InThe Hadza, Frank Marlowe provides a quantitative ethnography of one of the last remaining societies of hunter-gatherers in the world. The Hadza, who inhabit an area of East Africa near the ...Serengeti and Olduvai Gorge, have long drawn the attention of anthropologists and archaeologists for maintaining a foraging lifestyle in a region that is key to understanding human origins. Marlowe ably applies his years of research with the Hadza to cover the traditional topics in ethnography-subsistence, material culture, religion, and social structure. But the book's unique contribution is to introduce readers to the more contemporary field of behavioral ecology, which attempts to understand human behavior from an evolutionary perspective. To that end,The Hadzaalso articulates the necessary background for readers whose exposure to human evolutionary theory is minimal.
Western lifestyles differ markedly from those of our hunter-gatherer ancestors, and these differences in diet and activity level are often implicated in the global obesity pandemic. However, few ...physiological data for hunter-gatherer populations are available to test these models of obesity. In this study, we used the doubly-labeled water method to measure total daily energy expenditure (kCal/day) in Hadza hunter-gatherers to test whether foragers expend more energy each day than their Western counterparts. As expected, physical activity level, PAL, was greater among Hadza foragers than among Westerners. Nonetheless, average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size. The metabolic cost of walking (kcal kg(-1) m(-1)) and resting (kcal kg(-1) s(-1)) were also similar among Hadza and Western groups. The similarity in metabolic rates across a broad range of cultures challenges current models of obesity suggesting that Western lifestyles lead to decreased energy expenditure. We hypothesize that human daily energy expenditure may be an evolved physiological trait largely independent of cultural differences.
Social networks show striking structural regularities, and both theory and evidence suggest that networks may have facilitated the development of large-scale cooperation in humans. Here, we ...characterize the social networks of the Hadza, a population of hunter-gatherers in Tanzania. We show that Hadza networks have important properties also seen in modernized social networks, including a skewed degree distribution, degree assortativity, transitivity, reciprocity, geographic decay and homophily. We demonstrate that Hadza camps exhibit high between-group and low within-group variation in public goods game donations. Network ties are also more likely between people who give the same amount, and the similarity in cooperative behaviour extends up to two degrees of separation. Social distance appears to be as important as genetic relatedness and physical proximity in explaining assortativity in cooperation. Our results suggest that certain elements of social network structure may have been present at an early point in human history. Also, early humans may have formed ties with both kin and non-kin, based in part on their tendency to cooperate. Social networks may thus have contributed to the emergence of cooperation.
Although few hunter‐gatherers or foragers exist today, they are well documented in the ethnographic record. Anthropologists have been eager to study them since they assumed foragers represented a ...lifestyle that existed everywhere before 10,000 years ago and characterized our ancestors into some ill‐defined but remote past. In the past few decades, that assumption has been challenged on several grounds. Ethnographically described foragers may be a biased sample that only continued to exist because they occupied marginal habitats less coveted by agricultural people.3 In addition, many foragers have been greatly influenced by their association with more powerful agricultural societies.4 It has even been suggested that Holocene foragers represent a new niche that appeared only with the climatic changes and faunal depletion at the end of the last major glaciation.5 Despite these issues, the ethnographic record of foragers provides the only direct observations of human behavior in the absence of agriculture, and as such is invaluable for testing hypotheses about human behavioral evolution.6.
When searching for food, many organisms adopt a superdiffusive, scale-free movement pattern called a Lévy walk, which is considered optimal when foraging for heterogeneously located resources with ...little prior knowledge of distribution patterns Viswanathan GM, da Luz MGE, Raposo EP, Stanley HE (2011) The Physics of Foraging: An Introduction to Random Searches and Biological Encounters . Although memory of food locations and higher cognition may limit the benefits of random walk strategies, no studies to date have fully explored search patterns in human foraging. Here, we show that human hunter–gatherers, the Hadza of northern Tanzania, perform Lévy walks in nearly one-half of all foraging bouts. Lévy walks occur when searching for a wide variety of foods from animal prey to underground tubers, suggesting that, even in the most cognitively complex forager on Earth, such patterns are essential to understanding elementary foraging mechanisms. This movement pattern may be fundamental to how humans experience and interact with the world across a wide range of ecological contexts, and it may be adaptive to food distribution patterns on the landscape, which previous studies suggested for organisms with more limited cognition. Additionally, Lévy walks may have become common early in our genus when hunting and gathering arose as a major foraging strategy, playing an important role in the evolution of human mobility.
Many animals both display and assess multiple signals. Two prominently studied traits are symmetry and sexual dimorphism, which, for many animals, are proposed cues to heritable fitness benefits. ...These traits are associated with other potential benefits, such as fertility. In humans, the face has been extensively studied in terms of attractiveness. Faces have the potential to be advertisements of mate quality and both symmetry and sexual dimorphism have been linked to the attractiveness of human face shape.
Here we show that measurements of symmetry and sexual dimorphism from faces are related in humans, both in Europeans and African hunter-gatherers, and in a non-human primate. Using human judges, symmetry measurements were also related to perceived sexual dimorphism. In all samples, symmetric males had more masculine facial proportions and symmetric females had more feminine facial proportions.
Our findings support the claim that sexual dimorphism and symmetry in faces are signals advertising quality by providing evidence that there must be a biological mechanism linking the two traits during development. Such data also suggests that the signalling properties of faces are universal across human populations and are potentially phylogenetically old in primates.
Recent studies of the evolution of religion have revealed the cognitive underpinnings of belief in supernatural agents, the role of ritual in promoting cooperation, and the contribution of morally ...punishing high gods to the growth and stabilization of human society. The universality of religion across human society points to a deep evolutionary past. However, specific traits of nascent religiosity, and the sequence in which they emerged, have remained unknown. Here we reconstruct the evolution of religious beliefs and behaviors in early modern humans using a global sample of hunter-gatherers and seven traits describing hunter-gatherer religiosity: animism, belief in an afterlife, shamanism, ancestor worship, high gods, and worship of ancestors or high gods who are active in human affairs. We reconstruct ancestral character states using a time-calibrated supertree based on published phylogenetic trees and linguistic classification and then test for correlated evolution between the characters and for the direction of cultural change. Results indicate that the oldest trait of religion, present in the most recent common ancestor of present-day hunter-gatherers, was animism, in agreement with long-standing beliefs about the fundamental role of this trait. Belief in an afterlife emerged, followed by shamanism and ancestor worship. Ancestor spirits or high gods who are active in human affairs were absent in early humans, suggesting a deep history for the egalitarian nature of hunter-gatherer societies. There is a significant positive relationship between most characters investigated, but the trait “high gods” stands apart, suggesting that belief in a single creator deity can emerge in a society regardless of other aspects of its religion.
We report quantitative estimates of intergenerational transmission and population‐wide inequality for wealth measures in a set of hunter‐gatherer populations. Wealth is defined broadly as factors ...that contribute to individual or household well‐being, ranging from embodied forms, such as weight and hunting success, to material forms, such as household goods, as well as relational wealth in exchange partners. Intergenerational wealth transmission is low to moderate in these populations but is still expected to have measurable influence on an individual’s life chances. Wealth inequality (measured with Gini coefficients) is moderate for most wealth types, matching what qualitative ethnographic research has generally indicated (if not the stereotype of hunter‐gatherers as extreme egalitarians). We discuss some plausible mechanisms for these patterns and suggest ways in which future research could resolve questions about the role of wealth in hunter‐gatherer social and economic life.
Researchers from across the social sciences have found consistent deviations from the predictions of the canonical model of self-interest in hundreds of experiments from around the world. This ...research, however, cannot determine whether the uniformity results from universal patterns of human behavior or from the limited cultural variation available among the university students used in virtually all prior experimental work. To address this, we undertook a cross-cultural study of behavior in ultimatum, public goods, and dictator games in a range of small-scale societies exhibiting a wide variety of economic and cultural conditions. We found, first, that the canonical model - based on self-interest - fails in all of the societies studied. Second, our data reveal substantially more behavioral variability across social groups than has been found in previous research. Third, group-level differences in economic organization and the structure of social interactions explain a substantial portion of the behavioral variation across societies: the higher the degree of market integration and the higher the payoffs to cooperation in everyday life, the greater the level of prosociality expressed in experimental games. Fourth, the available individual-level economic and demographic variables do not consistently explain game behavior, either within or across groups. Fifth, in many cases experimental play appears to reflect the common interactional patterns of everyday life.
Abstract The foraging and food sharing of hunter-gatherers have provided the backdrop to several different evolutionary hypotheses about human life history. Men’s foraging has often been ...characterized as primarily targeting animals, with high variance and high rates of failure. To the best of our knowledge, however, there are as yet no quantitative studies reporting the amounts of food that men eat while foraging, before returning to their households either empty-handed or with foods. Here, we document this under-reported part of forager’s diets—men’s eating while out of camp on foray. Our dataset consists of 146 person/day follows (921 hours total) collected over a period of 12 years (from 2001–2013, including 12 camps). Hadza men consumed a substantial amount of food while out of camp foraging. Men did more than just snack while out of camp foraging, they consumed a mean of 2,405 kilocalories per foray, or approximately 90% of what is estimated to be their mean daily Total Energy Expenditure (TEE). The characterization of men’s foraging strategies as “risky”, in terms of calorie acquisition, may be exaggerated. Returning to camp empty-handed did not necessarily mean the forager had failed to acquire food, only that he failed to produce enough surplus to share. Surprisingly, the vast majority of the kilocalories eaten while out of camp came from honey (85%). These observations are relevant to evolutionary theories concerning the role of male provisioning. Understanding primary production and consumption is critical for understanding the nature of sharing and the extent to which sharing and provisioning supports reproduction in hunter-gatherers.
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