Ruff C B
Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Am J Phys Anthropol. 1995 Dec;98(4):527-74. doi: 10.1002/ajpa.1330980412.
A complex of traits in the femur and pelvis of Homo erectus and early "erectus-like" specimens has been described, but never satisfactorily explained. Here the functional relationships between pelvic and femoral structure in humans are explored using both theoretical biomechanical models and empirical tests within modern samples of diverse body form (Pecos Amerindians, East Africans). Results indicate that a long femoral neck increases mediolateral bending of the femoral diaphysis and decreases gluteal abductor and hip joint reaction forces. Increasing biacetabular breadth along with femoral neck length further increases M-L bending of the femoral shaft and maintains abductor and joint reaction forces at near "normal" levels. When compared to modern humans, Homo erectus and early "erectus-like" specimens are characterized by a long femoral neck and greatly increased M-L relative to A-P bending strength of the femoral shaft, coupled with no decrease in hip joint size and a probable increase in abductor force relative to body size. All of this strongly suggests that biacetabular breadth as well as femoral neck length was relatively large in early Homo. Several features preserved in early Homo partial hip bones also indicate that the true (lower) pelvis was very M-L broad, as well as A-P narrow. This is similar to the lower pelvic shape of australopithecines and suggests that nonrotational birth, in which the newborn's head is oriented transversely through the pelvic outlet, characterized early Homo as well as Australopithecus. Because M-L breadth of the pelvis is constrained by other factors, this may have limited increases in cranial capacity within Homo until rotational birth was established during the late Middle Pleistocene. During or after the transition to rotational birth biacetabular breadth decreased, reducing the body weight moment arm about the hip and allowing femoral neck length (abductor moment arm) to also decrease, both of which reduced M-L bending of the proximal femoral shaft. Variation in femoral structural properties within early Homo and other East African Early Pleistocene specimens has several taxonomic and phylogenetic implications.
直立人和早期“类直立人”标本的股骨和骨盆中的一系列特征已被描述，但从未得到令人满意的解释。在此，利用理论生物力学模型和对不同体型现代样本（佩科斯美洲印第安人、东非人）的实证测试，探索了人类骨盆与股骨结构之间的功能关系。结果表明，股骨颈较长会增加股骨干的内外侧弯曲，并降低臀中肌和髋关节的反应力。髋臼宽度与股骨颈长度同时增加，会进一步增加股骨干的内外侧弯曲，并使外展肌和关节反应力维持在接近“正常”的水平。与现代人相比，直立人和早期“类直立人”标本的特征是股骨颈较长，且相对于股骨干的前后弯曲强度，内外侧弯曲强度大幅增加，同时髋关节大小没有减小，相对于体型而言外展肌力可能增加。所有这些都有力地表明，早期人类的髋臼宽度以及股骨颈长度相对较大。早期人类部分髋骨中保留的几个特征也表明，真正的（下部）骨盆在内外侧非常宽，而在前后方向上较窄。这与南方古猿的下部骨盆形状相似，表明早期人类以及南方古猿的分娩方式为非旋转式，即新生儿的头部横向通过骨盆出口。由于骨盆的内外侧宽度受到其他因素的限制，这可能在中更新世晚期建立旋转式分娩之前限制了人类颅容量的增加。在向旋转式分娩过渡期间或之后，髋臼宽度减小，减少了身体重量绕髋关节的力臂，并使股骨颈长度（外展肌力臂）也减小，这两者都减少了股骨近端干的内外侧弯曲。早期人类和其他东非早更新世标本中股骨结构特性的变化具有若干分类学和系统发育学意义。
