Barbara B. Smuts

Male aggression against women : An evolutionary perspective.

Male aggression against females in primates, including humans, often functions to control female sexuality to the male’s reproductive advantage. A comparative, evolutionary perspective is used to generate several hypotheses to help to explain cross-cultural variation in the frequency of male aggression against women. Variables considered include protection of women by kin, male-male alliances and male strategies for guarding mates and obtaining adulterous matings, and male resource control. The relationships between male aggression against women and gender ideologies, male domination of women, and female sexuality are also considered.

The evolutionary origins of patriarchy.

This article argues that feminist analyses of patriarchy should be expanded to address the evolutionary basis of male motivation to control female sexuality. Evidence from other primates of male sexual coercion and female resistance to it indicates that the sexual conflicts of interest that underlie patriarchy predate the emergence of the human species. Humans, however, exhibit more extensive male dominance and male control of female sexuality than is shown by most other primates. Six hypotheses are proposed to explain how, over the course of human evolution, this unusual degree of gender inequality came about. This approach emphasizes behavioral flexibility, cross-cultural variability in the degree of partriarchy, and possibilities for future change.

Use of signature whistles during separations and reunions by wild bottlenose dolphin mothers and infants

We examine the contexts and patterns of “signature” whistle production by wild bottlenose dolphin mother-infant pairs (Tursiops spp.) to gain insight into the functional significance of whistles. Results are based on focal observations and simultaneous recordings of underwater vocalizations. Whistles occur primarily when mother-infant pairs are separated, and the probability of whistles increases with distance of separation. The timing of whistles during separations varies, but whistles tend to be produced in repetitive series and are generally concentrated toward the later stages of the separation, i.e., during the process of reunion. Although we focused on infants, mothers do not appear to whistle during separations as frequently as infants. Infant whistles may function to facilitate reunions by conveying information to the mother concerning the infants motivation to reunite and/or its location. Infant whistles could induce a cooperative response from the mother including approach, slowing to allow the infant to catch up or whistling. Highly individualized signature whistles may be particularly useful in a fission-fusion society in which individuals (mothers and infants as well as adults) join and leave temporary parties in a fluid manner, yet maintain consistent, long-term associations with particular individuals.

Social Relationships and Ritualized Greetings in Adult Male Baboons (Papio cynocephalus anubis)

Greetings involving exchanges of ritualized sexual gestures are a common form of interaction among adult male baboons, although relatively little attention has been paid to them. In this study, we investigate how greetings reflect important aspects of the males social relationships, including dominance rank, age/residence status, and cooperative tendencies. The results are based on over 600 greetings among 12 adult males recorded during a 4-month study of a troop of wild olive baboons near Gilgil, Kenya. Four of the adult males were older, lower-ranking, long-term residents, which frequently formed coalitions to take estrous females away from the eight young, higher-ranking males. Virtually all dyads greeted: greetings occurred more than twice as often as other types of male-male interactions; and nearly all greetings occurred in a neutral context, in which there was no resource at stake. The percentage of greetings completed, the frequency with which different gestures were employed, and the roles adopted by each male varied significantly across old-old, old-young, and young-young dyads. Greetings between young adult males were often interrupted or actively resisted, consistent with their unstable and ambiguous dominance relationships. Greetings between old-old dyads were usually completed and appeared consistent with their cooperative relationships. One pair of old males formed a stable, reciprocal coalition against young males, and this pairs greetings showed remarkable symmetry of roles. Greetings, we hypothesize, function to allow males to negotiate important aspects of their relationships, including cooperation.

Quantity-based judgments in the domestic dog (Canis lupus familiaris).

We examined the ability of domestic dogs to choose the larger versus smaller quantity of food in two experiments. In experiment 1, we investigated the ability of 29 dogs (results from 18 dogs were used in the data analysis) to discriminate between two quantities of food presented in eight different combinations. Choices were simultaneously presented and visually available at the time of choice. Overall, subjects chose the larger quantity more often than the smaller quantity, but they found numerically close comparisons more difficult. In experiment 2, we tested two dogs from experiment 1 under three conditions. In condition 1, we used similar methods from experiment 1 and tested the dogs multiple times on the eight combinations from experiment 1 plus one additional combination. In conditions 2 and 3, the food was visually unavailable to the subjects at the time of choice, but in condition 2, food choices were viewed simultaneously before being made visually unavailable, and in condition 3, they were viewed successively. In these last two conditions, and especially in condition 3, the dogs had to keep track of quantities mentally in order to choose optimally. Subjects still chose the larger quantity more often than the smaller quantity when the food was not simultaneously visible at the time of choice. Olfactory cues and inadvertent cuing by the experimenter were excluded as mechanisms for choosing larger quantities. The results suggest that, like apes tested on similar tasks, some dogs can form internal representations and make mental comparisons of quantity.

A Mechanism for the Evolution of Altruism among Nonkin: Positive Assortment through Environmental Feedback

The evolution of altruism often requires genetic similarity among interactors. For structured populations in which a social trait affects all group members, this entails positive assortment, meaning that cooperators and noncooperators tend to be segregated into different groups. Several authors have claimed that mechanisms other than common descent can produce positive assortment, but this claim has not been generally accepted. Here, we describe one such mechanism. The process of “environmental feedback” requires only that the cooperative trait affects the quality of the local environment and that individuals are more likely to leave low‐quality than high‐quality environments. We illustrate this dynamic using an agent‐based spatial model of feeding restraint. Depending on parameter settings, results included both positive assortment (required for the evolution of altruism) and negative assortment (required for the evolution of spite). The mechanism of environmental feedback appears to be a general one that could play a role in the evolution of many forms of cooperation.

Cooperation and competition during dyadic play in domestic dogs, Canis familiaris

Social play involves a dynamic combination of competition and cooperation, yet few studies have systematically evaluated the cooperative side of play. We studied dyadic play in domestic dogs to investigate factors influencing variation in cooperative play strategies like self-handicapping and role reversal. Dyadic play bouts were videotaped and coded for asymmetric behaviours. We predicted that variation in play style would reflect salient aspects of the canine social system, including dominance relationships and age and size differences, but not sex differences. Our results refute the 50:50 rule proposed by some researchers, which asserts that participants must equalize their behaviour to maintain a playful atmosphere. We observed divergence from 50:50 symmetry to varying degrees across dyads. This variability was especially linked to dominance and age advantages, such that higher-ranking and/or older dogs generally showed higher proportions of attacks and pursuits and lower proportions of self-handicapping than their disadvantaged play partners. These results contradict the notion that more advantaged individuals consistently relinquish their advantage to facilitate play. Role reversals did occur, but certain social conventions apparently dictated which behaviours could be used during role reversals. For example, role reversals occurred during chases and tackles, but never during mounts, muzzle bites or muzzle licks, suggesting that these latter behaviours may be invariant indicators of formal dominance during play in domestic dogs. Play signalling was linked to self-handicapping behaviour but not to attack/pursuit behaviour, indicating that perhaps self-handicapping and play signalling work together to communicate playful intent and reinforce existing roles.

Rough‐and‐tumble play as a window on animal communication

Rough‐and‐tumble play (RT) is a widespread phenomenon in mammals. Since it involves competition, whereby one animal attempts to gain advantage over another, RT runs the risk of escalation to serious fighting. Competition is typically curtailed by some degree of cooperation and different signals help negotiate potential mishaps during RT. This review provides a framework for such signals, showing that they range along two dimensions: one from signals borrowed from other functional contexts to those that are unique to play, and the other from purely emotional expressions to highly cognitive (intentional) constructions. Some animal taxa have exaggerated the emotional and cognitive interplay aspects of play signals, yielding admixtures of communication that have led to complex forms of RT. This complexity has been further exaggerated in some lineages by the development of specific novel gestures that can be used to negotiate playful mood and entice reluctant partners. Play‐derived gestures may provide new mechanisms by which more sophisticated communication forms can evolve. Therefore, RT and playful communication provide a window into the study of social cognition, emotional regulation and the evolution of communication systems.

Third-party interventions in dyadic play between littermates of domestic dogs, Canis lupus familiaris

Interventions occur when animals interfere in competitive interactions between two or more individuals. Interveners can alter the nature of the ongoing interaction by targeting one party (attacking, biting) and supporting the other. Three theories have been proposed to account for intervention behaviour: kin selection, reciprocity and direct benefits. The kin selection hypothesis predicts that interveners will selectively support relatives over nonrelatives; the reciprocity hypothesis predicts that when intervener ‘A’ supports individual ‘B’, later ‘B’ will intervene and support ‘A’; and the direct benefits hypothesis predicts that target/support patterns should serve the immediate interests of the intervener. We tested the reciprocity and direct benefits hypotheses by exploring third-party interventions in play fighting among littermates of domestic dogs. Interveners in dyadic play did not preferentially target or support preferred playmates of the intervener. Interveners targeted the dog in the losing role at the time of the intervention, and they did not show reciprocity in support. Taken together, these last two findings suggest that littermates benefit directly and use interventions opportunistically to practise offence behaviours directed at littermates already behaving subordinately. Opportunities to practise targeting in a playful setting may help structure dominance relationships among littermates. Additionally, the tendency for puppies to do what the other is doing (target the dog in the losing role) may pave the way for synchronizing cooperative behaviours during group hunting and territorial defence. The types of behaviours used to intervene changed over development, but the outcome following an intervention remained stable.

Dominance relationships in a group of domestic dogs (Canis lupus familiaris)

We investigated the extent to which dominance relationships, as described for feral dogs and wolves, applied to a group of 24 neutered companion dogs at a dog daycare facility. Similar to other studies of dogs and wolves, we found significant linear dominance hierarchies based on highly unidirectional displays of submission and aggression. Submission was the most frequent, unidirectional and linear type of agonistic behaviour and, therefore, a better indicator of status than aggression or dominance displays. Aggression was low intensity, consisting mainly of ritualized threats with no physical contact, and conflicts involving physical contact were never injurious. Older dogs out-ranked younger dogs, but size was unrelated to dominance rank. Dominance relationships were more often expressed in same-sex dyads than between males and females. The coverage of dominance relationships in the daycare group was low compared to that reported for sexually intact dogs and wolves, which was probably a result of reduced competition due to neutering and other human influences. In many dyads dogs never exchanged agonistic behaviours, but bi-directional relationships were rare, and most dogs formed some dominance relationships with other dogs. Except for their low coverage, muzzle licks met the criteria for a formal display of submission. Our results suggest that dominance remains a robust component of domestic dog behaviour even when humans significantly reduce the potential for resource competition. The possible proximate benefits of dominance relationships for dogs are discussed.