Inferring lumbar lordosis in Neandertals and other hominins

Abstract

Lumbar lordosis is a key adaptation to bipedal locomotion in the human lineage. Dorsoventral spinal curvatures enable the body's center of mass to be positioned above the hip, knee, and ankle joints, and minimize the muscular effort required for postural control and locomotion. Previous studies have suggested that Neandertals had less lordotic (ventrally convex) lumbar columns than modern humans, which contributed to historical perceptions of postural and locomotor differences between the two groups. Quantifying lower back curvature in extinct hominins is entirely reliant upon bony correlates of overall lordosis, since the latter is significantly influenced by soft tissue structures (e.g. intervertebral discs). Here, we investigate sexual dimorphism, ancestry, and lifestyle effects on lumbar vertebral body wedging and inferior articular facet angulation, two features previously shown to be significantly correlated with overall lordosis in living individuals, in a large sample of modern humans and Neandertals. Our results demonstrate significant differences between postindustrial cadaveric remains and archaeological samples of people that lived preindustrial lifestyles. We suggest these differences are related to activity and other aspects of lifestyle rather than innate population (ancestry) differences. Neandertal bony correlates of lumbar lordosis are significantly different from all human samples except preindustrial males. Therefore, although Neandertals demonstrate more bony kyphotic wedging than most modern humans, we cast doubt on proposed locomotor and postural differences between the two lineages based on inferred lumbar lordosis (or lack thereof), and we recommend future research compare fossils to modern humans from varied populations and not just recent, postindustrial samples.

Homo naledi lumbar vertebrae and a new 3D method to quantify vertebral wedging

“…Individuals demonstrating obvious pathologies, especially those affecting the bilateral symmetry of vertebral bodies (e.g., scoliosis), were not included. Postindustrial peoples possess more exaggerated lumbar lordosis than preindustrial, "traditional-living" peoples (Williams et al, 2022), so the sample used here is a global archeological A.L. 288-1aa, A.L.…”

“…Individuals demonstrating obvious pathologies, especially those affecting the bilateral symmetry of vertebral bodies (e.g., scoliosis), were not included. Postindustrial peoples possess more exaggerated lumbar lordosis than preindustrial, “traditional‐living” peoples (Williams et al, 2022), so the sample used here is a global archeological sample (with specimens from southern, eastern, and northern Africa, South and East Asia, Northern Europe, Polynesia, Australia, and the Americas). Additionally, we created surface scans of the H. naledi lumbar vertebrae (U.W.…”

“…Other available fossil hominin specimens, including australopiths and Neandertals, similarly fall within the range of preindustrial modern human variation (cf. Whitcome et al, 2007;Williams et al, 2022). This method is useful on vertebral bodies lacking midline measurements, either through damage, pathology, or natural aspects of morphology, but its utility on partial vertebral bodies is more limited, with some states of preservation preventing its use.…”

The Sima de los Huesos thorax and lumbar spine: Selected traits and state‐of‐the‐art

“…Currently, it is not possible to estimate the lumbar lordosis of the SH hominins based on other methods that quantify the lumbar vertebral morphology. On the one hand, the most complete association of lumbar vertebrae from SH, that is, those associated to Pelvis 1, are pathological (Bonmatí perceived difference, especially given the differences found between the lordosis between preindustrial and postindustrial populations (Williams et al, 2022).…”

Did the Industrial Revolution Lead to an Important Alteration in the Shape of the Human Spine?

“…Scott A. Williams, PhD, and colleagues studied vertebrae from three different groups: humans who lived and died before the industrial revolution, humans who lived in the postindustrial era, and a handful of Neandertals who lived thousands of years previously. (See Williams et al, 2022. )…”