Revisiting scoliosis in the KNM-WT 15000 Homo erectus skeleton.
Owing to its completeness, the 1.5 million year old Nariokotome boy skeleton KNM-WT 15000 is central for understanding the skeletal biology of Homo erectus. Nevertheless, since the reported asymmetries and distortions of Nariokotome boy's axial skeleton suggest adolescent idiopathic scoliosis, possibly associated with congenital skeletal dysplasia, it is questionable whether it still can be used as a reference for H. erectus. Recently, however, the presence of skeletal dysplasia has been refuted. Here, we present a morphological and morphometric reanalysis of the assertion of idiopathic scoliosis. We demonstrate that unarticulated vertebral columns of non-scoliotic and scoliotic individuals can be distinguished based on the lateral deviation of the spinous process, lateral and sagittal wedging, vertebral body torsion, pedicle thickness asymmetry, and asymmetry of superior and inferior articular facet areas. A principal component analysis of the overall asymmetry of all seven vertebral shape variables groups KNM-WT 15000 within non-scoliotic modern humans. There is, however, an anomaly of vertebrae T1-T2 that is compatible with a short left convex curve at the uppermost thoracic region, possibly due to injury or local growth dysbalance. Asymmetries of the facet joints L3-L5 suggest a local right convex curve in the lower lumbar region that probably resulted from juvenile traumatic disc herniation. This pattern is incompatible with adolescent idiopathic scoliosis or other types of scoliosis, including congenital, neuromuscular or syndromic scoliosis. It is, however, consistent with a recent reanalysis of the rib cage that did not reveal any asymmetry. Except for these possibly trauma-related anomalies, the Nariokotome boy fossil therefore seems to belong to a normal H. erectus youth without evidence for adolescent idiopathic scoliosis or other severe pathologies of the axial skeleton.
Anthropological Institute and Museum, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich, Switzerland.
Regula
R
Schiess
Orthopaedische Universitaetsklinik Balgrist, Forchstrasse 340, 8008 Zuerich, Switzerland; Centre for Evolutionary Medicine, Institute of Anatomy, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich, Switzerland.
Thomas
T
Boeni
Centre for Evolutionary Medicine, Institute of Anatomy, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich, Switzerland.
Frank
F
Rühli
Anthropological Institute and Museum, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich, Switzerland; Centre for Evolutionary Medicine, Institute of Anatomy, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich, Switzerland. Electronic address: MartinFelix.Haeusler@uzh.ch.
Martin
M
Haeusler
D000293:Adolescent; D000818:Animals; D000885:Anthropology, Physical; D005075:Biological Evolution; D002648:Child; D005260:Female; D015186:Hominidae / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D012600:Scoliosis / Q000473:pathology*; D013131:Spine / Q000473:pathology*
Adolescent idiopathic scoliosis; Early hominins; Human evolution; Palaeopathology; Vertebral column