Humans are unusual among animals for continuing to provision and care for their offspring until adulthood. This “prolonged dependency” is considered key for the evolution of other notable human traits, such as large brains, complex societies, and extended postreproductive lifespans. Prolonged dependency must therefore have evolved under conditions in which reproductive success is gained with parental investment and diminished with early parental loss. We tested this idea using data from wild chimpanzees, which have similarly extended immature years as humans and prolonged mother-offspring associations. Males who lost their mothers after weaning but before maturity began reproducing later and had lower average reproductive success. Thus, persistent mother-immature son associations seem vital for enhancing male reproductive success, although mothers barely provision sons after weaning. We posit that these associations lead to social gains, crucial for successful reproduction in complex social societies, and offer insights into the evolution of prolonged dependency.

人类在动物中是不寻常的，因为它会继续提供和照顾他们的后代直到成年。这种“长期依赖”被认为是其他显着人类特征进化的关键，例如大脑大、社会复杂和生殖后寿命延长。因此，长期依赖一定是在通过父母投资获得生殖成功并随着早期失去父母而减少的条件下进化的。我们使用来自野生黑猩猩的数据测试了这个想法，它们与人类一样延长了未成熟的年龄，并延长了母子关系。在断奶后但在成熟之前失去母亲的雄性开始繁殖较晚，平均繁殖成功率较低。因此，持续的母子关系似乎对提高男性生殖成功至关重要，尽管母亲在断奶后几乎没有为儿子提供食物。我们假设这些关联会带来社会收益，这对于复杂社会社会中的成功繁殖至关重要，并为长期依赖的演变提供了见解。