An ontogenetic framework linking locomotion and trabecular bone architecture with applications for reconstructing hominin life history.
The ontogeny of bipedal walking is considered uniquely challenging, due in part to the balance requirements of single limb support. Thus, locomotor development in humans and our bipedal ancestors may track developmental milestones including the maturation of the neuromuscular control system. Here, we examined the ontogeny of locomotor mechanics in children aged 1-8, and bone growth and development in an age-matched skeletal sample to identify bony markers of locomotor development. We show that step-to-step variation in mediolateral tibia angle relative to the vertical decreases with age, an indication that older children increase stability. Analyses of trabecular bone architecture in the distal tibia of an age-matched skeletal sample (the Norris Farms #36 archaeological skeletal collection) show a bony signal of this shift in locomotor stability. Using a grid of eleven cubic volumes of interest (VOI) in the distal metaphysis of each tibia, we show that the degree of anisotropy (DA) of trabecular struts changes with age. Intra-individual variation in DA across these VOIs is generally high at young ages, likely reflecting variation in loading due to kinematic instability. With increasing age, mean DA converges on higher values and becomes less variable across the distal tibia. We believe the ontogeny of distal tibia trabecular architecture reflects the development of locomotor stability in bipeds. We suggest this novel bony marker of development may be used to assess the relationship between locomotor development and other life history milestones in fossil hominins.
School of Anthropology, University of Arizona, Tucson, AZ 85721, USA. Electronic address: raichlen@email.arizona.edu.
David A
DA
Raichlen
Department of Anthropology, University at Albany, Albany, NY 12222, USA.
Adam D
AD
Gordon
School of Anthropology, University of Arizona, Tucson, AZ 85721, USA.
Adam D
AD
Foster
School of Anthropology, University of Arizona, Tucson, AZ 85721, USA.
James T
JT
Webber
Department of Anthropology, Pennsylvania State University, University Park, PA 16802, USA.
Simone M
SM
Sukhdeo
Department of Anthropology and Center for Human Evolutionary Studies, Rutgers University, New Brunswick, NJ 08901, USA.
Robert S
RS
Scott
Department of Anthropology, The Ohio State University, Columbus, OH 43210-1106, USA.
James H
JH
Gosman
Department of Anthropology, Pennsylvania State University, University Park, PA 16802, USA; Center for Quantitative Imaging, EMS Energy Institute, Pennsylvania State University, University Park, PA 16802, USA.
Timothy M
TM
Ryan
D000818:Animals; D001130:Arizona; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D002648:Child; D002675:Child, Preschool; D005260:Female; D015186:Hominidae / Q000502:physiology; D006801:Humans; D007087:Illinois; D007223:Infant; D008297:Male; D013977:Tibia / Q000033:anatomy & histology* / Q000254:growth & development*; D016138:Walking
Degree of anisotropy; Development; Evolution of bipedalism; Kinematics; Stability