New Delhi, Jan. 21 -- Genghis Khan's conquering armies fed on dried curd as they crossed the vast steppes of Eurasia, ancient Romans imported pungent cheeses from France, and Bedouin tribes crossing the Arabian Desert have for centuries survived on camel's milk.
Dairy has been central to people's existence since at least 6,500 years BC.
But a mystery lies at its heart which, if solved, could help explain the rising number of modern dietary problems ranging from food intolerances to allergies, researchers say.
Scientists are trying to explain why people began consuming animals' milk before they developed genetic mutations which enabled them to digest it properly.
The mutations mean people produce lactase - an enzyme which breaks down mil...