Prehistoric Rock Art Might be Early Representations of Giant Ground Sloths 

Prehistoric Rock Art Might be Early Representations of Giant Ground Sloths

In the Amazon rainforests in the country of Colombia, there is a place called Serranía La Lindosa, with rock cliffs decorated in ancient drawings. There are thousands of paintings covering 12 kilometers (8 miles) of rock in an area that has been largely inaccessible. Some of the paintings depict animals easily recognizable to modern people, such as turtles, guanacos, or humans—and just possibly, giant sloths.

 

Juancho Torres/Anadolu Agency via Getty Images

 

A study by José Iriarte and his colleagues published in the journal Philosophical Transactions of the Royal Society proposes the following:

“We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas.”

Daily life scenes

The paintings of the Serranía de la Lindosa are surprisingly well preserved. Some of the scenes seem to show the first contemporary humans in early Amazonia going about their daily life, while others seemingly depict ritual scenes, hunting, interacting with plants, and forest and savannah animals.

 

Photo: Wikipedia / Julianruizp

 

Pictures of birds, turtles, and other animal species that inhabit this large tropical forest require little interpretation; however, there is controversy among paleontologists and archaeologists about whether the other creatures represented are in fact giant sloths, elephants, and prehistoric horses.

A giant sloth with a baby?

One of the pictures is the silhouette of a large animal that might be a giant ground sloth, along with a miniature version of itself that it is probably safe to call its offspring. As any would-be artist of modern sloths can tell you, they are not creatures with particularly distinctive shapes.

 

Ice Age megafauna rock art in the Colombian Amazon? José Iriarte, Michael J. Ziegler, Alan K. Outram, Mark Robinson, Patrick Roberts, Francisco J. Aceituno, Gaspar Morcote-Ríos and T. Michael Keesey

 

Interpretation of the silhouette as a sloth relies heavily on the assumption that the ancient artists faithfully represented the proportions of the creature in question, which—given the depictions of the nearby human figures—they did not always do.

 

(a) Giant sloth painting at La Lindosa: 1. massive claws; 2. short rostrum; 3. large head; 4. robust thorax; 5. inverted pes; 6. offspring; 7. miniature men. (b) Artistic reconstruction of Eremotherium patterned after its closest living relative Bradypus. (c) Artistic reconstruction of Arctotherium patterned after its closest living relative, Tremarctos ornatus (Mike Keesey). Keesey’s reconstructions are figurative works of art, where he took the liberty of adding features that are not visible in the rock art like fur, ear canals and wrinkles, among other features. (Online version in color.).

 

“ Its overall morphology, large head, short rostrum, robust thorax, reduced number of digits on the pes, and prominent claws recall a giant ground sloth. Presented in a quadrupedal stance, the sizable forearms appear to be longer than the hindlimbs. The manus consists of three to four digits extended distally, whereas the pes appears to have five digits with varied orientations.

Notably, the depicted animal appears to exhibit pedolaterality, that is, the characteristic inverted pes, where the dorsal surface of the foot faces laterally and the planar surface of the foot faces medially. Three transversal lines compartmentalize the body in four parts and give the figure an appearance of surficial texture.

The white mark on its head seems to be representing an eye. Behind the head, there appear to be a few protuberances along the dorsal surface that might represent prominent scapula and shoulder musculature. The animal is accompanied by an offspring and surrounded by animated miniature men, some of whom extend their arms towards the painting.

The relationship of the animal with the men appears to be central to the artist’s message. The comparatively smaller illustrated humans that accompany the animal appear to provide a perspective on a scale that points to the sheer size of the specimen.”

 

The controversy

Interpreting ancient rock art is a much more difficult process than it initially seems. For example, how old is “ancient”? The art on the cliffs of Serranía La Lindosa is made with mineral pigments that are not suitable for carbon dating, so inferences must be drawn from organic materials in the area that CAN be carbon dated, such as bone tools that might have been paintbrushes, or food remains from the human settlements nearby.

 

Ice Age megafauna rock art in the Colombian Amazon?
José Iriarte, Michael J. Ziegler, Alan K. Outram, Mark Robinson, Patrick Roberts, Francisco J. Aceituno, Gaspar Morcote-Ríos and T. Michael Keesey

Jorge Peña and Fernando Urbina of the National University of Colombia believe that the paintings may be much more recent than the last ice age. In their 2016 publication “War dogs, horses, cattle and other themes in the rock art of the Serranía de la Lindosa (Guayabero River, Guaviare, Colombia): A conversation” they argue that many of the paintings in La Lindosa might be much newer, even post-European-contact. If the paintings are only a few hundred years old, it would explain their exceptional state of preservation, but would certainly rule out interpretations of pre-historic humans hunting ice-age megafauna.

Urbina says: “(The paint) shows a quadruped with an offspring, caught in a trap. Its size, in relation to the human figures facing it, could suggest that it is extinct megafauna. However, the exaggeration in size may depend on various symbolic reasons. Also, it could happen that the human figures correspond to children or dwarfs, or dwarf children. Federmann in his chronicle speaks of the encounter with members of an ethnic group of very short stature. Finally, it could be perspective management”

Until we have better estimates on the age of the paintings (which could happen as soon as late 2022), the question of the species remains unanswered. Do these mysterious cliffside drawings capture the brief moment of overlap between the last of the giant ground sloths and the first humans of South America? What did the drawings mean to the artists that created them? What animals did they see, what stories went along with the pictures, and what would they have to say to us about the splendor of the world as it was?

-Cecilia Pamich & Ames Reeder

Mylodon Giant Sloth, opportunistic omnivore?

Mylodon Giant Sloth, Opportunistic Omnivore?

Sloths these days are small, tree-dwelling animals that live high up in the rainforest canopy and do a good imitation of the plants they eat. They’re slow, they’re green, and they can’t jump—but a new study published in the journal Scientific Reports suggests their ancestors weren’t the strict vegetarians their reputation would have us believe.

There are six living species of sloths: four species of three-fingered and two species of two-fingered sloths. The slower, smaller three-fingered sloths are obligate folivores (they eat only leaves), and the two-fingered sloths eat a greater variety of leaves and occasionally supplement with fruit.

giant sloth
Illustration: Franklin Rodríguez

Once upon a time

In the ancient Pleistocene sloths made up a large part of the South American ecosystem. Sometimes literally large: the giant ground sloth Mylodon darwinii was three to four meters (over 10 feet) long and weighed up to two tonnes (about 4,400 lbs).

Based on fossil records of its teeth and current sloth dietary habits, Mylodon was assumed to be an herbivore—although scientists often wondered how the gut-to-body weight ratio of this giant ground sloth supported a strictly vegetarian diet.

Paleoecology is a difficult field to study. Scientists have to use indirect evidence of bones and fossils to extrapolate things like diet and behavior, and the giant ground sloths lack the sharp teeth and claws that most modern carnivores use to capture and kill prey.

 

giant sloth mylodon
Illustration of a Mylodon darwinii by Néstor Toledo

 

This is where a relatively new technique called “amino acid compound-specific isotope analysis” comes in: this is a measurement of certain nitrogen isotopes found in hair, nails, and some parts of the bones and teeth, and can tell us where the animal in question got its dietary amino-acids from. This analysis can differentiate between amino acids based in plants or animals, and even tell if the diet was primarily seafood or land-based meat.

Comparing samples from modern animals, including sloths, anteaters (which are related to sloths), and a range of omnivores, researchers from the American Museum of Natural History have determined that Mylodon was in fact also an omnivore.

 

Mylodon giant sloth omnivorous
Mylodon Reconstruction by Jorge Blanco

How to be an omnivore giant sloth

This immediately begs the question of: how? After all, the number of animals that can out-run a modern sloth are basically all of them, and ancient ground sloths do not show signs of being speedy creatures. The speculation is that the giant Mylodon might have foraged for bird eggs or scavenged meat from animals killed by other predators—after all, it doesn’t take an impressive turn of speed to hunt down a corpse.

Not all giant ground sloths turned their teeth to meat-eating; like all modern sloths, Mylodon’s North American cousin Nothrotheriops shastensis was purely herbivorous.

Humanity’s ancient ancestors certainly fed upon the giant ground sloths, and it is interesting to think that some of them might have occasionally returned the favor. Luckily for modern humans, we are safe from the small two- and three-fingered sloths of today, and they would surely be happy to be kept safe from us as well.

 

humans hunting giant sloth
A recreation of humans hunting giant sloths / Illustration: Alex Macclelland, Bournemouth University

 

 

Journal Reference:

Julia V. Tejada, John J. Flynn, Ross MacPhee, Tamsin C. O’Connell, Thure E. Cerling, Lizette Bermudez, Carmen Capuñay, Natalie Wallsgrove, Brian N. Popp. Isotope data from amino acids indicate Darwin’s ground sloth was not an herbivore. Scientific Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-97996-9

 

-Ames Reeder