Martin Haeusler

New vertebral and rib material point to modern bauplan of the Nariokotome Homo erectus skeleton.

The double S shape of the vertebral column is one of the most important evolutionary adaptations to human bipedal locomotion, providing an optimal compromise between stability and mobility. It is commonly believed that a six element long lumbar spine facilitated the critical adoption of lumbar lordosis in early hominins, which contrasts with five lumbars in modern humans and four in chimpanzees and gorillas. This is mainly based on the juvenile Homo erectus skeleton KNM-WT 15000 from Nariokotome, Kenya. Yet, the biomechanical advantage of a long lumbar spine is speculative. Here we present new vertebral and rib fragments of KNM-WT 15000. They demonstrate that the sixth to the last presacral vertebra possesses rib facets and therefore indicate the presence of only five lumbar and twelve thoracic segments, as is characteristic of modern humans. Moreover, they show that no additional element was located between the sixth to the last presacral vertebra and Th11 as suggested in the original description. The transition from thoracic to lumbar type orientation of the facet joints that takes place at Th11 is thus at the same segment as in over 40% of modern humans, suggesting an identical lumbar mobility and capacity for lordosis. Taken together, KNM-WT 15000 had one vertebra less than previously thought irrespective of whether rib-free lumbar vertebrae or vertebrae that bear lumbar-like articular processes are counted. Furthermore, the new rib fragments imply a rearrangement of the ribs that results in a symmetrical rib cage. This challenges previous claims for idiopathic or congenital scoliosis. We conclude that the bauplan of the hominin axial skeleton is more conservative than previously thought.

Evidence for juvenile disc herniation in a Homo erectus boy skeleton

Study Design. An analysis and differential diagnosis of bony alterations in the lower lumbar vertebrae of a Homo erectus boy skeleton. Objective. To analyze low back problems during early human evolution. Summary of Background Data. Back problems in modern humans are often attributed to our upright, bipedal locomotion that is thought to place huge mechanical stresses on the vertebral column. However, little is known of this situation during the course of human evolution. Methods. We analyzed the lower lumbar spine of the most complete early hominid skeleton, the 1.5-million-year-old Homo erectus boy KNM-WT 15000 from Nariokotome, Kenya, who died at an age of approximately 8 years. We use bony alterations as indirect evidence for disc disease in the absence of soft tissue. Results. We describe an extensive osteophytic anterior curved remodeling of the left superior articular process of L5 and formation of a new joint at the underside of the left pedicle of L4. This indicates collisional facet joint subluxation, most likely as the result of juvenile traumatic disc herniation. Conclusions. This indirect evidence of possible juvenile disc herniation in a Homo erectus boy skeleton represents the earliest known case of this typical human ailment that is intricately linked to upright bipedalism. The extensive bony remodeling of the articular processes of L4 and L5 suggests that the disc herniation occurred several months before his death. Disabling backache and recurrent sciatica might have, at least, temporarily restricted his daily activities, which indicates advanced social care and nursing in early Homo. We hypothesize that the early Homo intervertebral discs were more vulnerable to injury compared with modern humans because of a relatively small vertebral cross-sectional area.

No skeletal dysplasia in the nariokotome boy KNM-WT 15000 (homo erectus)—A reassessment of congenital pathologies of the vertebral column

The Nariokotome boy skeleton KNM-WT 15000 is the most complete Homo erectus fossil and therefore is key for understanding human evolution. Nevertheless, since Latimer and Ohman (2001) reported on severe congenital pathology in KNM-WT 15000, it is questionable whether this skeleton can still be used as reference for Homo erectus skeletal biology. The asserted pathologies include platyspondylic and diminutive vertebrae implying a disproportionately short stature; spina bifida; condylus tertius; spinal stenosis; and scoliosis. Based on this symptom complex, the differential diagnosis of spondyloepiphyseal dysplasia tarda, an extremely rare form of skeletal dysplasia, has been proposed. Yet, our reanalysis of these pathologies shows that the shape of the KNM-WT 15000 vertebrae matches that of normal modern human adolescents. The vertebrae are not abnormally flat, show no endplate irregularities, and thus are not platyspondylic. As this is the hallmark of spondyloepiphyseal dysplasia tarda and related forms of skeletal dysplasia, the absence of platyspondyly refutes axial dysplasia and disproportionate dwarfism. Furthermore, we neither found evidence for spina bifida occulta nor manifesta, whereas the condylus tertius, a developmental anomaly of the cranial base, is not related to skeletal dysplasias. Other fossils indicate that the relatively small size of the vertebrae and the narrow spinal canal are characteristics of early hominins rather than congenital pathologies. Except for the recently described signs of traumatic lumbar disc herniation, the Nariokotome boy fossil therefore seems to belong to a normal Homo erectus youth without pathologies of the axial skeleton.

Palaeopathology: Current challenges and medical impact

Palaeopathology is the science which studies ancient human diseases. Throughout its relatively young history it underwent tremendous technological and methodological improvements (from pure morphology and histology to CT scanning) that have constantly reshaped its scientific rationale. Among other achievements, the study of mummies and fossilized hominids has allowed to effectively extract ancient DNA, prove the existence of atherosclerosis in ancient times, demonstrate the presence of disease vectors, better clarify the etiology of infectious diseases otherwise only postulated on the basis of ancient accounts as well as to show the presence of spine pathology in our hominid ancestors. The research levels in this discipline are three: basic research, individual cases, population. The first and the third levels contribute most to the discipline, while the second is the one more appealing to the general public on account of its description of important cases reports. In addition, a recently introduced sub‐specialty of palaeopathology, pathography is aiming to use an interdisciplinary approach to find traces of diseases in ancient literary sources and artistic representations. In spite of its discoveries, palaeopathology is not always viewed positively by clinicians because certain old‐fashioned techniques are still due to technical restrictions. The authors provide a set of suggestions on how to strengthen the scientific recognition of this subject and explain at length how it could contribute to the progress of medical research. Clin. Anat. 29:816–822, 2016.

How Did the Pelvis and Vertebral Column Become a Functional Unit during the Transition from Occasional to Permanent Bipedalism

The functional linkage between pelvis and spine remained long hidden to science. Here, we recount the history of research that led in 1992 to the discovery of the “angle of sacral incidence” by the team of G. Duval‐Beaupère. This angle, formed between a ray from the hip joint center to the superior sacral surface and the perpendicular to the sacral surface, was later called pelvic incidence. Specific to each individual, pelvic incidence is tightly correlated with the degree of lumbar lordosis. It is each individuals “signature” for an efficient sagittal balance since it represents the sum of two positional parameters, sacral slope and pelvic tilt. The simultaneous experimental determination of the trunk line of gravity permitted Duval‐Beaupères team to elucidate the conditions of an efficient sagittal balance of the trunk on the lower limbs. We present an in vivo EOS study of eight spino‐pelvic parameters describing the sagittal balance in 131 adults. We observe a chain of correlations between the six angular parameters and discuss the functional significance of these results. We show that pelvic incidence increases and lumbar lordosis develops when the infant learns to walk, leading to a correlation between these parameters. This process of association between pelvis and spine might have acquired a solid genetic basis during hominid evolution by natural selection acting on both pelvis and spine. We suggest that this process of functional integration was only possible in the context of bipedal locomotion becoming permanent and stereotyped, expressed by a relatively invariant, periodic walking cycle. Anat Rec, 300:912–931, 2017.

Increasing variability of body mass and health correlates in Swiss conscripts, a possible role of relaxed natural selection?

The distribution of height, weight, and body mass index of Swiss conscripts widened over the last 140 years. There are now more underweight and overweight conscripts who show similar increases in inflam-matory and metabolic fault blood parameters. Both facts indicate a possible role of relaxed natural selection on genes affecting metabolism and body composition.