The research helps resolve a debate over whether the adoption of domesticated plants and animals introduced to Great Britain from the European mainland was a gradual or rapid process, said Michael Richards, an archaeologist at the University of Bradford in England.
The diet of Neolithic humans changed suddenly 5,000 years ago. The shift from surf to turf corresponds with the arrival of domesticated animals in Great Britain. Britain's fish and chips did not become popular until the nineteenth century.
By 4000 B.C. the archaeological record shows that pottery and large stone-built tombs and domesticated plants and animals were present in Great Britain, but it is not clear whether they replaced the marine-based hunter-gatherer lifestyle quickly or piecemeal over several hundred years.
Mark Copley, a chemist at the University of Bristol in England who studies the Neolithic diet by analyzing residues left on shards of ancient pottery, said understanding how quickly diet changed in England provides insight to what happened to the people who lived in Great Britain during the Mesolithic (9,000 to 5,200 years ago). The ensuing Neolithic period (5,200 to 4,500 years ago) is the last phase of the Stone Age.
"Farming really took off in Britain during the Neolithic. The main questions concerning the speed of change relates to how quickly Mesolithic peoples adapted—or otherwise—to the new farming methods and/or the spread of farming into Britain by new farming communities," he said.
The research by Richards and colleagues Rick Schulting at Queen's University Belfast and Robert Hedges at the University of Oxford tracks the shift in diet by examining the dietary signature stored in the bones.
They find that the shift was rapid and complete at the onset of the Neolithic. "Marine foods, for whatever reason, seem to have been comprehensively abandoned," the researchers conclude in the September 25 issue of the journal Nature.
You Are What You Eat
As the maxim "you are what you eat" goes, our bones and bodily tissues are made up of elements taken from the food we consume. As a result, our bones and bodily tissues contain a record of the food we have eaten over the course of our lives.
When we die, our skin usually decomposes, leaving behind bones. By examining the elements in the bones of a person long dead, researchers can determine the main constituents of that individual's diet.
Richards and colleagues looked at the dietary signatures left behind in bones of inland and coastal-dwelling inhabitants of Britain during the Neolithic and the preceding 3,800 years (Mesolithic) to determine what they ate.
Specifically, the team looked at the ratios of stable carbon isotopes. Marine foods and land-based foods have distinct stable carbon isotope signatures, said Richards.
"We determined that after the introduction of domesticates, as well as the other artifacts associated with the Neolithic, the isotope values showed that marine foods were not used anymore," he said. "We then infer that this is a switch from wild foods such as fish and shellfish to the new domesticates that arrive at this time."
While the bone analysis alone does not directly say the shift was from seafood to domesticates, it coincides with their arrival. Richards and colleagues say this suggests that the arrival of the new farming lifestyle must have been very attractive, even to coastal dwellers who had a well-established marine economy in the Mesolithic.
Changing Diet
Richards said there are three plausible reasons why the British abandoned seafood from the beginning of the Neolithic: the domesticated plants and animals presented a steady source of food; the shift was forced by a climate change; or cultural pressure.
Of those, Richards said a climate change is the least likely since there were several climate changes during the Mesolithic yet marine foods continued to be used.
"The previous hunting-fishing-gathering way of life was extremely successful for humans—it is the main way we have obtained food for most of our existence—so it seems strange that we would give this up so readily to start farming and stock-keeping within a generation or two," said Richards.
According to Copley, this research highlights how advantageous the Neolithic diet of farm animals, dairy products, and cereals must have been. For example, he said, it allowed populations to boom and larger, more complex societies to emerge.
"Of course, it poses more questions," he said. "For example, are marine foods still consumed during the Neolithic but in much lower abundances? And why is there this very quick shift in diets?"
The carbon isotope signatures are not sensitive enough to rule out the possibility that the British had an occasional fish fillet at dinner, but it clearly shows a shift from a high-level of marine food consumption in the Mesolithic, said Richards.
Fish once again became an important force in the British diet when the Romans invaded Great Britain during the first century A.D., but even then it was likely seldom eaten and only then by the upper classes.
"In the medieval and later periods we see much more use of fish, but in Britain we never see the levels of fish consumption seen in the Mesolithic period," said Richards.
Fish and chips, the world-famous British dish, became popular in the 19th century. The battering and deep frying of the fish killed off bacteria and kept it warm for long periods of time to feed mill workers, said Richards.
By John Roach in "National Geographic News", September 24, 2003. Digitized, adapted and illustrated to be posted by Leopoldo Costa.
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