Neck function in early hominins and suspensory primates: Insights from the uncinate process

摘要: Objectives Uncinate processes are protuberances on the cranial surface of subaxial cervical vertebrae that assist in stabilizing and guiding spinal motion. Shallow uncinate reduce stability but confer an increased range motion clinical studies. Here we assess among extant primates model kinematics early fossil hominins. Materials Methods We compare six hominin with 48 Homo sapiens 99 nonhuman across 20 genera. We quantify morphology via geometric morphometric methods to understand how process shape relates allometry, taxonomy, mode locomotion. Results Across primates, allometry explains roughly 50% variation, as small, narrow feature relatively tallest, most pronounced processes, whereas larger, wider typically reduced uncinates. Taxonomy only weakly residual however, association between Uncinate Shape locomotion is robust, bipeds suspensory occupy opposite extremes morphological continuum distinguished from arboreal generalists. Like humans, Australopithecus afarensis erectus exhibit shallow A. sediba resembles more taxa, not fully primates. Discussion Suspensory uncinates, likely maintain visual field stabilization. East African hominins compared apes sediba, signaling different degrees neck motility modes locomotion. Although soft tissues constrain flexibility beyond limits suggested by osteology alone, this study may modeling positional behaviors extinct taxa.