School of Social Work, Lakehead University, Orillia, ON, Canada L3V 0B9;
Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1.
Proc Natl Acad Sci U S A. 2017 Aug 29;114(35):9290-9295. doi: 10.1073/pnas.1705910114. Epub 2017 Aug 15.
Maternal grandmothers invest more in childcare than paternal grandmothers. This bias is large where the expression of preferences is unconstrained by residential and lineage norms, and is detectable even where marriage removes women from their natal families. We maintain that the standard evolutionary explanation, paternity uncertainty, is incomplete, and present an expanded model incorporating effects of alloparents on the mother as well as on her children. Alloparenting lightens a mother's load and increases her residual nepotistic value: her expected fitness from later investments in personal reproduction and in her natal relatives. The mother's mother derives fitness from all such investments, whereas her mother-in-law gains only from further investment in children sired by her son, and thus has less incentive to assist the mother even if paternity is certain. This logic extends to kin other than grandmothers. We generate several hypotheses for future research.
祖母比祖父在照顾孙辈上投入更多。在偏好不受居住和血统规范限制的情况下，这种偏见很大，即使婚姻使女性离开娘家，这种偏见也能被察觉到。我们认为，标准的进化解释——父权不确定性——是不完整的，并提出了一个扩展的模型，该模型将所有对母亲及其子女的代际影响纳入其中。代际抚养减轻了母亲的负担，增加了她的剩余亲缘价值：她从以后的个人生殖投资和对娘家亲属的投资中获得的预期适应性。母亲的母亲从所有这些投资中获得适应性，而她的岳母则只能从她儿子所生的孩子的进一步投资中获益，因此即使父权确定，她也没有更多的动力来帮助母亲。这种逻辑也适用于除祖母以外的其他亲属。我们为未来的研究提出了几个假设。
