Indians, Europeans share a milky past

London, Sept 8 - In a major study, researchers in the UK have discovered that lactose tolerant milk-drinkers in India and Europe could be related to the same person who lived at some point in the last 10,000 years.

 The Cambridge University team, in association with fellow researchers at CCMB Hyderabad, UCL, University of Tartu, Harvard and University of Chennai, were studying genetic changes that allow some 32 per cent of the world's population to be lactase persistent able to digest lactose, the sugar in milk. To their surprise they found the same mutation, with the same origin, at high frequency in Europe and India.

 The focus of the Cambridge-led study was India the world's largest producers and consumers of milk.

 The team's study may also help scientists' understanding of evolutionary processes such as biological adaptation and how culture and economic developments affect human biology.

 Its authors say the study has shown that with a little kick from natural selection, genes can spread far, wide and fast, a university release said.

 Lactase persistence is common in Europe, the Middle East and some parts of Africa and India areas where domesticated cattle are widespread - but either rare or absent in most other parts of the world.

 When someone who is not lactase persistent drinks milk they will often suffer symptoms such as abdominal pain, bloating, nausea and diarrhoea otherwise known as lactose intolerance.

 While all babies produce the gut enzyme lactase, essential for the digestion of lactose in milk, the production of the enzyme is usually shut down some time before adulthood.

 Although once thought of as normal, lactase persistence was found in the 1960s to be an unusual trait in humans and seems to be completely absent from other mammals whose lactase production diminishes significantly after being weaned and is never resumed.

 The team looked at nearly 2,300 DNA samples from across the Indian subcontinent from all major language groups and geographic regions the first study of its kind.

 Previous studies had shown that lactase persistence had evolved at least four times in the last 10,000 years, independently in Europe, the Middle East and Africa.

 However, little was known about its genetic causes in India, until now.

 Cambridge's Irene Gallego Romero, the lead author, said: ÒIndia was an unknown quantity. But since lactase persistence had evolved independently in the Middle East and Africa, and because cattle had been domesticated independently in India around seven or eight thousand years ago, we were expecting to see uniquely Indian genetic causes.