Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: population affinities and pathological abnormalities

Abstract

Liang Bua 1 (LB1) exhibits marked craniofacial and postcranial asymmetries and other indicators of abnormal growth and development. Anomalies aside, 140 cranial features place LB1 within modern human ranges of variation, resembling Australomelanesian populations. Mandibular and dental features of LB1 and LB6/1 either show no substantial deviation from modern Homo sapiens or share features (receding chins and rotated premolars) with Rampasasa pygmies now living near Liang Bua Cave. We propose that LB1 is drawn from an earlier pygmy H. sapiens population but individually shows signs of a developmental abnormality, including microcephaly. Additional mandibular and postcranial remains from the site share small body size but not microcephaly.

Fig. 1.

Absence of external chin is common in Australomelanesian populations. Here we show Rampasasa individual No. 26, who lacks a chin. Our work on the Rampasasa population determined that 93.4% of the sample have neutral (flat) or negative chins. Absence of a chin cannot be a valid taxonomic character for the Liang Bua mandibles. (Photograph is by E.I.)

Fig. 2.

LB1 in three different views to illustrate facial asymmetry. (Left) The actual specimen. (Center) The right side doubled at the midline and mirrored. (Right) The left side doubled and mirrored. Differences in left- and right-side facial architectures are apparent and illustrate growth abnormalities of LB1. (Original photograph in Left is by E.I.; original photographs in Center and Right are by D.W.F.)

Fig. 3.

Partial to 90° premolar rotation is common in the Rampasasa pygmy sample from Flores. (Left) Rampasasa 041 is a 32-year-old female showing an upper left third premolar with 90° rotation, so that the buccal aspect is in the mesial position (arrow). All other teeth in both jaws are positioned normally. (Right) Rampasasa 033 is a 25-year-old female with a lower right fourth premolar rotated nearly 90°, with the usual buccal aspect oriented distally here (arrow). The tooth also has an anomalous shape, resembling an upper premolar. (Original photographs are by E.I.)

Fig. 4.

Anterior aspect of the humerus. Note near absence of deltoid tuberosity as well as minimal difference in subdeltoid and supradaltoid width of the shaft. These indicators of extremely weak muscle development are consistent developmentally with an abnormally low degree of humeral torsion.

Fig. 5.

LB1 femora. (A) Lateral views of both femora, showing antimeric contrasts in diameters as well as sizes and orientations of lesser trochanters. Note thin cortex in the small postmortem break on shaft of left femur. (B) Posterior aspect of both femora. Note shortness of linea aspera and large size of popliteal areas.

Fig. 6.

CT scans of LB1 leg bones (vertical scales are subdivided into 10-mm units). (Top) Longitudinal scan of the left femur (up, anterior). (Middle) Midshaft cross-section of left (Left) and right (Right) femora (in all cross-sections, down is anterior). Note differences in cross-sectional outlines and internal structures, indicative of same evident left-right asymmetry also seen in Fig. 5. (Bottom Left) Cross-section of left tibia at level of tibial tuberosity. (Right) Cross-section of left tibia at midshaft. Note that cortical bone (completely radio-opaque area) in all sections is only ≈2 mm thick, abnormal for an adult primate of either sex, and body length >1 m.