In order to digest milk, adult humans need to have a gene which produces an enzyme called lactase to break down lactose, one of the main sugars it contains.
Without it, a drink of milk proves an uncomfortable experience, causing bloating, stomach cramps and diarrhoea.
Today, more than 90% of people of northern European origin have the gene.
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Working with scientists from Mainz University in Germany, the UCL team looked for the gene that produces the lactase enzyme in Neolithic skeletons dating between 5480BC and 5000BC.
These are believed to be from some of the earliest farming communities in Europe.
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The big question for scientists now is how the human population changed and took advantage of milk consumption.
One theory suggests that small groups who could tolerate lactose became dominant because they could then farm cattle for milk.
But the UCL team says it is more likely that the genetic mutation allowing the digestion of milk arose at some point after dairy farming began.
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Anna Denny, a scientist with the British Nutrition Foundation, said ‘lactase deficiency’ affected about 5% of white British people, and a larger proportion of those from some ethnic minorities.
In some parts of the world, such as Asia and Africa, the vast majority of people are lactose intolerant to some degree.
milk, dna, gene, enzyme, University College London, ucl, eu, evolution, farming, mutation, Nutrition
