Jesus College, University of Cambridge, Jesus Lane, Cambridge CB5 8BL, UK
Deparment of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Biol Lett. 2018 Oct 10;14(10):20180515. doi: 10.1098/rsbl.2018.0515.
Cooperation among kin is common across the natural world and can be explained in terms of inclusive fitness theory, which holds that individuals can derive indirect fitness benefits from aiding genetically related individuals. However, human kinship includes not only genetic kin but also kin by marriage: our affines (in-laws) and spouses. Can cooperation between these genetically unrelated kin be reconciled with inclusive fitness theory? Here, we argue that although affinal kin and spouses do not necessarily share genetic ancestry, they may have shared genetic interests in future reproduction and, as such, can derive indirect fitness benefits though cooperating. We use standard inclusive fitness theory to derive a coefficient of shared reproductive interest () that predicts altruistic investment both in genetic kin and in spouses and affines. Specifically, a behaviour that reduces the fitness of the actor by and increases the fitness of the recipient by will be favoured by natural selection when > We suggest that the coefficient of shared reproductive interest may provide a valuable tool for understanding not only the evolution of human kinship but also cooperation and conflict across the natural world more generally.
亲缘间的合作在自然界中十分常见，可以用适合度广义理论来解释，该理论认为个体可以从帮助遗传上相关的个体中获得间接适合度利益。然而，人类的亲属关系不仅包括遗传亲属，还包括姻亲：我们的姻亲（姻亲）和配偶。这些没有遗传关系的亲属之间的合作能否与适合度广义理论相协调？在这里，我们认为，虽然姻亲和配偶不一定有共同的遗传祖先，但他们可能在未来的繁殖中有共同的遗传利益，因此可以通过合作获得间接适合度利益。我们使用标准的适合度广义理论来推导出一个共享生殖利益系数（），该系数可以预测在遗传亲属和配偶及姻亲中利他投资。具体来说，当 > 时，一种使施动者适合度降低 ，使接受者适合度增加 的行为将受到自然选择的青睐。我们认为，共享生殖利益系数可能是理解人类亲属关系进化以及更广泛地理解自然界中合作与冲突的一个有价值的工具。
