Throughout the course of human history, people have had but two questions when encountering strangers: One, will this person try to kill me, and 2) if not, can I have sex with them? People from a different tribe? Sure, light some candles and put on some music. Modern humans and Neanderthals, technically different species? No problem, let’s do this. According to a new study, though, there’s at least one group of ancient peoples who stood in stark contrast to this time-honored tradition: Researchers from the University of Copenhagen found that the earliest Arctic inhabitants lived in isolation from their neighbors for 4,000 years, mixing neither culturally nor sexually.

“Elsewhere, as soon as people meet each other, they have sex,” says evolutionary geneticist Eske Willerslev. “Even potentially different species like Neanderthals [and modern humans] had sex, so this finding is extremely surprising.”

The people, dubbed the Paleo-Eskimos by archeologists and known as the Tunit in Inuit folklore, entered North America about 5,000 years ago, some 10,000 years after the migration that brought the first Americans across the Bearing Straight. Even in early times, the Inuit regarded the Tunit as reclusive (along with claiming they were strong enough to kill and haul adult walruses with their bare hands). At least one of those things appears to be true.

A low level of genetic diversity reveals another startling discovery: The Paleo-Eskimo population contained shockingly few women. In fact, the genetic record suggests that the first migrant population may have contained as few as one single (and apparently very accommodating) woman. DNA sampling proved difficult due to the Tunit’s propensity for burying their dead at the surface, rather than attempting to dig proper graves into the impenetrable permafrost.

Adding to the strangeness, the Paleo-Eskimos developed what’s called the Dorset culture, which researchers describe as “cult-like.” Besides eschewing “modern” tools like bows and arrows, the culture was deeply spiritual, leading meany to point to this as the reason for their genetic insularity. Ancestors of the modern Inuit seem to have found them just as odd, which would explain the Tunits’ place in their folklore. It’s a good thing they did, because scientists believe disease from Viking traders may have killed off the Tunit just 300 years after the early Inuits arrived.