Hundreds of human skulls and jawbones recovered from an ancient cemetery in southwest Arkansas are the remains of ancestors of the Caddo Nation, according to a new study published in the Journal of Archaeological Science.
There was some speculation that they might be trophies of war.
But that is not the case, said John Samuelsen, science and technology administrator for the Arkansas Archeological Survey, and lead author of the study.
By comparing lead and strontium isotopes in the teeth of ancient animals with those of the human remains, researchers were able to determine that the human remains were of people who had grown up in the area.
"Our study tested and ultimately refutes hypotheses that the Crenshaw remains are 'trophy skulls' killed during raiding expeditions," said Samuelsen, who is also a graduate faculty member in the Department of Anthropology at the University of Arkansas, Fayetteville.
"Demonstrating that the remains are Caddo ancestors provides both researchers and the Caddo Nation a clear answer to questions that have long persisted about the site and the remains," he said.
The Crenshaw site was a large village and ceremonial center occupied from about AD 700 to 1400 along the Red River in Miller County, according to the Encyclopedia of Arkansas.
Since its discovery in the 1960s, researchers have debated the meaning of the skull-and-mandible cemetery, as it has come to be known.
Samuelsen said 114 human skulls (with mandibles) and 238 separate mandibles were found at the Crenshaw site, representing 352 people. He said hundreds more may be buried there.
"When deposits of severed heads and mandibles are discovered at an archaeological site, warfare may first come to mind," according to the study. "Skull deposits are a worldwide phenomenon, the origins of which are often contested by scholars. Isotopic studies of skull deposits in ancient Mesoamerica and South America often conclude they are foreign victims of warfare or sacrifices."
But that's not necessarily so farther to the north.
Southwest Arkansas was at the intersection between the Eastern Woodlands and the Southern Plains cultures, circa 1200 and 1500 AD, shortly before European contact.
"A hasty interpretation of the skull-and-mandible cemetery might be trophy taking as a result of interregional warfare, but there is little archaeological evidence of warfare among the ancient Caddo," according to the study.
"If interregional warfare was occurring at all, it does not appear to have involved the Caddo," according to the study. "This clearly changed sometime around European contact when tensions between the Caddo and other tribes boiled over."
The Fourche Maline culture at Crenshaw appears to have undergone a population decline as residents presumably moved away to live in scattered farmsteads in the Red River valley, according to D. Glen Akridge of the Arkansas Archeological Society, writing for the Encyclopedia of Arkansas. This transition coincided with the beginnings of Caddo cultural traditions in the area.
"After about A.D. 1000 and for the next 400 years, the site is thought to have been used primarily as a ceremonial center, occupied by only a few Caddo elites and their families," according to Akridge. "The dispersed Caddo population may have returned to Crenshaw at various times during the year to conduct ceremonies, to bury their dead among relatives at their ancestral homeland, and to mark special occasions."
While they were dispersed geographically, people were still in the vicinity of southwest Arkansas and would return to Crenshaw for rituals, ceremonies or other public events, said Samuelsen.
The research indicates the Caddo were participating in a form of ancestor veneration that emphasized the importance of certain families within the community, according to the study.
"The severing of the head or mandible allowed for a larger and more geographically dispersed community to have their remains buried at Crenshaw, without having to transport entire bodies over long distances," according to the study. "The practice of skull and mandible burial and potential storage or display of the remains in charnel structures is consistent with Native American practices related to ancestor veneration."
The Crenshaw site is on private property, and researchers try to keep its location a secret. It's not open to the public, but the Caddo Nation has given UA researchers permission to study the site.
The remains of the skull-and-mandible cemetery were uncovered due to farming practices in the 1960s. Then looters dug in the area for some time.
Researchers from the UA and Archeological Survey tested lead and strontium isotopes in the teeth of human remains from the Crenshaw site and compared them to 180 animal teeth from 28 ancient sites in the south-central U.S., according to the study.
Samuelsen, 41, of Tampa, Fla., developed a method of examining lead isotopes in tooth enamel that was used to determine whether the remains in the skull-and-mandible cemetery belonged to locals. It was employed in conjunction with a method that he has previously used to examine strontium isotopes in tooth enamel. Lead has six isotope ratios, compared with one for strontium, making it a better marker for the research.
"A new approach became necessary when strontium isotopes failed to regionally differentiate the skulls and mandibles," according to the study. "A large-scale, multiregional lead and strontium isotopic background was constructed using ancient non-migratory animal tooth enamel for comparison to the skull-and-mandible deposits at Crenshaw."
Samuelsen said isotopes in the tooth enamel of the human remains corresponded with those of non-migratory animals that lived in the same area at about the same time.
"They matched the animals in the local area," he said in an email. "The humans did not match the animals from other regions."
Lead and strontium are elements that occur naturally and would have been in the soil and plants. Humans and animals were both eating plants in the same areas, so it doesn't matter if they weren't eating the same plants, Samuelsen said.
"You're assessing the human's location based on the ratio of lead in animal teeth," he said.
Animal tooth samples used in the study came from as far away as Illinois.
"Animals sampled included deer, rabbit/cottontail, opossum, squirrel, pocket gopher, raccoon, beaver, ground hog, black bear, grey fox, skunk, dog, rat, and other small rodents," according to the study.
The university in Fayetteville is one of the few places that has equipment capable of doing the research, said Samuelsen, referring to a Nu Plasma multicollector inductively coupled plasma mass spectrometer, which measures how much of each isotope is present in lead or strontium.
For the Crenshaw study, Samuelsen worked with Adriana Potra, associate professor in the UA's Department of Geosciences, who is co-author of the study.
Their study of the Crenshaw site is the first to use lead isotopes in ancient animal teeth from many different regions to evaluate where humans lived, according to a news release from the university. These isotopes in tooth enamel are set during childhood tooth formation and reflect the isotopes in the underlying geology where the children grew up.