For quite a few years I have been preparing a book ‘Markets in Nature’, to be published by Cambridge UP. All chapters have now been written, apart from a short concluding one. I am currently processing reviews, adding pictures, and doing technical stuff. The contents can be found in the Table below. Chapters without Abstracts are still under review.

Contents

Introduction

Part 1 – Markets in biology

1 Why biological markets?

Box 1 - A biological market glossary

Box 2 - Market misconceptions

Abstract: In the 1980ies ‘partner control’ was a core element of most evolutionary explanations of cooperation (interactions between members of the same species that benefit all participants) and mutualism (idem between members of different species). Baboon males forming coalitions (simultaneous aggression against a third party) and alliances (series of coalitions formed by two partners) inspired me to focus on partner choice as a key mechanism. It provokes outbidding competition among potential partners, and stronger outbidding leads to steeper concessions to the choosing agent. The term ‘biological markets’ was chosen while comparable processes operate on human markets. Biological market theory (BMT) takes cues from economics, but also sexual selection theory, notably to help explain the evolutionary repercussions of partner choice. I advocate avoiding anthropomorphic terms, such as ‘cheating’, ‘deception’, and ‘stealing’, in the context of cooperation, because these can misleadingly suggest intentionality and lead to confusion between proximate mechanisms and ultimate functions.

Keywords: altruism; cooperation vs mutualism; partner choice vs partner control; cooperative vs non-cooperative game theory; cheating; deception; short-changing; free-riding

2 Theoretical issues and models

Box 1 - Models germane to biological markets

Abstract: Cooperation research has long been dominated by ‘partner control’ models, mostly based on the two-player iterated prisoners’ dilemma and similar theoretical games. They focus on ways in which agents can prevent losses caused by cheating or defecting partners, but are silent on how partners find each other and divide investments and returns. Including partnership formation in models implies paying attention to partner choice, which induces outbidding competition among potential partners and other phenomena typical for markets such as exchange rates tracking changing supply-demand ratios. Partner choice prompts new questions: what are choice criteria, how reliable is information provided by partners, and how much should agents invest in choice mechanisms and in outbidding competitors? Choice models do not make control models obsolete. They become relevant when high thresholds de facto prohibit partner switching. Credible threats of partner switching also have effects comparable to threats of defecting in control models. 

Keywords: partner control; partner choice; partner switching; outside options; sanctioning; screening; contract theory; advertisement; honest signalling; competitive altruism

3 Economic vs Biological markets

Abstract: The biological market paradigm was inspired by human trading behaviour, but does micro-economic theory indeed apply to cooperative exchanges among non-human organisms? Firstly, to which kind of human markets should one compare? Good candidates are markets on which long-lasting relationships and reputations are important, such as ‘embedded’ markets with person-to-person bartering and labour markets. Secondly, which are the similarities and dissimilarities between ‘economic’ and biological markets? Similarities can be found in the motivations for partner choice, and the way in which supply and demand, negotiations, and outbidding competition determine exchange rates. ‘Transaction costs’ in economics translate to ‘partner choice costs’ in biology, and the market-firm dichotomy reminds of horizontal vs vertical symbiont acquisition. Biological equivalents of common currencies and binding contracts are exceptional. Services that can be exchanged against multiple commodities, such as grooming, can have currency-like characteristics. Natural contracts can become binding through mechanisms that make commodity transfers inevitable.

Keywords: biological market theory vs micro-economic theory; binding contract; common currency; Aristotle, grooming; transaction costs; negotiation; embedded markets; labour markets; market-firm dichotomy

Part 2 – Intra-specific markets

4 Coalitions and alliances

Box 1 - Negotiation without words

Box 2 - Weak partners

Abstract: ‘Coalitions’ are formed by individuals aggressing conspecifics simultaneously. ‘Alliances’ are series of coalitions formed by the same partners. There is a continuum between one-off coalitions formed opportunistically and long-term alliances serving multiple purposes. Biological Market Theory was initially inspired by adult male baboons showing how important partner choice is for alliance formation. Males with multiple options can play their partners off against each other and thus claim the lion’s share of benefits, among which access to receptive females. Forming coalitions repeatedly against strong adversaries demands trustworthy partners that are available at crucial moments. Investments in a limited number of reliable allies raise the thresholds for partner switching, resulting in lasting alliances resembling human friendships. Factors that explain different aspects of coalition formation, such as steepness of hierarchies and kinship, are identified by comparing baboons with chimpanzees and other primates, but also with dolphins, hyenas, and eider ducks.

Keywords: coalition; alliance; social bond; friendship; negotiation; Veto game; baboon; chimpanzee; dolphin; hyena; eider

5 Primate groups as marketplaces 

Box 1 - Economic exchanges or bonds?

Box 2 – Despos and Egalos: Primate socio-ecology in a rather nutty nutshell

Abstract: Grooming resembles a currency that is exchanged against various commodities including tolerance and support, but also grooming itself. Both short-term fluctuations in supply and demand and investments in long-term ‘bonds’ determine grooming rates. Grooming bouts are used as payments for instant returns, such as mating opportunities and access to newborns, but also as regular down payments, notably to ensure receiving tolerance in food patches and support during fights over long periods. The power of partner choice can be shown in experiments in which individuals can choose partners with whom they can obtain rewards through dyadic cooperation. Market effects can also be shown experimentally by measuring changes in grooming rates of individuals before and after giving them the opportunity to provide their group with food. Most trade among primates involves grooming, but in a few species other affiliate behaviours are used instead and sometimes commodities are exchanged directly without additional grooming.

Keywords: grooming market; baby market; mating market; tolerance; support-in-conflict; non-human primates; baboon; chimpanzee; macaque; vervet monkey; market experiment

6 Breeders trading with helpers

Abstract: Partner choice and outbidding competition distinguish a Biological Market approach from explanations for helping behaviour based on reproductive skew theory and various hypotheses such as ‘ecological constraints’, ‘paying-for-staying’ and ‘paying-for-help’. In my first ‘market’ paper (Noë et al., 1991), market effects in cooperatively breeding birds provided a key example. We were inspired by males in pied kingfishers showing outbidding competition when feeding breeding females unrelated to them. Further convincing examples of ‘helper markets’ remained scarce, however, perhaps because helpers and breeders are usually related and eventual effects due to partner choice are masked by the favourable treatment of close kin. Many breeders also simply lack surplus helpers to choose from, or cognitive and physical constraints prevent them from monitoring the investments made by helpers, and rewarding and/or punishing them accordingly. Nevertheless, indications for ‘helper markets’ have been found for mongoose species, cichlid fish, paper wasps, and callitrichid primates. 

Keywords: helpers-at-the-nest; cooperative breeding; reproductive skew theory; ecological constraints; paying-for-staying; pied kingfisher; meerkat; mongoose; cichlid; callitrichids 

7 Mating markets

Box 1 - Coming to terms with mating

Abstract:  ‘Mating markets’ are studied intensively in biology and the social sciences. A large chunk of this chapter is devoted to an inventory of similarities and dissimilarities between these fields. Sexual Selection Theory (SST) offers evolutionary explanations for a number of physical and behavioural traits, and notably explains why some secondary sexual traits can seemingly defy the forces of natural selection. The social sciences offer both descriptions of a large variety of mating markets and a wealth of experimental data on mating behaviour. A common denominator is a strong interest in the link between sex ratios, which largely determine supply and demand on mating markets, and mating behaviour. Deviations from balanced sex ratios offer insights into mating strategies of both human and non-human subjects. Biological Market Theory (BMT) can contribute by focussing on adaptations that allow individuals to make optimal use of local and temporal market conditions.

Keywords: mating market; marriage market; mate choice; mate value; assortative mating; sexual selection theory; sex ratio distortion; commodity control; conditional mating strategy; Local Mating Market

Part 3 – Inter-specific markets

8 Cleaning mutualisms

9 Nursery pollination

10 Protection by ants

11 Underground markets

Box 1 - Underground adaptation levels

Part 4 – The future of BMT

12 What’s in store (not finished yet)

 last update of this page:  2 MAR 2026