They were interred in what’s been described as “the richest burial known in the Southwest” — 14 men and women buried over the course of 330 years in the same crypt, some accompanied by pieces of pottery and pendants, others lavished with thousands of turquoise and shell beads.
Archaeologists believe these 14 people, buried between the years 800 and 1130, were among the elite leadership of the Ancestral Puebloan society whose influence radiated for hundreds of miles from Chaco Canyon.
And new analysis of DNA from the 14 sets of remains shows that these elites weren’t merely members of the same influential class — indeed, they were all members of the same extended family, a “dynasty” that traced its ancestry to a single woman.
“This is an incredibly significant study that I think will precipitate a lot of other studies in societies around the world,” said Dr. Douglas Kennett of Penn State University, in an interview.
“Now the technology is there where you can start asking questions about specific relationships between individuals.”
With his colleagues, Kennett sought to learn how the people laid to rest in the burial chamber in Pueblo Bonito — known as Room 33 — were connected to each other.
The answer could shed important light on how the leaders of this Ancestral Puebloan community attained their status, explained Dr. Stephen Plog, anthropologist at the University of Virginia.
“To have 14 people buried in one room is unusual in the Southwest, and that room is so unusual in so many ways,” said Plog, a co-author of the new study.
“There’s all the turquoise, all the shell [beads]. There’s abalone shell from the Pacific Ocean. There’s a conch-shell trumpet. There’s a wooden plank floor separating the two rich burials at the bottom from the burials above them.”
“So it seemed like a reasonable question to ask whether these people were related to each other.”
To get at the answer, Kennett, Plog, and their colleagues obtained samples of the protein collagen from each of the skulls that were found in the burial chamber.
(See another recent skull study: “Severed Heads, Skull Bowls Found in California Graves Were Tributes, Not War Trophies, Study Finds“)
Nine of the samples turned out to be well-preserved enough to be analyzed.
In studying the proteins, the team focused first on what’s known as mitochondrial DNA.
This is not the DNA that serves as your body’s molecular blueprint; instead, this so-called mtDNA is a smaller, simpler bit of genetic code that appears on mitochondria, tiny organelles in your cells that are responsible for turning food into energy.
This mitochondrial DNA is especially useful to anthropologists, because it’s only inherited from the mother, so it can reveal a person’s ancestry for generations, by way of the maternal genetic code.
And when the team compared the mitochondrial DNA of the nine people from the burial chamber, they were stunned by what they found.
“When the results came back, it was remarkable,” Kennett said.
“It was so remarkable that at first we said, this can’t be true.”
After conducting a series of tests to verify that the samples hadn’t been contaminated, they realized that their findings were indeed correct.
“All of the individuals with well-preserved mitochondrial DNA have the same exact, identical mitochondrial DNA, indicating that they’re related through the female line,” Kennett said.
While it’s possible for two individuals to have mtDNA that’s similar, he noted, all of the mitochondrial DNA they studied was “basically identical,” he said.
“So there’s a woman in the past that had this genome that basically is shared all the way through the population of this elite lineage.”
To further explore the relationships among the dead in Room 33, Kennett and his team also collected samples of the remains’ nuclear DNA — that’s the DNA that holds all of your specific, individual genetic information.
And here, too, the results were surprising, Kennett said.
“Not everyone in that crypt is directly related to one another in terms of a nuclear family,” he said. “But we do demonstrate that, in two cases, we can see the specific familial relationships.”
By determining how much of their genomes these elites had in common, researchers were able to extrapolate who were first-degree relatives — that is, members of the same nuclear family — and who were second-degree relatives — like grandparents and grandchildren.
This molecular evidence was then cross-checked with radiocarbon dates, which confirmed when each of the people lived.
For example, a 45-year-old female turned out to be the mother of another female buried later, when she was about 23.
Likewise, a 40-year-old female was the grandmother of a 35-year-old male, whose genome showed two generations of distance between them.
(Learn about another grave with family ties: “Mass Grave of ‘Prodigal Sons’ in California Poses Prehistoric Mystery“)
“We used multiple lines of evidence to draw the conclusions that we did,” Kennett said.
Combined, these findings provide a new, possibly clearer view of class, status, wealth, and power in this hub of Ancestral Puebloan culture.
“We’re not entirely sure what the structure of Chacoan society was,” Kennett said.
“But basically what we’re looking at is hereditary inequality.”
“There were individuals in this society that had greater access to wealth and had greater influence, and they gained that because of who they’re related to,” he said.
Plog agreed, adding that the new findings take on even greater significance in light of another new study, which used chemical analysis to determine that the people buried in Room 33 were almost entirely born and raised in Chaco Canyon, and weren’t immigrants from other regions, as some experts surmised.
(Learn all about it: “Chaco’s Elites Were Natives of Chaco Canyon, Not Migrants, Their Remains Show“)
“In many ways, the DNA study reinforces the [earlier] study, in that you had early on in the history of Chaco an elite family that developed and that was extremely important,” he said.
“It controlled most of the access to the turquoise, to the shells, to a lot of the key items that may have been important to ritual, and it may have controlled access to the prime agricultural land as well.
“There’s a good chance that that lineage played a key role in getting Chaco going.”
(See new insights into another lavish ancient grave: “New Discoveries From Cahokia’s ‘Beaded Burial’ May Rewrite Story of Ancient American City“)
All told, the findings may provide a glimpse into the first family of one of the continent’s most influential early cultures, Kennett added.
“This is one of the earliest complex societies to develop in North America, and now we know that there was a hereditary basis to the emergence of this remarkable complex society,” he said.
“One of the things that I think is important is that this social and political form persisted for 330 years. So it was remarkably stable.
“And I think that understanding its overall structure and that it had a matrilineal foundation is important for thinking about the rise of this complex society, its persistence, and possibly its decline.
“It’s an open question as to why Chaco went into decline and then people dispersed from this location,” Kennett noted.
“But this family was at the center of it.”
Kennett, Plog, and their colleagues report their findings in the journal Nature Communications.
Kennett, D., Plog, S., George, R., Culleton, B., Watson, A., Skoglund, P., Rohland, N., Mallick, S., Stewardson, K., Kistler, L., LeBlanc, S., Whiteley, P., Reich, D., & Perry, G. (2017). Archaeogenomic evidence reveals prehistoric matrilineal dynasty Nature Communications, 8 DOI: 10.1038/ncomms14115