Lactose intolerance is not a modern or first world problem. On Tuesday, researchers reported in the journal Nature Communications evidence that ancient Europeans remained lactose intolerant well after they began keeping cattle and goats for milk production.

Researchers at University College Dublin examined the petrous bones of the skulls of ancient Europeans recovered from the Great Hungarian Plain, a place known for existing “at crossroads of major cultural transformations.” The bones represent Central European Neolithic farmers that remained persistently lactose intolerant some 5,000 years after adopting cheese-making.

The findings indicate that genetic changes probably accompanied major technological transitions in Central Europeans beginning in the Neolithic Age and extending through the Bronze Age to the Iron Age. The team of scientists extracted ancient nuclear DNA from 13 skeletons, particularly from the petrous bones, which were hard enough to offer the most intact DNA protected over the millennia from the elements.

“The high percentage DNA yield from the petrous bones exceeded those from other bones by up to 183-fold. This gave us anywhere between 12 [percent] and almost 90 [percent] human DNA in our samples compared to somewhere between 0 [percent] and 20 [percent] obtained from teeth, fingers and rib bones,” said Ron Pinhasi of the Earth Institute and School of Archaeology, University College Dublin.

The genetic analysis provided insight into the prevalence of the genetic marker of lactose intolerance in these skeletons for the very first time. Also revealed was a transition toward lighter skin tone, suggesting that the hunter-gatherers and non-local farmers began inter-marrying.

Overall, the results suggest that the domestication of milk-producing livestock preceded the ability to tolerate lactose in the human diet.

“Our results also imply that the great changes in prehistoric technology including the adoption of farming, followed by the first use of the hard metals, bronze and then iron, were each associated with the substantial influx of new people,” said study co-author Dan Bradley of Trinity College Dublin. “We can no longer believe these fundamental innovations were simply absorbed by existing populations in a sort of cultural osmosis.”