Isolated teeth from La Ferrassie: Reassessment of the old collections, new remains, and their implications.

OBJECTIVES: We provide the description and comparative analysis of six new teeth from the site of La Ferrassie. Our goal is to discuss their taxonomic attribution, and to provide an updated inventory of Neandertal and modern human remains from La Ferrassie in their associated archeological context. MATERIALS AND METHODS: We use external and internal anatomy, classic morphometrics, and geometric morphometrics. The teeth from La Ferrassie are compared to several samples of contemporary Neandertals and upper Paleolithic modern humans and to recent modern humans. RESULTS: Three specimens are classified as Neandertals, two as modern humans, and one remains unclassified. DISCUSSION: Based on the previously known fossil samples and the new teeth reported here, there are currently a minimum of four adult and five immature Neandertal individuals coming from the "Grand Abri" and a minimum of two modern human adult individuals: one from "Grand Abri" and one from "Grotte." It is noteworthy that the spatial distribution of the recovered Neandertal remains is not restricted to the area where the LF1-LF 8 were found but now covers the full extension of the excavated area. Moreover, while both Neandertal and modern human occupations have yielded isolated human remains, the partial-to-complete skeletons only belong to Neandertals. These considerations open new perspectives for the understanding of the occupation and use of the La Ferrassie site.

Evolution of the hominin knee and ankle.

The dispersal of the genus Homo out of Africa approximately 1.8 million years ago (Ma) has been understood within the context of changes in diet, behavior, and bipedal locomotor efficiency. While various morphological characteristics of the knee and ankle joints are considered part of a suite of traits indicative of, and functionally related to, habitual bipedal walking, the timing and phylogenetic details of these morphological changes remain unclear. To evaluate the timing of knee and ankle joint evolution, we apply geometric morphometric methods to three-dimensional digital models of the proximal and distal tibiae of fossil hominins, Holocene Homo sapiens, and extant great apes. Two sets of landmarks and curve semilandmarks were defined on each specimen. Because some fossils were incomplete, digital reconstructions were carried out independently to estimate missing landmarks and semilandmarks. Group shape variation was evaluated through shape-and form-space principal component analysis and fossil specimens were projected to assess variation in the morphological space computed from the extant comparative sample. We show that a derived proximal tibia (knee) similar to that seen in living H. sapiens evolved with early Homo at ∼2 Ma. In contrast, derived characteristics in the distal tibia appear later, probably with the arrival of Homo erectus. These results suggest a dissociation of the morphologies of the proximal and distal tibia, perhaps indicative of divergent functional demands and, consequently, selective pressures at these joints. It appears that longer distance dispersals that delivered the Dmanisi hominins to Georgia by 1.8 Ma and H. erectus to east-southeast Asia by 1.6 Ma were facilitated by the evolution of a morphologically derived knee complex comparable to that of recent humans and an ankle that was morphologically primitive. This research sets the foundation for additional paleontological, developmental, and functional research to better understand the mechanisms underlying the evolution of bipedalism.

Ontogeny of modern human longitudinal body and transverse shoulder proportions.

OBJECTIVES: Whereas variation of modern human adult body size and shape has been widely studied in the context of ecogeographical clines, little is known about the differential growth patterns of transverse and longitudinal dimensions among human populations. Our study explored the ontogenetic variation of those body proportions in modern humans. METHODS: We compared results from four different approaches to study cross-sectional skeletal samples of Africans (n = 43), Amerindians (n = 69) and Europeans (n = 40) from 0 to 14 years of age. Clavicle, humerus, and femur intermetaphyseal lengths, and femoral distal metaphyseal breadth, were measured. Average ontogenetic trajectories were computed in order to compare the growth patterns of the three groups. RESULTS: Our findings demonstrated that the three geographical groups shared similar absolute and relative patterns of change with age for the four dimensions considered. Although interpopulation differences existed in transverse to longitudinal as well as in interlimb proportions, those differences did not seem to remain constant throughout ontogeny, similar to what has been shown for intralimb proportions. Growth rates of transverse shoulder proportions differed between populations from different regions after 10 years, whereas those for longitudinal proportions were very similar. CONCLUSIONS: The ontogeny of transverse shoulder proportions is more complex than what is observed for bi-iliac breadth, suggesting that transverse shoulder to limb proportions are not solely influenced by ecogeographical conditions. Our analysis demonstrates that methodologies that incorporate critical dimensions of body form could shed new light on human adaptation in both paleontological and neontological contexts.

Technical note: a novel geometric morphometric approach to the study of long bone shape variation.

Procrustes-based geometric morphometrics (GM) is most often applied to problems of craniofacial shape variation. Here, we demonstrate a novel application of GM to the analysis of whole postcranial elements in a study of 77 hominoid tibiae. We focus on two novel methodological improvements to standard GM approaches: 1) landmark configurations of tibiae including 15 epiphyseal landmarks and 483 semilandmarks along articular surfaces and muscle insertions along the tibial shaft and 2) an artificial affine transformation that sets moments along the shaft equal to the sum of the moments estimated in the other two anatomical directions. Diagrams of the principal components of tibial shapes support most differences between human and non-human primates reported previously. The artificial affine transformation proposed here results in an improved clustering of the great apes that may prove useful in future discriminant or clustering studies. Since the shape variations observed may be related to different locomotor behaviors, posture, or activity patterns, we suggest that this method be used in functional analyses of tibiae or other long bones in modern populations or fossil specimens.

Postnatal ontogeny of tibia and femur form in two human populations: a multivariate morphometric analysis.

OBJECTIVES: Adult population differences in relative and absolute limb size often are explained as adaptations to different climates. Less is known about other aspects of limb bone form and their population-specific growth patterns. METHODS: We study postnatal ontogenetic development of tibial and femoral form by a multivariate morphometric approach in a cross-sectional sample of South African (N = 97) and European (N = 81) modern humans from 0 to 20 years of age. Because the epiphyses ossify and fuse to the diaphysis in this time period, we separately analyze two sets of variables. Average ontogenetic trajectories are computed to compare the growth patterns of the African and the European groups. RESULTS: For both the tibia and the femur, we could show that Africans and Europeans have a very similar average length and average shape until about 10 years of age. During adolescence Africans have a higher growth rate leading to longer adult bones with narrower epiphyses relative to the diaphysis. Despite substantial individual overlap, the average crural index is higher in Africans than in Europeans, from birth on through adulthood. CONCLUSIONS: The prenatal origin of population differences in the crural index indicates a genetic determination of these differences whereas limb length and relative epiphyseal width likely are both genetically and environmentally determined.