Appendicular robusticity and the paleobiology of modern human emergence

The emergence of modern humans in the Late Pleistocene, whatever its phylogenetic history, was characterized by a series of behaviorally important shifts reflected in aspects of human hard tissue biology and the archeological record. To elucidate these shifts further, diaphyseal cross-sectional morphology was analyzed by using cross-sectional areas and second moments of area of the mid-distal humerus and midshaft femur. The humeral diaphysis indicates a gradual reduction in habitual load levels from Eurasian late archaic, to Early Upper Paleolithic early modern, to Middle Upper Paleolithic early modern hominids, with the Levantine Middle Paleolithic early modern humans being a gracile anomalous outlier. The femoral diaphysis, once variation in ecogeographically patterned body proportions is taken into account, indicates no changes across the pre-30,000 years B.P. samples in habitual locomotor load levels, followed by a modest decrease through the Middle Upper Paleolithic.

Primate postcrania from the late middle Eocene of Myanmar

Fossil primates have been known from the late middle to late Eocene Pondaung Formation of Myanmar since the description of Pondaungia cotteri in 1927. Three additional primate taxa, Amphipithecus mogaungensis, Bahinia pondaungensis and Myanmarpithecus yarshensis, were subsequently described. These primates are represented mostly by fragmentary dental and cranial remains. Here we describe the first primate postcrania from Myanmar, including a complete left humerus, a fragmentary right humerus, parts of left and right ulnae, and the distal half of a left calcaneum, all representing one individual. We assign this specimen to a large species of Pondaungia based on body size and the known geographic distribution and diversity of Myanmar primates. Body weight estimates of Pondaungia range from 4,000 to 9,000 g, based on humeral length, humeral midshaft diameter, and tooth area by using extant primate regressions. The humerus and ulna indicate that Pondaungia was capable of a wide variety of forelimb movements, with great mobility at the shoulder joint. Morphology of the distal calcaneus indicates that the hind feet were mobile at the transverse tarsal joint. Postcrania of Pondaungia present a mosaic of features, some shared in common with notharctine and adapine adapiforms, some shared with extant lorises and cebids, some shared with fossil anthropoids, and some unique. Overall, Pondaungia humeral and calcaneal morphology is most consistent with that of other known adapiforms. It does not support the inclusion of Pondaungia in Anthropoidea.