Article

Females drive primate social evolution

Stockholm University, Tukholma, Stockholm, Sweden
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.29). 03/2004; 271 Suppl 3:S101-3. DOI: 10.1098/rsbl.2003.0114
Source: PubMed

ABSTRACT Within and across species of primates, the number of males in primate groups is correlated with the number of females. This correlation may arise owing to ecological forces operating on females, with subsequent competition among males for access to groups of females. The temporal relationship between changes in male and female group membership remains unexplored in primates and other mammalian groups. We used a phylogenetic comparative method for detecting evolutionary lag to test whether evolutionary change in the number of males lags behind change in the number of females. We found that change in male membership in primate groups is positively correlated with divergence time in pairwise comparisons. This result is consistent with male numbers adjusting to female group size and highlights the importance of focusing on females when studying primate social evolution.

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    • "In nonhuman primates, females typically drive the evolution of the social system, highlighting the importance of focusing on females when studying primate social evolution [Clutton-Brock & Lukas, 2012; Lindenfors et al., 2004]. Female primate social structures vary greatly between species, ranging from females forming loose and changing associations, to females establishing stable bonds with a subset of partners [Wrangham, 1980]. "
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    ABSTRACT: In primates, females typically drive the evolution of the social system and present a wide diversity of social structures. To understand this diversity, it is necessary to document the consistency and/or flexibility of female social structures across and within species, contexts, and environments. Macaques (Macaca sp.) are an ideal taxon for such comparative study, showing both consistency and variation in their social relations. Their social styles, constituting robust sets of social traits, can be classified in four grades, from despotic to tolerant. However, tolerant species are still understudied, especially in the wild. To foster our understanding of tolerant societies and to assess the validity of the concept of social style, we studied female crested macaques, Macaca nigra, under entirely natural conditions. We assessed their degree of social tolerance by analyzing the frequency, intensity, and distribution of agonistic and affiliative behaviors, their dominance gradient, their bared-teeth display, and their level of conciliatory tendency. We also analyzed previously undocumented behavioral patterns in grade 4 macaques: reaction upon approach and distribution of affiliative behavior across partners. We compared the observed patterns to data from other populations of grade 4 macaques and from species of other grades. Overall, female crested macaques expressed a tolerant social style, with low intensity, frequently bidirectional, and reconciled conflicts. Dominance asymmetry was moderate, associated with an affiliative bared-teeth display. Females greatly tolerated one another in close proximity. The observed patterns matched the profile of other tolerant macaques and were outside the range of patterns of more despotic species. This study is the first comprehensive analysis of females’ social behavior in a tolerant macaque species under natural conditions and as such, contributes to a better understanding of macaque societies. It also highlights the relevance of the social style concept in the assessment of the degree of tolerance/despotism in social systems.
    American Journal of Primatology 01/2013; 75:361-375. DOI:10.1002/ajp.22114 · 2.14 Impact Factor
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    • "(Examples are approximations.) and predator risk determine the distribution of females, which determines the distribution of males (Leutenegger & Kelly, 1977; Lindenfors, Froberg, & Nunn, 2004). If females form groups or are solitary but closely dispersed, they may be collectively defensible by a single male. "
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    ABSTRACT: Literature in evolutionary psychology suggests that mate choice has been the primary mechanism of sexual selection in humans, but this conclusion conforms neither to theoretical predictions nor available evidence. Contests override other mechanisms of sexual selection; that is, when individuals can exclude their competitors by force or threat of force, mate choice, sperm competition, and other mechanisms are impossible. Mates are easier to monopolize in two dimensional mating environments, such as land, than in three-dimensional environments, such as air, water, and trees. Thus, two-dimensional mating environments may tend to favor the evolution of contests. The two-dimensionality of the human mating environment, along with phylogeny, the spatial and temporal clustering of mates and competitors, and anatomical considerations, predict that contest competition should have been the primary mechanism of sexual selection in men. A functional analysis supports this prediction. Men's traits are better designed for contest competition than for other sexual selection mechanisms; size, muscularity, strength, aggression, and the manufacture and use of weapons probably helped ancestral males win contests directly, and deep voices and facial hair signal dominance more effectively than they increase attractiveness. However, male monopolization of females was imperfect, and female mate choice, sperm competition, and sexual coercion also likely shaped men's traits. In contrast, male mate choice was probably central in women's mating competition because ancestral females could not constrain the choices of larger and more aggressive males through force, and attractive women could obtain greater male investment. Neotenous female features and body fat deposition on the breasts and hips appear to have been shaped by male mate choice.
    Evolution and Human Behavior 05/2010; 31(3):157-175. DOI:10.1016/j.evolhumbehav.2010.02.005 · 2.87 Impact Factor
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    • "Most primates live in closely bonded social groups in which individuals have differentiated social relationships (Cheney & Seyfarth 1990; Silk 2007). Group size itself correlates with relative neocortex size in primates (Dunbar 1998; Lindenfors et al. 2004; Dunbar & Shultz 2007). While this has been interpreted as being synonymous with greater social complexity, analyses of group structure have suggested that large social groups are not simply small groups writ large: rather, large groups seem to be more sub-structured (Kudo & Dunbar 2001), mainly because, in large groups, animals deliberately reduce their social engagement in order to invest in core coalition partners. "
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    ABSTRACT: Most primates are intensely social and spend a large amount of time servicing social relationships. In this study, we use social network analysis to examine the relationship between primate group size, total brain size, neocortex ratio and several social network metrics concerned with network cohesion. Using female grooming networks from a number of Old World monkey species, we found that neocortex size was a better predictor of network characteristics than endocranial volumes. We further found that when we controlled for group size, neocortex ratio was negatively correlated with network density, connectivity, relative clan size and proportional clan membership, while there was no effect of neocortex ratio on change in connectivity following the removal of the most central female in the network. Thus, in species with larger neocortex ratios, females generally live in more fragmented networks, belong to smaller grooming clans and are members of relatively fewer clans despite living in a closely bonded group. However, even though groups are more fragmented to begin with among species with larger neocortices, the removal of the most central individual does cause groups to fall apart, suggesting that social complexity may ultimately involve the management of highly fragmented social groups while at the same time maintaining overall social cohesion. These results emphasize a need for more detailed brain data on a wider sample of primate species.
    Proceedings of the Royal Society B: Biological Sciences 09/2009; 276(1677):4417-22. DOI:10.1098/rspb.2009.1409 · 5.29 Impact Factor

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