Bones excavated from a German cave shed light on how hunter-gatherers and farmers lived side by side 7,500 years ago.

Fossil skeletons taken from the Blätterhöhle cave near Hagen in North Rhine-Westphalia reveal that indigenous hunter-gatherers lived alongside farmers who migrated to Central Europe from the Near East, archaeologists say. While the two groups tolerated each other, they did not mesh, the Washington Post reports.

Using DNA samples from bones taken from the cave, researchers found that for 2,000 years the two groups coexisted in the same region but did not mate – proving the hunter-gatherer lifestyle died out much later than previously thought.

"It is commonly assumed that the Central European hunter-gatherers disappeared soon after the arrival of farmers," Dr. Ruth Bollongino, lead author of the study, said in a statement. "But our study shows that the descendants of Mesolithic Europeans maintained their hunter-gatherer way of life and lived in parallel with the immigrant farmers, for at least 2,000 years.”

The findings, published in the journal Science, revealed how researchers used mitochondrial DNA analysis and isotope analysis to find out migration patterns, lineages and diets of the two groups.

In 2004, Blätterhöhle was discovered by archaeologists who excavated more than 450 skeletal fragments. Carbon dating reveals the cave was used in the Mesolithic period, between 9210 and 8340 B.C., and in the Neolithic period, between 3986 and 2918 B.C., most likely as a burial ground, LiveScience reports.

Mitochondrial DNA results taken from 25 of the skeletons indicated that some were hunter-gatherers while others were farmers. It was only when the isotope content of the samples were analyzed did researcher discover that the hunter-gatherers sustained a diet of fish while farmers relied on domesticated animals, Bollongino said. The two groups rarely interbred.

“It wasn’t until we saw the isotopes that we realized we were going to have to rewrite the paper completely,” Bollongino told the Washington Post. “They shared the same burial place for something between 400 and 600 years, so it would be very hard to explain that they did not know each other. We believe that they were close neighbors and had contact with each other and traded with each other. But still they didn’t mix.”

The results may prove who modern Europeans descended from. "Neither hunter-gatherers nor farmers can be regarded as the sole ancestors of modern-day Central Europeans,” Dr. Adam Powell, population geneticist at the JGU Institute of Anthropology, said. “European ancestry will reflect a mixture of both populations, and the ongoing question is how and to what extent this admixture happened."