Milk ran deep in prehistoric England. (Dairying pioneers).

Farmers who settled in England around 6,000 years ago literally milked cattle and other grazing animals for all they were worth. A chemical analysis of broken pots found at 14 ancient British sites confirms archaeological evidence suggesting that early farmers raised livestock for dairy products as well as for meat.

The new study, directed by chemist Richard P. Evershed of the University of Bristol in England, employed a recently developed mass spectrometric technique to identify milk fats on pots from the ancient sites, which range from about 1,500 to 6,000 years old.

"This is the first direct evidence of milk use at the time farming began in Britain, 6,000 years ago," says archaeologist and study coauthor Sebastian Payne of English Heritage in London, a public agency that supports archaeological work.

These findings, described in an upcoming Proceedings of the National Academy of Sciences, reveal only that many pots once contained milk or milk products. "We don't know the extent to which prehistoric people drank milk or converted it into products such as cheese and butter," he says.

Some archaeologists suspect that only after several thousand years of farming did milk make its way into people's diets because lactose, a sugar in milk, commonly elicits allergic reactions. In accordance with that view, Payne speculates that early farmers in England primarily used milk to make lower-lactose dairy products, at least until widespread biological tolerance for the sugar had evolved.

Evershed and his colleagues studied more than 950 pot fragments found among the remains of villages spanning England's Neolithic, Bronze, and Iron ages. Small samples taken from each fragment were ground to a powder and chemically treated using a method that identifies the amounts of different carbon isotopes. Milk fats display a signature ratio of carbon isotopes, distinctive from that for meat fats.

"Evershed's chemical technique is the breakthrough we've been waiting for to investigate prehistoric nutrition," comments archaeologist Andrew Sherratt of the University of Oxford in England.

Many pottery pieces from each site that Evershed's team investigated--including the three oldest sites--contained milk-fat residue, the scientists say. Even the earliest English farmers seem to have employed a variety of agricultural practices, such as domesticating animals, cultivating crops, and dairying, Payne notes.

The new chemical data set the stage for researchers to look for milk-fat residues on pottery from comparably ancient sites in central Europe, adds archaeologist Peter Bogucki of Princeton University. Clues to dairying at these locations consist of large numbers of adult female cattle bones and ceramic strainers possibly used in cheese production, Bogucki says.

Evershed and Payne, with Sherratt, are now searching for milk-fat residues on pottery from about a dozen prehistoric sites in southeastern Europe, Turkey, and the Middle East. Payne suspects that Middle Eastern villagers milked farm animals at least 7,000 years ago. Various farming practices developed slowly there and then spread into Europe as a "package," he speculates.

At this point, it's hard to know precisely where dairying and milk consumption began and how they spread from those origins, Sherratt notes. "The milk story is getting fuzzier and more interesting," he says.