James L. Boone

Intergroup aggression in chimpanzees and humans.

The occurrence of fatal attacks during intergroup encounters among chimpanzees suggests that certain aspects of chimpanzee and human intergroup aggression may be explicable in similar ways. This paper addresses three questions: What conditions favor the evolution of lethal raiding in intergroup aggression? Why is intergroup aggression in these two species predominantly the domain of males? Under what circumstances do groups compete over access to females as opposed to material resources? Examination of comparative data on nonhuman primates and crosscultural study of foraging societies suggests that attacks are lethal because where there is sufficient imbalance of power their cost is trivial, that these attacks are a male and not a female activity because males are the philopatric sex, and that it is resources of reproductive interest to males that determine the causes of intergroup aggression.

The evolution of magnanimity : When is it better to give than to receive?

Conspicuous consumption associated with status reinforcement behavior can be explained in terms of costly signaling, or strategic handicap theory, first articulated by Zahavi and later formalized by Grafen. A theory is introduced which suggests that the evolutionary raison d’être of status reinforcement behavior lies not only in its effects on lifetime reproductive success, but in its positive effects on the probability of survival through infrequent, unpredictable demographic bottlenecks. Under some circumstances, such “wasteful” displays may take the form of displays of altruistic behavior and generosity on the part of high status individuals, in that is signals the ability to bear the short-term costs of being generous or “cooperative,” while at the same time reinforcing the long-term benefits of higher status.

Is It Evolution Yet? A Critique of Evolutionary Archaeology

The application of Darwinian evolutionary theory to archaeology has taken two divergent and rather distinct paths over the past two decades. According to one program, often referred to as evolutionary archaeology, cultural change as seen in the archaeological record can best be explained in terms of the direct action of natural selection and other Darwinian processes on heritable variation in artifacts and behavior. The other approach, referred to as evolutionary or behavioral ecology, explains cultural and behavioral change as forms of phenotypic adaptation to varying social and ecological conditions, using the assumption that natural selection has designed organisms to respond to local conditions in fitness‐enhancing ways. We argue that the primary conflict between the two approaches centers on fundamental differences in the way they view the explanatory role of phenotypic variation and more specifically a disagreement over whether behavioral innovation is random with respect to adaptive value (including related issues of current versus future selective advantage and the explanatory role of intentions). These differences lead to contrasts in explanatory scope, empirical application, and theoretical conclusions, which in turn provide the basis for our evaluation of the relative utility of each approach for explaining archaeological phenomena.

More Status or More Children? Social Status, Fertility Reduction, and Long-Term Fitness

Abstract A model is presented that shows that reduced fertility in humans can be explained as part of an evolved strategy to maximize long-term fitness in the face of periodic calamities that result in demographic crashes. Three conditions must be met for this model to be plausible: (1) human population history has been characterized by local periods of growth punctuated by recurrent crashes caused by calamities such as climatically induced resource shortfalls; (2) a strategy is available to individuals that increases the probability of survival through a crash, but that, to implement, requires diverting resources away from producing more offspring; and (3) long-term fitness benefits to increased survivorship through a crisis must outweigh or equal the fitness benefits that would accrue to putting the same resources into higher fertility. We present a model that shows that increases in survivorship can outweigh the benefits of higher fertility even if crises are neither very frequent nor particularly severe.

Subsistence strategies and early human population history: an evolutionary ecological perspective

One of the keystones of the evolutionary ecological approach is the concept of energy budget, in which time and energy allocation is conceptually divided into somatic effort (growth, development and maintenance, and includes subsistence activities) and reproductive effort (which is further divided into mating effort and parental effort). Time and energy allocated to one component must be traded off against allocation to another. Using this energy budget approach in conjunction with some of the general implications of foraging theory, this article will explore the relationship between population dynamics and subsistence intensification. My discussion will revolve around two basic propositions regarding long-term human population history: 1) the near-zero growth rates that have prevailed through much of prehistory are likely due to long-term averaging across periods of relatively rapid local population growth interrupted by infrequent crashes caused by density-dependent and density-independent factors; and 2) broad changes in population growth rates across subsistence modes in prehistory are probably best explained in terms of changes in mortality due to the dampening or buffering of crashes rather than significant increases in fertility.

Why Intensive Agriculturalists Have Higher Fertility: A Household Energy Budget Approach

It is widely held that human population growth rates began to increase markedly after the Pleistocene/Holocene transition largely as a consequence of the adoption of agriculture and sedentism. A common explanation for this increase in growth rates has been that circumstances associated with food production and/or the accompanying decrease in mobility allowed for higher fertility rates, but over the past decade a number of empirical studies and simulation analyses have revealed that the relationship between mode of subsistence and fertility is more complex than had previously been realized. In 1988, Campbell and Wood published a cross-cultural compilation of total fertility rates (TFR) of 70 forager, horticultural, and intensive agricultural societies from the contemporary ethnographic record that showed no significant differences in TFRs across subsistence regimes. Hewlett (1991) published a similar analysis of 40 mobile and sedentary foragers and pastoralists that indicated slightly higher fertility rates among pastoralists, although the difference was not significant. In 1993, Bentley et al. published an extensive critique and reanalysis of the Campbell and Wood study, presenting a new cross-cultural comparison of 57 forager, horticultural, and intensive agricultural groups (Bentley, Jasien-