Research Group 2: Evolutionary Genetics

Adult females are significantly more affiliative with paternal half-sisters than with nonkin!

Paternal relatedness and age proximity regulate social relationships among adult female rhesus macaques

Anja Widdig*¹, Peter Nürnberg*², Michael Krawczak^*3, Wolf Jürgen Streich^*4 & Fred Bercovitch ^*5:

Proc Natl Acad Sci USA 98, 13769-13773 (2001).

*¹Institut für Medizinische Genetik, Universitätsklinkum Charité, Humboldt-Universität, 10098 Berlin, Germany
*¹Institut für Biologie, Humboldt-Universität, Invalidenstr. 43, 10115 Berlin, Germany
^*2Gene Mapping Center, Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
^*3Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK
^*4Institut für Zoo-und Wildtierforschung, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany
^*5Caribbean Primate Research Center, P. O. Box 1053, Sabana Seca PR 00952, USA

Kin selection promotes the evolution of social behavior that increases the survival and reproductive success of close relatives. Among primates, maternal kinship frequently coincides with a higher frequency of grooming and agonistic aiding, but the extent to which paternal kinship influences adult female social relationships has not yet been investigated.

Here we examine the effect of both maternal and paternal kinship, as well as age proximity, on affiliative interactions among semi-free-ranging adult female rhesus macaques, Macaca mulatta. Kinship was assessed using both microsatellites and DNA-fingerprinting.

Our study confirms that the closest affiliative relationships characterize maternal half-sisters. We provide the first evidence that adult females are significantly more affiliative with paternal half-sisters than with nonkin. Furthermore, paternal kin discrimination was more pronounced among peers than among nonpeers, indicating that age proximity has an additional regulatory effect on affiliative interactions. We propose that kin discrimination among cercopithecine primates emerges from ontogenetic processes that involve phenotype matching based on shared behavioral traits, such as inherited personality profiles, rather than physiological or physical characteristics.