Archaeology: Ancient humans were consuming milk long before they could digest it

Prehistoric people in Europe may have started consuming milk from domesticated animals thousands of years before they evolved the gene to digest it, suggests a study published in Nature. The findings offer new insights into milk consumption and the evolution of lactose tolerance.

It is believed that milk consumption in ancient humans played an important role in the evolution of the persistence of the lactase enzyme in adults, which enables the digestion of lactose from milk. However, considerable uncertainty remains because the intensity of milk consumption can vary a lot by geography and through time. To further explore the co-evolution of dairy farming and lactase persistence, Richard Evershed and colleagues built a comprehensive map of prehistoric milk consumption by analysing 6,899 animal fat residues derived from 13,181 fragments of pottery from 554 archaeological sites. The evidence suggests that milk use was widespread in Europe from the Neolithic period onwards (from around 7,000 BC) but varied across different regions and times. They also examined the frequency of the main lactase persistence gene variant among Eurasians through time, based on published ancient DNA data from 1,786 prehistoric European and Asian individuals. The results showed that lactase persistence was not common until around 1,000 BC, nearly 4,000 years after it was first detected around 4,700–4,600 BC.

Together, these findings indicate that in Europe milk use was widespread when prehistoric people were still largely lactose intolerant, raising questions about whether milk consumption is a key driver for lactase persistence. Modelling genetic and archaeological data did not show a strong link between milk consumption and the rise of lactase persistence either, the authors add. Instead, they found that indicators for famine and pathogen exposure better explained its evolution. The findings of the study challenge the prevailing narrative about how the lactase persistence gene evolved, and provide new perspectives for future research into other plausible hypotheses, the authors conclude.