Researchers investigating the impact of the Neolithic, Copper, Bronze, and Iron Ages on "Europe's genetic landscape" analyzed DNA extracted from the petrous bones of 13 Hungarian skeletons dating from between 5,700 BC (Early Neolithic) and 800 BC (Iron Age).
The international research team, made up of scientists from Ireland, Hungary, Germany, the UK, and the US, "surprisingly" observed "no Neolithic presence of lactase persistence."
Lactose intolerance occurs when the small intestine does not make enough lactase, an enzyme essential to digest lactose, a natural sugar found in milk and dairy products.
When lactose moves though the large intestine without being properly digested, it can cause uncomfortable symptoms such as gas, stomach pain, and bloating.
It is assumed, based on earlier research, that humans in this region developed lactase persistence - the genetic ability to digest milk sugar lactose as an adult - around 5,500 BC, in line with the emergence of cheese making.
In the DNA analysis of the 13 Hungarian remains, however, lactase persistence first became evident in the Bronze Age skeletons.
“Absence of the lactase persistence allele has been reported before from Neolithic specimens although the selective sweep has been modeled as originating between Central Europe and the Balkans 4-6,000 BC," said the study, published in the Nature Communications journal.
“Its absence here until the late Bronze Age, 1,000 years BC, suggests a more recent dating of this recent dating of this extremely interesting episode in the dynamic history of European genomes.”
Commenting on the results, Professor Ron Pinhasi from the University College Dublin's (UCD) Earth Institute and School of Archaeology, one member of the research team, said: “Our findings show progression towards lighter skin pigmentation as hunter and gatherers and non-local farmers intermarried, but surprisingly no presence of increased lactose persistence or tolerance to lactose.”
“This means that these ancient European would have had domesticated animals like cows, goats and sheep, but they would not yet have genetically developed a tolerance for drinking large quantities of milk from mammals," he said.
Source: Nature Communications doi:10.1038/ncomms6257
Title: Genome flux and stasis in a five millennium transect of European prehistory
Authors: C Gamba, E Jones, M Teasdale, R McLaughlin, G Gonzalez-Fortes, V Mattiangeli, L Domboroczki, I Kovari, I Pap, A Anders, A Whittle, J Dani, P Raczky, T Higham, M Hofreiter, D Bradley, R, Pinhasi.