The remains of ancient humans offer clues about the people who migrated to Rome during its Imperial Era at the turn of the millennium.

According to Live Science, the researchers identified the people - three adult males and one unidentifiable adolescent - as migrants by their teeth. Past studies have estimated five percent of Rome's population at the time were migrants, but evidence of their existence has been scarce.

"The individuals were mostly children and men, and the authors suggest their burial in a necropolis indicates that they may have been poor or even slaves," read a press release detailing the study published in the journal PLOS One. "They also found that their diet probably changed significantly when they moved to Rome, possibly adapting to the local cuisine, comprising mostly wheat and some legumes, meat and fish. The authors note that further isotope and DNA analysis is needed to provide more context for their findings. Nonetheless, they state that their study provides the first physical evidence of individual migrants to Rome during this period."

Kristina Killgrove, a biological anthropologist at the University of West Florida and one of the study's two authors, said the teeth were highly important to the research, because they "are kind of like little time capsules in your mouth."

"Up to a million people were living there," she told Live Science. "This population ebbed and flowed. You had people who were migrating in, and you had people who were dying and [people who were] migrating out."