The scene, discovered by archaeologists in Illinois more than 40 years ago, depicts one of the most extravagant acts of violence ever documented in ancient America: A thousand-year-old pit found under a tall earthen mound, lined from corner to corner with skeletons — 53 in all — neatly arranged two bodies deep, each layer separated by woven fiber mats.

The victims all appeared to be women, mostly in their late teens or early 20s. Evidence suggested they were strangled, or perhaps cut at the throat, at the edge of their shared mass grave, and then interred, meters away from an ornate burial of two men thought to be clan elders, political leaders, spiritual guides, or all three.

But the women were not alone.

At the other of end the mound were three more mass graves, containing another 65 skeletons between them, also apparently of females.

By the time the entire mound had been excavated, two dozen burial pits had emerged, cradling some 270 human remains, each betraying signs of various degrees of violence — from having their jaws broken to being buried alive.

Archaeologists first uncovered this grim tableau in 1967 while excavating the prehistoric city of Cahokia, at its peak from 1050 to 1150 CE, the seat of the ancient Mississippian culture.

Now little more than a series of grassy hillocks outside St. Louis, Cahokia was once the metropole of a civilization whose trade routes and religious influence stretched from the Great Lakes to the Deep South, and whose culture shaped the ways of the Plains and Southern Indians.

(Learn more about Cahokia’s ancient rituals: “Ancient Americans Pounded Vomit-Causing ‘Black Drink’ 6 Times Stronger Than Coffee”)

As the largest display of ritual killing found anywhere north of Mexico, the cluster of Cahokia mass graves — known as Mound 72 — has been one of the most studied features in the country.

But the four “all-female” mass graves — and the one holding the 53 women in particular — have become something of a fixed idea in American archaeology: Experts have described their remains as “unblemished”; some speculated that they were virgins; others, taking a more economic view, suggested that their deaths were meant as a display of wealth, since women were the core of Cahokia’s workforce. Still others thought it was a way of eliminating possible future rivals in a matrilineal society.

But new research casts doubt on this most-touted trait of Mound 72. A study published in the July issue of the American Journal of Physical Anthropology finds that men were also likely among the unfortunate dead, in all four of the mass graves.

“The idea of all-female sacrifice pits in Mound 72 has been reverberated in discussions of Cahokia and Mississippian culture in general for many years,” said the study’s author, Dr. Andrew Thompson, by email. “It is a very interesting and controversial idea.”

But even when the mound was first excavated in the 1960s and ’70s, there was little evidence that the victims were all women, he says.

Thompson, who conducted his research while a doctoral student in physical anthropology at Indiana University, points out that original analyses of Mound 72 found most of the skeletons were too badly decomposed to identify their sex.

Of the approximately 270 total remains found in the mound, he reports, only 117 could be sexed at the time.

And in those four graves in particular, there were 118 remains, of which only 56, or 47 percent, were confidently thought to be female.

Nonetheless, for decades those features in Mound 72 — especially the pit with the 53 bodies stacked chock-a-block — have been, and continue to be, described as “all-female” graves.

So in an effort to get a more accurate view of whom the graves held, Thompson turned to the hardest and most durable structures in the human body: teeth.

“Basically I took measurements of all the teeth that were recovered from Mound 72 and used those measurements to reassess sex in the four burial pits that were reported as being all female,” he said.

“In case you’re wondering,” he added, “teeth are indeed reliable indicators of sex—there is a measurable difference in the size of male vs. female teeth. There is, of course, quite a bit of overlap in tooth size between sexes, and this varies between populations.”

To account for these variations, Thompson created a baseline for average tooth size in Cahokia, by measuring teeth from other nearby graves. Specifically, he used samples from two local sites that held remains of people who lived at about the same time and place as the Mound 72 victims but were much better preserved and therefore easier to sex.

Using these averages for male and female tooth size as a yardstick for the general population, Thompson then compared them against teeth recovered from the four putative female-only graves in Mound 72 — representing a total of 88 victims.

Based on his measurements, Thompson estimates that 15 out of the 88 skeletons — or 17% — are male.

And in the grave with the 53 neatly-stacked bodies — the feature most often described as the “female burial pit” — he found at least 8 male victims.

Since sex has been so central to the graves’ interpretations, Thompson took an extra step: He went back to the skeletal remains of those 8 possible men, to look for clues in the bones themselves as to whether they were male or female.

“I didn’t find much supporting evidence in this regard,” Thompson says.

“Most of the skeletal material is highly fragmented, which limits the observable features, and what material was observable was mostly inconclusive, at best.”

In the end, Thompson estimates that each of the four mass graves in the mound had at least 2 skeletons that could be classified as male by his measurements.

He concludes that it’s “questionable” that the dead found in any of Mound 72’s mass graves were all female.

Still, he acknowledges that, even by his estimates, 80% of the dead still appear to be women — so their sex is still likely a key to deciphering what happened at Mound 72 a thousand years ago.

But since so many theories have been based on the idea that the victims were entirely women, Thompson suggests that some theories about what its macabre scene means may need to be reconsidered.

“I think the main significance of my study is that it questions one of the central discussions surrounding the events that led up to the construction of Mound 72,” he says.

“Females played a critical role in society during this time period. The idea of removing such a large segment of young women from a population is interesting both from demographic and socioeconomic perspectives.

“Many view the interment of such a large and specific segment of society as a statement of power and influence, two themes that are often discussed in Mississippian politics.

“If my study is accurate and not all of the individuals were biologically female, it would require some reinterpretation of the events involved with the construction of Mound 72.”

Sources:

• “Odontometric Determination of Sex at Mound 72, Cahokia,” American Journal of Physical Anthropology, Vol. 151, Issue 3

• Cahokia: Ancient America’s Great City on the Mississippi by Timothy Pauketat (2010) *Western Digs Book Club Selection*

Updated 8/12 to reflect that the research studied four “all-female” graves among the approximately 24 grave features in the Mound, and that there were 118 bodies in those graves and 270 in the mound total.