Differential Investment Behavior between Grandparents and Grandchildren: The Role of Paternity Uncertainty

Abstract

Kin selection theory predicts that grandparents will differentially invest in their grandchildren as a function of paternity certainty. This study explored the hypothesis of “discriminative grandparental solicitude” (Euler and Weitzel, 1996; Smith, 1988) in a sample of college students. Students with four living grandparents were asked to indicate the frequency of various behaviors received from or directed to each grandparent. A significant linear trend on a majority of the measures supported this hypothesis. Reported contact and closeness were highest with the maternal grandmother (most genetically certain) and lowest with the paternal grandfather (least genetically certain); maternal grandfathers and paternal grandmothers were intermediate. The “preferential investment hypothesis” (Laham, Gonsalkorale, and von Hippel, 2005) predicts that the investment behavior of the maternal grandfather and the paternal grandmother should differ only when there are cousins through the father's sisters. Contrary to the predictions of this hypothesis, grandchildren did not rate the maternal grandfather consistently higher on any of the indices when more certain investment outlets were available to the paternal grandmother.

European grandparents’ solicitude

“…By combining coefficients for grandparental gender and parental gender in our data, it is possible to infer levels of care for maternal grandmothers, maternal grandfathers, paternal grandmothers and paternal grandfathers while controlling for other factors. When this is done for grandparents with a partner (Bishop et al, 2009), we find the same expected ordering in our analyses as in recent contributions from evolutionary psychology (Danielsbacka et al, 2011). This pattern could thus in fact be predicted from three alternative strands: evolutionary theory, rational choice arguments and normative explanations.…”

“…One fundamental strand is evolutionary theory based on assumptions about kin selection mechanisms (Euler and Weitzel, 1996). The idea is that becoming a grandparent marks a change in reproductive strategy, subsequently helping one's child in his/her reproductive efforts (Bishop et al, 2009;Daly and Wilson, 1980;Danielsbacka et al, 2011;Symons, 1979). It follows, for instance, that maternal grandparents are expected to care more for the grandchild than paternal grandparents.…”

“…It focuses on empirical implications from two alternative theoretical strands -normative explanations and rational choice approaches (Friedman et al, 2008) -which in part predict similar influences of gender; nevertheless, they also postulate different consequences for grandparental caregiving from being without a life partner. Using this analytical framework, I assess which of these two alternative arguments appears the more credible, while also reviewing recent studies in evolutionary psychology (Bishop et al, 2009;Danielsbacka et al, 2011).…”

Matrilateral Bias in Human Grandmothering

“…Even before Smith, researchers with no evolutionary overview had reported that American children feel closer, on average, to their MGMs than to their PGMs (e.g., Kahana and Kahana, 1970;Hoffman, 1980;Hartshorne and Manaster, 1982), and after Smith, studies in several countries have replicated his frequency of contact results (e.g., Eisenberg, 1988;Uhlenberg and Hammill, 1998;Laham et al, 2005), and/or demonstrated other sorts of biased engagement and investment favoring the maternal side (e.g., Eisenberg, 1988;Tyszkowa, 1991;Boon and Brussoni, 1996;Euler and Weitzel, 1996;Salmon, 1999;Dubas, 2001;Chrastil et al, 2006;Pashos and McBurney, 2008;Bishop et al, 2009;Kirchengast and Putz, 2016).…”

Sex Differences in Violent versus Non-Violent Life-Threatening Altruism

“…Because mothers invest a great deal of time and resources during gestation, and have complete maternal certainty, they are much more likely than fathers to tend to the needs of their offspring, which includes protecting them from predators, sharing precious resources (e.g., food, water, and shelter), and general interest in the offspring during development (Babchuck, Hames, and Thompson, 1985;Taylor et al, 2000). Also, multitudes of studies have found that paternity uncertainty decreases the likelihood of altruism and investment in many types of family members, including parents, cousins, aunts and uncles, and grandparents (Bishop, Meyer, Schmidt, and Gray, 2009;Daly and Wilson, 1980;Gaulin, McBurney, and Brakeman-Wartell, 1997;Euler and Weitzel, 1996;Jeon and Buss, 2007); so it would not be surprising to find that females would be more likely than males to be violently altruistic to save their offspring. However, the current study examined the influence that violence may have on altruism toward siblings, cousins, and friends -siblings and friends are unaffected by the paternity uncertainty principle, and previous research on altruism toward cousins did not find any sex differences (Jeon and Buss, 2007).…”