Inferring lumbar lordosis in Neandertals and other hominins

Scott A Williams; Iris Zeng; Glen J Paton; Christopher Yelverton; ChristiAna Dunham; Kelly R Ostrofsky; Saul Shukman; Monica V Avilez; Jennifer Eyre; Tisa Loewen; Thomas C Prang; Marc R Meyer

doi:10.1093/pnasnexus/pgab005

Inferring lumbar lordosis in Neandertals and other hominins

PNAS Nexus. 2022 Mar 2;1(1):pgab005. doi: 10.1093/pnasnexus/pgab005. eCollection 2022 Mar.

Authors

Scott A Williams^{1

2

3

4}, Iris Zeng⁵, Glen J Paton⁶, Christopher Yelverton^{4

6}, ChristiAna Dunham^{1

7}, Kelly R Ostrofsky⁸, Saul Shukman¹, Monica V Avilez^{1

2}, Jennifer Eyre^{1

9}, Tisa Loewen¹⁰, Thomas C Prang¹¹, Marc R Meyer¹²

Affiliations

¹ Center for the Study of Human Origins, Department of Anthropology, New York University, New York, NY 10003, USA.
² New York Consortium in Evolutionary Primatology, New York, NY 10024, USA.
³ Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
⁴ Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
⁵ Department of Architecture, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
⁶ Department of Chiropractic, Faculty of Health Sciences, University of Johannesburg, 2094, Johannesburg, South Africa.
⁷ Department of Anthropology, Texas State University, San Marcos, TX 78666, USA.
⁸ Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11569, USA.
⁹ Department of Anthropology, Bryn Mawr College, Bryn Mawr, PA 19010, USA.
¹⁰ School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA.
¹¹ Department of Anthropology, Texas A&M University, College Station, TX 77843, USA.
¹² Department of Anthropology, Chaffey College, Rancho Cucamonga, CA 91737, USA.

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.