A new study that details a large-toothed human ancestor provided further evidence that humans once spent many years living alongside other close human relatives.

In the study, published in the journal Proceedings of the National Academy of Sciences, researchers examined DNA from a tooth discovered in a cave in Siberia. Analysis revealed the tooth to belong to a member of the Denisovans, an early human species only discovered about five years ago.

Todd Disotell, a molecular anthropologist at New York University not involved in the study, told The New York Times the Earth "was a lot like Middle-earth" millions of years ago. But instead of "elves and dwarves and hobbits and orcs... we had a ton of hominins that are closely related to us," he told the newspaper.

Svante Pääbo, a researcher at the Max Planck Institute for Evolutionary Anthropology who participated in the study, was part of the research team that found and analyzed the remains from the Siberian cave in 2010.

"It's an amazing place," Pääbo told National Geographic, "because it's actually the only place in the world where we know that three different groups of humans with very different histories all lived."

Denisovans are still relatively new to the science community, so studies like this are helping researchers piece their species together. As far as genetic diversity goes, Live Science noted, they lie somewhere below modern humans and above Neanderthals.

"This is the first time we can look at genetic variation among Denisovan individuals," Pääbo told Live Science. "There must have been quite many of them over quite a long time."