Across vertebrates, species with intense male mating competition and high levels of sexual dimorphism in body size generally exhibit dimorphism in age-specific fertility. Compared with females, males show later ages at first reproduction and earlier reproductive senescence because they take longer to attain adult body size and musculature, and maintain peak condition for a limited time. This normally yields a shorter male duration of effective breeding, but this reduction might be attenuated in species that frequently use coalitionary aggression. Here, we present comparative genetic and demographic data on chimpanzees from three long-term study communities (Kanyawara: Kibale National Park, Uganda; Mitumba and Kasekela: Gombe National Park, Tanzania), comprising 581 male risk years and 112 infants, to characterize male age-specific fertility. For comparison, we update estimates from female chimpanzees in the same sites and append a sample of human foragers (the Tanzanian Hadza). Consistent with the idea that aggressive mating competition favors youth, chimpanzee males attained a higher maximum fertility than females, followed by a steeper decline with age. Males did not show a delay in reproduction compared with females, however, as adolescents in both sites successfully reproduced by targeting young, subfecund females, who were less attractive to adults. Gombe males showed earlier reproductive senescence and a shorter duration of effective breeding than Gombe females. By contrast, older males in Kanyawara generally continued to reproduce, apparently by forming coalitions with the alpha. Hadza foragers showed a distinct pattern of sexual dimorphism in age-specific fertility as, compared with women, men gained conceptions later but continued reproducing longer. In sum, both humans and chimpanzees showed sexual dimorphism in age-specific fertility that deviated from predictions drawn from primates with more extreme body size dimorphism, suggesting altered dynamics of male-male competition in the two lineages. In both species, coalitions appear important for extending male reproductive careers.

在脊椎动物中，雄性交配竞争激烈且体型性别二态性高的物种通常表现出特定年龄生育力的二态性。与雌性相比，雄性在第一次繁殖时表现出较晚的年龄和较早的繁殖衰老，因为它们需要更长的时间才能达到成年体型和肌肉组织，并在有限的时间内保持巅峰状态。这通常会缩短雄性有效繁殖的持续时间，但这种减少可能会在经常使用联合攻击的物种中减弱。在这里，我们展示了来自三个长期研究社区（Kanyawara：乌干达 Kibale 国家公园；Mitumba 和 Kasekela：坦桑尼亚 Gombe 国家公园）的黑猩猩的比较遗传和人口统计数据，包括 581 个男性风险年和 112 名婴儿，以表征男性特定年龄的生育能力。为了比较，我们更新了同一地点雌性黑猩猩的估计值，并附上了人类觅食者（坦桑尼亚哈扎人）的样本。与激进的交配竞争有利于年轻人的观点一致，黑猩猩雄性的最大生育能力高于雌性，随后随着年龄的增长而急剧下降。然而，与女性相比，男性并没有表现出繁殖延迟，因为两个地点的青少年都通过针对对成年人吸引力较小的年轻、生育能力低下的女性成功地进行了繁殖。Gombe雄性比Gombe雌性表现出更早的生殖衰老和更短的有效繁殖时间。相比之下，Kanyawara 的年长雄性通常会继续繁殖，显然是通过与 alpha 结成联盟。Hadza 觅食者在特定年龄的生育力中表现出明显的性别二态性模式，因为，与女性相比，男性受孕较晚，但持续生育时间较长。总而言之，人类和黑猩猩在特定年龄的生育能力上都表现出性别二态性，这与从具有更极端体型二态性的灵长类动物得出的预测不同，这表明这两个谱系中雄性-雄性竞争的动态发生了改变。在这两个物种中，联盟似乎对延长雄性生殖事业很重要。