Limited evidence for third party affiliation during development in wild chimpanzees (Pan troglodytes schweinfurthii)

Examining the ontogeny of conflict-mitigating behaviors in our closest living relatives is an important component of understanding the evolutionary origins of cooperation in our species. In this study, we used 26 years of data to investigate the emergence of third party affiliation (TPA), defined as affiliative contact given to recipients of aggression by uninvolved bystanders (regardless of initiation), in wild immature eastern chimpanzees (Pan troglodytes schweinfurthii) of Gombe National Park, Tanzania. We also characterized TPA by mothers in the same dataset as an adult benchmark for interpreting immature TPA patterns. In summary, we found that immatures did not express TPA as measured by grooming between the ages of 1.5 - 12.0 years and that there was limited evidence that immatures expressed TPA via play. We also found that mothers did express TPA to offspring, although mothers did not show TPA towards non-offspring. Cases of TPA by mothers to other adults were too few to analyze ...探究与人类亲缘关系最近的现存灵长类的冲突缓解行为个体发育过程，是理解人类合作行为演化起源的重要组成部分。本研究依托长达26年的观测数据，对坦桑尼亚贡贝国家公园野生幼年东部黑猩猩（Pan troglodytes schweinfurthii）的第三方亲和行为（third party affiliation, TPA）的出现模式展开了调查。第三方亲和行为被定义为：未卷入冲突的旁观者对攻击受害者作出的亲和接触（无论攻击由谁发起）。本研究同时基于同一数据集，对母猿的第三方亲和行为进行特征刻画，以此作为解读幼年个体第三方亲和行为模式的成年参照基准。综上，本研究发现：1.5至12.0岁的幼年个体未表现出以理毛行为为衡量标准的第三方亲和行为，且仅有有限证据表明幼年个体可通过游戏行为展现该行为。此外，研究还发现母猿会对后代展现第三方亲和行为，但不会针对非后代个体作出此类行为；母猿对其他成年个体作出第三方亲和行为的案例数量过少，不足以开展分析……