Lineage, Sex, and Wealth as Moderators of Kin Investment
- 160 Downloads
Supporting Hamilton’s inclusive fitness theory, archival analyses of inheritance patterns in wills have revealed that people invest more of their estates in kin of closer genetic relatedness. Recent classroom experiments have shown that this genetic relatedness effect is stronger for relatives of direct lineage (children, grandchildren) than for relatives of collateral lineage (siblings, nieces, nephews). In the present research, multilevel modeling of more than 1,000 British Columbian wills revealed a positive effect of genetic relatedness on proportions of estates allocated to relatives. This effect was qualified by an interaction with lineage, such that it was stronger for direct than for collateral relatives. Exploratory analyses of the moderating role of benefactors’ sex and estate values showed the genetic relatedness effect was stronger among female and wealthier benefactors. The importance of these moderators to understanding kin investment in modern humans is discussed.
KeywordsGenetic relatedness Inclusive fitness Inheritance Kin investment Lineage Prosocial behavior Resource allocation Wills
We thank the staff of the Vancouver Probate Office for their assistance in helping us access the probated wills, and the Canada Manpower Summer Student Works Project, who paid the salaries of the students who worked on this project.
This material is based on work supported by the National Institute of Mental Health under Training Grant Award PHS 2 T32 MH014257 entitled “Quantitative Methods for Behavioral Research” (to M. Regenwetter, Principal Investigator). This research was completed while the first author was a postdoctoral trainee in the Quantitative Methods Program of the Department of Psychology, University of Illinois at Urbana–Champaign. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Institute of Mental Health.
This research was previously presented by the first author at the 17th annual meeting of the Human Behavior and Evolution Society in Austin, Texas, in June 2005.
- Bowlby, J. (1969). Attachment and loss. New York: Basic Books.Google Scholar
- Chagnon, N. A. (1988). Male Yanomamö manipulations of kinship classifications of female kin for reproductive advantage. In L. Betzig, M. Borgerhoff Mulder, & P. Turke (Eds.) Human reproductive behavior: A Darwinian perspective (pp. 23–48). New York: Cambridge University Press.Google Scholar
- Cohen, J., Cohen, P., West, S. G., & Aiken, L. S. (2003). Applied multiple regression/correlation analysis for the behavioral sciences (3rd ed.). Mahwah, NJ: Erlbaum.Google Scholar
- Cooper, J. P. (1976). Patterns of inheritance and settlement by great landowners from the fifteenth to the eighteenth centuries. In J. Goody, J. Thirsk, & E. P. Thompson (Eds.) Family and inheritance: Rural society in Western Europe, 1200–1800 (pp. 192–327). New York: Cambridge University Press.Google Scholar
- Daly, M., Salmon, C., & Wilson, M. (1997). Kinship: The conceptual hole in psychological studies of social cognition and close relationships. In J. A. Simpson, & D. T. Kenrick (Eds.) Evolutionary social psychology (pp. 265–296). Mahwah, NJ: Erlbaum.Google Scholar
- DeKay, W. T. (1995). Grandparental investment and the uncertainty of kinship. Paper presented at the seventh annual meeting of the Human Behavior and Evolution Society, Santa Barbara, CA.Google Scholar
- Euler, H. A., & Weitzel, B. (1996). Discriminative grandparental solicitude as reproductive strategy. Human Nature, 7, 39–59.Google Scholar
- Goody, J. (1983). The development of family and marriage in Europe. New York: Cambridge University Press.Google Scholar
- Judd, C. M., & McClelland, G. H. (1989). Data analysis: A model comparison approach. San Diego: Harcourt Brace Jovanovich.Google Scholar
- Le Roy Ladurie, E. (1976). Family structures and inheritance customs in sixteenth-century France. In J. Goody, J. Thirsk, & E. P. Thompson (Eds.) Family and inheritance: Rural society in Western Europe, 1200–1800 (pp. 37–70). New York: Cambridge University Press.Google Scholar
- Raudenbush, S. W., & Bryk, A. S. (2002). Hierarchical linear models (2nd ed.). Thousand Oaks, CA: Sage Publications.Google Scholar
- Raudenbush, S. W., Bryk, A. S., Cheong, Y. F., & Congdon Jr., R. T. (2004). HLM6: Hierarchical linear and nonlinear modeling. Lincolnwood, IL: Scientific Software International.Google Scholar
- Tooby, J., & Cosmides, L. (1992). Psychological foundations of culture. In J. Barkow, L. Cosmides, & J. Tooby (Eds.) The adapted mind: Evolutionary psychology and the generation of culture (pp. 19–136). New York: Oxford University Press.Google Scholar
- Trivers, R. L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.) Sexual selection and the descent of man: 1871–1971 (pp. 136–179). Chicago: Aldine.Google Scholar
- Trivers, R. L. (1974). Parent–offspring conflict. American Zoologist, 14, 249–264.Google Scholar
- Webster, G. D. (2004). Human kin investment as a function of genetic relatedness and lineage. Evolutionary Psychology, 2, 129–141.Google Scholar
- Webster, G. D. (2006). Kin-based resource allocation: Inclusive fitness and emotional closeness. Unpublished Ph.D. dissertation, University of Colorado at Boulder.Google Scholar