Found: The Remains of a 27,000-Year-Old Sloth That Got Stuck in a Sinkhole
The sloth’s tooth, which was discovered in a deep pool in Belize, is helping scientists learn about the animal’s diet and the climate in which it lived
/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/8b/94/8b947707-caf4-4877-93bf-a6b729e9783f/sloth_tooth.jpg)
In 2014, divers were searching for Maya artifacts in a deep sinkhole in central Belize when they stumbled upon the remains of a creature that long predated this ancient civilization. The hefty humerus, femur and tooth that were pulled from the pool once belonged to a now-extinct giant sloth—and as Ashley Strickland reports for CNN, analysis of the tooth has revealed a wealth of insight into what the animal ate, the climate that it lived in, and how it may have died.
The researchers who studied the tooth hoped to learn more about the environment in which megafauna went extinct thousands of years ago, but giant sloth chompers can be difficult to analyze, they explain in the journal Paleontology. For one, the animal’s teeth were devoid of enamel, which scientists use to learn about the diet of humans and some animal species. Ancient sloth teeth are also often fossilized, meaning that minerals have replaced much of the original bone and tissue.
For the new study, researchers relied on a technique known as “cathodoluminescence microscopy,” which causes minerals to glow and, in this case, helped the team hone in on the tooth’s surviving tissue. Fortunately, the researchers discovered that a dense type of tissue known as orthodentin was largely intact. They were able to extract 20 samples from the sloth tooth, which in turn allowed them to “trace monthly and seasonal changes in the sloth's diet and climate for the first time, and also to select the best part of the tooth for reliable radiocarbon dating,” explains Stanley Ambrose, study co-author and professor of anthropology at the University of Illinois.
The investigation revealed the tooth to be around 27,000 years old, and also indicated that the sloth was not living amid the dense tropical forests that cover this region of Belize today. Instead, it had been slowly making its way through a relatively open savanna. By analyzing stable carbon and oxygen isotopes in the dental tissue, the researchers were able to determine that in the last year of its life, the sloth had been eating a variety of vegetation during a fluctuating climate: a short wet season, followed by a dry season that lasted around seven months, followed by another short wet season.
“We were able to see that this huge, social creature was able to adapt rather readily to the dry climate, shifting its subsistence to relying upon what was more available or palatable,” says Jean Larmon, University of Illinois graduate student and lead author of the study.
The study’s findings align with what researchers already know about the climate in the Central American Lowlands during the Last Glacial Maximum, when large ice sheets sucked up much of the Earth’s moisture and led to low global sea levels. The region of modern-day Belize was arid and cool, and the “lower water table would have left much of the Cara Blanca area [where the sloth remains were found] desiccated,” the study authors write.
So while the sloth was quite adaptable in terms of diet, it was likely having a difficult time finding water. The researchers think it descended into the sinkhole in search of a drink—and though it stood around 13 feet tall, it wasn’t able to make it out of the pool, which is around 200 feet deep and quite steep. According to the study authors, the area is ringed with megafauna fossils, suggesting other unfortunate creatures met the same fate.
Scientists don’t know for certain why the ancient giant sloth went extinct, but the new study suggests that climate change wasn’t the lone culprit, since the animal appears to have adjusted well to the changing environment. Another potential factor is predation due to “the arrival of humans on the scene 12,000 to 13,000 years ago,” says Lisa Lucero, study co-author and professor of anthropology at the University of Illinois.
The study also shows how modern microscopy techniques can provide a detailed look at the final days of a long-extinct creature—based on a single, partially fossilized tooth.