The project SKIN: Social Kinships and Cooperative Care investigates to what extent relatedness in later prehistoric societies was based on more than biological ties, and instead, included social concepts complementing and extending the nuclear family. Kinship is currently a burning issue of research across the humanities, social and life sciences, with implications for both the past and the present. In archaeology, it is critical to understanding major themes of past societies such as social organization, which includes the concept of family and the role of heredity as a determining factor for social inequalities. Anthropologists generally agree that kinship was central to social, economic and political structures in prehistoric societies, but often assume it is merely biologically constructed. However, ethnography has demonstrated that the human species is precisely the only one with an extensive cooperation among biologically unrelated individuals. One of the greatest advantages of broader social kinship is cooperative breeding and child rearing, which means that other members of the community provide essential support during the lengthy child development. This allows mothers to return to productive activities sooner and/or have new offspring. Non-maternal caregivers (allomothers) are extensively documented in contemporary small communities of similar size to prehistoric ones. Social concepts of kinship may extend to adoption, fostering and apprenticeships, which may give rise to close emotional bonds as well as cause people to share living spaces and work.
The SKIN project explores kinship and social relationships in prehistoric Iberia by analyzing multiple and double burials from the Copper and Bronze Ages (c. 3000-1000 BC). These types of graves provide crucial insights into past social structures, as individuals buried together likely shared a meaningful connection in life. Focusing on the exceptional burial site of Humanejos (Parla, Madrid, Spain)—which contains around 170 individuals, including a remarkably high number of non-adults—SKIN will examine how prehistoric communities defined kinship and caregiving beyond mere genetic ties. By integrating archaeological, bioarchaeological, and ethnographic approaches, the project will employ aDNA, Sr-isotope, and peptides analyses to investigate whether co-buried individuals were related by blood or if social constructs played a key role in their relationships. Special attention will be given to allomothering and cooperative care, two widespread but understudied practices in prehistory.
This research is particularly relevant to understanding the profound cultural and demographic transformations of the third and second millennia BC. While the Copper Age saw the rise of social hierarchy and inherited wealth—especially during the Bell Beaker period—the transition to the Bronze Age brought about an apparent return to egalitarianism, as seen in simpler graves with fewer signs of status differentiation.
The project is structured around four scientific research objectives:
1) analysing social kinship and allomothering patterns in a sample of ethnographic societies with
similar characteristics to prehistoric ones and developing a conceptual framework to interpret social relatedness in later prehistoric funerary contexts
2) determining the nature of the relationship between children and women buried together in the
study area through a) osteological analysis (morphological traits of biological relatedness and lifecourse events), b) aDNA (biological kinship) c) Strontium analysis (mobility and residence patterns) and d) peptide analysis (biological sex)
3) investigating i) if relatedness was more socially than biologically constructed in Copper and
Bronze Age societies of Iberia, ii) if those non-biological relationships between women and children can be explained as cooperative care or allomothering from different members of the group and iii) if these characteristics detected for the Iberian societies were similar to those of Central Europe
4) exploring the crucial role of social cooperation, beyond the purely biological links, for the survival of our species in past and present societies
