The earliest humans in North America were far more diverse than previously thought with evidence they came from the arctic, Europe and elsewhere, according to new research.

The findings, which have stunned the anthropological world, came from the study of human remains found within one of the world’s most extensive underwater cave systems in Mexico.

The remains, discovered in the caverns of the state of Quintana Roo, represent just four of the earliest North Americans, all of whom lived between 9,000 and 13,000 years ago.

They’re important because North American remains from the first millennia of human habitation in the Americas are rare, said study

Study leader, Professor Mark Hubbe, an anthropologist at Ohio State University, said the remains were important because they are so rare; fewer than two dozen individuals have been discovered.

Prof Hubbe said what made the four individuals from Mexico interesting is that none were alike.

One resembles peoples from the Arctic, another has European features and one looks much like early South American skulls, while the last doesn’t share features with any one population.

“The differences we see among these Mexican skulls are on the same magnitude as the most different populations globally nowadays,” Prof Hubbe told the journal PLOS ONE.

The settlement of the Americas is mystery because of the lack of archaeological findings from 15,000 to 20,000 years ago, which is most likely when the first humans set foot on the continent.

Because the path to South America for the earliest people must have included stops in North America or along the Pacific coast, the assumption has been that early people in South America looked a lot like early people in North America.

“But the new research suggests otherwise. Instead, early North American populations look far more diverse than early South American populations,” Prof Hubbe aid.

“For whatever reason, when they went to South America, part of this diversity disappeared,” Hubbe said.

Of the four skulls studied in the new research, one came from a young adult woman who lived around 13,000 years ago; one belonged to a young adult male from the same era; one was from a middle-aged woman who lived between about 9,000 and 12,000 years ago; and the fourth was that of a middle-aged man from around 10,000 years ago.

The researchers found that the 13,000-year-old young woman had features that most closely matched Arctic North Americans from Greenland and Alaska.

The young man from 13,000 years ago, on the other hand, looked most similar to people from European populations.

The middle-aged female from between 9,000 and 12,000 years ago looked much like the earliest settlers of South America. Finally, the middle-aged man from around 10,000 years ago showed no clear pattern. He had features seen in several American and Asian populations.

The new evidence also contradicts the genomic data researchers have collected. Genomics suggest that all Native Americans, with the exception of a few later migrants, descend from a single migration of people from Asia.