Schmitt Daniel
Department of Biological Anthropology and Anatomy, Duke University, Durham NC, USA.
J Exp Biol. 2003 May;206(Pt 9):1437-48. doi: 10.1242/jeb.00279.
An understanding of the evolution of human bipedalism can provide valuable insights into the biomechanical and physiological characteristics of locomotion in modern humans. The walking gaits of humans, other bipeds and most quadrupedal mammals can best be described by using an inverted-pendulum model, in which there is minimal change in flexion of the limb joints during stance phase. As a result, it seems logical that the evolution of bipedalism in humans involved a simple transition from a relatively stiff-legged quadrupedalism in a terrestrial ancestor to relatively stiff-legged bipedalism in early humans. However, experimental studies of locomotion in humans and nonhuman primates have shown that the evolution of bipedalism involved a much more complex series of transitions, originating with a relatively compliant form of quadrupedalism. These studies show that relatively compliant walking gaits allow primates to achieve fast walking speeds using long strides, low stride frequencies, relatively low peak vertical forces, and relatively high impact shock attenuation ratios. A relatively compliant, ape-like bipedal walking style is consistent with the anatomy of early hominids and may have been an effective gait for a small biped with relatively small and less stabilized joints, which had not yet completely forsaken arboreal locomotion. Laboratory-based studies of primates also suggest that human bipedalism arose not from a terrestrial ancestor but rather from a climbing, arboreal forerunner. Experimental data, in conjunction with anatomical data on early human ancestors, show clearly that a relatively stiff modern human gait and associated physiological and anatomical adaptations are not primitive retentions from a primate ancestor, but are instead recently acquired characters of our genus.
了解人类两足行走的进化过程，可以为洞察现代人类运动的生物力学和生理特征提供有价值的见解。人类、其他两足动物以及大多数四足哺乳动物的行走步态，最好用倒立摆模型来描述，在这个模型中，肢体关节在站立阶段的弯曲变化最小。因此，人类两足行走的进化似乎是一个简单的转变，即从陆地祖先相对僵硬的四足行走，过渡到早期人类相对僵硬的两足行走。然而，对人类和非人类灵长类动物运动的实验研究表明，两足行走的进化涉及一系列更为复杂的转变，最初是一种相对灵活的四足行走方式。这些研究表明，相对灵活的行走步态使灵长类动物能够通过大步幅、低步频、相对较低的垂直力峰值以及相对较高的冲击减震率来实现快速行走速度。一种相对灵活的、类似猿类的两足行走方式与早期原始人类的解剖结构相符，对于关节相对较小且稳定性较差、尚未完全放弃树栖运动的小型两足动物来说，可能是一种有效的步态。对灵长类动物的实验室研究还表明，人类的两足行走并非起源于陆地祖先，而是源于一种攀爬的、树栖的祖先。实验数据与早期人类祖先的解剖数据相结合，清楚地表明，现代人类相对僵硬的步态以及相关的生理和解剖适应性并非灵长类祖先的原始保留特征，而是我们这个属最近才获得的特征。
