Department of Anthropology, University of New Mexico, Albuquerque, NM 87131;
Peabody Museum of Archaeology and Ethnology, Harvard University, Cambridge, MA 02138.
Proc Natl Acad Sci U S A. 2020 May 26;117(21):11223-11225. doi: 10.1073/pnas.2004371117. Epub 2020 May 11.
Arboreal primates such as chimpanzees exhibit pronounced curvature in their hand and foot phalanges, which is assumed to develop throughout life in response to mechanical loads produced by grasping and hanging from branches. Intriguingly, ancient fossil hominins also exhibit substantial phalangeal curvature, which, too, has been interpreted as a direct result of habitual arboreality during life. Here, we describe the phalangeal curvature of a chimpanzee who was raised during the 1930s in New York City to live much like a human, including by having very few opportunities to engage in arboreal activities. We show that the degree of hand and foot phalangeal curvature in this individual is indistinguishable from that of wild chimpanzees and distinct from humans. Thus, rather than being a direct effect of mechanical loads produced by lifetime arboreal activities, phalangeal curvature appears to be shaped largely by genetic factors. An important implication of this finding is that phalangeal curvature among fossil hominins is evidently best interpreted as a primitive trait inherited from an arboreal ancestral species rather than proof of engagement in arboreal activities during life.
树栖灵长类动物，如黑猩猩，其手部和足部指骨具有明显的弯曲度，这种弯曲度被认为是在一生中对树枝抓握和悬挂产生的机械负荷的反应而逐渐形成的。有趣的是，古代化石人类也表现出明显的指骨弯曲度，这也被解释为生活中习惯性树栖的直接结果。在这里，我们描述了一只在 20 世纪 30 年代在纽约市被抚养长大的黑猩猩的指骨弯曲度，它的生活方式与人类非常相似，包括几乎没有机会进行树栖活动。我们发现，这只黑猩猩的手部和足部指骨弯曲度与野生黑猩猩没有区别，与人类明显不同。因此，指骨弯曲度似乎主要是由遗传因素决定的，而不是一生中树栖活动产生的机械负荷的直接影响。这一发现的一个重要意义是，化石人类中的指骨弯曲度显然最好被解释为从树栖祖先物种继承的原始特征，而不是生活中进行树栖活动的证据。
