Russell Greaves

Sex differences in range size and navigation are widely reported, with males traveling farther than females, being less spatially anxious, and in many studies navigating more effectively. One explanation holds that these differences are the result of sexual selection, with larger ranges conferring mating benefits on males, while another explanation focuses on greater parenting costs that large ranges impose on reproductive-aged females. We evaluated these arguments with data from a community of highly monogamous Maya farmers. Maya men and women do not differ in distance traveled over the region during the mate-seeking years, suggesting that mating competition does not affect range size in this monog-amous population. However, men's regional and daily travel increases after marriage , apparently in pursuit of resources that benefit families, whereas women reduce their daily travel after marriage. This suggests that parental effort is more important than mating effort in this population. Despite the relatively modest overall sex difference in mobility, Maya men were less spatially anxious than women, thought themselves to be better navigators, and pointed more accurately to distant locations. A structural equation model showed that the sex by marital status interaction had a direct effect on mobility, with a weaker indirect effect of sex on mobility mediated by navigational ability.

Much of our success as a species derives from the ability to adapt hunting and gathering to diverse ecologies and incorporate a wide range of food resources. Hunteregatherers maintain broad dietary options through an array of alternative and fallback strategies. While many decisions facing foragers have been analyzed, few paired nutritional and return rate data are available, especially in relation to the value of wild roots. Ethnoarchaeological data from a group of South American hunteregatherers allow us to comparatively assess the value of root resources by observing what mobile foragers do when presented with the option to retain or replace wild foods with domesticates. Nutritional content and foraging returns indicate that cultivated tubers provide no clear nutritional or labor advantages. Evidence also does not suggest that wild roots are inferior resources. This may explain why some foragers incorporate domesticates without replacing dependence on wild foods, or signaling a transition to an agrarian economy. This perspective has archaeological implications for modeling of past subsistence during initial and early exploitation of cultigens.

The thymus plays an important role in the development of the immune system, yet little is known about the patterns and sources of variation in postnatal thymic development. The aim of this study is to contribute cross-cultural data on thymus size in infants from two South American native populations, the Tsimane of Bolivia and the Pumé of Venezuela. Thymic ultrasonography was performed and standard anthropometric measures collected from 86 Tsimane and Pumé infants. Patterns of infant growth and thymus size were compared between the two populations and the relationship between nutritional status and thymus size was assessed. Despite nearly identical anthropometric trajectories, Tsimane infants had larger thymuses than Pumé infants at all ages. Population, infant age, and infant mid-upper arm circumference were significant predictors of thymus area in the Tsimane and Pumé infants. This finding reveals a cross-cultural difference in thymus size that is not driven by nutritional status. We suggest that future studies focus on isolating prenatal and postnatal environmental factors underlying cross-cultural variation in thymic development.

... Young women also appear to participate in fewer long‐distance dry‐season foraging trips (Hilton and Greaves 2004 ... of weaned offspring and other dependents is positively and strongly correlated with greater work effort by mothers (Hurtado, Hawkes, and Kaplan 1985; Hurtado ...

Much of our success as a species derives from the ability to adapt hunting and gathering to diverse ecologies and incorporate a wide range of food resources. Throughout their history foragers have been making strategic decisions about whether to incorporate new resources and technologies. This appears to be both the strength and resilience of hunter-gatherer lifeways. Despite recognition that hunting and gathering includes broad-spectrum subsistence options, an assumption is commonly made that the incorporation of domesticates leads to a directional shift toward greater reliance on food production. In this chapter we consider instead how the adoption of some horticultural practices supports the continued viability of, and primary reliance on, hunting and gathering. Although the Pumé live in close proximity to and interact with their horticultural relatives, they have not assimilated into their communities or become sedentary and increasingly reliant on horticulture. We explore how a combination of both economic and social factors are critical to their retention of a mobile foraging way of life and helps to explain why hunting and gathering remains a viable, and even desirable subsistence choice in the twenty-fi rst century.

Enhancing our understanding of the skeletal biology of modern hunter-gatherers and developing more sophisticated models of fossil and prehistoric hominin locomotor behavior and subsistence activities requires information on male and female forager mobility patterns. Unlike other primates, modern human foragers expend considerable energy in activities involving the transport of resources across the landscape. Although male foragers are often associated with high mobility in comparison to their female counterparts, female foragers are seen to engage in subsistence tasks incorporating a high frequency of burden carrying. This paper examines the influence of age and sex on mobility and resource transport in a group of Pumé foragers located in the savanna-wetlands of southwestern Venezuela.