Dr. Timothy Gaudin holds a giant sloth skull. Photo by Angela Foster.
When Dr. Tim Gaudin arrived at the University of Tennessee at Chattanooga 30 years ago, his sights were set on teaching.
“I wanted to be at a place where teaching was valued and important,” said Gaudin, a UC Foundation professor in the Department of Biology, Geology and Environmental Science. “That’s really important to me.”
Behind the scenes, however, Gaudin found additional value in his research—and it paid off. This spring, that work earned him a huge milestone: co-authorship on a paper about sloths published in Science, one of the world’s most prestigious scientific journals.
College of Arts and Sciences Dean Pam Riggs-Gelasco explained the significance of this accomplishment.
“Science is widely acknowledged as one of the top journals for disseminating significant scientific research,” Riggs-Gelasco said. “Papers selected for publication must pass through a rigorous editorial and peer-review process and only papers that are influential in their fields and that substantially advance scientific understanding are selected for publication.
“As the premier journal of the American Association for the Advancement of Science, Dr. Gaudin’s article in Science will be broadly disseminated to an international audience of scientists in all disciplines.”
Dr. Gretchen Potts, the department head for Biology, Geology and Environmental Science, shared similar thoughts.
“Dr. Gaudin’s international collaboration has been a great foundation for impactful research,” Potts said. “Disseminating this important scholarship in “Science” is a significant accomplishment and brings notoriety to the department, the college and the University.”
Gaudin is one of two known faculty members at UTC to have ever been published in Science. It also isn’t his first time. He co-authored a paper that Science published in 2013 about the evolutionary relationships of modern and extinct placental mammals showing they likely emerged after the extinction of the dinosaurs.
This year’s paper focuses on a specific mammal—sloths.
Gaudin worked with a team of colleagues from around the world, including Alberto Boscaini—a former Ph.D. student he mentored at the Argentine Institute of Nivology, Glaciology and Environmental Sciences. Together, they were able to uncover new information about the evolution of sloths.
“Sloths, right? Everybody sort of knows about the tree sloth that you see in zoos and on T-shirts and mugs,” he said. “Sloths have become very popular.”
These sloths include seven different species that fall into two genera, or types: the two-toed sloth and the three-toed sloth. The modern sloth, however, is just a glimpse into the evolutionary history of the animal, which stretches millions of years.
According to Gaudin, over a hundred extinct sloth genera have spread throughout the Americas.
“There’s an enormous radiation of extinct sloths that shows up in South America, probably very shortly after the dinosaurs went extinct,” he said. “In terms of what actually appears in the fossil record, we get our first glimpse of them somewhere around 45 million years ago.”
So, what did the sloths that roamed the Earth that long ago even look like? Terrifyingly, the largest sloth was comparable in size to the modern African elephant.
“They were about 15 feet tall and could stand up on their hind legs. They probably weighed about 6,000 kilograms,” Gaudin said.
Fortunately, for some of the first humans, the sloths were slow-moving herbivores. Unfortunately for the sloths, this made them an easy target, and this is why these giant sloths disappeared roughly 15,000 years ago.
“They’re slow, they’re large,” Gaudin said. “So, they would’ve been attractive sources for hunting. And they have a really unfortunate defensive behavior where they would rear up on its hind legs and try to slash you with its claws. If you have a spear, that’s a pretty bad way to react.
“There are actually cave paintings in South America and Brazil of people hunting sloths. We have sloth bones that were clearly butchered by people, so we know people were hunting and eating sloths.”
The reason for the research, Gaudin explained, was to explore how sloth body size evolved and why some species grew to enormous sizes while others stayed small.
“What Alberto and my co-authors were interested in is sort of exploring this size variation and how does it come about,” he said. “Where did sloths start out and how does body size change through time and what factors are driving that?”
By comparing the evolution of different sloth species, the team looked at patterns tied to climate, movement and habitat preference. Sloths that lived in trees were the smallest, semi-arboreal species were mid-sized and terrestrial sloths showed the greatest range, including the giants.
They also saw a climate connection over time.
“When it gets warmer, the sloths get a little bit smaller,” he said. “When it gets cold … they get bigger again.”
For Gaudin, researching sloths is not new territory. The niche interest has spanned most of his career and has connected him with a community of other researchers.
“We go to conferences, we review one another’s papers, we collaborate with one another,” he said. “The people that work on sloths, for the most part, we all really like each other.”
The recognition of this work, which he described as “really important in the fossil history of South America,” is validation of years of research.
It also means a lot to UTC.
“UTC is not an R1 university,” he said. “It’s not a place that has a reputation as a big research institution. It’s something that you keep in the back of your head. ‘Well, that would be really cool,’ but you don’t come here to do something like that.
“To get something like that, it’s like icing on the cake. It feels like a really nice fulfillment to my research career, and it’s lovely to have that kind of recognition for your work.”
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