The ecology and evolution of intergroup conflict in animal societies: theory and tests

Lead Research Organisation: University of Exeter
Department Name: Biosciences

Abstract

The history of life on earth has been dominated by a series of cooperative transitions in biological organisation, in which lower-level entities have banded together to form higher-level cooperative groups. The evolution of cooperation creates opportunities for productive coordination and teamwork within groups, but also the potential for destructive conflict and violence between groups. Humans, for example, are capable of astonishing feats of altruism and cooperation, but are at once among the most murderous and violent animals we know. In other animals there is great variation in the intensity and form of intergroup conflict, but we have a very poor understanding of the causes of this variation. The link between intergroup conflict and cooperation is also unclear: in some species intergroup conflict leads to greater social cohesion, whereas in other species it leads to greater within-group aggression.

Our project combines new theory and empirical testing to explain these conflicting observations and to advance conceptual understanding of the biological roots of intergroup conflict. Our theoretical models will predict the ecological and social factors that promote or inhibit intergroup aggression, and how individuals and groups should respond to changes in levels of intergroup conflict. We will carry out the first tests of these models on an ideally suited wild mammal system, the banded mongoose Mungos mungo, which we have studied for 20 years at site in Uganda. Banded mongooses live in highly cooperative, territorial groups which engage in frequent intergroup fights. Intergroup aggression is more severe in banded mongooses than in meerkats, chimpanzees, or any other non-human mammal. Yet there is also great individual and group variation in levels of intergroup aggression, providing an opportunity to test our theoretical predictions using experiments and long-term observations.

The research will provide a better understanding of patterns of competition in nature, and clarify the link between intergroup conflict and cooperation. We will leave a testable theoretical framework that can be applied to a very wide range of species, from microbes to humans. The project will be of much interdisciplinary interest, with the potential to influence future research in evolution, psychology, economics and political science.

Planned Impact

Who will benefit from this research?
A major group of beneficiaries is other academics, with whom we will engage via standard science communication activities (publishing our research in interdisciplinary and high profile journals, presenting scientific seminars, attending conferences). Our research topic has broad cross-disciplinary relevance so we will actively seek engagement with economists, psychologists, and political scientists working on intergroup conflict in human society.

In addition, the main non-academic beneficiaries from the proposed research will be 1) the general public, secondary teachers and their students; and 2) the Uganda Wildlife Authority and Uganda Tourist Board.

How will they benefit
We will contribute to an improved conceptual understanding of an issue that is of great interdisciplinary interest in academia, and great topical interest for most people. Researchers in economics, psychology and political science will benefit from a tested theoretical framework that is capable of predicting adaptive behavioural responses to changes in the ecological and social environment. While our research is largely curiosity-driven, our findings and theoretical work will have relevance and influence in these disciplines that link directly to societal policy and strategy.

The topic and research subjects are of intrinsic interest to the general public, and we aim to capitalise on this interest to improve the public understanding of science. The general public, teachers and their students will benefit through education, international cultural exchange, and engagement with scientific research.

The project teach has long-standing relations with the Uganda Wildlife Authority and Uganda Tourist board who will benefit from through the information exchange aspects of the project, and the interest in our project from international wildlife filmmakers. Our media and knowledge sharing activities will help to promote ecotourism and investment in Uganda's protected areas, and increase local and international awareness of the value of Uganda's natural resources.

Finally, the project team including the early career researchers (the RCo-I and PDRA) will benefit from developing new skills and experience with outreach and engagement with beneficiaries of the research, which will enhance career development.

Publications

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Johnstone RA (2019) Evolution of menopause. in Current biology : CB

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Vitikainen EIK (2019) Live long and prosper: durable benefits of early-life care in banded mongooses in Philosophical Transactions of the Royal Society B: Biological Sciences

 
Description Intergroup conflict has been proposed as a major force promoting the evolution of altruism in animals as diverse as insects and primates. A long-standing hypothesis is that groups under attack from rivals should become more altruistic. While previous research has examined the impact of intergroup conflict on cohesion and affiliative behavior, no research to date has tested the effect of conflict on altruism, such as helping behaviour in cooperative breeders. We have carried out the first such test using long term data on wild banded mongooses, a species that features both intense intergroup conflict and conspicuous helping behaviour. Contrary to expectations, contributions to babysitting pups at the den decreased following intergroup fights, resulting in elevated pup mortality. Contributions to 'escorting', the care of offspring after they emerge form the den, remained unchanged. These different responses may reflect a fundamental difference in the personal costs of the two forms of cooperation, since babysitters are vulnerable to intergroup attack, while escorts enjoy the safety of the group. Our findings suggest that intergroup conflict may promote or inhibit altruism, depending on the nature of costs involved. We have begun to develop new theory to understand how intergroup conflict shapes the evolution of cooperation, and test the predictions of this theory using mammal and insect systems.

In 2020 we published a paper showing that female banded mongooses initiate conflict, while males pay the cost. We also developed new theory showing that this decoupling of leaders from the costs that they incite, which we term 'exploitative leadership' can explain the evolution of damaging and severe intergroup conflict in this species. The findings were published in a top journal (PNAS) and received much media attention, resulting in an altmetric score of over 1200. The paper was downloaded over 10,000 times in the first 60 days since publication.
Exploitation Route The results show that the impact of conflict on internal group cohesion depends on the form and nature of the costs of cooperation. This finding in a non-human animal mirrors theories in psychology developed in the 19th Century, and further highlights the parallels between the study of the evolutionary origins of intergroup conflict and its role in human behaviour and evolution. Our theory and empirical work will continue to have a major impact in drawing together and synthesising findings from evolutionary biology and social sciences, with relevance to a very broad scientific audience.
Sectors Education,Environment,Financial Services, and Management Consultancy,Government, Democracy and Justice,Security and Diplomacy

 
Description Leaders of war: the evolution of collective decision-making in the face of intergroup conflict
Amount £647,771 (GBP)
Funding ID NE/S009914/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 05/2019 
End 05/2022
 
Title Data supporting Johnstone, Cant, Cram & Thompson (2020) Exploitative leaders incite intergroup warfare in a social mammal 
Description This data supports the following publication:
Rufus A. Johnstone, Michael A. Cant, Dominic L. Cram & Faye J. Thompson (2020) Exploitative leaders incite intergroup warfare in a social mammal. Proceedings of the National Academy of Sciences.
Please read the "Read Me.txt" file for a full description of the data contained in each data set 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://figshare.com/articles/dataset/Data_supporting_Johnstone_Cant_Cram_Thompson_2020_Exploitative...
 
Title Data supporting Johnstone, Cant, Cram & Thompson (2020) Exploitative leaders incite intergroup warfare in a social mammal 
Description This data supports the following publication:
Rufus A. Johnstone, Michael A. Cant, Dominic L. Cram & Faye J. Thompson (2020) Exploitative leaders incite intergroup warfare in a social mammal. Proceedings of the National Academy of Sciences.
Please read the "Read Me.txt" file for a full description of the data contained in each data set 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://figshare.com/articles/dataset/Data_supporting_Johnstone_Cant_Cram_Thompson_2020_Exploitative...
 
Description Collaboration on developing and testing the theory of intergroup conflict 
Organisation University of California, Santa Cruz
Country United States 
Sector Academic/University 
PI Contribution Through our interest in intergroup conflict we have set up a collaboration with Prof Suzanne Alonzo at the University of Santa Cruz, to develop and test new theory about the role of intergroup conflict in social evolution. The theoretical predictions outlined in the grant can be tested using controlled experiments on a model insect system, the dampwood termite Zootermopsis angusticollis, which complements our field research objectives on social mammals and provides a strong test of the generality of the theoretical models we are developing.
Collaborator Contribution Prof Alonzo has provided advice on logistics and marking of animals, and has provided access to her laboratory facilities at the University of Santa Cruz as required.
Impact We are in the process of discussing and developing theoretical models.
Start Year 2019