I don't think these men would have been rebel gladiators of any kind. The slaves and gladiators executed during the Servile Wars were almost always crucified. Decapitation was a relatively more "honorable" form of execution, usually reserved for citizens, and I think there's a certain respect in the way the heads were placed near the bodies. (Other methods of execution in Republican Rome involved being pushed off the Tarpeian rocks or just being placed in a sack and thrown into the Tiber or, often, strangulation. For parricide, the worst of sins in Rome, you were flayed alive and then sewn into a sack with wild animals and tossed into the river. Later on, they probably were just tossed into the local Circus for the wild animals.)
As for cowardice in battle, the punishment probably varied, but most often it was stoning or being flogged to death. In extreme circumstances of mass cowardice or desertion, sometimes the decimatio was used where the custom was for the men to be rounded up in groups of ten, one man then being chosen by lot from among the ten, and the other nine were forced to beat him to death. Horrific, but probably effective. Theft was often punished by clubbing or whipping or being put into a sack with snakes and then thrown into a nearby lake or river.
https://en.wikipedia.org/wiki/Roman_military_decorations_and_punishments#Punishments
It doesn't make much sense to me that they were rebels against Roman rule, either, or even marauders or raiders from north of the Wall. The enemy dead weren't treated in this way. The leaders were brought to Rome in chains, strangled and then tossed into the Cloaxa or the Tiber, and the "commoners" were either killed in battle and dumped into mass graves, or enslaved. I don't think we'd see cemeteries or this kind of care taken with the remains.
Also, we have to consider that from what I can tell, these burials stretched over the entire 100-300 AD period. (It would be important to know if the tested remains all date from the same time period, but I can't find a break-out by precise date for them, much less for the remainder of them.)
If the beheaded samples, which are a little more than 50% of the 80 or so found, all bore marks of battle in one form or another, but stem from various periods, then perhaps it was a gladiator cemetery, although I still have a hard time accepting that dead gladiators would be treated with this kind of respect. Perhaps it's more likely that they were soldiers, drawn indeed from around the Empire and then executed relatively painlessly for some infraction?
It's pretty clear that some were native Britons, however, which shouldn't be surprising. Some tribes allied with Rome pretty early, and more and more as time went on. There are dozens of books on the topic, but you can see the following for a description of the work of the British auxiliaries. Of course, some of them wound up in legions on the continent.
https://books.google.com/books?id=y...rving in the Roman legions in Britain&f=false
Perhaps some were executed by their leaders for one infraction or another, but it's also possible they were soldiers killed in border skirmishes whose bodies were retrieved and buried, some with their heads still nearby but others where they couldn't find the head. The "Celts" were well known for taking the heads of their enemies.
"
Siculus, in his 1st-century
History had this to say about Celtic head-hunting:
They cut off the heads of enemies slain in battle and attach them to the necks of their horses. The blood-stained spoils they hand over to their attendants and striking up a paean and singing a song of victory; and they nail up these first fruits upon their houses, just as do those who lay low wild animals in certain kinds of hunting. They embalm in
cedar oil the heads of the most distinguished enemies, and preserve them carefully in a chest, and display them with pride to strangers, saying that for this head one of their ancestors, or his father, or the man himself, refused the offer of a large sum of money. They say that some of them boast that they refused the weight of the head in gold."
https://en.wikipedia.org/wiki/Decapitation#Celts
Of course, some of this may have been standard trash talking about the enemy.
To return to the subject of the "British" origin of these particular samples, this article in the National Geographic shows that they knew in 2010 that many of the 80 men were of "foreign" origin.
"Oxygen and strontium isotopes in the bones of the headless Romans indicate that just 5 of the 18 individuals tested came from the York area, the team reports in the new study, published in the current issue of the
Journal of Archaeological Science.
The rest of the men came from elsewhere in England or mainland Europe, possibly from France, Germany, the Balkans, or the Mediterranean."
These must be among those included in the study, right?
"Traces of carbon and nitrogen show that five of the headless Romans ate very different foods from York's local population. And two individuals had a carbon signature from a group of food plants—including sorghum, sugarcane, and maize—not known to have been cultivated in England at that time."
Other than the "Syrian", I don't think any of these would have been included, right?
Where the heck did they grow sorghum, sugarcane and maize at this time period in or around Europe?
"In fact, millet is the only food plant from this group that was being grown anywhere in mainland Europe, she added.
The archaeologist noted 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.
Müldner's team thinks the headless millet-eaters hailed from colder climates, perhaps parts of Eastern Europe that were beyond the borders of the Roman Empire.
It might have been the Alps as well, or any higher mountains," Müldner said."
The Romans did eat millet, in porridge form, but preferred wheat. In fact, in the legions you were downgraded from wheat to millet rations for minor infractions. I know it can't be used with leavening agents.
Anyway: "It was a staple of the Sumerians and treasured plant grown in the hanging gardens of Babylon...There is evidence that millet was grown during the Stone Age by lake dwellers in Switzerland and was eaten in Northern Europe at least since the Iron Age. It was a staple in arid areas of India and Africa for thousands of years."
http://www.edenfoods.com/articles/view.php?articles_id=122
In the Middle Ages it was consumed more than wheat.
You'd think they might have informed readers of the paper of the yDna signature of the sample(s) in the study which shows millet consumption in childhood or the isotope signature of the continent.
However, the remains tested here, other than the "Syrian", overlap with the Welsh above all. Now, one could say, well, maybe people in France and central Europe were all "Welsh like" at that time. That's possible, I suppose, but doesn't the isotope analysis make it clear that of the tested samples in the paper all but the Near Easterner and one other were born and raised not only in Britain, but in the northeast of Britain?