Investigations into the role of selection in the origin of human bipedalism using ape models have relied heavily on behavioral frequency data. However, analysis of video of wild apes has the advantage of capturing the details of the entirety of each rare, brief bipedal bout witnessed, not just the moment detected in observational studies. We used video to explore the behavioral context and effects of several variables on bipedalism across all ages in wild forest-dwelling chimpanzees from Ngogo, Uganda. We found, as in earlier studies, that adult chimpanzees used bipedalism in the context of foraging; however, unlike earlier studies, we found that while foraging was the predominant behavioral context during arboreal bipedalism, terrestrial bipedalism was more varied in contextual composition. We also found that these different behavioral contexts of bipedalism were associated with different variables. Specifically, foraging was associated with arboreality, hand assistance, and adulthood; antagonism was associated with adulthood, locomotion, and males; play was associated with terrestriality and subadulthood; and travel was associated with locomotion and females. Given that several variables influence bipedalism across multiple behavioral contexts in chimpanzees, it is likely that the early evolution of human bipedalism occurred under the influence of numerous factors. This exploratory study thus suggests that more comprehensive models should be used when reconstructing the transition to bipedalism from the Last Common Ancestor of humans and chimpanzees.

中文翻译：

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多个变量对野生黑猩猩双足环境的影响：对古人类双足进化的影响

使用猿模型研究选择在人类两足行走起源中的作用在很大程度上依赖于行为频率数据。然而，对野生猿视频的分析具有捕捉所目睹的每一次罕见的、短暂的双足比赛的整体细节的优势，而不仅仅是观察研究中检测到的时刻。我们使用视频来探索乌干达恩戈戈野生森林黑猩猩各个年龄段的行为背景和几个变量对两足行走的影响。正如早期的研究一样，我们发现成年黑猩猩在觅食时使用两足行走。然而，与早期的研究不同，我们发现，虽然觅食是树栖两足行走期间的主要行为背景，但陆地两足行走的背景构成更加多样化。我们还发现，两足行走的这些不同行为背景与不同的变量相关。具体来说，觅食与树栖、手部辅助和成年有关。拮抗作用与成年、运动和男性有关；玩耍与陆地生活和亚成年期有关；旅行与运动和女性有关。鉴于多个变量影响黑猩猩多种行为背景下的两足行走，人类两足行走的早期进化很可能是在多种因素的影响下发生的。因此，这项探索性研究表明，在重建人类和黑猩猩最后共同祖先到两足行走的过渡时，应该使用更全面的模型。