Department of Organismal Biology and Anatomy, University of Chicago, 1027 E 57th Street, Chicago, 60637, USA; Center for the Study of Human Origins and Department of Anthropology, New York University, 25 Waverly Place, New York, 10003, USA; New York Consortium in Evolutionary Primatology, New York, USA.
J Hum Evol. 2024 Sep;194:103567. doi: 10.1016/j.jhevol.2024.103567. Epub 2024 Jul 27.
Hominoids exhibit a strikingly diverse set of locomotor adaptations-including knuckle-walking, brachiation, quadrumanuous suspension, and striding bipedalism-while also possessing morphologies associated with forelimb suspension. It has been suggested that changes in limb element integration facilitated the evolution of diverse locomotor modes by reducing covariation between serial homologs and allowing the evolution of a greater diversity of limb lengths. Here, I compare limb element integration in hominoids with that of other primate taxa, including two that have converged with them in forelimb morphology, Ateles and Pygathrix. Ateles is part of a clade that, such as hominoids, exhibits diverse locomotor adaptations, whereas Pygathrix is an anomaly in a much more homogeneous (in terms of locomotor adaptations) clade. I find that all atelines (and possibly all atelids), not just Ateles, share reduced limb element integration with hominoids. Pygathrix does not, however, instead resembling other members of its own family. Indriids also seem to have higher limb integration than apes, despite using their forelimbs and hindlimbs in divergent ways, although there is more uncertainty in this group due to poor sample size. These results suggest that reduced limb integration is characteristic of certain taxonomic groups with high locomotor diversity rather than taxa with specific, specialized locomotor adaptations. This is consistent with the hypothesis that reduced integration serves to open new areas of morphospace to those clades while suggesting that derived locomotion with divergent demands on limbs is not necessarily associated with reduced limb integration.
人科动物表现出一系列引人注目的运动适应特征，包括指节行走、臂行、四足悬挂和跨步双足行走，同时还具有与前肢悬挂相关的形态特征。有人认为，肢体元素整合的变化通过减少同源物之间的共变和允许更多不同长度的肢体进化，促进了多种运动模式的进化。在这里，我比较了人科动物与其他灵长类动物的肢体元素整合，包括与它们在前肢形态上趋同的两种灵长类动物，即蜘蛛猴和白臀叶猴。蜘蛛猴属于一个与人类一样表现出多种运动适应特征的分支，而白臀叶猴则是一个在运动适应方面更为同质的分支中的异类。我发现所有的卷尾猴（可能包括所有的长尾猴）都与人科动物一样，肢体元素整合程度较低。然而，白臀叶猴并非如此，它更类似于自己家族的其他成员。大狐猴的前肢和后肢的使用方式虽然不同，但似乎也比猿类具有更高的肢体整合度，尽管在这个群体中，由于样本量较小，存在更多的不确定性。这些结果表明，肢体整合度的降低是某些具有高度运动多样性的分类群的特征，而不是具有特定、专门运动适应的分类群的特征。这与肢体整合度降低有助于为那些分支开辟新的形态空间的假说一致，同时表明，具有不同需求的衍生运动不一定与肢体整合度降低有关。
