When the sloths were alive, the landscape would have featured a "stream going through gently rolling grasslands," he said. The site today is somewhat similar.
Just last month, another team of researchers in nearby Brazil brought together artifacts -- including cave paintings and ceramic art -- from Serra da Capivara national park in Brazil's northeastern Piaui state. The oldest artifacts date to 30,000 years ago.
Franco-Brazilian archaeologist Niéde Guidon, who worked on the project and has led explorations of Piaui's interior, said that, in light of the findings from Uruguay and Brazil, she believes that it is time to reconsider how and when the Americas were first populated.
Piecing together the latest evidence, she believes that humans came to South America at least 30,000 years ago, and possibly much earlier, by water.
"130,000 years before the present, Africa suffered from a very dry climate, which was the origin of the deserts (there)," she said. "People tried to find food in the sea, and the streams and winds (flow) from Africa to the northeast of Brazil. It is possible to think that some boats arrived at the coast of Piaui."
To this day, these same water and wind currents benefit cruise ships coming into Brazil.
The indigenous people from Piaui and surrounding regions had ancestors with "dark skin (and) their hair was black, but smooth and not curly," Guidon said.
Visitors to Uruguay will soon be able to see the Arroyo del Vizcaíno artifacts.