The Spine of Early Pleistocene Homo

Abstract

In this chapter, we summarize vertebral remains from early Pleistocene Homo, including H. erectus, as well as H. naledi and H. floresiensis fossils from the Middle and Late Pleistocene, respectively. Two partial immature H. erectus skeletons where vertebrae are well represented are KNM-WT 15000 (“Turkana boy”) and the D2700 individual from Dmanisi. Vertebrae from H. naledi are also considered here, including those from the LES1 partial skeleton (“Neo”), despite their younger date to the Middle Pleistocene. We review the fossil record of presacral vertebrae in early Homo, and summarize work on the functional morphology, metameric patterning, and postcranial neuroanatomy of early Homo, comparing and contrasting the presacral spine with their putative australopith forbears and extant apes and humans. Based on the current evidence, the vertebral column of H. erectus possessed a modal number of twelve thoracic and five lumbar segments, as is the case in australopiths, as well as modern humans. The spine of H. erectus reveals key changes relative to earlier hominins, with an expanded thoracolumbar spinal canal offering increased neurovascular capacities, and a ventral pillar (formed by the vertebral bodies) better equipped to mitigate compressive loads and provide energy return. These biological developments are germane to understanding the advent of derived human behaviors, including efficient long-range locomotion and the first hominin expansion out of Africa.