TUCSON, Oct. 24 (UPI) -- Researchers say ancient graves unearthed in the American Southwest suggest the region played host to violent tribal feuds thousands of years ago.
A new study -- published this week in the journal Current Anthropology -- details the discovery of several dozen bodies found unceremoniously deposited in burial sites between 2100 B.C. and A.D. 50.
The burial sites were unearthed in the southwestern United States and northwestern Mexico and featured many who had met violent ends. The remains also showed evidence of post-mortem injuries, likely inflicted as they were tossed haphazardly into the grave pits.
Over several years, James Watson -- lead author of the new study and a bioarchaeologist at the University of Arizona -- found dozens of skeletons splayed in unflattering final resting positions. Watson and his colleagues believe the bones belong to victims of ancient blood feuds.
"These people were buried very differently than the rest of the community, and we're trying to understand why that is," Watson, an associate curator at the Arizona State Museum, explained in a news release. "We're arguing that the way they were tossed into these pits is a form of continued desecration of the body. It's moving from violence on the living individual, through to the process of death, to violence on the corpse."
Some archaeologists and local historians have suggested such hostile burials may have been given to those suspected of witchcraft. Watson doesn't think so. Suspected witches were typically dismembered.
Instead, Watson and his colleagues believe the remains are evidence of cyclical family or tribal violence -- violence that may have become enculturated among some communities in the ancient Southwest.
Researchers argue the violence was in part a product of the times -- tough times.
"This was right when agriculture came into the area, and these were the earliest villages, so we think that some of this violence comes from growing pains, as villages are established and people are claiming territory and farming the desert river valleys," Watson said. "Social tensions develop between communities, or even within communities, and end up boiling over into violence."
Watson's study analyzes the violence from a biological perspective, likening the killings and unfeeling burials to "costly signaling theory," the phenomenon that describes physiological attributes or behaviors that can be both rewarding and risky. Bright bird feathers, for example, can attract both mates and predators.
"By creating these atypical burials -- where they're basically desecrating the bodies of the people killed -- they're signaling their prowess to gain status, but it's at a very significant potential cost, and that is either their life or lives in their community or family," Watson explained.
Watson believes his findings may help scientists better understand how violence becomes engrained among modern communities.