Supernumerary lumbar rib in human prehistory

Abstract

Unlike their cervical counterparts, supernumerary lumbar ribs are generally considered to be of little clinical significance, though they do constitute a topic of anthropological interest. The two most complete Neandertal lumbar regions (Kebara 2 and Shanidar 3) both show evidence of articular facets for bilateral lumbar ribs and a high incidence of the condition has been reported in the prehistoric Sadlermiut Eskimo. This pilot study tests the association of bi‐iliac breadth with the presence of supernumerary lumbar rib in two wide‐bodied prehistoric populations: Pt. Hope Inupiat (n=25), Tierra del Fuegan/Aonikenk (n=25), and one narrow‐bodied prehistoric population: South African Zulu (n=25). Moreover, as mouse models have shown a correlation between 12th rib length and lumbar rib presence, this was also investigated. Of the populations studied, only the Pt. Hope Inupiat evinced lumbar ribs (16%) even though their bi‐iliac breadth was not significantly greater than that seen in the Tierra del Fuegan/Aonikenk. Additionally, significantly longer ribs were observed for the Pt. Hope Inupiats in agreement with the predicted model. These results suggest that the presence of supernumerary lumbar rib in human prehistory is indicative of other basic alterations of the axial skeleton and is most likely related to population history.Grant Funding Source: National Science Foundation Doctoral Dissertation Improvement Grant #0752723 and the Wenner‐Gren Foundation for Anthropological Research.