Search

Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage.sup.1-3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity.sup.3-5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of footprints at site A are readily distinguished from those at site G, indicating that a minimum of two hominin taxa with different feet and gaits coexisted at Laetoli. Reanalysis of bipedal trackways from Laetoli site A in Tanzania suggest that the footprints were made by a hominin that coexisted with at least one other hominin species., Author(s): Ellison J. McNutt [sup.1] [sup.2] , Kevin G. Hatala [sup.3] , Catherine Miller [sup.4] [sup.5] , James Adams [sup.6] [sup.7] , Jesse Casana [sup.4] [sup.5] , Andrew S. Deane [...]

The 'negrito' and African 'pygmy' phenotypes are predominately exhibited by hunter-gatherers living in rainforest habitats. Foraging within such habitats is associated with a unique set of locomotor behaviors, most notably habitual vertical climbing during the pursuit of honey, fruit, and game. When performed frequently, this behavior is expected to correlate with developmentally plastic skeletal morphologies that respond to mechanical loading. Using six measurements in the distal tibia and talus that discriminate nonhuman primates by vertical climbing frequency, we tested the prediction that intraspecific variation in this behavior is reflected in the morphology of the ankle joint of habitually climbing human populations. First, to explore the plasticity of climbing-linked morphologies, we made comparisons between chimpanzees, gorillas, and orangutans from wild and captive settings. The analysis revealed significant differences in two climbing-linked traits (anterior expansion of the articular surface of the distal tibia and increased degree of talar wedging), indicating that these traits are sensitive to climbing behavior. However, our analyses did not reveal any signatures of climbing behavior in the ankles of habitually climbing hunter-gatherers. These results suggest that the detection of fine-grained differences in human locomotor behaviors at the ankle joint, particularly those associated with arboreality, may be obscured by the functional demands of terrestrial bipedalism. Accordingly, it may be difficult to use population-level characteristics of ankle morphology to make inferences about the climbing behavior of hominins in the fossil record, even when facultative arborealism is associated with key fitness benefits. KEY WORDS: NEGRITO, PYGMY, VERTICAL CLIMBING, ANKLE, FUNCTIONAL MORPHOLOGY., Anthropologists of the early twentieth century debated whether the African 'pygmy' and Asian 'negrito' phenotypes were the result of recent shared ancestry or convergent evolution. Recently, this pygmdenproblem (Schmidt 1910) [...]

Early growth cessation and reproduction are predicted to maximize fitness under conditions of high adult mortality, factors that could explain the pygmy phenotype of many rainforest hunter-gatherers. This life-history hypothesis is elegant but contentious in part because it lacks a clear biological mechanism. One mechanism stems from the field of human immunological ecology and the concept of inflammation 'memory' across the life cycle and into subsequent generations. Maternal exposures to disease can influence immunological cues present in breast milk; because maternal provisioning via lactation occurs during critical periods of development, it is plausible that these cues can also mediate early growth cessation and small body size. Such epigenetic hypotheses are difficult to test, but the concept of developmental programming is attractive because it could explain how the stature of a population can change over time, in terms of both secular increases and rapid intergenerational decreases. Here we explore this concept by focusing on the Aeta, a population of former hunter-gatherers, and the Ilocano, a population of rice farmers. We predicted that Aeta mothers would produce breast milk with higher concentrations of four bioactive factors due to high infectious burdens. Further, we predicted that the concentrations of these factors would be highest in the cohort of women born in the early 1990s, when exposure to infectious disease was acute following the eruption of Mount Pinatubo in June 1991. We analyzed levels of adiponectin, C-reactive protein, and epidermal growth factor in the milk of 24 Aeta and 31 Ilocano women and found no detectable differences, whereas levels of transforming growth factor-[β.sub.2] were elevated among the Aeta, particularly as a function of maternal age. We found no difference between cohorts divided by the volcanic eruption (n = 43 born before, n = 12 born after). We discuss the implications of our findings for the terminal investment hypothesis and we suggest that the historical ecology of the Aeta is a promising model system for testing epigenetic hypotheses focused on the evolution of small body size. KEY WORDS: AETA, ADIPONECTIN, C-REACTIVE PROTEIN, EPIDERMAL GROWTH FACTOR, NEGRITO, PHENOTYPIC PLASTICITY, PHILIPPINES, TRANSFORMING GROWTH FACTOR BETA., Tropical rainforests can be challenging environments for hunter-gatherers; parasitic and infectious disease species abound at low latitudes (Guernier et al. 2004), and the risk of predation is high for some [...]

Periodic episodes of food scarcity may highlight the adaptive value of certain anatomical traits, particularly those that facilitate the acquisition and digestion of exigent fallback foods. To better understand the selective pressures that favored the distinctive dental and locomotor morphologies of gibbons and orangutans, we examined the foraging and ranging behavior of sympatric Hylobates albibarbis and Pongo pygmaeus wurmbii during an episode of low fruit availability at Tuanan, Kalimantan Tengah, Indonesia. We found that Hylobates ranged 0.5 km [day.sup.-1] or 33% farther than did Pongo, but the overall daily ranging of both species did not vary as fruit availability decreased by as much as 50%. Among gibbons, we observed dietary switching to fallback foods; in particular, there was a progressively greater reliance on figs, liana products, and unripe fruit. Orangutans relied heavily on unripe fruit and fracture-resistant bark and pith tissues. Despite these divergent fallback patterns, the stiffness of fruit mesocarp consumed by Hylobates and Pongo did not differ. We discuss canine and molar functional morphology with respect to dietary mechanics. Next, to contextualize these results, we discuss our findings with respect to forest structure. The rain forests of Southeast Asia have been described as having open, discontinuous canopies. Such a structure may inform our understanding of the ranging behavior and distinctive locomotion of apes in the region, namely richochetal brachiation and quadrumanous clambering. Our approach of integrating behavioral ecology with physical measures of food may be a powerful tool for understanding the functional adaptations of primates. Am J Phys Anthropol 140:716-726, 2009. KEY WORDS primate diet; food mechanics; dental morphology; forest structure; locomotion DOI 10.1002/ajpa.21119

Cooperation is the cornerstone of lion social behavior. In a notorious case, a coalition of two adult male lions from Tsavo, southern Kenya, cooperatively killed dozens of railway workers in 1898. The 'man-eaters of Tsavo' have since become the subject of numerous popular accounts, including three Hollywood films. Yet the full extent of the lions' man-eating behavior is unknown; estimates range widely from 28 to 135 victims. Here we use stable isotope ratios to quantify increasing dietary specialization on novel prey during a time of food limitation. For one lion, the [[delta].sup.3]C and [[delta].sup.15]N values of bone collagen and hair keratin (which reflect dietary inputs over years and months, respectively) reveal isotopic changes that are consistent with a progressive dietary specialization on humans. These findings not only support the hypothesis that prey scarcity drives individual dietary specialization, but also demonstrate that sustained dietary individuality can exist within a cooperative framework. The intensity of human predation (up to 30% reliance during the final months of 1898) is also associated with severe craniodental infirmities, which may have further promoted the inclusion of unconventional prey under perturbed environmental conditions. individual dietary specialization | Panthera leo | Taita | Tsavo www.pnas.org/cgi/doi/10.1073/pnas.0905309106

Survival and reproductive success hinge on the perception of environmental stimuli. In this regard, foraging efficiency depends on discerning predictive signals in food. A widespread occurrence of ethanol in fruits indicates a sustained historical exposure of frugivores to this compound. Accordingly, Dudley (2000, Quart. Rev. Biol. 75:3-15) proposed that ethanol could represent a prominent sensory cue to primates because of direct and indirectly associated caloric and physiological rewards. However, little is known regarding the extent to which ethanol correlates with such parameters. This information is essential to estimating the importance of detecting and detoxifying ethanol in fruits. Here I present a preliminary analysis of fruits from Southeast Asia; low levels of ethanol were present in fruits of all developmental stages (range: 0.005-0.48%). Moreover, ethanol correlated positively with concentrations of soluble sugars, suggesting that it could be a valuable foraging cue. Recent findings on the sensitivity of primate olfaction and gustation to ethanol are consistent with this notion. However, when primates smell fruits deliberately, it often occurs together with digital and/or dental evaluation of texture. Here I show that softening texture also characterizes the fruit ripening process, and that color is of ambiguous importance to primates possessing trichromatic vision. I discuss the relevance of these findings to the origins of primates and the ecology of key sensory systems and deduce that detecting and selecting fruits on the basis of cues other than color is a persistent theme in primate evolution. Ethanol has likely played a significant and underestimated role in the regulation of primate foraging behavior.

Author(s): Nathaniel J. Dominy (corresponding author); Peter W. Lucas Trichromatic colour vision, characterized by three retinal photopigments tuned to peak wavelengths of [similar]430 nm, [similar]535 nm and [similar]562 nm (refs [...]

The correlation among visual ecology and the physiochemical properties of fruits and leaves, consumed by four species of catarrhine primate, is described.

The trichomatic vision in female tamarins does not confer an advantage for detecting yellow fruit rewards against mature foliage. The hypothesis of trichomatic pltyrrhines that use visual cues to detect fruit rewards more successfully than males do is tested and the study reveals that females and male do not defer in ability to locate or discriminate between feeding sites.

Evolution of the red-green visual subsystem in trichromatic primates is linked to foraging advantages, namely the detection of either ripe fruits or young leaves amid mature foliage. Competing hypotheses was tested globally for eight primate taxa: five with routine trichromatic vision and three without it.

Young leaves on many rain forest trees are red possibly due to invertebrate herbivores lacking a red vision receptor. Herbivore density generally relates to the quantity of edible foliage, in turn suggesting crypsis, or lack of visibility to herbivores, is the most probable reason for red leaf incidence.