Paleomission: in search of the ancient sloth – conclusion





Radiocarbon dating was attempted to determine the age of the bones. Unfortunately, the process failed because the collagen, which is the material used for dating, deteriorated in the underwater environment. As a result, we will probably never know the age of the bones, but based on other radiocarbon-dated sloth remains from Cuba, we believe these animals lived no later than 4000 years ago.

One obvious difference between the Megalocnus and Neocnus bones is their colour. The white, chalky appearance of the Megalocnus bones suggests that they were exposed to the air for a long period of time before they ended up in the water. This indicates a possible change in the environment in this part of the cave, or perhaps human disturbance, but additional tests will be needed to confirm this.

Project director Matthew Peros in his laboratory at Bishop’s University, where many of the scientific analyses are being undertaken (used with permission).

The bones we are studying are technically “subfossils”, rather than “fossils”, because a fossil has been completely mineralized (or fossilized), which has not occurred with these bones. However, some paleontologists believe that the bones of extinct species should also be called fossils, regardless of whether they have been mineralized or not.



Sediment cores collected in the cave contain seeds from the fruit trees Cecropia and Ficus. The seeds may have been deposited by fruit-eating bats and birds, and indicate that these trees were growing outside the cave thousands of years ago. Interestingly, today, two- and three-toed sloths subsist largely on Cecropia and Ficus leaves. Whether these trees contributed to the diet of Neocnus and Megalocnus is unclear, but it does suggest an intriguing connection between modern sloths and their extinct relatives.

High magnification images of Cecropia seeds from the sediment cores. The seed is approximately 2 mm long.


High magnification image of Ficus seeds from the sediment cores. Each seed is approximately 1 mm long.


Three-toed sloths such as Bradypus variegatus  spend most of their lives in, and eat the leaves of, Cecropia trees.

Bradypus varietgatus





Geochemical analyses of stalactites and stalagmites (which grow on the roofs and floors of caves, respectively) can be used to infer changes in ancient precipitation.

Stalactites (top) and stalagmites (bottom) in Cueva Margarita 1. These features formed when the cave was dry as water dripped from the cave roof. The chemical composition of stalactites and stalagmites reflects, in part, that of the local rainwater, which enables paleoclimatologists to study ancient precipitation. ©Jill Heinerth


Cuba is home to the tallest stalagmite in the world. It is located in Cueva Martín Infierno and measures 66 m tall!



Our research at Cueva Margarita 1 is a work in progress. We have not yet discovered the answers to many of our questions. Doing so will require significant resources and years of work!

The broad question of ancient extinctions and climate change and our work at Cueva Margarita 1 has ongoing relevance for conservation. By looking into the past we may be able to better predict the possible fate of endangered species in the face of climate change and human impacts on island environments.

Lastly, as an example of international and interdisciplinary collaboration, we hope our efforts will serve as a model for others in their pursuit to understand and protect the natural world.

(From left to right): Elián López Cabrera, Arsel Rodríguez Ramos, Patricia Gámez O’Connor, Kenny Broad, Edey Bermúdez, Jill Heinerth, Miguel Angel Pereira Sosa, Bil Phillips, Joao Gabriel Martínez López, Matthew Peros.




The project

The work

The discovery



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