Person: Glowacki, Luke
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Glowacki
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Luke
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Glowacki, Luke
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Publication When cooperation begets cooperation: the role of key individuals in galvanizing support(The Royal Society, 2015) McAuliffe, Katherine; Wrangham, Richard; Glowacki, Luke; Russell, Andrew F.Life abounds with examples of conspecifics actively cooperating to a common end, despite conflicts of interest being expected concerning how much each individual should contribute. Mathematical models typically find that such conflict can be resolved by partial-response strategies, leading investors to contribute relatively equitably. Using a case study approach, we show that such model expectations can be contradicted in at least four disparate contexts: (i) bi-parental care; (ii) cooperative breeding; (iii) cooperative hunting; and (iv) human cooperation. We highlight that: (a) marked variation in contributions is commonplace; and (b) individuals can often respond positively rather than negatively to the contributions of others. Existing models have surprisingly limited power in explaining these phenomena. Here, we propose that, although among-individual variation in cooperative contributions will be influenced by differential costs and benefits, there is likely to be a strong genetic or epigenetic component. We then suggest that selection can maintain high investors (key individuals) when their contributions promote support by increasing the benefits and/or reducing the costs for others. Our intentions are to raise awareness in—and provide testable hypotheses of—two of the most poorly understood, yet integral, questions regarding cooperative ventures: why do individuals vary in their contributions and when does cooperation beget cooperation?Publication Incentives for War in Small-Scale Societies(2015-04-30) Glowacki, Luke; Wrangham, Richard W.; Pinker, Steven; McDermott, Rose; Kramer, Karen L.; Hinde, Katherine J.This dissertation investigates why men in small-scale societies participate in warfare. The answer to this question has implications for understanding the role of war in our species’ history, as well as the evolution of cooperation. I explore this question through ethnographic research using data from small-scale societies. A central component of this research was undertaken through fieldwork among the Nyangatom, a group of pastoralists in East Africa still practicing small-scale warfare. Chapter One provides an introduction to the primary question of this dissertation. It also provides details on the methods used as well as background on the fieldwork I conducted. Chapter Two develops the cultural-rewards hypothesis, which posits that cultures encourage participation in warfare through the development of positive cultural incentives for warriors. It tests this hypothesis using cross-cultural data from 20 small-scale societies and shows a positive relationship between cultural reward systems and risk-taking in warfare. Chapter Three introduces the Nyangatom, a group of nomadic pastoralists living along the border of Ethiopia, South Sudan, and the Ilemi Triangle. Chapter Four provides a detailed ethnographic description of warfare among the Nyangatom, including the first documented account of many ritual elements in warfare for any Ateker group. Chapter Five focuses on the question of whether warriors have additional wives or children compared to other men. Over a lifetime, warriors who participated in more small livestock raids had a greater number of wives and children. Leaders of large raids, however, did not have an increased number of wives and children. Chapter Six evaluates the role of sanctions in motivating participation in raiding parties for three groups, including the Nyangatom. It shows a possibly important role of verbal sanctions for raiding party participation but provides little support for the importance of more serious sanctions. Chapter Seven summarizes the results of this dissertation and briefly sketches future research that will continue to explore the question of why individuals participate in intergroup conflict.Publication Modeling the Role of Networks and Individual Differences in Inter-Group Violence(Public Library of Science, 2016) Isakov, Alexander; Holcomb, Amelia; Glowacki, Luke; Christakis, Nicholas A.There is significant heterogeneity within and between populations in their propensity to engage in conflict. Most research has neglected the role of within-group effects in social networks in contributing to between-group violence and focused instead on the precursors and consequences of violence, or on the role of between-group ties. Here, we explore the role of individual variation and of network structure within a population in promoting and inhibiting group violence towards other populations. Motivated by ethnographic observations of collective behavior in a small-scale society, we describe a model with differentiated roles for individuals embedded within friendship networks. Using a simple model based on voting-like dynamics, we explore several strategies for influencing group-level behavior. When we consider changing population level attitude changes and introducing control nodes separately, we find that a particularly effective control strategy relies on exploiting network degree. We also suggest refinements to our model such as tracking fine-grained information spread dynamics that can lead to further enrichment in using evolutionary game theory models for sociological phenomena.Publication Warfare and reproductive success in a tribal population(Proceedings of the National Academy of Sciences, 2014) Glowacki, Luke; Wrangham, Richardntergroup conflict is a persistent feature of many human societies yet little is known about why individuals participate when doing so imposes a mortality risk. To evaluate whether participation in warfare is associated with reproductive benefits, we present data on participation in small-scale livestock raids among the Nyangatom, a group of nomadic pastoralists in East Africa. Nyangatom marriages require the exchange of a significant amount of bridewealth in the form of livestock. Raids are usually intended to capture livestock, which raises the question of whether and how these livestock are converted into reproductive opportunities. Over the short term, raiders do not have a greater number of wives or children than non-raiders. However, elders who were identified as prolific raiders in their youth have more wives and children than other elders. Raiders were not more likely to come from families with fewer older maternal sisters or a greater number of older maternal brothers. Our results suggest that in this cultural context raiding provides opportunities for increased reproductive success over the lifetime.Publication Self-Interest and the Design of Rules(Springer Nature, 2017-08-24) Singh, Manvir; Wrangham, Richard; Glowacki, LukeRules 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.