We thank the authors of the invited commentary ‘Becoming uniquely human? Comparing chimpanzee to human infancy’ for providing thought-provoking interpretations of our recently published study (Bründl et al., 2021). The authors point out that our study fills an important gap in describing early developmental milestones in wild chimpanzees, aiding comparison with human development. They then focus on species-comparisons of two superficially comparable social traits, laughing and comforting, that we show to emerge at a later average age in our chimpanzee population than seen in humans. The authors argue that the relatively early emergence of these social traits in humans indicates more ‘prosocial tendencies that foster cooperation’. They state that ‘already by about 2 years of age, human children outperform their great ape cousins, the chimpanzees, in terms of their social cognitive skills’. While we agree with the validity of the author's initial question, we urge caution in such interpretation that we feel goes beyond the current knowledge of early-life great ape social development and the scope of the descriptive dataset we have presented.

As we mention in our paper, social and communication milestones are not always easily comparable in humans and chimpanzees. We urge caution in advocating an explanation of species differences based on only two comparable social traits. Further, we make no claim that ‘comforting’ behaviour in chimpanzees is empathic. Whether this is prosocial behaviour in human infants would need to be proven—as it would in chimpanzees. Also, the authors discuss both laughing and smiling, which may differ functionally. While we included laughter, the chimpanzee ‘play face’ facial expression used when initiating play and playing, and which potentially has a similar emotional origin to a smile (Hooff & Preuschoft, 2013), was not included in our study. We expect play face emergence earlier in wild chimpanzees than laughing (as in humans; Bard et al., 2011).

Socioecology in both human and chimpanzee populations seems likely to impact the development and plasticity of behavioural and cognitive traits (Boesch, 2020, 2021; Nielsen & Haun, 2016). This, together with our study that demonstrates overlap in the age of trait emergence in chimpanzees and humans, strongly indicates that valid comparative assessments must carefully match subjects from each species to control for potentially influencing variables, such as comparative age, sex and social history, as is standard practice in human psychological studies (Chiang et al., 2015; Martin et al., 1993). Wild chimpanzees live in complex socioecological environments and like in humans, rely on cooperative, long-term relationships (Samuni et al., 2018; Suchak et al., 2016). As in humans, social drivers are expected to shape ontogenetic capacities to establish and maintain positive social relationships with group members in chimpanzees.

Overall, we strongly agree with the authors to encourage future studies investigating theoretical claims of human's advanced social cooperation, using comparable data from a combination of observational and experimental studies. We advocate following comparative research protocols using matched subjects, where diversity of the socioecological spectrum across chimpanzee and human populations is appropriately considered.

我们感谢特邀评论“成为独一无二的人类？将黑猩猩与人类婴儿期进行比较”，为我们最近发表的研究提供发人深省的解释（Bründl 等人，2021）。作者指出，我们的研究填补了描述野生黑猩猩早期发育里程碑的重要空白，有助于与人类发育进行比较。然后，他们将重点放在对两种表面上可比的社会特征（笑和安慰）的物种比较上，我们发现它们在黑猩猩种群中出现的平均年龄比在人类中看到的要晚。作者认为，这些社会特征在人类中较早出现表明更多的“促进合作的亲社会倾向”。他们指出，“在大约 2 岁时，人类儿童在社交认知能力方面的表现已经超过了他们的类人猿堂兄弟黑猩猩”。虽然我们同意作者最初问题的有效性，

正如我们在论文中提到的，人类和黑猩猩的社交和交流里程碑并不总是很容易比较。我们敦促谨慎提倡仅基于两个可比较的社会特征来解释物种差异。此外，我们没有声称黑猩猩的“安慰”行为是移情的。这是否是人类婴儿的亲社会行为需要得到证实——就像在黑猩猩身上一样。此外，作者讨论了大笑和微笑，这可能在功能上有所不同。虽然我们包括笑声，但黑猩猩在开始玩耍和玩耍时使用的“玩耍脸”面部表情，可能与微笑具有相似的情感起源（Hooff & Preuschoft，2013)，不包括在我们的研究中。我们预计野生黑猩猩会比笑更早地出现玩脸（就像人类一样；Bard et al., 2011）。

人类和黑猩猩种群的社会生态学似乎可能会影响行为和认知特征的发展和可塑性（Boesch, 2020 , 2021 ; Nielsen & Haun, 2016）。这与我们的研究表明黑猩猩和人类特征出现的年龄重叠，强烈表明有效的比较评估必须仔细匹配每个物种的受试者，以控制潜在的影响变量，例如比较年龄、性别和社会历史，正如人类心理学研究的标准做法（Chiang et al., 2015 ; Martin et al., 1993）。野生黑猩猩生活在复杂的社会生态环境中，与人类一样，依赖合作的长期关系（Samuni 等人，2018 年；Suchak 等人，2016 年）。与人类一样，社会驱动力有望塑造个体发育能力，以与黑猩猩的群体成员建立和维持积极的社会关系。

总体而言，我们强烈同意作者鼓励未来研究调查人类先进社会合作的理论主张，使用来自观察和实验研究相结合的可比数据。我们提倡使用匹配的受试者遵循比较研究协议，其中适当考虑黑猩猩和人类群体的社会生态谱的多样性。