Deep inside the 650-room Chaco Canyon compound in New Mexico lies the richest burial in the U.S. Southwest: the body of a 40-year-old man, surrounded by rare shells; a conch trumpet; and more than 11,000 turquoise beads and pendants. Lacking written records of his people, researchers have long puzzled over how the complex 1000-year-old Chacoan society was organized. Now, using ancient DNA from the bones of the man and 13 others buried alongside him, scientists have come to a surprising conclusion—elite status passed down the maternal line, from mothers to their sons and daughters.
Most societies in the ancient world were patrilineal—that is, leadership or status passed through the father’s line. But there are some exceptions, including matrilineal societies like the Lycians of ancient Turkey, in which elite status and kinship passed from mothers to sons and daughters. That isn’t to say that such societies were ruled by women, but it does show that women were given an important role in carrying on the family line. Scholars have long debated whether the Chacoans, who lived in multistory buildings that were long the largest in North America, had an egalitarian—or equal—society or a hierarchical society with an entrenched elite.
To find out whether the bodies themselves could shed some light on the debate, a team led by archaeologist Douglas Kennett of Pennsylvania State University in State College analyzed their remains, found in room 33 of the Pueblo Bonito complex and now stored at the American Museum of Natural History in New York City, using DNA sequencing. First, the team determined the order in which the bodies were buried using radiocarbon dating, Kennett says. The oldest were from the very beginning of the Chacoan era, about 800 C.E., and the youngest were dated to the end of Chacoan society, about 1130. Then, the team used genetic analysis to look at mitochondrial DNA, which can pass only along the maternal line. They found that nine of the individuals shared the same mitochondrial DNA, meaning they were related through the maternal line, the team writes today in Nature Communications. Where preservation was sufficient, nuclear DNA studies also showed a mother-daughter relationship between two individuals and a grandmother-grandson relationship between two others.
"The fact that all of these individuals are in the same crypt and have the same mitochondrial DNA indicates that there's a linkage through the maternal line,” Kennett says. “And the fact that it's an elaborate burial crypt indicates that it was an elite matriline.” That means that elite status—and possibly leadership—passed along from mothers to sons and daughters in Pueblo Bonito, he says.
"I can see that this paper might generate some controversy, in terms of using biological data to determine sociological structures," says Angelique Corthals, a forensic anthropologist at the City University of New York in New York City, who was not involved in the research. "But the authors built their case very convincingly, by using both archaeological data and genomics data."
"These results are transformational in that they demonstrate the power of ancient DNA research and suggest that some members of a particular matrilineage formed an elite hierarchy with far more prestige than most members of the society," says Robert Hard, an anthropologist at the University of Texas in San Antonio, who was not involved in the research.
But it’s also possible that the remains represent the experience of just one elite family, and not all of Chacoan society. "Additional aDNA samples from other contexts at Pueblo Bonito would allow us to better appreciate the patterns represented by these nine individuals. For example, we would like to know if other burial clusters are from different matrilines or the same matilineage or other patterns altogether," Hard says.