Biomechanics of the hip and birth in early Homo
1995/12/01 by Christopher B. Ruff · 37 citations
Social Sciences · Arts and Humanities · Earth and Planetary Sciences · #Pleistocene-Era Hominins and Archaeology #Forensic Anthropology and Bioarchaeology Studies #Evolution and Paleontology Studies
paper · doi:10.1002/ajpa.1330980412
Abstract
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.
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- Complex and changing patterns of natural selection explain the evolution of the human hip
- Hominin Obstetrics and the Evolution of Constraints
- Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene
- Body proportions of Homo habilis reviewed
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- Further assessment of a ~2-million-year-old hominin pelvis (DNH 43) from Drimolen Main Quarry, South Africa
- Femoral and pelvic morpho-structure in extant primates and fossil Homo: insights into locomotor adaptations
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- A Wider Pelvis Does Not Increase Locomotor Cost in Humans, with Implications for the Evolution of Childbirth
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- Highly selective cannibalism in the Late Pleistocene of Northern Europe reveals Neandertals were targeted prey. [europepmc]
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