Megafauna Remains Suggest Humans Arrived in Argentina Over 20,000 Years Ago
Prehistoric humans ate giant armadillos in South America
Academics disagree on when humans first arrived in South America. The debate also rages on the nature of human-megafauna interactions and their potential role in megafauna extinctions.
Some say humans hunted the megafauna to extinction, others claim a changing climate led to their demise, and others still claim it’s a mix, but the extent to which each factor played varies.
I think the mix theory holds the most weight. Remember, 20,000 years ago, each hunting group was probably only a few dozen strong, and in a given area, a couple dozen more may have joined that number. It is likely that climate change, caused in part by the end of the last ice age, drove down many megafaunal populations. Around the same time, humans began arriving in the Americas.
The pressure of a changing climate decimated local megafauna populations, and a newfound threat, human hunters, who would have killed off the remaining surviving stragglers, likely caused many megafauna extinctions.
If you were a child or had a child in the early 2000s, you probably remember the Ice Age movies. When I watched them, I thought the movie featured ugly turtles, but it turned out that these turtle-armadillo-looking creatures were glyptodonts, an extinct species of megafauna found in Southern America thousands and even millions of years ago.
In a study published in PLoS One by archaeologist Mariano Del Papa and his colleagues, the fossil of an extinct Neosclerocalyptus (a genus of Glyptodont) was analyzed and dated. The finding of this extinct species with cut marks pushed back the earliest known date of the presence of humans and human-megafauna interactions in southern South America by 6000 years, back to 21,090–20,811 cal Before Present (BP).
The History of South American Human-Megafauna Interactions
Generally speaking, the archaeological record of extinct megafauna in the Argentine Pampas (where the fossil was found) is scarce. On top of that, the timing and process of the peopling of South America has been a highly debated topic since the mid-19th century.
You need evidence to determine when humans first arrived and elucidate when humans-megafauna interactions began hunting in any given region.
But how do you determine when humans arrived and when they began interacting with the local megafauna in any given place or time?
There are two ways: direct and indirect evidence. Indirect evidence takes one finding, say a stone tool (lithic) within a site, and links it to something else. So, if a researcher finds a stone tool and a hearth at a site, he can indirectly conclude that humans lived there at a specific time. On the other hand, direct evidence would be if a researcher found a human skeleton in a site in a specific layer.
Early researchers focused on when and how humans and local extinct mammals interacted. They based their research and findings on both direct and indirect evidence.
For example, sites with hearths and lithics (stone tools) associated with fossil remains were indirect evidence of human-megafauna interactions. Meanwhile, megafauna bones that had been modified, perhaps shaped into tools, provided direct evidence.
The earliest research on this topic in South America dates back to 1880. It was based on cultural evidence, modified fossils, and the geological context of the finds.
This research and evidence were later revised and, in some cases, discredited in the early 20th century. After that, scholars working on southern South American archaeology largely stopped being interested in when humans arrived and how humans and megafauna interacted.
When radiocarbon dating and new methodological approaches were developed, interest in the initial peopling and megafauna interactions was revived. However, evidence and understanding on both topics remain poorly understood and scarce.
A few sites across South America exhibit human and megafaunal remains. Still, these sites are clustered in specific regions, leaving significant gaps in our understanding of the blank spaces in the map where nothing has been found.
When they are found, it becomes a question of whether you have human activity or a direct interaction between humans and megafauna. A stone tool lying next to an extinct species means nothing unless you can prove their association. Similarly, bones with cut marks need to be proven to be cut marks, not the result of carnivore teeth or taphonomic processes (various processes after deposition that can affect a find, from trampling and rodent activity to root etching and flooding).
The Fossil of Reconquista River
In the northern Pampas region of Argentina, along the margins of the Reconquista River near Merlo Town, the fossilized bones of a megafaunal creature were discovered. It comprised a carapace (the shell), various tail parts, and hip bones. Using the distinct markings of the carapace and part of the tail, the genus Neosclerocalyptus could be assigned. It was named CRS-10.
Neosclerocalyptus was an extinct genus of glyptodont. Glyptodonts lived in southern South America during the Pliocene, Pleistocene, and parts of the Holocene, with various genuses going extinct in between. While still large compared to modern standards, at the time, Neosclerocalyptus was among the smaller glyptodonts, ca. 2m long and weighing an average of 360kg.
CRS-10 was among the first fossils of megafauna from the northern Pampas region, and what made it more remarkable were the cut marks found all over it.
However, researchers had to prove that these marks were cut marks; if they could, they would have direct evidence of humans butchering and consuming a megafaunal species in the Northern Pampas.
The researchers analyzed the surrounding sediment to find evidence of microliths and trace elements that could indicate human tool use or the environmental conditions at the site at the time of death respectively. Using radiocarbon, they determined the creature's age. Furthermore, using a ridiculously meticulous analysis of the markings, they could tell if the lines and marks resulted from humans or something else.
The Results
On CRS-10, thirty-two cut marks were identified. They were not the result of carnivore teeth (which leave a U-shaped mark) or micro striations caused by the bones tumbling around the sand and being trampled on. Neither were the marks made when the bone was dry; rather, they occurred when it was fresh.
The location of the marks indicated that they were made where, in life, the animal would have had nearly 70% of its muscle mass located. This means the humans that butchered it were targeting the high-energy and meat-rich parts of the body for consumption.
The sediment analysis and radiocarbon dates revealed that when this animal lived 21,090–20,811 cal BP, it was the wet season in an otherwise semi-dry climate. The bones had been buried rapidly, undergoing minor post-depositional modification.
They are among the earliest reliable evidence of the exploitation of megafauna in southern South America and the first ever in the northern Pampas region. Not only that, but they push back the earliest known date of humans first coming to the region, nearly 6000 years, from ca. 16,000 BP to 21,090 years BP.
Archaeologists in Argentina have discovered the CRS-10 fossil, which has provided new insights into the understanding of early human-megafauna interactions.
It provides the first evidence of megafauna in the Northern Pampas region. It pushes back the known date for human-megafaunal interaction in southern South America by 6000 years to 21,090 thousand years ago. These findings were based on the cut marks across the fossil, which resulted from butchering processes.
The fossil provides critical evidence to help modern researchers understand how and when various large mammals went extinct in South America and what role humans and the environment may have played in their extinction.
With increasing interest in South America about early human arrival in the region and their roles in the lives of the animals around them, perhaps new sites will be found, especially in the otherwise megafauna-free zones of South America.
What do you think led to the extinction of megafauna, climate change, humans, disease, or something else entirely?
Let me know your thoughts, and if you’d like to support me further, why not Buy Me A Coffee?
References
- iNaturalist. (n.d.). Genus Neosclerocalyptus. [online] Available at: https://www.inaturalist.org/taxa/602070-Neosclerocalyptus [Accessed 19 Jul. 2024].
- Mariano Del Papa, De, M., Poiré, D.G., Nicolás Rascovan, Jofré, G. and Delgado, M. (2024). Anthropic cut marks in extinct megafauna bones from the Pampean region (Argentina) at the last glacial maximum. PloS one, 19(7), pp.e0304956–e0304956. doi:https://doi.org/10.1371/journal.pone.0304956.
- Quiñones, S.I., De los Reyes, M., Zurita, A.E., Cuadrelli, F., Miño-Boilini, Á.R. and Poiré, D.G., 2020. Neosclerocalyptus Paula Couto (Xenarthra, Glyptodontidae) in the late Pliocene-earliest Pleistocene of the Pampean region (Argentina): Its contribution to the understanding of evolutionary history of Pleistocene glyptodonts. Journal of South American Earth Sciences, 103, p.102701.
