1 Environment and Sustainability Institute, University of Exeter Cornwall Campus , Penryn TR10 9FE , UK.
2 Department of Zoology, University of Cambridge , Downing Street, Cambridge CB2 3EJ , UK.
Philos Trans R Soc Lond B Biol Sci. 2019 Apr 15;374(1770):20180111. doi: 10.1098/rstb.2018.0111.
Numerous studies have shown that social adversity in early life can have long-lasting consequences for social behaviour in adulthood, consequences that may in turn be propagated to future generations. Given these intergenerational effects, it is puzzling why natural selection might favour such sensitivity to an individual's early social environment. To address this question, we model the evolution of social sensitivity in the development of helping behaviours, showing that natural selection indeed favours individuals whose tendency to help others is dependent on early-life social experience. In organisms with non-overlapping generations, we find that natural selection can favour positive social feedbacks, in which individuals who received more help in early life are also more likely to help others in adulthood, while individuals who received no early-life help develop low tendencies to help others later in life. This positive social sensitivity is favoured because of an intergenerational relatedness feedback: patches with many helpers tend to be more productive, leading to higher relatedness within the local group, which in turn favours higher levels of help in the next generation. In organisms with overlapping generations, this positive feedback is less likely to occur, and those who received more help may instead be less likely to help others (negative social feedback). We conclude that early-life social influences can lead to strong between-individual differences in helping behaviour, which can take different forms dependent on the life history in question. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.
大量研究表明，早期生活中的社会逆境会对成年后的社会行为产生持久的影响，而这些影响可能会传递给后代。鉴于这些代际效应，令人费解的是，自然选择为什么会青睐个体对早期社会环境的这种敏感性。为了解决这个问题，我们在帮助行为的发展中模拟了社会敏感性的进化，结果表明，自然选择确实有利于那些倾向于帮助他人的个体，而这种倾向取决于个体的早期社会经历。在具有非重叠世代的生物中，我们发现自然选择可以有利于积极的社会反馈，即早期生活中得到更多帮助的个体在成年后也更有可能帮助他人，而没有得到早期生活帮助的个体在以后的生活中帮助他人的倾向较低。这种积极的社会敏感性之所以受到青睐，是因为存在代际相关反馈：有许多帮手的群体往往更具生产力，导致当地群体内部的亲缘关系更高，这反过来又有利于下一代更高水平的帮助。在具有重叠世代的生物中，这种积极的反馈不太可能发生，而且那些得到更多帮助的个体可能反而不太可能帮助他人（负面的社会反馈）。我们的结论是，早期的社会影响会导致帮助行为在个体之间产生强烈的差异，而这种差异的形式取决于所讨论的生活史。本文是“发展差异：早期影响和进化医学”主题特刊的一部分。
