Kristen Hawkes

Hadza Women's Time Allocation, Offspring Provisioning, and the Evolution of Long Postmenopausal Life Spans

Extended provisioning of offspring and long postmenopausal life spans are characteristic of all modern humans but no other primates. These traits may have evolved in tandem. Analysis of relationships between womens time allocation and childrens nutritional welfare among the Hadza of northern Tanzania yields results consistent with this proposition. Implications for current thought about the evolution of hominid food sharing, life history, and social organization are discussed.

Showing off: Tests of an hypothesis about men's foraging goals

Abstract It is widely assumed that among hunter-gatherers, men work to provision their families. However, men may have more to gain by giving food to a wide range of companions who treat them favorably in return. If so, and if some resources better serve this end, mens foraging behavior should vary accordingly. Aspects of this hypothesis are tested on observations of food acquisition and sharing among Ache foragers of Eastern Paraguay. Previous analysis showed that different Ache food types were differently shared. Resources shared most widely were game animals. Further analysis and additional data presented here suggest a causal association between the wide sharing of game and the fact that men hunt and women do not. Data show that men preferentially target resources in both hunting and gathering which are more widely shared, resources more likely to be consumed outside their own nuclear families. These results have implications for 1) the identification of male reproductive trade-offs in human societies, 2) the view that families are units of common interest integrated by the sexual division of labor, 3) current reconstructions of the evolution of foraging and food sharing among early hominids, and 4) assessments of the role of risk and reciprocity in hunter-gatherer foraging strategies.

Hadza Hunting, Butchering, and Bone Transport and Their Archaeological Implications

A study of Hadza hunting and scavenging practices, patterns of medium/large mammal carcass dismemberment and transport from kill sites to base camps, and subsequent processing and disposal of bones reveals archaeological bone assemblage formation processes among these hunter-gatherers in northern Tanzania. Body part transport patterns are highly variable, but they probably are understandable in terms of the goal of maximizing net nutritional benefit relative to the costs of field processing and transport. The Hadza data have implications for some widely held views about patterns of bone transport among hunters, for particular reconstructions of past human or hominid behavior based on those views, for the problem of distinguishing hunting versus scavenging as contributors to assemblage composition, and for current thought about the suitability of modern hunters as a source of inference about the prehistoric past.

Why hunter-gatherers work: An ancient version of the problem of public goods.

People who hunt and gather for a living share some resources more widely than others. A favored hypothesis to explain the differential sharing is that giving up portions of large, unpredictable resources obligates others to return shares of them later, reducing everyones variance in consumption. I show that this insurance argument is not empirically supported for !Kung, Ache, and Hadza foragers. An alternative hypothesis is that the cost of not sharing these resources is too high to pay. If exclusion costs are high, then these resources are like public goods. If so, why does anyone provide them? I briefly review treatments of the problem of public goods by economists and use a simple model to show why self-interested actors will rarely find the consumption value they place on collective goods sufficient reason to supply them. The model underlines the obvious corollary that individuals get more to consume if others provide collective goods. This is a reason to prefer neighbors and associates who are suppliers. Such a preference may itself be a benefit worth seeking. I construct another simple model to explore this. Taken together the models suggest wo competing foraging oals: feeding ones family and gaining social benefits instead. This highlights conflicts of economic interest among family members. It is a direct challenge to influential scenarios of human evolution built on the assumption that men are primarily paternal investors who hunt to support their spouses and offspring.

Reanalysis of large mammal body part transport among the Hadza

Abstract Data on 54 cases of large mammal body part transport among the Hadza are reanalysed. Results are consistent with those previously reported. Within species, parts are ranked on a uni-dimensional scale for transport: high ranked parts are more likely to be moved from kill sites to base camps, low ranked parts less likely. For most species in the sample, rank order is inconsistent with that described in the widely cited White/Perkins and Daly model. Archaeological interpretations based on this aspect of the model are therefore suspect. The number of parts moved from Hadza kills varies with transport costs, measured by carcass size and/or kill site-base camp distance. This result fits predictions from the White/Perkins and Daly model. Further application of these results to archaeological problems requires that the Hadza pattern be explained in general terms. The potential relevance of a transport model recently formulated by Metcalfe is noted.

Neotropical hunting among the Ache of eastern Paraguay.

Publisher Summary Hunting has been considered a behavior of importance in the physical and social evolution of humans. Ache hunters are efficient predators. This chapter presents the models derived from the optimal foraging theory to account for the total set of species hunted, using different technologies. The comparison of Ache hunting to other hunter-gatherers shows a wide range of variation. The difference in hunting behavior between the Ache and the !Kung is the difference in the game species. The !Kung hunt large game animals, which single men stalk and shoot with poison arrows. The present study tests the hypotheses concerning the applicability of optimal foraging models to hunter-gatherer subsistence behavior. The Ache demonstrates that in the appropriate ecological setting humans are efficient predators and get good returns hunting with simple technology. The tropical forests of this part of lowland South America are well endowed with game that is easily killed by human hunters.

Female Subsistence Strategies Among Ache Hunter- Gatherers of Eastern Paraguay

Anthropologists have frequently proposed that sexual division of labor is produced by childcare constraints on womens subsistence work. We present data on the forest activities of Ache women that show that differences in parental investment partially account for variation in food acquisition among individual women. Data also suggest that childcare constraints are important in understanding the sexual division of labor.

Foraging decisions among Aché hunter-gatherers: New data and implications for optimal foraging models

This article summarizes 5 years of research on resource choice and foraging strategy among Ache foragers in eastern Paraguay. Successes and failures of simple models from optimal foraging theory (OFT) are discussed and revisions are suggested in order to bring the models in line with empirical evidence from the Ache. The following conclusions emerge: (1) Energetic returns from various alternative resources and foraging strategies is probably the best single predictor of foraging patterns. (2) Nutrient constraints should be added only when they significantly improve the predictive power of the model. Importance of meat versus vegetable resources may be one important modification based on nutrients that enhances the ability of OFT models to account for empirical reality in human foragers. (3) Mens and womens abilities and foraging patterns differ enough that they should be treated separately in all OFT analyses. (4) Opportunity costs associated with resources that are processed when foraging is not possible may be sufficiently low to predict that high processing time resources will be included in the optimal diet even when their associated return rates (including processing) are lower than mean foraging returns. (5) When food sharing is extensive and foraging bands include several adult males and females, foragers may not need to modify foraging strategies in other ways in order to reduce the risk of not eating on some days.

Hunting and nuclear families: some lessons from the Hadza about men's work

Hadza hunter-gatherers display economic and social features usually assumed to indicate the dependence of wives and children on provisioning husbands and fathers. The wives and children of better Hadza hunters have been found to be better-nourished, consistent with the assumption that men hunt to provision their families. Yet, as is common among foragers, the Hadza share meat widely. Analyses of meat-sharing data confirm that little of the meat from large prey went to the hunters own household. These analyses also show that neither a mans hunting success nor the time he spent hunting made any difference in how much meat his family got from the kills of others. Here we address questions posed by this set of observations. What explains the better nutrition of the children of better hunters if they did not get differential rations of meat? If better hunters got no more meat for their effort and poorer hunters were not punished with less, what incentive could account for the continuing disproportionate contribution that some men made to the groups nutrition? If women were not dependent on their husbands hunting success for meat, an obvious incentive for women to marry hunters disappears. We briefly consider the implications of these patterns for the evolution of marriage and nuclear families.

Seasonal Variance in the Diet of Ache Hunter-Gatherers in Eastern Paraguay

Seasonal variance in the diet of Ache hunter-gatherers is examined. Fluctuation in the number of calories of honey consumed daily contributed most to the differences in total calories consumed daily during different seasons of the year. Meat, the most important resource in the diet, provided the greatest number of calories daily, and varied little across seasons. The vegetable component of the diet is characterized by low variance in absolute numbers of calories, but high variance in species composition. The mean number of calories consumed daily per capita is high (3827 calories) compared to that reported for other hunter-gathers. Differences in energy expenditure and consumption among modern hunter-gatherers is discussed.