It never occurred to me that these two occupations might be interconnected.  Nor would I have ever described the image below as what it actually is: placer gold mining.

 [image of a water monitor, placer gold mine in Quartz Creek, courtesy of the Government of Yukon. Can you find the rainbow?]

That water jet is called a ‘monitor’, and it slowly melts the permafrost, exposing the alluvial gold from the gravel below.

It also reveals fossils.

“Since the beginning of the Gold Rush, people have been finding Ice Age fossils there,” explained Dr. Grant Zazula by phone.

The Gold Rush, an event that peaked in 1898, brought people from all over the world to the Klondike area of the Yukon.  It was once solely the home of several indigenous cultures, including the Inuit, Han, Tagish, Tlingit and Tutchone. But the hope of finding treasure—in an industry that required inexpensive equipment (a pan, a rock pick)—brought thousands to an area that most would consider inhospitable.

 

 

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[image of gold miner, Gerry Ahnert, courtesy of the Government of Yukon]

One of the techniques used to find gold at that time was borrowed from California mining: water monitors.  Monitors were also relatively inexpensive and highly effective.

Back then, as now, these monitors revealed not only gold, but a wealth of fossils.

[image of Paleontologist Elizabeth Hall organizing a day’s collection of bones at the field camp near Dawson City, courtesy of the Government of Yukon]

“I’m always pretty fascinated by these stories immediately post-Gold Rush of people finding mammoth skulls,” said Dr. Zazula.

One can see a number of black-and-white images of these and other fossil finds in Ice Age Klondike, written by Dr. Zazula and Duane Froese.  Finds such as this prompted museums to send representatives out to the region to bring back fossils for their collections. One such expedition in 1907 and 1908 is detailed in the Bulletin of the American Museum of Natural History in NY.

“Without the gold mining, these fossils would never be found,” Dr. Zazula continued, referring to today’s fossil discoveries. “They’re using heavy equipment and other types of equipment to move this frozen ground because [it] is essentially locked in permafrost that wouldn’t be accessible without the gold mining.”

 [images of gold mines near Dawson City, courtesy of the Government of Yukon]

Melting the frozen ground with these jets isn’t as damaging to fossils as one might imagine. Dr. Zazula described a process in which fossils are slowly removed from the heights of the muck—the frozen silt—and slide down into the valleys below.  When remarkable fossils are seen by paleontologists, the miners always accommodate them, enabling Dr. Zazula and his colleagues to excavate them manually.

 [fossil Arctic Ground Squirrel skull emerging from the muck, image courtesy of the Government of Yukon]

[Dr. Grant Zazula sampling frozen sediment along a vast wall of muck at Quartz Creek, courtesy of the Government of Yukon]

 

It’s an incredible partnership, one that began in the 1960’s with Dr. Richard Harington of the Canadian Museum of Nature. Dr. Harington made annual summer trips to visit the miners and discuss their fossil finds.  It is a tradition that Dr. Zazula and the other two Yukon paleontologists before him have maintained.

But consider the expanse of the Yukon Territory.

[image of land near Dawson City, courtesy of the Government of Yukon]

And consider that, as Dr. Zazula stated, “[t]here are 100 active gold mines, give or take a few dozen here or there. And virtually all of them produce Ice Age fossils.  So in a summer, we can collect 5,000 specimens. There’s a lot of material coming out of the ground, and we’re trying to recover it as much of it as we can. It’s almost industrial-scale paleontology.”

This gave me pause: one Yukon paleontologist in the entire Territory, who—in addition to keeping in touch with about 100 mines in the Klondike—is responsible for all of the other fossil discoveries and research of the area.

“Prior to 3 years ago, it was really a one-person operation and that was me,” he admitted.

With the acquisition of funds, however, Dr. Zazula now has two assistants in the field: Elizabeth Hall and Susan Hewitson.

[image of Elizabeth Hall, Dick Mol holding a fossil Bootherium skull, and Susan Hewitson, courtesy of the Government of Yukon]

They have established a field camp near Dawson City in close proximity to the gold mines. This enables them to be in daily contact with the miners in the short mining season—the end of May through October.  Dr. Zazula described this work as driving on back roads to the various mines, getting to know the miners and collecting the fossils released from the permafrost.

 

[image of Elizabeth Hall recording bones at a gold mine, courtesy of the Government of Yukon]

“Since we’ve done that, our collection has just exploded in terms of the quantity of material that we’re finding.  But it also really establishes and strengthens the relationships that we have made with the gold miners as well.”

 [Dawson City, the previous capital of the Yukon Territory until 1953; At the height of the Gold Rush, this town consisted of numerous wooden buildings and a sea of canvas tents behind them; image courtesy of the Government of Yukon]

“[The] program really hinges on [these] two people,” Dr. Zazula wrote. “Elizabeth Hall oversees most of the field work in the Klondike and is the collections manager, and Susan Hewitson [is] a field technician in the summer months.

“They do most of the work to collect the fossils, clean the fossils, identify the fossils, catalog the fossils and organize the database. This really frees up my time to write, do research and other outreach work.”

[image of Elizabeth Hall holding a baby mammoth tooth, courtesy of the Government of Yukon]

[image of Elizabeth Hall, Susan Hewitson and her husband collecting fossils, courtesy of the Government of Yukon]

 

“Elizabeth started her as a summer student assistant about 10 years ago, and we finally created a full time position for her 3 years ago. We were also students together at Simon Fraser University. She is in the middle of completing a masters degree in Earth and Atmospheric Sciences at University of Alberta; her thesis work is on fossil microtine rodents from Old Crow, Yukon.”

[image of Elizabeth Hall, courtesy of the Government of Yukon]

“When it’s good for gold, it’s a good time to be an Ice Age paleontologist in the Yukon because there’s so much material that’s coming out of the ground.”

 [Paleontologist Tyler Kuhn with a mammoth tusk found at a placer mine in Dawson City, Yukon; courtesy of the Government of Yukon]

 

Again, an enormous thank you to Dr. Grant Zazula for his fascinating insight and most generous time.  

Thank you, again, to Dick Mol.  

And thank you to all of the gold miners who enable Dr. Zazula, Elizabeth Hall and Susan Hewitson to conduct their research and collect fossils!!

[image of Grant Zazula and Dick Mol, holding a steppe bison skull; taken by Florian Breier, courtesy of Dick Mol]

———————

Yukon Paleontology Program: http://www.tc.gov.yk.ca/palaeontology.html

Yukon Beringia Interpretive Centre: http://www.beringia.com/

Publications and articles referenced:

• Ice Age Klondike, by Grant Zazula and Duane Froese, Government of Yukon, 2011
• Ice Age Old Crow, by Grant Zazula and Duane Froese, Government of Yukon, 2013
• Ice Age Mammals of Yukon, by Grant Zazula and Tyler Kuhn, Government of Yukon, 2014
• Yukon At-a-Glance, Government of Yukon
• Yukon Factsheet, Government of Yukon
• Gold Diggers: Striking It Rich in the Klondike by Charlotte Gray, Counterpoint, 2010
• “Notes on Alaskan Mammoth Expeditions – 1907 & 1908”, Bulletin of the American Museum of Natural History, Article IX, L.S. Quackenbush

Exciting New Info About Mastodons and Humans – Yukon Paleontology, Part 1

“Good morning!”

It’s not just a greeting; it sounds like a proclamation.

The voice on the other end of the phone is deep, melodic, and—as our conversation progresses—punctuated with moments of laughter.  We have been discussing paleontology in the Yukon, and with each new detail, I begin to wonder why this territory is not making regular international headlines.

Dr. Grant Zazula’s work is fascinating, and it is neither a short phone call nor the only communication we’ve exchanged. And yet, it is all that I can do not to encourage him to keep going, long after social decorum dictates that he has been more than generous with his time.

[image of Dr. Grant Zazula with a mastodon ulna, part of the Earl Bennett mastodon, courtesy of the Government of Yukon]

Dr. Zazula is the Yukon paleontologist, a job that has only existed since 1996. His own tenure began in 2006.  With an office in Whitehorse, the capital of the territory, his work oversees an expanse of Canada that abuts Alaska.  It is a land of dramatic beauty, where colors dance in the sky and mountains tower in silent grandeur.

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His most recent paper, co-written with 14 other people, made news throughout the world and continues to attract media attention. In it, the scientists present data that completely overturns previously believed information about extinct animals and the impact that humans may or may not have had upon their survival.

“[T]here were two radiocarbon dates in the literature from Yukon mastodons,” he explained in an email. “One that was ~18,000 and the other 24,000 years old.”

“Based on analysis of the paleoecology, that was a time when steppe-tundra grasslands covered Alaska, Yukon and Beringia. There were probably no trees, few shrubs and almost no standing water. It was very cold and, especially, dry. This seemingly is not good mastodon habitat. So either the dates were incorrect, or our understanding of mastodon ecology, behavior and adaptations need[s] to be revised.”

Various species of mastodon once existed throughout the world.  Although their fossils look elephantine, they are not believed to be direct ancestors of today’s elephants. They are, however, part of the same umbrella mammalian group: the Proboscidea (so-named for the trunks possessed by many—but not all–of their members).  In North America, that group contained the American mastodon (Mammut americanum), the woolly mammoth (Mammuthus primigenius), and the Columbian mammoth (Mammuthus columbi).

 [image of the Cohoes mastodon, NY State Museum, Albany; taken by the author]

Mastodons tended to have straighter tusks and were shorter than their mammoth cousins. They also ate hardier vegetation, food that required a much different tooth structure than mammoths.

[image of mastodon tooth, courtesy of the Indiana State Museum]

[image of mammoth tooth, courtesy of the Indiana State Museum; for more info about the differences between mammoths and mastodons, see this post.]

Parts of Siberia, Alaska and the Yukon were once connected in an area known as “Beringia.”  The Bering Strait did not yet exist, enabling animals and eventually the first humans to cross into our continent.  It is believed that humans arrived in what is now North America about 14,000 years ago.

And this is where the research of Dr. Zazula and his colleagues becomes particularly important.

Prior to their paper, one theory to mastodon extinction laid the blame upon first humans: it was proposed that they overhunted these animals.

Sampling 36 fossils and presenting 53 new radiocarbon dates, Dr. Zazula and his colleagues found that mastodons within Alaska and the Yukon were much, much older than the originally published dates.  In other words, their research suggests that mastodons from what was once Eastern Beringia were no longer present when the first humans appeared.

The path to this remarkable research did not happen overnight.

The foundation appears to have been laid by two different events: by the chance meeting of Dr. Zazula and a gold miner, and later, by the PhD work of a graduate student.

If one reads the acknowledgements on the aforementioned paper, Dr. Zazula references Earl Bennett as both the donor of a partial mastodon skeleton and his inspiration to learn more about mastodons within the Yukon.

“Earl is a great Yukoner,” Dr. Zazula wrote when asked about this. “He mined for gold underground in the winters with a pick and shovel, decades ago. He worked on big gold dredge machines. And, he loves paleontology.

“While mining, he made collections of Ice Age bones that were just left around the mining camp or were encountered while mining. He eventually amassed an amazing collection.

“In the early 1970’s a gold dredge on Bonanza Creek hit a skeleton of a mastodon. An incredibly rare find! Someone collected it and was looking to sell it. So, Earl bought the skeleton just to make sure that it never left the Yukon. He had it in his garage for decades.

“One day a mutual friend introduced me to him in a coffee shop, about a year after starting my job [as the Yukon paleontologist]. He said that he had a mastodon skeleton and wanted me to see it. I ‘corrected’ him, saying that it was more likely a mammoth, because we almost never find mastodons in the Yukon. He assured me he know the difference and said he would see me tomorrow at my office.

“The next day he backed his truck up and in it was a partial mastodon skeleton. I couldn’t believe it. There were several postcranial bones, some vertebra, scapula, parts of the skull and parts of the mandible with teeth. It was amazing. I wanted to find out how old it was, and that was one of the inspirations for this project. Earl is a good friend now and big supporter of our research.”

[Paleontologist Grant Zazula with a partial American mastodon (Mammut Americanum) skeleton found on Bonanza Creek and donated to the Yukon fossil collection by Earl Bennett, from Ice Age Klondike, courtesy of the Government of Yukon]

That partial skeleton was indeed one of the many fossils sampled for the paper.

Dr. Jessica Metcalfe, one of the co-authors, also prompted this research when conducting work for her PhD.

“[S]he was doing a project looking at stable isotope ecology of mammoths and mastodons in various places in North America,” said Dr. Zazula.

[image of Dr. Jessica Metcalfe with mammoth bone, courtesy of the Government of Yukon]

Her work included Yukon fossils that were sent to the lab at the University of Arizona to be radiocarbon dated.   Those dates turned out to be older then 50,000 years old.

“So that’s what got me thinking,” he continued, “‘well, maybe those original published dates are wrong.’”

“The first step was to re-date [the specimens that had produced the original published dates]. The new dates turned out to be >50,000 years. So we knew there was a problem with the previous dates. We figured then we should date as many as we could get our hands on.”

This lead Dr. Zazula to connect with Dr. Ross McPhee, another co-author.

“I got in touch with him early because he oversees collections at the American Museum of Natural History, [and] he has a big interest and lots of experience working on Ice Age extinctions. [H]e’s an excellent writer and really kind of kept us going with some of the writings. He was really integral to keeping things together.”

The paper eventually involved a total of 15 people.

“I feel pretty strongly that if you worked on it and contributed to it, then you should be considered an author,” Dr. Zazula stated.  “So it ended up being a long list.”

One of the first aspects their paper addresses is the reason behind why the original published dates are incorrect: the dating analyses were contaminated by fossil conservation methods.

“Humic acids in soils can be absorbed by the bones and teeth and chemically bind themselves to the collagen,” he wrote, explaining further. “So, modern ‘young’ carbon in those acids basically contaminates the ‘old’ collagen in the ancient fossil. And, it can be tricky to remove.

“The same with consolidants in museums. Varnish, glue, and other substances to preserve fossils can be absorbed into the bone and chemically bind with the collagen in the bone. These substances probably contain young, modern carbon which messes up the radiocarbon dating measurements.”

When asked whether museums continue to use the same preservation products that contaminated the dates, he wrote, “Yes, for sure. The thing is now museums keep better records of what they use. Many of the fossils we dated were collected in the 1940’s or at least several decades ago. Museums were not that vigilant about keeping detailed records on those things then. Also, they seemed to put preservatives on everything. Now, at least if we know what was put on it, the chemistry can by developed to remove it. Most of the common preservatives now are soluble in alcohol or acetone and can be dealt with. The problem is when they are unknown.”

We discussed this further by phone.

“One thing about Alaska and the Yukon,” he said, “is that the Ice Age bones that come out of the ground are so well preserved because of the permafrost. In other localities, say, the deserts of the American Southwest or the Great Basin or the Plains, where bones have been out in the sun and [are] dry and hot, they [sometimes] fall apart really easily when they come out of the ground. They need to be glued and consolidated with these various types of museum products.

“So you kind of have to weigh the different values.

“Say if it’s a specimen that’s already been radiocarbon dated, and it starts to slowly disintegrate, well, then you kind of have to intervene or else you’re just going to end up with a box of dust and broken bone. You have to decide whether the importance is more with display or preservation of the morphology versus needing to radiocarbon date or other types of analysis.

“[Y]ou have to look at the pro’s and con’s of whether the sampling [for radiocarbon dating] will ruin the specimen or not, and what is the potential information that can be gained by doing it. To me, I feel that having a research collection [in the Yukon], it’s all about research and learning new things from these specimens.”

Ultimately, I wondered whether Dr. Zazula expected the results he and his colleagues uncovered.

“I wasn’t quite sure,” he answered. “I had the gut feeling that these previously published radiocarbon dates were probably wrong. It didn’t make a lot of sense ecologically to have mastodons living in the far North when it was seemingly habitat they couldn’t live in: habitat with grassland and cold, dry steppe tundra conditions, no trees and very few shrubs.

“But there [was] also a part in the back of my mind that thought, ‘well, if those [previously published dates] were right, that’s maybe even more interesting because they are telling us something about mastodons and their behavior and their adaptations that we didn’t know before.’”

————

It was a great honor and pleasure to connect with Dr. Grant Zazula! Not only patient with my myriad questions, he is an adept and fascinating ambassador for the Yukon. A Mammuthus columbi-sized thank you to him!

A Mammuthus columbi-sized thank you to Dick Mol, as well, who is the reason behind this post!

[image of Dick Mol with fossil horse skull, found near Dawson City, Yukon; courtesy of the Government of Yukon]

Yukon Paleontology Program: http://www.tc.gov.yk.ca/palaeontology.html

Articles and publication referenced:

• American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change, Grant D. Zazula et al, Proceedings of the National Academy of Sciences of the United States of America (PNAS), vol. 111, no. 52, December 30, 2014
• Ice Age Klondike, by Grant Zazula and Duane Froese, Government of Yukon, 2011
• Nursing, weaning, and tooth development in woolly mammoths from Old Crow, Yukon, Canada: Implications for Pleistocene extinctions, Jessica Z. Metcalfe et al, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 298, Issues 3–4, 15 December 2010, Pages 257–270

 

Listen to Dr. Zazula discuss his paper on the CBC’s Quirks & Quarks: http://www.cbc.ca/radio/quirks/quirks-quarks-for-dec-6-2014-1.2864605/mastodons-made-an-early-exit-from-the-north-1.2864634