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Previous studies have referred to the degree of dorsal canting of the base of the proximal phalanx as an indicator of human-like metatarsophalangeal joint function and thus a diagnostic trait of habitual bipedality in the fossil record. Here, we used a simple method to investigate differences in forefoot function on a finer scale. Building on Duncan et al.'s (Am J Phys Anthropol 93 [1994] 67-81) research, we tested whether dorsal canting reflects differences between sexes in locomotor behavior, whether habitual shoe wear influences dorsal canting in humans, and whether proximal joint morphology differs between rays in Pan and humans. Our results corroborate previous research in showing that humans have proximal phalanges with joint orientations that are significantly more dorsal than, but overlap with, those of great apes. We also found that male gorillas have significantly more dorsally canted second proximal phalanges than their female counterparts, while the opposite pattern between the sexes was found in Pan troglodytes. Inter-ray comparisons indicate that Pan have more dorsally canted first proximal phalanges than second proximal phalanges, while the opposite pattern was found in humans. Minimally shod humans have slightly but significantly more dorsally canted second proximal phalanges than those of habitually shod humans, indicating that phalanges of unshod humans provide the most appropriate comparative samples for analyses of early hominins. Overall, our analysis suggests that though the measurement of dorsal canting is limited in its sensitivity to certain intraspecific differences in function, phalangeal joint orientation reflects interspecific differences in joint function, with the caveat that different patterns of forefoot function during gait can involve similar articular sets of metatarsophalangeal joints. Am J Phys Anthropol 141:116-123, 2010. [c] 2009 Wiley-Liss, Inc. KEY WORDS Australopithecus afarensis; dorsal canting; hallux; metatarsophalangeal joint DOI 10.1002/ajpa.21121

There is considerable debate over the level of size dimorphism and inferred social behavior of Australopithecus afarensis. Most previous studies have analyzed size variation in single variables or multiple variables drawn from single elements. These approaches suffer from small sample sizes, underscoring the need for new techniques that incorporate measurements from multiple unassociated elements, reducing the influence of random sampling on size variation in fossil samples. One such technique, the template method, has recently been proposed but is limited to samples with a template specimen and is sensitive to a number of assumptions. Here we present two new resampling methods that do not require a template specimen, allow measurements from multiple unassociated elements to be included in a single analysis, and allow for significance tests between comparative and fossil multivariate data sets with missing data. Using these new methods, multivariate postcranial size dimorphism is measured using eight measurements of the femur, tibia, humerus, and radius in samples of A. afarensis, modern humans, chimpanzees, gorillas, and orangutans. Postcranial dimorphism in A. afarensis is similar to that of gorillas and orangutans, and significantly greater than in modern humans and chimpanzees. Because studies in living primates have examined the association of behavior with dimorphism in body mass and craniodental measurements, not postcrania, relationships between postcranial dimorphism and social behavior must be established to make robust behavioral inferences for A. afarensis. However, the results of this and past studies strongly suggest behavioral and mating strategies differed between A. afarensis and modern humans. KEY WORDS resampling methods; geometric mean; hominin evolution; Monte Carlo methods

Some of the most long-standing questions in paleoanthropology concern how and why human bipedalism evolved. Over the last century, many hypotheses have been offered on the mode of locomotion from which bipedalism originated. Candidate ancestral adaptations include monkey-like arboreal or terrestrial quadrupedalism, gibbon- or orangutan-like (or other forms off climbing and suspension, and knuckle-walking. This paper reviews the history of these hypotheses, outlines their predictions, and assesses them in light of current phylogenetic, comparative anatomical, and fossil evidence. The functional significance of characteristics of the shoulder and arm, elbow, wrist, and hand shared by African apes and humans, including their fossil relatives, most strongly supports the knuckle-walking hypothesis, which reconstructs the ancestor as being adapted to knuckle-walking and arboreal climbing. Future fossil discoveries, and a clear understanding of anthropoid locomotor anatomy, are required to ultimately test these hypotheses. If knuckle-walking was an important component of the behavioral repertoire of the prebipedal human ancestor, then we can reject scenarios on the origin of bipedalism that rely on a strictly arboreal ancestor. Moreover, paleoenvironmental data associated with the earliest hominins, and their close relatives, contradict hypotheses that place the agents of selection for bipedality in open savanna habitats. Existing hypotheses must explain why bipedalism would evolve from an ancestor that was already partly terrestrial. Many food acquisition and carrying hypotheses remain tenable in light of current evidence. Yrbk Phys Anthropol 44:70-105, 2001. KEY WORDS human evolution; hominin origins; functional anatomy; locomotor behavior; bipedalism; wrist

Author(s): Brian G. Richmond (corresponding author); David S. Strait Bipedalism has traditionally been regarded as the fundamental adaptation that sets hominids apart from other primates. Fossil evidence demonstrates that by [...]

The first known fossil ape from the early-middle Miocene of Fejej, Ethiopia, is described here. The specimen, FJ-18SB-68, is a partial ulna from a locality dated by 40Ar/39Ar and paleomagnetic methods to a minimum age of 16.18 MYA. Compared to a variety of extant and fossil ulnae, FJ-18SB-68 is most similar to Turkanapithecus, Proconsul, and Pliopithecus, and appears to have been an arboreal quadruped with substantial forearm rotational mobility. Among the extant ulnae, canonical variates analysis successfully discriminates platyrrhines from catarrhines and within the latter, cercopithecoids from hominoids. Basal catarrhines (e.g., Aegyptopithecus) are platyrrhine-like in their morphology. Two basic trends appear to evolve from this generalized template: one with less mobile and more habitually pronated forearms, as seen in living and fossil cercopithecoids (including Victoriapithecus and Paracolobus), and another with greater forearm rotational mobility in fossil and modern hominoids. Primitive Miocene apes, including Proconsul, Turkanapithecus, and FJ-18SB-68, share with extant hominoids a more laterally positioned and laterally facing radial notch and an incipient trochlear keel. This morphology, along with a large insertion area for m. brachialis, suggests a departure from the more habitually pronated hand posture of monkeys and may indicate greater climbing abilities in these arboreally quadrupedal apes. Later Miocene apes, such as Oreopithecus and Dryopithecus share additional morphological features with hominoids, indicating considerable suspensory and climbing capabilities. KEY WORDS fossil apes; anthropoids; postcranium; forelimb; Turkanapithecus; Pliopithecus; multivariate analysis