Kinship ties across the lifespan in human communities.
Jeremy Koster, Dieter Lukas, David Nolin, Eleanor Power, Alexandra Alvergne, Ruth Mace, Cody T Ross, Karen Kramer, Russell Greaves, Mark Caudell, Shane MacFarlan, Eric Schniter, Robert Quinlan, Siobhan Mattison, Adam Reynolds, Chun Yi-Sum, Eric Massengill
Author Information
Jeremy Koster: 1 Department of Anthropology, University of Cincinnati , Cincinnati, OH 45221-0380 , USA.
Dieter Lukas: 2 Department of Human Behavior, Ecology, and Culture, Max Planck Institute of Evolutionary Anthropology , Deutscher Platz 6, 04103 Leipzig , Germany.
David Nolin: 3 Department of Anthropology and Population Research Institute, Penn State University , University Park, PA 16802 , USA.
Eleanor Power: 4 Department of Methodology, The London School of Economics and Political Science , Houghton Street, London WC2A 2AE , UK.
Alexandra Alvergne: 5 School of Anthropology and Museum Ethnography, University of Oxford , 51 Banbury Road, Oxford OX2 6PE , UK.
Ruth Mace: 6 Department of Anthropology, University College London , 14 Taviton St, London WC1H 0BW , UK.
Cody T Ross: 2 Department of Human Behavior, Ecology, and Culture, Max Planck Institute of Evolutionary Anthropology , Deutscher Platz 6, 04103 Leipzig , Germany.
Karen Kramer: 8 Department of Anthropology, University of Utah , Salt Lake City, UT 84112 , USA.
Russell Greaves: 8 Department of Anthropology, University of Utah , Salt Lake City, UT 84112 , USA.
Mark Caudell: 9 Paul G. Allen School for Global Animal Health, Washington State University , Pullman, WA 99164 , USA.
Shane MacFarlan: 8 Department of Anthropology, University of Utah , Salt Lake City, UT 84112 , USA.
Eric Schniter: 10 Economic Sciences Institute, Chapman University , Orange, CA 92866 , USA.
Robert Quinlan: 11 Department of Anthropology, Washington State University , Pullman, WA 99164 , USA.
Siobhan Mattison: 12 Department of Anthropology, University of New Mexico , Albuquerque, NM 87131 , USA.
Adam Reynolds: 12 Department of Anthropology, University of New Mexico , Albuquerque, NM 87131 , USA.
Chun Yi-Sum: 12 Department of Anthropology, University of New Mexico , Albuquerque, NM 87131 , USA.
Eric Massengill: 12 Department of Anthropology, University of New Mexico , Albuquerque, NM 87131 , USA.
A hypothesis for the evolution of long post-reproductive lifespans in the human lineage involves asymmetries in relatedness between young immigrant females and the older females in their new groups. In these circumstances, inter-generational reproductive conflicts between younger and older females are predicted to resolve in favour of the younger females, who realize fewer inclusive fitness benefits from ceding reproduction to others. This conceptual model anticipates that immigrants to a community initially have few kin ties to others in the group, gradually showing greater relatedness to group members as they have descendants who remain with them in the group. We examine this prediction in a cross-cultural sample of communities, which vary in their sex-biased dispersal patterns and other aspects of social organization. Drawing on genealogical and demographic data, the analysis provides general but not comprehensive support for the prediction that average relatedness of immigrants to other group members increases as they age. In rare cases, natal members of the community also exhibit age-related increases in relatedness. We also find large variation in the proportion of female group members who are immigrants, beyond simple traditional considerations of patrilocality or matrilocality, which raises questions about the circumstances under which this hypothesis of female competition are met. We consider possible explanations for these heterogenous results, and we address methodological considerations that merit increased attention for research on kinship and reproductive conflict in human societies. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'.
