Many male traits are well explained by sexual selection theory as adaptations to mating competition and mate choice, whereas no unifying theory explains traits expressed more in females. Anne Campbell's “staying alive” theory proposed that human females produce stronger self-protective reactions than males to aggressive threats because self-protection tends to have higher fitness value for females than males. We examined whether Campbell's theory has more general applicability by considering whether human females respond with greater self-protectiveness than males to other threats (...) beyond aggression. We searched the literature for physiological, behavioral, and emotional responses to major physical and social threats, and found consistent support for females' responding with greater self-protectiveness than males. Females mount stronger immune responses to many pathogens; experience a lower threshold to detect, and lesser tolerance of, pain; awaken more frequently at night; express greater concern about physically dangerous stimuli; exert more effort to avoid social conflicts; exhibit a personality style more focused on life's dangers; react to threats with greater fear, disgust, and sadness; and develop more threat-based clinical conditions than males. Our findings suggest that in relation to threat, human females have relatively heightened protective reactions compared to males. The pervasiveness of this result across multiple domains suggests that general mechanisms might exist underlying females' unique adaptations. An understanding of such processes would enhance knowledge of female health and well-being. (shrink)

Chimpanzee and hunter-gatherer intergroup aggression differ in important ways, including humans having the ability to form peaceful relationships and alliances among groups. This paper nevertheless evaluates the hypothesis that intergroup aggression evolved according to the same functional principles in the two species—selection favoring a tendency to kill members of neighboring groups when killing could be carried out safely. According to this idea chimpanzees and humans are equally risk-averse when fighting. When self-sacrificial war practices are found in humans, therefore, they result (...) from cultural systems of reward, punishment, and coercion rather than evolved adaptations to greater risk-taking. To test this “chimpanzee model,” we review intergroup fighting in chimpanzees and nomadic hunter-gatherers living with other nomadic hunter-gatherers as neighbors. Whether humans have evolved specific psychological adaptations for war is unknown, but current evidence suggests that the chimpanzee model is an appropriate starting point for analyzing the biological and cultural evolution of warfare. (shrink)

Parallels in anatomy between humans and domesticated mammals suggest that for the last 300,000 years, Homo sapiens has experienced more intense selection against the propensity for reactive aggression than any other species of Homo. Selection against reactive aggression, a process that can also be called self-domestication, would help explain various physiological, behavioral and cognitive features of humans, including the unique system of egalitarian male hierarchy in mobile hunter-gatherers. Here I review nine leading proposals that could potentially explain why self-domestication occurred (...) in H. sapiens, whether by selecting in favor of cooperation and tolerance or by selecting against aggressiveness. To account for the domestication syndrome, proposals must explain what led to a decline in fitness of highly aggressive males, and why the explanatory factor applies only to H. sapiens rather than to other species of Homo. The proposed explanations invoke genetic group selection; group-structured culture selection (also known as cultural group selection); social selection by female mate choice; social selection by male partner choice; increased self-control; cooperative breeding; high population density; use of lethal weapons; and language-based conspiracy. Most proposals face difficulties in accounting for the origins and/or maintenance of self-domestication. I conclude that the evolution of language-based conspiracy, which is a form of collective intentionality, was the key factor initiating and maintaining self-domestication in H. sapiens, because it is the most convincing mechanism for explaining the selective pressure against individually powerful fighters. Sophisticated language enabled males of low fighting prowess to coordinate in executing physically aggressive and domineering alpha males. This system is known today as a leveling mechanism in small-scale societies. Group-structured culture selection possibly accelerated the process. (shrink)

In the absence of explicit punitive sanctions, why do individuals voluntarily participate in intergroup warfare when doing so incurs a mortality risk? Here we consider the motivation of individuals for participating in warfare. We hypothesize that in addition to other considerations, individuals are incentivized by the possibility of rewards. We test a prediction of this “cultural rewards war-risk hypothesis” with ethnographic literature on warfare in small-scale societies. We find that a greater number of benefits from warfare is associated with a (...) higher rate of death from conflict. This provides preliminary support for the relationship between rewards and participation in warfare. (shrink)

Rules regulating social behavior raise challenging questions about cultural evolution in part because they frequently confer group-level benefits. Current multilevel selection theories contend that between-group processes interact with within-group processes to produce norms and institutions, but within-group processes have remained underspecified, leading to a recent emphasis on cultural group selection as the primary driver of cultural design. Here we present the self-interested enforcement (SIE) hypothesis, which proposes that the design of rules importantly reflects the relative enforcement capacities of competing parties. (...) We show that, in addition to explaining patterns in cultural change and stability, SIE can account for the emergence of much group-functional culture. We outline how this process can stifle or accelerate cultural group selection, depending on various social conditions. Self-interested enforcement has important bearings on the emergence, stability, and change of rules. (shrink)

The evolution of nonconceptive sexuality in bonobos and chimpanzees is discussed from a functional perspective. Bonobos and chimpanzees have three functions of sexual activity in common (paternity confusion, practice sex, and exchange for favors), but only bonobos use sex purely for communication about social relationships. Bonobo hypersexuality appears closely linked to the evolution of female-female alliances. I suggest that these alliances were made possible by relaxed feeding competition, that they were favored through their effect on reducing sexual coercion, and that (...) they are ultimately responsible for the relaxed social conditions that allowed the evolution of “communication sex.”. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Killing Our Way Out of ViolenceEngaging Wrangham's The Goodness ParadoxChris Haw (bio) and Richard Wrangham (bio)Wrangham's Goodness Paradox (GP) offers excellent anthropological research for mimetic theorists interested in the questions of human evolution and violence. It theorizes a framework of how group killing played a selective function in the emergence of our species, but it leaves open plenty of questions and concerns for productive, critical dialogue. Wolfgang Palaver has (...) written a short affirmation of the book, and Melvin Konner reviewed it for The Atlantic.1 But as one who has taken keen interest in the evolutionary and theological dimensions of mimetic theory,2 I offer here a longer engagement with the book and the author. I begin by extrapolating Wrangham's argument, I offer some critique, and then I share an edited version of my extended conversation with him.Wrangham's overall paradox is that humanity emerged through killing our way out of violence. More precisely, proactive coalitionary killing against aggressive, alpha-male individuals selected out, in a genetic pressure over hundreds of thousands of years, the more temperamental threads of Homo, resulting in a species (sapiens) who are relatively more domesticated and docile.3 [End Page 63]The argument proceeds as follows. First: Domestication is a real, genetic thing. Various domesticated species tend to share an odd, seemingly unrelated set of features called a "domestication syndrome." This refers to some combination of phenotype differences as compared to nondomesticated cousins: reduced skeleton mass, reduced/rounder cranium sizes and jaw lines, floppier ears, white patches of fur, extended juvenility, more frequent fertile periods, males with greater approximation to female characteristics, and so on. Beneath all these is a genetic reduction in "reactive aggression," which is the propensity for violence related to irascibility and short-fused tempers.Two: Domestication can happen intentionally or just randomly in nature. Humans have domesticated foxes in quick succession, breeding only ones with reduced reactive aggression, resulting in a domestication syndrome.4 The same seems to have happened slowly, with increasing intentionality over time, in the domestication of wolves into dogs. (This perhaps first began with the natural selection of wolves who were least aggravated by getting near humans to eat their camp detritus.) But domestication can also happen outside the human sphere, as in bonobos, who are basically a domesticated cousin of chimpanzees—evidenced not only in their reduced aggression but in their own domestication syndrome.5 This happened, he argues, largely through contingent, niche ecological features related to landscape, dramatic climate variations, and changes in competition over food.Three: It has long been asked whether humans are a "domesticated" species or whether such a thought is just anthropocentrism. The answer is definitely yes, but who domesticated us? A traditional answer, of course, was that God made us (or that some humans are properly domesticated, and others savage); but what if we ask in a more specifically scientific, causal framework? One early anthropologist posed that perhaps some now-extinct super-species domesticated us.6 Wrangham's answer is that we unintentionally domesticated ourselves by persistently killing off the genetic lines of the most aggressive individuals. This has resulted in Homo sapiens being basically a domesticated version of Homo neanderthalensis, erectus, and so on. Girard's not-unrelated answer is that religion domesticated us. By "religion" Girard means an integrated pattern of chaotic/exceptional and ordered/normal behaviors that contain violence, mediated through our mimetic capacity: chaotic mimetic violence restrained and channeled through mimetic ritual, taboo, and myth. This created an increasing feedback loop that exercised and intensified our mimetic capacity while protecting against its dangerous excess. Whatever the case, compared with our hominin cousins, the human phenotype shows strong signs of a domestication [End Page 64] syndrome: reduced cranium and jaw sizes, smaller skeleton mass, and a likely decreased reactive aggression in comparison to previous Homo.Fourth, and finally: Wrangham argues this domestication is related to a long, prehuman arc of transition, throughout the mid-Pleistocene (the Pleistocene ranges from about 2 million years ago to the thawing of the last ice age, 12,000 years ago), from older alpha-dominance patterns to tyrannies of egalitarian patriarchy. Wrangham draws upon hunter... (shrink)

Extending Campbell's staying alive theory beyond aggression, we reviewed evidence that females are more self-protective than males. Many commentators provided additional supporting data. Sex differences in life-history adaptations, in the optimal relation between survival and reproduction, and in the mechanisms underlying trade-offs involved with self-protection remain important topics with numerous opportunities for improved understanding.

Recent research suggests that some human-like social skills evolved in dogs during domestication as an incidental by-product of selection for “tame” forms of behavior. It is still possible, however, that the social skills of certain dog breeds came under direct selection that led to further increases in social problem solving ability. To test this hypothesis, different breeds of domestic dogs were compared for their ability to use various human communicative behaviors to find hidden food. We found that even primitive breeds (...) with little human contact were able to use communicative cues. Further, “working” dogs were more skilled at using gestural cues than were non-working breeds. This difference in performance existed regardless of whether the working breeds were more or less genetically wolf-like. These results suggest that subsequent to initial domesticating selection giving rise to cue-following skills, additional selection on communicative abilities in certain breeds has produced substantive differences in those breeds’ abilities to follow cues. (shrink)