A large hairy elephant approaches an ancient Nacaome River— near Quebrada Honda in the canton of Nicoya— looking for water. Suddenly, a flash flood from the river or a landslide buries it for thousands of years, until 1978, when a man from the area named Vetsalio Rivas found some strange bones: the fossil remains of a mastodon.
It’s hard to know exactly how this animal died, but it’s likely that it happened that way, explained the technical coordinator of the geology division of the National Museum of Costa Rica’s natural history department, Ana Lucia Valerio.
People in our rural areas are very curious. They always walk in the fields and sometimes they find strange stones. Many times these strange stones aren’t stones, but rather are the remains of fossilized bones from some prehistoric animal,” added Valerio.
In the early 1990s, the museum’s anthropology department excavated the same site to find out if the mastodon was hunted by humans. Since then, paleontology specialists have found at least three extinct species that inhabited the area.
Before finding out if some “great-great Chorotega grandparents” were running around Guanacaste after these giants with spears and axes, we asked Valerio to go a little further back in time to learn how these animals came to the area.
A New Bridge called Costa Rica
For millions of years, North America and South America were two great land masses isolated from each other. When the lands that make up Costa Rica and the rest of the Central American countries began to form, they created a bridge that North American animal species, such as mastodons, used to migrate south and South American species used to go north. This event is known as the Great American Biotic Interchange (GABI).
I imagine that they were looking for better climatic and feeding conditions, so they migrated,” she deduced.
The geologist points out that there are many theories about their extinction. One of them suggests that they were restricted to specific areas and began to breed among themselves, causing disease and decimating their populations. Another possibility is that a climate change left them without food.
“Maybe many things influenced it and not just one. These animals ate a lot, so it’s possible that as temperatures and vegetation changed, populations began to decline more and more,” added Valerio.
An ecosystem without enough plants to feed on must have been a very hostile environment for these large herbivores. The mastodon was a distant relative of today’s elephants. It had a hump near its head and was about 2.7 meters (8.8 feet) tall. It was big and hairy, but not as big as mammoths.
Fourteen years after recognizing the remains of the mastodon, the department of anthropology visited the site again. At that time, they found new remains that they linked to another giant: a glyptodon.
It was also an extinct herbivore, which shows a kinship with armadillos. It had a large rounded shell made up of small plates and a sharp, pointed tail with which it may have competed for food or to win mating rights.
During the visits in the early 90s, in the same paleontological site, they also found an animal that doesn’t fall into the category of megafauna: an American horse. These animals came from North America and became extinct in South America. The horses that are currently on the continent were brought by the Spanish after the conquest.
The glyptodon and the mastodon coexisted for several thousand years with the first humans that populated the continent, and that is also a possible cause of their disappearance.
So, the species found at the Nacaome paleontological site coexisted with humans?
A research project carried out by the museum in 1992 indicates that “the existence of marks like incisions in some of the mastodon’s bones draws attention.”
However, Ana Valerio explained that they found no human evidence associated with these fossil remains.
“That’s why the specimens are now in the department of natural history, in the geology section, because they don’t have cultural evidence,” such as knives or tools that link them, she added.
Valerio explained that nothing organic remains and these bones are highly lithified. In other words, the degree of compaction turned these sediments into rock. That’s why she estimates that this paleontological site dates to the Upper Pleistocene age, about 12,700 years ago.
By then, there were already humans populating the continent, but Javier Oviedo, a geologist and anthropologist from the University of Costa Rica, added that at that time, there still weren’t any complex societies.
“There were isolated groups of humans who lived nomadically, moving from one point to another, looking for prey and gathering food. They created temporary camps, but there was a defined social structure,” he affirmed.
Several thousand years would still pass before the Chorotegas reached these lands.