Spa Mark, Young Euan A, Lummaa Virpi, Postma Erik, Dugdale Hannah L
Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
Department of Biology, University of Turku, Turku, Finland.
Proc Biol Sci. 2025 Sep;292(2054):20251525. doi: 10.1098/rspb.2025.1525. Epub 2025 Sep 3.
Siblings are an important part of an individual's early-life environment and may therefore play an important role in shaping an individual's survival. The quantification of sibling effects on survival is challenging, however, especially in long-lived species with extended parental care and overlapping generations, such as humans. Here, we use historical parish data from Switzerland to quantify how the number of older siblings and their survival status, age and sex are associated with childhood survival. Across 2941 focal individuals born between 1750 and 1870, the total number of older siblings did not predict an individual's childhood survival probability. However, distinguishing between siblings by their survival status, age and sex revealed several associations, which in some cases also interacted with the sex of the focal individual: while older brothers close in age reduced the survival of girls (but not boys), having more older sisters close in age improved their younger sibling's survival. Our results therefore suggest that older siblings play an important role in shaping early-life survival and highlight that the strength and direction of sibling-related associations are context-dependent and can arise through both biological and cultural factors.
兄弟姐妹是个人早期生活环境的重要组成部分，因此可能在塑造个体生存方面发挥重要作用。然而，量化兄弟姐妹对生存的影响具有挑战性，尤其是在人类等具有长期亲代照料和世代重叠的长寿物种中。在这里，我们使用来自瑞士的历史教区数据来量化哥哥姐姐的数量及其生存状况、年龄和性别与儿童期生存之间的关联。在1750年至1870年间出生的2941名重点个体中，哥哥姐姐的总数并不能预测个体儿童期的生存概率。然而，按生存状况、年龄和性别区分兄弟姐妹后发现了几种关联，在某些情况下，这些关联还与重点个体的性别相互作用：年龄相近的哥哥会降低女孩（而非男孩）的生存概率，而年龄相近的姐姐数量越多则会提高其弟弟妹妹的生存概率。因此，我们的研究结果表明哥哥姐姐在塑造早期生存方面发挥着重要作用，并强调兄弟姐妹相关关联的强度和方向取决于具体情况，且可能通过生物和文化因素产生。
