Forensic science used to determine who's who in pre-Columbian Peru

The social unit (ayllu) of Native South Americans is thought to be based on kin relationships. The establishment of ayllu-based communities is also associated with funereal monuments (chullpas) which are thought to be important social sites not only because of their religious importance but because they housed the venerated ayllu's ancestors. Ancestor worship and a belief in a common ancestor, central to the ayllu, still exists in the traditions of the Q'ero community.

Researchers from University of Warsaw, in collaboration with Universidad Catolica de Santa Maria, used DNA analysis to reconstruct the family trees of individuals buried in six chullpas near the Coropuna volcano is southern Peru. Despite prior looting, the unique nature of this site, 4000m up the Cora Cora mountain, allowed an extraordinary preservation of human remains and of DNA within both teeth and bone.

mtDNA analysis showed that the groups were of Andean origin and indicated a 500 year continuity, up to modern Andeans, without any major impact by European colonisation.

The social structure of an aylla was established using Y (male) chromosome and autosomal microsatellites analysis, in conjunction with the mtDNA. Family connections were clearly strongest within each chullpa, since individuals buried in the same chullpa were more closely related than those buried in different chullpas, and all males buried together shared identical Y chromosome profiles. In two of the chullpas several generations of related males were found. This matches current thought that the ancient Andians would swap women between families -- so called 'sister exchange' while the men retained the ancestral land.

The combinations of DNA analysis used allowed for an unprecedented level of detail in social behaviour to be discerned. In one chullpa three different Y chromosome lineages were found. Comparison of mtDNA within this chullpa suggests that two of the males had the same mother but different fathers, and the third male was related to one of the females, probably a half brother.

Mateusz Baca explained, "Our results show that this community of llama and alpaca herders was (genetically) an extended patriarchal society. The use of chullpas as family graves is consistent with the idea of ayllu-based communities based around strong kinship relationships. However, the chullpa with mixed male heritage shows that this social structure could also be flexible and the strict rules governing marriage and family could be intentionally, or unintentionally, relaxed."