Ancient farmers and hunter-gatherers living thousands of years ago in today’s Romania had sex, according to a new study. The finding adds to our understanding of how different groups of ancient humans interacted with each other — painting a more nuanced picture of how farming spread across Europe.

Researchers analyzed the ancient DNA of three individuals dated to over 8,000 years ago, as well as one individual dated to 5,000 years ago — all found in Romania. The DNA of the more recent specimen showed that farmers and hunter-gatherers in this area of Europe were intermixing with each other and having children. The study was published today in the journal Current Biology.

The advent of farming is one of the most revolutionary advances in human history. People began domesticating plants and animals, forever changing the world around them. Farming is believed to have started around 10,000 years ago in the Near East, an area roughly comprising today’s Syria, Lebanon, Jordan, Iraq, and Turkey. From there, it spread across Europe — but when and how exactly people gave up hunting and gathering for farming has been at the center of long-standing debates.

Did farmers just spread across Europe, bringing the technology with them, and outcompete local hunter-gatherers? Or did hunter-gatherers get in contact with farmers, learn their technological advances, and switch to farming? Recent research shows that the answer is complicated, and how farming spread differs from place to place. Studies suggest that in Western and Central Europe, farmers from Anatolia (the Asian portion of Turkey) came in and replaced hunter-gatherer populations. But in the Baltic region, local hunter-gatherers seem to have just adopted farming, without being overtaken by farmers.

In the area comprising today’s Romania, however, the transition to farming seems to have been more nuanced. Archaeological evidence — such as artifacts, burial grounds, and diets — suggests that in this area, farmers and hunter-gatherers mixed, says Eppie Jones, a researcher from the University of Cambridge and co-author of today’s study. This is why the researchers were interested in analyzing the genetic data of the ancient people living in this area: they wanted to test whether this “cultural” exchange also resulted in people actually mixing with each other.

So the researchers took the bones of four individuals from Romania — three dated to over 8,000 years ago, and one dated to 5,300 years ago. They analyzed the petrous bones — the hard part of the skull behind the ear that “preserves DNA best,” says study co-author Michael Hofreiter, a professor of evolutionary adaptive genomics at the University of Potsdam in Germany. The genetic analysis showed that three individuals from over 8,000 years ago were all hunter-gatherers. (The researchers also analyzed the bones of two hunter-gatherers from Spain, dated to about 9,000 and 7,000 years ago, to have a better sampling of what hunter-gatherers across Europe looked like genetically.)

The individual dated to 5,300 years ago, however, turned up to be genetically about 60 percent hunter-gatherer and 40 percent Anatolian farmer. “It’s really mixed between the two populations,” Hofreiter says. That means that this person was the multigenerational child of hunter-gatherers and farmers mixing together. In short, in this area of Europe, hunter-gatherers and farmers weren’t just trading objects or swapping ideas, they were actually having sex.

“It’s the first time we can really show that hunter-gatherers and farmers really mixed,” Hofreiter says. “There was no positive evidence before.” The finding shows that, when it comes to the spread of farming across Europe, “actually the situation is very variable,” says study co-author Clive Bonsall, a professor of early prehistory at the University of Edinburgh.

A lot of questions remain unanswered. For example, does the fact that hunter-gatherers and farmers had sex mean they actually lived together? Was this mixing friendly, or aggressive? Was it constricted to this particular region, or part of a larger phenomenon? We can’t tell, says Jones.

To answer these questions — as well as why farming spread so differently in different parts of Europe — we need to analyze more specimens. But for now, today’s finding is already pretty neat: “I think it changes our understanding of the history of Europeans,” Jones says.