Rebecca Bliege Bird

Turtle hunting and tombstone opening. public generosity as costly signaling.

Costly signaling theory (CST) offers an explanation of generosity and collective action that contrasts sharply with explanations based on conditional reciprocity. This makes it particularly relevant to situations involving widespread unconditional provisioning of collective goods. We provide a preliminary application of CST to ethnographic data on turtle hunting and public feasting among the Meriam of Torres Strait, Australia. Turtle hunting appears to meet the key conditions specified in CST: it is (1) an honest signal of underlying abilities such as strength, risk-taking, skill, and leadership; (2) costly in ways not subject to reciprocation; (3) an effective means of broadcasting signals, since the collective good (a feast) attracts a large audience; and (4) seems to provide benefits to signalers (turtle hunters) as well as recipients (audience). We conclude with some suggestions as to the broader implications of this research, and the costly signaling paradigm in general, for understanding collective action and generosity in human social groups.

The hunting handicap: costly signaling in human foraging strategies

Abstract. Humans sometimes forage or distribute the products of foraging in ways that do not maximize individual energetic return rates. As an alternative to hypotheses that rely on reciprocal altruism to counter the costs of inefficiency, we suggest that the cost itself could be recouped through signal benefit. Costly signaling theory predicts that signals can provide fitness benefits when costs are honestly linked to signaler quality, and this information is broadcast to potential mates and competitors. Here, we test some predictions of costly signaling theory against empirical data on human food acquisition and sharing patterns. We show that at least two types of marine foraging, turtle hunting and spearfishing, as practiced among the Meriam (a Melanesian people of Torres Strait, Australia) meet key criteria for costly signaling: signal traits are (1) differentially costly or beneficial in ways that are (2) honestly linked to signaler quality, and (3) designed to effectively broadcast the signal. We conclude that relatively inefficient hunting or sharing choices may be maintained in a population if they serve as costly and reliable signals designed to reveal the signalers qualities to observers.

Cooperation and conflict: The behavioral ecology of the sexual division of labor

When it comes to subsistence, men and women in almost all societies do it differently. One long‐standing explanation for this sexual division of labor is that men and women pair up to provision offspring and specialize in subsistence activities in order to maximize household productivity. This model of cooperative parental provisioning has generally been supported by the proposal that both male and female reproductive success is maximized by provisioning current offspring rather than deserting them in order to seek new mating opportunities. But recent analyses of bird behavior have often failed to support this premise. We now know that among many species conflicting reproductive strategies between males and females often result in less than optimal compromises with regard to mating and parenting. This new focus on the role of sexual selection in creating compromise and conflict between the sexes has the potential to illuminate many puzzling aspects of human partnerships between men and women. To demonstrate its potential, I compare the explanatory power of a cooperative provisioning model of sex difference in human foraging and food sharing with a model incorporating conflicting reproductive goals.

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.

IN PURSUIT OF MOBILE PREY : MARTU HUNTING STRATEGIES AND ARCHAEOFAUNAL INTERPRETATION

By integrating foraging models developed in behavioral ecology with measures of variability in faunal remains, zooarchaeological studies have made important contributions toward understanding prehistoric resource use and the dynamic interactions between humans and their prey. However, where archaeological studies are unable to quantify the costs and benefits associated with prey acquisition, they often rely on proxy measures such as prey body size, assuming it to be positively correlated with return rate. To examine this hypothesis, we analyze the results of 1,347 adult foraging bouts and 649 focal follows of contemporary Martu foragers in Australias Western Desert. The data show that prey mobility is highly correlated with prey body size and is inversely related to pursuit success—meaning that prey body size is often an inappropriate proxy measure of prey rank. This has broad implications for future studies that rely on taxonomic measures of prey abundance to examine prehistoric human ecology, including but not limited to economic intensification, socioeconomic complexity, resource sustainability, and overexploitation.

Constraints of knowing or constraints of growing

Recent theoretical models suggest that the difference between human and nonhuman primate life-history patterns may be due to a reliance on complex foraging strategies requiring extensive learning. These models predict that children should reach adult levels of efficiency faster when foraging is cognitively simple. We test this prediction with data on Meriam fishing, spearfishing, and shellfishing efficiency. For fishing and spearfishing, which are cognitively difficult, we can find no significant amount of variability in return rates because of experiential factors correlated with age. However, for shellfish collecting, which is relatively easy to learn, there are strong age-related effects on efficiency. Children reach adult efficiency more quickly in fishing as compared to shellfish collecting, probably owing to the size and strength constraints of the latter.

Why Women Hunt Risk and Contemporary Foraging in a Western Desert Aboriginal Community

An old anthropological theory ascribes gender differences in hunter‐gatherer subsistence to an economy of scale in household economic production: women pursue child‐care‐compatible tasks and men, of necessity, provision wives and offspring with hunted meat. This theory explains little about the division of labor among the Australian Martu, where women hunt extensively and gendered asymmetry in foraging decisions is linked to men’s and women’s different social strategies. Women hunt primarily small, predictable game (lizards) to provision small kin networks, to feed children, and to maintain their cooperative relationships with other women. They trade off large harvests against greater certainty. Men hunt as a political strategy, using a form of “competitive magnanimity” to rise in the ritual hierarchy and demonstrate their capacity to keep sacred knowledge. Resources that can provision the most people with the most meat best fit this strategy, resulting in an emphasis on kangaroo. Men trade off reliable consumption benefits to the hunter’s family for more unpredictable benefits in social standing for the individual hunter. Gender differences in the costs and benefits of engaging in competitive magnanimity structure men’s more risk‐prone and women’s more risk‐averse foraging decisions.

Risk and reciprocity in Meriam food sharing

Abstract Foragers who do not practice food storage might adapt to fluctuating food supplies by sharing surplus resources in times of plenty with the expectation of receiving in times of shortfall. In this paper, we derive a number of predictions from this perspective, which we term the risk reduction reciprocity (RRR) model, and test these with ethnographic data on foraging (fishing, shellfish collecting, and turtle hunting) among the Meriam (Torres Strait, Australia). While the size of a harvest strongly predicts that a portion will be shared beyond the household of the acquirer, the effects of key measures of foraging risk (e.g., failure rate) are comparatively weak: Harvests from high-risk hunt types are usually shared more often than those from low-risk hunt types in the same macropatch, but increases in risk overall do not accurately predict increases in the probability of sharing. In addition, free-riders (those who take shares but do not reciprocate) are not discriminated against, those who share more often and more generously do not predictably receive more, and most sharing relationships between households (over 80%) involve one-way flows.

Children on the reef

Meriam children are active reef-flat collectors. We demonstrate that while foraging on the reef, children are significantly less selective than adults. This difference and the precise nature of children’s selectivity while reef-flat collecting are consistent with a hypothesis that both children and adults attempt to maximize their rate of return while foraging, but in so doing they face different constraints relative to differences in walking speeds while searching. Implications of these results for general arguments about factors that shape differences between child and adult behavior and human life-histories are explored.

Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands

Across diverse ecosystems, greater climatic variability tends to increase wildfire size, particularly in Australia, where alternating wet–dry cycles increase vegetation growth, only to leave a dry overgrown landscape highly susceptible to fire spread. Aboriginal Australian hunting fires have been hypothesized to buffer such variability, mitigating mortality on small-mammal populations, which have suffered declines and extinctions in the arid zone coincident with Aboriginal depopulation. We test the hypothesis that the relationship between climate and fire size is buffered through the maintenance of an anthropogenic, fine-grained fire regime by comparing the effect of climatic variability on landscapes dominated by Martu Aboriginal hunting fires with those dominated by lightning fires. We show that Aboriginal fires are smaller, more tightly clustered, and remain small even when climate variation causes huge fires in the lightning region. As these effects likely benefit threatened small-mammal species, Aboriginal hunters should be considered trophic facilitators, and policies aimed at reducing the risk of large fires should promote land-management strategies consistent with Aboriginal burning regimes.