All animals show some kind of social behaviour. They compete for scarce resources, like food or shelter, but may also cooperate. Biologists have long studied how behaviour can increase the fitness of animals, which is usually defined as their ability to pass on their genes to subsequent generations. In a new book that has been 10 years in the making, three biologists describe the many dimensions that shape the evolution of social behaviour.
For some thirty-five years, evolutionary ecologist Jan Komdeur has studied the evolution of social behaviour in a great variety of social species, including the Seychelles warbler, the burying beetle, and ground tits in Tibet, with the goal of discovering why and how animals cooperate or compete with each other. His work established the Seychelles warbler as one of the best-known model systems in evolutionary ecology.
A few hundred birds live on the tiny Seychelles island of Cousin in just over 100 territories, each with a dominant breeding pair, some with helpers, often a daughter. Why does a helper invest so much time and energy into feeding another bird’s young? Somehow, the fitness benefits for the helper must be higher than the costs. Ultimately, Komdeur wants to know what drives the evolution of group living and cooperative breeding, or how unpredictable environmental changes affect how animals cooperate or compete with one another.
Cooperation is an altruistic behaviour that provides a benefit to another individual and is found across all major evolutionary transitions and at all levels of biological organization. The question ‘how did cooperative behaviour evolve?’ was defined as one of the top 25 questions for scientists in the journal Science in 2005. Despite the extensive efforts of many scientists, the evolution of cooperation remains a central paradox in biology: why help others if it is costly for the helper?
In cooperation with his colleagues Michael Taborsky, Professor of Behavioural Ecology at the University of Bern (Switzerland) and Michael A. Cant, Professor of Evolutionary Biology at the University of Exeter (UK), Komdeur wrote the book The evolution of social behaviour, which aims to create a greater consensus in the study of social behaviour. The project started over 10 years ago, when his co-authors came by train and boat to Komdeur’s home. ‘We talked for a day, wrote an outline and spent the next five months reading up on the relevant issues.’
‘Over the entire period, we met regularly for short retreats in beautiful and isolated places. Together, we read over ten thousand papers from different fields of science, not just biology, but also anthropology for example. And we used concepts from economics as well.’ An important part of their work was to identify general principles guiding the evolution of social behaviour. ‘The problem is that different scientists can describe the same phenomenon in different terms, creating a Babel of confusion.’ The introductory chapter of the book therefore contains a glossary.
The focus of the book is on animals, from unicellular organisms to humans. They all compete for resources, like food, shelter, and mates or social partners. ‘After a year and a half, we had identified three ways in which this competition plays out: a race to be the first to reach a resource, a fight for resources, or the sharing of resources through cooperation.’
The three scientists describe experimental and theoretical studies over a range of organisms in which the selective pressure of behaviour is studied. In boxed texts, case studies provide in-depth insights, for example into the cooperative breeding of the Seychelles warbler, the social behaviour of cichlids, beetles, mongoose, paper wasps, and other species, or the mystery of the menopause since female humans can live for decades after their ability to reproduce has ended. Humans share this trait with killer whales, and comparing these species leads to interesting conclusions.
‘We assess the benefits of social behaviour, but also the costs. Conflicts, for example, are costly behaviour. This side hasn’t been studied so much as the benefits have’, says Komdeur. Furthermore, biologists often tend to see the benefits as the ability to produce more offspring. This can be myopic: the offspring will have to reproduce as well. So raising two young, who each produce two young themselves, is better than raising five young that die without further offspring. All this makes the cost/benefit calculation more complicated.
The book provides an in-depth look at social behaviour. By clarifying confusing terminology and exploring general mechanisms, Komdeur and his fellow authors hope to inspire new kinds of research questions in their peers, as well as among a new generation of students. ‘It could provide the seed of change in the way that we study social behaviour. What is needed is a combination of field work, experiments, and theoretical studies to measure the benefits and costs of social behaviour.’
The book provides the first comprehensive overview of the evolution of social behaviour and shows how the intriguing diversity of social systems can be explained with only a few basic principles. It combines results from empirical and theoretical studies for an integrative insight into principles of social evolution, and spans the whole range of organisms and evolutionary principles. Thus, it enables a comparative evaluation of sociality and its underlying mechanisms across biology.
Just weeks after the official presentation of the book, the authors have already received lots of compliments, and requests for papers and lectures as well as for collaboration. They have planned another retreat later this year, to write a review article summarizing the points made in the book. Komdeur looks forward to this: ‘The three of us will continue to cooperate, there is a real chemistry between us. And we do cooperate in joint research, but we also sometimes compete over funding.’
Book information: Michael Taborsky, Michael A. Cant, Jan Komdeur: The Evolution of Social Behaviour. Cambridge University Press 2021. Paperback, 410 pages £39.99.
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