American Journal of Physical Anthropology

doi: 10.1002/ajpa.22679pmid: 25449341

Schniter, Eric; Gurven, Michael; Kaplan, Hillard S.; Wilcox, Nathaniel T.; Hooper, Paul L.

doi: 10.1002/ajpa.22757pmid: 25921880

ABSTRACT Objectives We investigate whether age profiles of Tsimane forager‐horticulturalists' reported skill development are consistent with predictions derived from life history theory about the timing of productivity and reproduction. Previous studies of forager skill development have often focused on a few abilities (e.g. hunting), and neglected the broad range of skills and services typical of forager economies (e.g. childcare, craft production, music performance, story‐telling). Materials and Methods By systematically examining age patterns in reported acquisition, proficiency, and expertise across a broad range of activities including food production, childcare, and other services, we provide the most complete skill development study of a traditional subsistence society to date. Results Our results show that: (1) most essential skills are acquired prior to first reproduction, then developed further so that their productive returns meet the increasing demands of dependent offspring during adulthood; (2) as postreproductive adults age beyond earlier years of peak performance, they report developing additional conceptual and procedural proficiency, and despite greater physical frailty than younger adults, are consensually regarded as the most expert (especially in music and storytelling), consistent with their roles as providers and educators. We find that adults have accurate understandings of their skillsets and skill levels –an important awareness for social exchange, comparison, learning, and pedagogy. Discussion These findings extend our understanding of the evolved human life history by illustrating how changes in embodied capital and the needs of dependent offspring predict the development of complementary skills and services in a forager‐horticulturalist economy. Am J Phys Anthropol 158:3–18, 2015. © 2015 Wiley Periodicals, Inc.

Alvarado, Louis Calistro; Muller, Martin N.; Emery Thompson, Melissa; Klimek, Magdalena; Nenko, Ilona; Jasienska, Grazyna

doi: 10.1002/ajpa.22771pmid: 26123405

Objectives Testosterone supports male reproduction through a broad range of behavioral and physiological effects, including the maintenance of sexually dimorphic muscle used in male‐male competition. Although it is often assumed that a persistent relationship exists between men's testosterone production and musculature, most studies either fail to find evidence for such a relationship, or document very weak associations. In nonhuman primates, by contrast, correlations between testosterone and muscle mass are higher. Here, we propose the “Paternal Provisioning Hypothesis,” which predicts that men's skeletal muscle is less dependent on the effects of androgens than that of other primates, and more sensitive to the physical demands of men's work. This permits human fathers to downregulate testosterone, which has negative impacts on pair‐bonding and parenting effort, but without sacrificing the strength and musculature necessary to provision mates and offspring. Methods We tested predictions of the Paternal Provisioning Hypothesis by assessing parental status, salivary testosterone levels, anthropometry, and strength among 122 men (ages 18–78) at the Mogielica Human Ecology Study Site in rural Poland. We chose this population because men practice subsistence agriculture, regularly engaging in physically demanding labor. Grip and chest strength were assessed using a dynamometer, and upper‐body musculature was estimated from arm muscle circumference. Results In this population, testosterone showed no association with measures of strength or musculature, and was lower in older men and pair‐bonded fathers. Marital and parental status and workload, by contrast, were positive predictors of muscle mass and strength measures. Discussion These findings offer support for the Paternal Provisioning Hypothesis. Am J Phys Anthropol 158:19–35, 2015. © 2015 Wiley Periodicals, Inc.

Hlusko, Leslea J.; Reiner, Whitney B.; Njau, Jackson K.

doi: 10.1002/ajpa.22765pmid: 26058378

ABSTRACT Objective Our aim was to recover new evidence of the evolution of the hominid lineage. Methods We undertook paleontological fieldwork at Olduvai Gorge, Tanzania, in one of the richest paleoanthropological sites in the world, documenting the evolution of our lineage and its environmental contexts over the last 2 million years. Results During field work in 2012, the Olduvai Vertebrate Paleontology Project discovered the distal end of a hominid ulna (OH 82) on the north side of Olduvai Gorge a few meters west of the Third Fault, eroding from Bed III sediments that are ∼1 million years in age. Discussion The size and morphology of this distal ulna falls within the normal range of variation seen in humans, although at the larger end of the distribution. Am J Phys Anthropol 158:36–42, 2015. © 2015 Wiley Periodicals, Inc.

Samuels, Joshua X.; Albright, L. Barry; Fremd, Theodore J.

doi: 10.1002/ajpa.22769pmid: 26118778

ABSTRACT Objective Primates were common in North America through most of the Eocene, but vanished in the Chadronian, about 35 million years ago. In the Arikareean, about 6 million years later, the enigmatic primate Ekgmowechashala appeared in the Great Plains and Oregon. This taxon shows little resemblance to other North American primates and its phylogenetic position has long been debated. New material of this taxon allows a revised assessment of its age and how it is related to other primates. Methods Recently collected Ekgmowechashala specimens from the Turtle Cove Member of the John Day Formation in Oregon are described. These specimens are compared to previously collected material from South Dakota and Nebraska, as well as other fossil primates from North America and Asia. Results Study of the John Day material allows diagnosis of a new, distinct species. Comparison of Ekgmowechashala to a pair of recently described Asian primates, Muangthanhinius and Bugtilemur, suggests that it is a strepsirrhine adapiform, rather than an omomyid. The well‐defined stratigraphy and dated marker beds of the Turtle Cove Member provide a refined age for Ekgmowechashala occurrences in Oregon, during the Oligocene (early Arikareean). Conclusions The age and morphology of these ekgmowechashaline taxa suggest that the group originated in Asia and dispersed to North America in the Oligocene, after the extinction of other primates in North America. Contemporaneous occurrences of Ekgmowechashala in Oregon and the Great Plains indicate the last non‐human primates vanished in North America about 26 million years ago. Am J Phys Anthropol 158:43–54, 2015. © 2015 Wiley Periodicals, Inc.

Foerster, Steffen; Kithome, Kiio; Cords, Marina; Monfort, Steven L.

doi: 10.1002/ajpa.22764pmid: 26060035

Objective: When resource competition within primate social groups is effective, high‐ranking individuals generally gain fitness benefits. Contrary to expectations, female Cercopithecus mitis form linear dominance hierarchies without evidence for rank‐related variation in fitness‐relevant measures, raising questions about the evolution of guenon social structure. Here, we test whether social status predicts gastrointestinal helminth infections, known to influence health and morbidity in other mammalian hosts. In addition, we assess whether infections contribute to stress responses as indicated by fecal glucocorticoid (fGC) levels. Methods: We quantified infections and hormone levels in 382 fecal samples from 11 adult female Sykes' monkeys (C. m. albogularis) over four months in one wild study group at Gede Ruins, Kenya. Using a generalized estimating equations technique, we modeled the odds of infection, relative infection intensity, and fGC variation. Results: High‐ranking females were less likely infected with Trichuris and Trichostrongylus, had lower fecal egg counts for both taxa, and overall lower helminth richness than low‐ranking females. An inverse relationship between rank and Trichuris egg counts existed also in a study population of blue monkeys (C. m. stuhlmanni), where we collected comparable data over a shorter period. Regardless of rank, lactating females were more likely than non‐lactating females to be infected with Trichuris, and had higher fecal egg counts for both Trichuris and Oesophagostomum. Lastly, we report evidence that Trichuris infections exacerbated energetic stress and that food supplementation by tourists increased infection levels. Conclusion: Our findings suggest that high‐rank may provide long‐term health and energetic benefits for female C. mitis, with potential fitness implications. Am J Phys Anthropol 158:55–66, 2015. © 2015 Wiley Periodicals, Inc.

Mosdossy, Krisztina N.; Melin, Amanda D.; Fedigan, Linda M.

doi: 10.1002/ajpa.22767pmid: 26010158

ABSTRACT Objectives: Fallback foods (FBFs) are hypothesized to shape the ecology, morphology, and behavior of primates, including hominins. Identifying FBFs is therefore critical for revealing past and present foraging adaptations. Recent research suggests invertebrates act as seasonal FBFs for many primate species and human populations. Yet, studies measuring the consumption of invertebrates relative to ecological variation are widely lacking. We address this gap by examining food abundance and entomophagy by primates in a seasonal forest. Materials and Methods: We study foraging behavior of white‐faced capuchins (Cebus capucinus)—a species renowned for its intelligence and propensity for extractive foraging—along with the abundance of invertebrates, dietary ripe fruits, pith, and bromeliads. Consumption events and processing time are recorded during focal animal samples. We determine abundance of vegetative foods through phenological and density records. Invertebrates are collected in malaise, pan, and terrestrial traps; caterpillar abundance is inferred from frass traps. Results: Invertebrates are abundant throughout the year and capuchins consume invertebrates—including caterpillars—frequently when fruit is abundant. However, capuchins spend significantly more time processing protected invertebrates when fruit and caterpillars are low in abundance. Discussion: Invertebrate foraging patterns are not uniform. Caterpillar consumption is consistent with a preferred strategy, whereas capuchins appear to fallback on invertebrates requiring high handling time. Capuchins are convergent with hominins in possessing large brains and high levels of sensorimotor intelligence, thus our research has broad implications for primate evolution, including factors shaping cognitive innovations, brain size, and the role of entomophagy in the human diet. Am J Phys Anthropol 158:67–77, 2015. © 2015 Wiley Periodicals, Inc.

Roffman, Itai; Savage‐Rumbaugh, Sue; Rubert‐Pugh, Elizabeth; Stadler, André; Ronen, Avraham; Nevo, Eviatar

doi: 10.1002/ajpa.22778pmid: 26119360

Objectives The tool‐assisted extractive foraging capabilities of captive (zoo) and semi‐captive (sanctuary) bonobo (Pan paniscus) groups were compared to each other and to those known in wild chimpanzee (Pan troglodytes) cultures. Materials and Methods The bonobos were provided with natural raw materials and challenged with tasks not previously encountered, in experimental settings simulating natural contexts where resources requiring special retrieval efforts were hidden. They were shown that food was buried underground or inserted into long bone cavities, and left to tackle the tasks without further intervention. Results The bonobos used modified branches and unmodified antlers or stones to dig under rocks and in the ground or to break bones to retrieve the food. Antlers, short sticks, long sticks, and rocks were effectively used as mattocks, daggers, levers, and shovels, respectively. One bonobo successively struck a long bone with an angular hammer stone, completely bisecting it longitudinally. Another bonobo modified long branches into spears and used them as attack weapons and barriers. Bonobos in the sanctuary, unlike those in the zoo, used tool sets to perform sequential actions. Discussion The competent and diverse tool‐assisted extractive foraging by the bonobos corroborates and complements the extensive information on similar tool use by chimpanzees, suggesting that such competence is a shared trait. Better performance by the sanctuary bonobos than the zoo group was probably due to differences in their cultural exposure and housing conditions. The bonobos' foraging techniques resembled some of those attributed to Oldowan hominins, implying that they can serve as referential models. Am J Phys Anthropol 158:78–91, 2015. © 2015 Wiley Periodicals, Inc.

Perry, Jonathan M.G.; Bastian, Meredith L.; St Clair, Elizabeth; Hartstone‐Rose, Adam

doi: 10.1002/ajpa.22779pmid: 26119490

ABSTRACT Objectives Maximum ingested food size (Vb) is an empirically tested performance variable that can shed light on feeding energetics and adaptation in the masticatory system. Until now, this variable had been tested in strepsirrhines alone among primates. Here, we present the first data on Vb in a broad sample of anthropoid primates and describe scaling patterns. Materials and Methods Vb data on anthropoids were collected under captive conditions at the Philadelphia Zoo and compared with published data on strepsirrhines. Data on Vb were scaled against individual body mass and were compared with experimentally determined toughness and stiffness values for the test foods. Results Unlike in strepsirrhines, where essentially Vb scales isometrically with body mass, Vb in anthropoids scales with negative allometry. There is a significant effect of food material properties on Vb, although bite size in anthropoids varies less based on food properties than in strepsirrhines. Large folivorous strepsirrhines follow the anthropoid trend in bite size scaling, but large frugivorous ones take especially large bites. Discussion Negative scaling of bite size in the anthropoids sampled could be due to reduced adaptation for gape. Some early anthropoids likely evolved adaptations for maximizing mechanical advantage and fatigue resistance in the chewing muscles, resulting in reduced gape. This might have channeled them toward smaller bites of more‐resistant foods and away from taking large bites. This might also be the case for some folivorous strepsirrhines. Am J Phys Anthropol 158:92–104, 2015. © 2015 Wiley Periodicals, Inc.

Tessone, Augusto; García Guraieb, Solana; Goñi, Rafael A; Panarello, Héctor O

doi: 10.1002/ajpa.22768pmid: 26010245

ABSTRAC Objectives: The timing and duration of breastfeeding and weaning in past hunter‐gatherer populations are discussed based on the results of stable carbon and nitrogen isotope analyses undertaken on a Late Holocene skeletal sample from Lake Salitroso in the Patagonian steppe (Argentina). Research in Lake Salitroso is part of a regional project that studies the relationship between hunter‐gatherer societies, their organizational systems and the environmental changes during the last 3,000 years in Patagonia. Methods: The sample included 52 individuals: 33 subadults and 19 adults of both sexes. They were recovered from 24 burial stone structures, locally called chenques, with dates ranging from ca. 800 BP to 350 BP. Ribs were selected for collagen extraction and measurement of 13C/12C and 15N/14N ratios. Results: A δ13C mean value of −18.7‰ ± 0.5‰ was obtained, with a range between −19.8‰ and −17.1‰ whereas δ15N recorded a mean of 11.9‰ ± 1.1‰ with a range between 10.1‰ and 14.8‰. δ15N data showed an age‐related pattern with particularly marked difference between values for subadults under the age of 4 and older individuals. As opposed to δ15N, δ13C showed little variation with age. Conclusions: An early incorporation of supplementary solid food between 0.75 and 2 years of age and a late cessation of breastfeeding at about 5–6 years of age were inferred. This suggests that among this Patagonian hunter–gatherer population weaning was a gradual and lengthy process. These results are consistent with the patterns observed in cross‐cultural studies and archaeological samples of hunter–gatherer groups. Am J Phys Anthropol 158:105–115, 2015. © 2015 Wiley Periodicals, Inc.