PART.2
Eerkens’s team measured the strontium in the teeth of those who had been buried with extra skulls, as well as in the bones of those who had been decapitated, and in one of the calottes.
They then compared those figures with the levels found in the rest of the burial population.
Their results showed that all of the burials contained the same strontium signature, which was specific to the Marsh Creek area.
“The stable isotope context is the key to determining if the people who had their heads removed, and the people buried with an extra skull, were from there or not,” Eerkens explained.
“And in this case the original interpretation” — that the extra skulls were taken as trophies from outsiders — “did not hold up.”
Moreover, Eerkens pointed out that the general profile and condition of the burials gave no suggestion that anyone buried at Marsh Creek had been killed or injured in battle.
Based on other mass graves that have been found in central California, signs of warfare are relatively easy to spot, he said.
“In those mass burial cases the individuals are all males, and they show clear evidence of violence as a probable cause of death: arrows embedded in bone, cranial fractures, et cetera,” he said.
“As well, the isotopic data show the men in those mass graves were not local to the site where they were buried — they were from somewhere else.”
“In this case, at Marsh Creek, we have both males and females represented, who were buried with an extra skull. There is no clear evidence of violence on anyone with such unusual burial treatment, and the isotope data show they were all locals — both the people buried with extra skulls, and the people lacking a skull.”
“The Marsh Creek pattern is inconsistent with warfare as an explanation for the presence of extra skulls and headless burials.”
Rather than being signs of conflict, Eerkens said, the skulls and calottes may have represented an opposite kind of relationship: one of kinship.
“The data are much more in line with ancestor worship, where sometimes mementos of people were kept and turned into artifacts — bowls, in this case, but we have examples of flutes and whistles [made from human bone] in other cases.”
“These items were probably used in rituals to remember the dead. Some individuals were later buried with these items, or other remains of one of their ancestors.”
To explore this theory, the researchers returned to the subjects’ teeth, where another surprising clue turned up, this time about their diet.
An archaeologist holds the calotte, or skull cap, from Burial 137, the only one to be chemically tested. (Photo courtesy Eerkens et al.)
The team analyzed teeth from two of the people who were buried with extra skulls — one male and one female — and focused on their levels of nitrogen, which can provide insights into the quality of nutrition that they received in childhood.
High levels of nitrogen found in the deepest, oldest layers of teeth — which form during infancy — correlate with a diet rich in breast milk, Eerkens explained. Low nitrogen levels, meanwhile, suggest a diet consisting of solid foods, such as acorns and roots.
The results showed that both of the people experienced a sudden drop in nitrogen in their diet when they were between 12 months to 21 months old.
To Eerkens, this means that both subjects had been weaned from their mothers, suddenly and at an unusually young age.
“We were surprised to learn that of the two we tested who were buried with an extra skull, both showed that they had been weaned at a very early age, earlier than anyone else we studied at the site,” he said.
This made the team wonder if there was a connection between being separated from a mother at a young age, and being buried with someone else’s head.
“One hypothesis we came up with is that their mothers may have died early, while they were still breastfeeding,” Eerkens said.
“As a result, they may have been adopted into another family.”
By this thinking, removing the skull from one of the person’s parents — whether biological or adopted — and burying it with them, may have been a way to re-unite child and parent after death.
“When the people who had been weaned early died themselves, there may have been conflict about where they should be buried: with their biological kin or their adopted families,” Eerkens explained.
“Burial with an extra skull from either their genetic or adopted families may have been a way to resolve this.”
Of course, such a scenario is purely speculative. But it could be tested, with the help of DNA evidence, Eerkens noted.
In the meantime, he said, the burials at Marsh Creek bear witness to the many forms that veneration can take, some of which may be difficult to recognize across cultures.
“I think it shows the strong connection native Californians had to their ancestors, and how they invested time and ritual effort in expressing that connection,” he said.
“That they kept mementos, like calottes fashioned into skull bowls, speaks to the importance of ancestors and the strong ties people had to their past.
“This is a theme that continues, of course, to the present. Native Californians today continue to have intimate and emotional ties to their ancestors and places that their ancestors lived.”
And the fact that Marsh Creek’s macabre artifacts were once thought to be war trophies is a reminder that, when studying a culture across the millennia, things are not always as they first appear.
“This is how archaeological science works,” Eerkens said.
“We have hypotheses about past human behavior, but we are always trying to falsify those hypotheses using independent lines of data.
“That’s how we advance our knowledge and understanding of the past.”
Eerkens and his colleagues report their findings in the journal American Antiquity.