Carrier David R
Department of Biology, 201 South Biology Building, University of Utah, Salt Lake City, Utah 84112, USA.
Evolution. 2007 Mar;61(3):596-605. doi: 10.1111/j.1558-5646.2007.00061.x.
Early hominins, australopiths, were similar to most large primates in having relatively short hindlimbs for their body size. The short legs of large primates are thought to represent specialization for vertical climbing and quadrupedal stability on branches. Although this may be true, there are reasons to suspect that the evolution of short legs may also represent specialization for physical aggression. Fighting in apes is a behavior in which short legs are expected to improve performance by lowering the center of mass during bipedal stance and by increasing the leverage through which muscle forces can be applied to the ground. Among anthropoid primates, body size sexual dimorphism (SSD) and canine height sexual dimorphism (CSD) are strongly correlated with levels of male-male competition, allowing SSD and CSD to be used as indices of male-male aggression. Here I show that the evolution of hindlimb length in apes is inversely correlated with the evolution of SSD (R(2)= 0.683, P-value = 0.006) and the evolution of CSD (R(2)= 0.630, P-value = 0.013). In contrast, a significant correlation was not observed for the relationship between the evolution of hindlimb and forelimb lengths. These observations are consistent with the suggestion that selection for fighting performance has maintained relatively short hindlimbs in species of Hominoidea with high levels of male-male competition. Although australopiths were highly derived for striding bipedalism when traveling on the ground, they retained short legs compared to those of Homo for over two million years, approximately 100,000 generations. Their short legs may be indicative of persistent selection for high levels of aggression.
早期人科动物南方古猿，就其体型而言，后肢相对较短，这一点与大多数大型灵长类动物相似。大型灵长类动物的短腿被认为是对垂直攀爬和在树枝上四足行走稳定性的一种特化。尽管可能如此，但有理由怀疑短腿的进化也可能代表了对身体攻击行为的特化。猿类的打斗行为是一种在两足站立时通过降低重心以及增加肌肉力量施加于地面的杠杆作用来提高表现的行为，在这种行为中短腿被认为具有优势。在类人猿灵长类动物中，体型两性异形（SSD）和犬齿高度两性异形（CSD）与雄性间竞争水平密切相关，使得SSD和CSD能够被用作雄性间攻击行为的指标。在此我表明，猿类后肢长度的进化与SSD的进化呈负相关（R(2)= 0.683，P值 = 0.006）以及与CSD的进化呈负相关（R(2)= 0.630，P值 = 0.013）。相比之下，后肢和前肢长度的进化之间未观察到显著相关性。这些观察结果与以下观点一致，即对于具有高水平雄性间竞争的人猿总科物种而言，对打斗表现的选择使得其后肢相对较短得以维持。尽管南方古猿在地面行走时高度适应大步态两足行走，但与人类相比，它们在超过两百万年、约100,000代的时间里一直保留着短腿。它们的短腿可能表明对高水平攻击行为的持续选择。
