You probably have a member of your family that you're not related to by blood—a step-parent, an adopted cousin, your mom's best friend who you grew up calling your aunt. They're indisputably part of your family, but a DNA test wouldn't hint at your relationship. Archaeologists are finding that this holds true for families from thousands of years ago, too. By comparing ancient burial practices with genetic information gleaned from the remains, researchers show that it's not uncommon for people who aren't related by blood to be treated as members of the same family—which means that ancient DNA doesn't tell the whole story of how families and societies worked.
"Even in prehistory, kinship was more than just blood relations," says Sabina Cveček, an archaeologist and Marie Skłodowska-Curie Global Fellow at the Field Museum in Chicago. "Many communities around the world have a concept of family that goes beyond this biological setting. So no matter how hard we push with ancient DNA research, we'll never know the whole story if we don't take diversity and cultural anthropological perspectives into account." Cveček is one of the lead authors of a special issue of the Cambridge Archaeological Journal dedicated to how archaeologists, anthropologists, and geneticists determine the relationships between ancient people, and how genetic research plays a role in our understanding of these societies.
This special issue, which Cveček edited with Maanasa Raghavan (University of Chicago) and Penny Bickle (University of York), includes research about the relationship between family and genetic relatedness around the world, over the course of thousands of years. Cveček, Raghavan, and Bickle emphasized in their introductory piece that kinship cannot be reduced to genetic relatedness, and that recent archaeogenetic work—while powerful—has tended to privilege biological descent and linear pedigrees.
"The piece intervenes by showing that this is only one 'code' of relatedness. Instead, ancient kinship research is in need of new approaches by closely considering ethics of sampling human remains, interdisciplinary training, collaborative research design, and new interpretations that consider multiple ways of becoming kin," says Cveček.
The team reviewed decades' worth of previous archaeological and genetic studies from sites in Europe and western Asia. For instance, at a site Çatalhöyük in what's now Türkiye (sometimes called Turkey), burials were often found below the house floors of ancient houses from 8,000 years ago."Archaeologists initially assumed that people buried within the same house would be genetically related," says Cveček. "But now, it is possible to map those people through ancient DNA analysis on genetic pedigrees, and geneticists often found people buried within the same house who are not at all genetically related, indicating social proximity rather than exclusively blood relations made kin at the site."
DNA degrades over time, but traces of DNA can remain inside human bones, including small bones such as petrous bone in the inner ear. In the past few decades, scientists have been able to extract DNA from these ancient bones and sequence it. The resulting genetic sequences are generally patchy, so "geneticists need to do a lot of computational analysis and statistics with genetic signatures from those broken pieces of ancient DNA to actually reconstruct biological relatedness of the past," says Cveček.
These findings suggest that in these ancient communities, the concept of family wasn't only dictated by blood. Since the same is true of many families today, that may not seem like an earth-shattering discovery. But it could be a critical piece of information for researchers attempting to reconstruct how ancient cultures built and passed down their family ties. DNA doesn't always tell the whole story.
"One of the aims of this paper is to debunk the Western perceptions of family kinship, which often seems to be based on blood. We cannot have just one proxy for understanding family or kinship around the world," says Cveček.
This broader concept of family goes beyond archaeological and anthropological research—we run into it every day when we handle health insurance, housing, childcare, and education. "The old saying, that it takes a village to raise a child, is true," says Cveček. "We all invest time and labor to build a world that looks after people beyond our biological dependents." Caring for people who aren't blood-related to us is part of what makes us human.
