Journal article

Publication year: 2011

Pages: 315-325

Journal: Evolution and Human Behavior

Volume number: 32

Issue number: 5

ISSN: 1090-5138

DOI Link: https://doi.org/10.1016/j.evolhumbehav.2010.11.004

Publisher: Elsevier

Abstract: 
Because only daughters inherit the paternal X-chromosome, an asymmetry in adaptive investment decisions has been suggested for certain patrilineal kin. Namely, paternal grandmothers (PGMs) may favor a granddaughter over a grandson, because (within the limits of paternity uncertainty) the former definitely carries one of their X-chromosomes, while the latter definitely does not. Here, we test the hypothesis that the PGMs' sex-specific favoritism influences reproductive scheduling. Using family-reconstitution data, we analyzed interbirth intervals (IBIs) in the historical population from the Krummhorn (Ostfriesland, Germany). In order to account for potentially timevarying effects on IBIs we applied (and combined) both the additive hazards regression of Aalen and the Cox proportional hazards model. We found that the presence of the PGM but not that of the maternal grandmother (MGM), correlates with the IBI following the birth of a grandchild as a function of the grandchild's sex. Specifically, in the presence of a PGM, the IBIs following the birth of a granddaughter are longer than in her absence. However, contrary to predictions from theoretical life history framework, model estimates for a PGM's effect on a mother's IBI did not significantly vary over time This study supports the hypothesis that PGM behavior differs according to her grandchild's sex. Further research should now explore the biological mechanism underlying this phenomenon. (C) 2011 Elsevier Inc. All rights reserved.

Harvard Citation style: Johow, J., Fox, M., Knapp, L. and Voland, E. (2011) The presence of a paternal grandmother lengthens interbirth interval following the birth of a granddaughter in Krummhorn (18th and 19th centuries), Evolution and Human Behavior, 32(5), pp. 315-325. https://doi.org/10.1016/j.evolhumbehav.2010.11.004

APA Citation style: Johow, J., Fox, M., Knapp, L., & Voland, E. (2011). The presence of a paternal grandmother lengthens interbirth interval following the birth of a granddaughter in Krummhorn (18th and 19th centuries). Evolution and Human Behavior. 32(5), 315-325. https://doi.org/10.1016/j.evolhumbehav.2010.11.004