Department of Anthropology, Tufts University, Medford, MA 02155;
Department of Anthropology, University of New Mexico, Albuquerque, NM 87131.
Proc Natl Acad Sci U S A. 2021 Mar 23;118(12). doi: 10.1073/pnas.2017144118.
Sex differences in physical aggression occur across human cultures and are thought to be influenced by active sex role reinforcement. However, sex differences in aggression also exist in our close evolutionary relatives, chimpanzees, who do not engage in active teaching, but do exhibit long juvenile periods and complex social systems that allow differential experience to shape behavior. Here we ask whether early life exposure to aggression is sexually dimorphic in wild chimpanzees and, if so, whether other aspects of early sociality contribute to this difference. Using 13 y of all-occurrence aggression data collected from the Kanyawara community of chimpanzees (2005 to 2017), we determined that young male chimpanzees were victims of aggression more often than females by between 4 and 5 (i.e., early in juvenility). Combining long-term aggression data with data from a targeted study of social development (2015 to 2017), we found that two potential risk factors for aggression-time spent near adult males and time spent away from mothers-did not differ between young males and females. Instead, the major risk factor for receiving aggression was the amount of aggression that young chimpanzees displayed, which was higher for males than females throughout the juvenile period. In multivariate models, sex did not mediate this relationship, suggesting that other chimpanzees did not target young males specifically, but instead responded to individual behavior that differed by sex. Thus, social experience differed by sex even in the absence of explicit gender socialization, but experiential differences were shaped by early-emerging sex differences in behavior.
人类文化中存在着跨性别身体攻击差异，人们认为这是受到积极性别角色强化的影响。然而，在我们的近亲黑猩猩中也存在攻击行为的性别差异，它们不进行积极的教学，但表现出较长的幼年期和复杂的社会系统，使不同的经验能够塑造行为。在这里，我们想知道在野生黑猩猩中，早期生活中的攻击行为是否存在性别差异，如果存在，那么早期社会的其他方面是否会导致这种差异。我们利用从 Kanyawara 社区的黑猩猩（2005 年至 2017 年）收集的 13 年全发生率攻击数据，确定了幼年雄性黑猩猩比雌性更容易受到攻击，差异在 4 到 5 次之间（即早期幼年期）。将长期攻击数据与针对社会发展的目标研究（2015 年至 2017 年）的数据相结合，我们发现两个潜在的攻击风险因素——与成年雄性在一起的时间和与母亲分开的时间——在幼年期雄性和雌性之间没有差异。相反，受到攻击的主要风险因素是年轻黑猩猩表现出的攻击量，整个幼年期雄性的攻击量都高于雌性。在多元模型中，性别并没有调节这种关系，这表明其他黑猩猩并没有特别针对年轻雄性，而是对不同性别的个体行为做出反应。因此，即使没有明确的性别社会化，社会经验也因性别而异，但经验差异是由早期出现的行为性别差异所塑造的。
