Nicholas B. Holowka

Form and function of the human and chimpanzee forefoot: implications for early hominin bipedalism

During bipedal walking, modern humans dorsiflex their forefoot at the metatarsophalangeal joints (MTPJs) prior to push off, which tightens the plantar soft tissues to convert the foot into a stiff propulsive lever. Particular features of metatarsal head morphology such as “dorsal doming” are thought to facilitate this stiffening mechanism. In contrast, chimpanzees are believed to possess MTPJ morphology that precludes high dorsiflexion excursions during terrestrial locomotion. The morphological affinity of the metatarsal heads has been used to reconstruct locomotor behavior in fossil hominins, but few studies have provided detailed empirical data to validate the assumed link between morphology and function at the MTPJs. Using three-dimensional kinematic and morphometric analyses, we show that humans push off with greater peak dorsiflexion angles at all MTPJs than do chimpanzees during bipedal and quadrupedal walking, with the greatest disparity occurring at MTPJ 1. Among MTPJs 2–5, both species exhibit decreasing peak angles from medial to lateral. This kinematic pattern is mirrored in the morphometric analyses of metatarsal head shape. Analyses of Australopithecus afarensis metatarsals reveal morphology intermediate between humans and chimpanzees, suggesting that this species used different bipedal push-off kinematics than modern humans, perhaps resulting in a less efficient form of bipedalism.

Anthropology stampede in Calgary.

C anada, home of some of the world’s oldest fossil tetrapods and mammals, was host to the annual meeting of the American Association of Physical Anthropologists (AAPA), which took place April 8–12, 2014. Calgary proved an ideal location to discuss the latest and greatest research in primate and human evolution and behavior. Session topics ranged from evolutionary developmental approaches to the study of human and primate evolution to anthropology of the Maya from the Yucatan, and everything in between.

The gateway to anthropology in st. Louis

T his year, St. Louis, Missouri, was host to the annual meeting of the American Association of Physical Anthropologists (AAPA), which took place March 25–28, 2015. More than 1,000 anthropologists from across the world met near St. Louis’s Gateway Arch, where exciting presentations covered a diverse array of topics, from genetics in Neanderthals to energetics in humans. New research explored physiology and competition in primatology and postcranial adaptations in functional morphology. Highlights also included the presentation of new fossils that promise to influence our current understanding of human evolution.

Eightieth annual meeting of the American Association of Physical Anthropologists

Among this year’s predominating themes were primate energetics and related topics, including causes and consequences of both intergroup and interspecific resource competition (Meg Crofoot, Smithsonian; Alice Elder, Stony Brook), stable isotopes and dietary change (Bryce Carlson, Emory; Scott Blumenthal, NYCEP), and ontogenetic changes in foraging strategies (Teague O’Mara, ASU). Authors discussed human and nonhuman primate foraging patterns using computer-based modeling systems. Scott Suarez (Miami, Ohio) and colleagues tested the hypothesis that repeated-route systems improve foraging efficiency of spider monkeys. Comparing observed foraging strategies with computer-based simulations, Suarez found that observed monkeys outperformed simulated monkeys in all cases (using all foraging strategies), suggesting that while route systems can improve foraging efficiency, ‘‘real’’ monkeys also incorporate spatial and ecological information when foraging along route-based systems. Paul Garber (Illinois) presented similar results for tamarins, which appear to use routebased rather than coordinate-based travel. Tamarins seem to accurately interpret spatial relationships among feeding and sleeping sites within their home ranges. On more than 90% of trials, these monkeys visited sites in more efficient sequences than those that were randomly generated. Using GPS technology, Dave Raichlen (Arizona) and colleagues tracked Hadza hunter-gatherers from central Tanzania, finding that Hadza men and women, much like many marine and terrestrial animals, used levy walks in nearly half of their foraging bouts. Given the Hadza foraging lifestyle, one might expect their daily energy expenditure (DEE) to be relatively higher than that of individuals living more sedentary lives. However, using the doubly labeled water method, Herman Pontzer (Hunter) and colleagues found that DEEs among Hadza hunter-gatherers were similar to those of individuals from industrial and agricultural societies. Thus, they proposed that human energy use may be a physiologically constrained product of human evolutionary history.