Robert S. Walker

Learn More
Extant apes experience early sexual maturity and short life spans relative to modern humans. Both of these traits and others are linked by life-history theory to mortality rates experienced at different ages by our hominin ancestors. However, currently there is a great deal of debate concerning hominin mortality profiles at different periods of evolutionary(More)
This study investigates the consequences of the human foraging niche and multiple dependent offspring on the optimal growth trajectory of humans. We test the hypothesis that the human pattern of slow human growth between age at weaning and puberty helps defer the compound energetic demand on parents with multiple dependents, by using growth and demographic(More)
In nature, many different types of complex system form hierarchical, self-similar or fractal-like structures that have evolved to maximize internal efficiency. In this paper, we ask whether hunter-gatherer societies show similar structural properties. We use fractal network theory to analyse the statistical structure of 1189 social groups in 339(More)
This study investigates variation in body growth (cross-sectional height and weight velocity) among a sample of 22 small-scale societies. Considerable variation in growth exists among hunter-gatherers that overlaps heavily with growth trajectories present in groups focusing more on horticulture. Intergroup variation tends to track environmental conditions,(More)
This paper assesses selective pressures that shaped primate life histories, with particular attention to the evolution of longer juvenile periods and increased brain sizes. We evaluate the effects of social complexity (as indexed by group size) and foraging complexity (as indexed by percent fruit and seeds in the diet) on the length of the juvenile period,(More)
This paper examines changes in hunting ability across the lifespan for the Ache of eastern Paraguay. Hunting ability is decomposed into two components-finding prey and probability of kill upon encounter- and analyzed for important prey species. Results support the argument that skill acquisition is an important aspect of the human foraging niche with(More)
Previous attempts to explain variation in human growth and development emphasize the energetic constraints imposed by malnutrition and disease. However, this approach does not address the evolutionary effects of mortality risk on ontogenetic variation, a common theme in life-history studies. The conventional approach can be reconciled with life-history(More)
Use of space by both humans and other mammals should reflect underlying physiological, ecological, and behavioral processes. In particular, the space used by an individual for its normal activities should reflect the interplay of three constraints: (i) metabolic resource demand, (ii) environmental resource supply, and (iii) social behaviors that determine(More)
The biogeographic expansion of modern humans out of Africa began approximately 50,000 years ago. This expansion resulted in the colonization of most of the land area and habitats throughout the globe and in the replacement of preexisting hominid species. However, such rapid population growth and geographic spread is somewhat unexpected for a large primate(More)