First steps of bipedality in hominids: evidence from the atelid and proconsulid pelvis

PeerJ

article

Allison L. Machnicki¹  Linda B. Spurlock²  Karen B. Strier³  Philip L. Reno¹  C. Owen Lovejoy² 

[1] Department of Anthropology, Pennsylvania State University, University Park;Department of Anthropology, Kent State University;Department of Anthropology, University of Wisconsin-Madison

关键词: Lordosis;    Ardipithecus;    Muriqui;    Bipedalism;    Sacrum;    Locomotion;    Australopithecus;    Proconsul;   

DOI  :  10.7717/peerj.1521

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Upright walking absent a bent-hip-bent-knee gait requires lumbar lordosis, a ubiquitous feature in all hominids for which it can be observed. Its first appearance is therefore a central problem in human evolution. Atelids, which use the tail during suspension, exhibit demonstrable lordosis and can achieve full extension of their hind limbs during terrestrial upright stance. Although obviously homoplastic with hominids, the pelvic mechanisms facilitating lordosis appear largely similar in both taxa with respect to abbreviation of upper iliac height coupled with broad sacral alae. Both provide spatial separation of the most caudal lumbar(s) from the iliac blades. A broad sacrum is therefore a likely facet of earliest hominid bipedality. All tailed monkeys have broad alae. By contrast all extant apes have very narrow sacra, which promote “trapping” of their most caudal lumbars to achieve lower trunk rigidity during suspension. The alae in the tailless proconsul Ekembo nyanzae appear to have been quite broad, a character state that may have been primitive in Miocene hominoids not yet adapted to suspension and, by extension, exaptive for earliest bipedality in the hominid/panid last common ancestor. This hypothesis receives strong support from other anatomical systems preserved in Ardipithecus ramidus.

【 授权许可】

CC BY