Ancient Europeans may have been lactose intolerant, and remained so for 5,000 years after cheese-making was adopted by Central European Neolithic farmers.
The researchers made their findings by looking at the petrous bones of the skulls of ancient Europeans, University College Dublin reported. The findings suggest major technological transitions in Central Europe between the Neolithic, Bronze Age and Iron Age also involved genetic changes.
The research team extracted nuclear ancient DNA from 13 skeletons buried on the Great Hungarian Plain, which is known to be "at the crossroads of major cultural transformations." Petrous bones proved to be the most promising in this experiment because they are the hardest in the human body, and most resistant to decay.
"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 Professor Ron Pinhasi from the UCD Earth Institute and UCD School of Archaeology, University College Dublin.
The analysis allowed the scientists to look genetic marker indicating lactose intolerance in these ancient skeletons for the first time. The findings revealed a move towards lighter skin pigmentation as the hunter-gatherers and non-local farmers started to inter-marry, but the researchers did not see a change in levels of lactose intolerance.
These findings suggest ancient Europeans domesticated animals such as cows and goats long before they were genetically adapted to consume large quantities of their milk.
"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. We can no longer believe these fundamental innovations were simply absorbed by existing populations in a sort of cultural osmosis," said Professor Dan Bradley from the Smurfit Institute of Genetics, Trinity College Dublin, co-senior author on the paper.
The findings were published Oct. 21 in the journal Nature Communications.