A study of DNA from skeletons suggest that all European adults living between 6,000 BC and 5,000 BC were lactose intolerant, backing the idea that the ability to digest milk only spread after the introduction of cattle farming in Europe in the past 9,000 years.
The rival idea, that dairy farming was pioneered by a small group of Neolithic farmers who were able to tolerate milk, is overturned by the genetic study by a team from University College London and Mainz University, Germany.
Instead, the Neolithic descendants of Palaeolithic (stone age) people evolved their tolerance of milk within the last 8000 years due to exposure to dairy products, making this "the most rapidly evolved European trait of the past 30,000 years," according to Dr Mark Thomas of UCL. "Lactose tolerance is very much a Neolithic invention."
Studies of the DNA extracted from bones excavated from the earliest organized communities suggests that:
...the first European cattle farmers used their herds for working the land, leather and meat. They moved on to yoghurt and cheese, which contain less lactose.
But, through exposure to milk, lactose tolerance - a persisent form of the lactase enzyme - evolved extremely rapidly so that it is now present in more than 90 per cent of the population of northern Europe and is also found in some African and Middle Eastern populations but is missing from the majority of the adult population globally. "The majority of Northern and Central Europeans can call a minority of lactase persistent dairying farmers that lived some 7.000 years ago their ancestors," said Prof Burger.
"The ability to drink milk is the most advantageous trait that's evolved in Europeans in the recent past," added Dr Thomas. "Without the enzyme lactase, drinking milk in adulthood causes bloating and diarrhoea. Although the benefits of milk tolerance are not fully understood yet, they probably include: the continuous supply of milk compared to the boom and bust of seasonal crops; its nourishing qualities; and the fact that it's uncontaminated by parasites, unlike stream water, making it a safer drink. All in all, the ability to drink milk gave some early Europeans a big survival advantage."