Britain's enigmatic "headless Romans" lost their heads far away from home, according to a multi-isotopic analysis of the 1,800-year-old skeletal remains.
Unearthed between 2004 and 2005 in a cemetery in York, England, the remains belong to 80 individuals, almost all males, who died violently at ages ranging between 19 and 45.
At least 46 of them had been carefully decapitated, with their heads placed by or between their legs or pelvis.
Believed by some to be gladiators, losing their heads after their last fight, the heavily built men were buried in one of the most prestigious cemeteries of York during the 2nd and 3rd century A.D.
At that time the town, then called Eboracum, was an important military base and urban settlement which grew to become the Roman Empire's northernmost provincial capital.
Although the gladiator theory is currently regarded as the most likely, their unusual burial still raises many questions.
"There are other possible explanations. For example, the burials could represent some form of unusual religious belief, perhaps reflecting an unusually diverse group of people," Kurt Hunter-Mann, a field officer at York Archaeological Trust,who led the original excavations, told Discovery News.
To shed some light on the origins of the headless Romans, Gundula Müldner, a bioarchaeologist at the University of Reading in the U.K, and colleagues from Reading and the NERC Isotope Geosciences Laboratory in Nottingham, UK, carried out a multi-isotopic analysis of the skeletal remains.
"We can say that these individuals stood out from the rest of the York population. They were a remarkable mix of people coming from different parts of Britain and the Roman Empire," Müldner told Discovery News.
Absorbed by our teeth and bones from our food, drinking water and the air, isotopes -- atoms of the same element with different atomic weights and mass number -- provide information on the geological setting and climate a person was raised in as well as their diet.
Müldner's team tested the isotopes of four elements: oxygen, strontium, carbon and nitrogen. Where possible all four isotopic systems were tested in the same individual.
Oxygen and strontium isotopes, which are fixed in dental enamel at the time of tooth formation, were tested in 18 subjects.
"These represent all individuals from this excavation with surviving dentitions. All were assessed 'male' or 'probably male' on the basis of skeletal morphology and 12 out of the 18 had been decapitated," the researchers wrote in the current issue of the Journal of Archaeological Science.
It emerged that just five of the 18 adults were born in the York area. The rest of the men came from other parts of Britain and mainland Europe, possibly from France, Germany, the Balkans, or the Mediterranean.
The researchers also tested 68 individuals for carbon and nitrogen in order to find clues about their diet. They discovered that five of the headless Romans ate very different foods from York's local population. Two in particular had consumed C4-plant based protein, probably millet, in their childhood.
"We have not seen similar values in Britain before, nor much in Europe in the Roman Period, at least so far," said Müldner.
Indeed, millet is not known to have been cultivated in Britain in the Roman period or at any time before.
"It seems that the Romans were not very fond of millet, and often, when they established a new province, other cereals such as wheat would replace millet as the principally grown crop," the researchers said.
Combined with oxygen isotope testing, the analysis suggested that at least one headless millet-eater came from Eastern Europe or somewhere with access to water from high altitudes.
According to Hunter-Mann, the research is "interesting and useful."
"We are currently undertaking osteological and forensics studies, but it will be some months before we have this information and we can compare it with the isotopic information," he said.
"I think this study, along with all the other skeletal, artefactual and stratigraphic research, will assist with the interpretation of these burials," Hunter-Mann told Discovery News.