What’s law got to do with it?

– by Michael Guttentag

Law has played a pivotal role in the emergence of human sociality. If this conjecture is correct many questions naturally follow. When and why did the turn to law emerge? How could law have played a role in the distant past if powerful sovereigns are a comparatively recent development? What distinctive contributions does the legal system make to the maintenance of social order?

In Evolutionary psychology and resource-sharing laws I explore these and other questions by considering laws that serve a particular purpose – sharing resources. Resource-sharing laws are laws that encourage cooperation and discourage competition.  One simple example of a resource-sharing law is a law that limits private property rights, because such a law will reduce the incentive to compete rather than cooperate for scarce resources.

Concepts of law

A first step in addressing questions about law and the emergence of human sociality is to note that there are a multitude of ideas about what law is. One concept of law views the law as the commands issued by a sovereign and backed by a credible threat of punishment. This concept of law was popularized by John Austin in the Nineteenth Century, and suggests that law is a relatively modern affair, contingent on the existence of a sovereign powerful enough to command obedience (Austin, 1863, The province of jurisprudence and uses of the study of jurisprudence).

An alternative conceptualization of what law is comes from H. L. A. Hart and his 1960 masterwork “The Concept of Law” (Hart, 1960, The concept of law). In Hart’s account law’s uniqueness comes from the combination of two distinctive features: normativity and a two-tiered rule structure. According to Hart, unlike commands obeyed under threat of force, laws are obeyed because people to at least some degree accept the law as describing how people ought to behave. This is the normative aspect of law.

The second defining feature of law according to Hart is the way legal systems are constructed. Unlike other normative systems, the law contains both rules and rules about rules, or, in Hart’s terminology, both primary rules and secondary rules. Primary rules delineate when people “are required to do or abstain from certain actions, whether they wish to or not,” and include “restrictions on the free use of violence, theft, and deception,” and “various positive duties to perform services or make contributions to the common life.” Secondary rules describe how to “introduce new rules of the primary type, extinguish or modify old ones, or in various ways determine their incidence or control their operations.”

The combination of primary and secondary rules, law’s two-tiered structure, creates a generative system for establishing normative obligations much as language provides a nuanced, flexible, and generative way for humans to communicate. The possibility that law has played a pivotal role in the emergence of human sociality makes sense if one begins from Hart’s view as to what makes law a distinctive normative system.

Outlawing polygyny

One historically important resource-sharing law is the polygyny prohibition. Studying this prohibition highlights several ways laws contribute to the maintenance of a cooperative society. The polygyny prohibition is typical of a resource-sharing law in that it works by reducing the gains that can be realized by engaging in competitive behavior, in this case reducing the benefits granted to those who secure additional mating partners. Laws prohibiting polygyny are among the first recorded laws, dating back to ancient Athens, and illustrate several of the benefits of using a legal system to share resources. First, the public process of defining that a rule is a law makes reversing course more difficult. In this way the law can make commitments to arrangements that discourage competition such as the polygyny prohibition more credible. Second, the presence of a law in the historical record provides a meme that is easy to replicate. The family law provisions adopted by Solon around 600 B.C.E. have provided a template for millennia of one way a society can modify marital practices to reduce competition for mates.

Origins of a law instinct or norm psychology

The use of legal rules to facilitate resource sharing can also provide insight into how an ability to use this kind of generative normative system (a law instinct or norm psychology) may have emerged. Big game hunting, a formative practice in shaping human behavior, presents the kinds of resource-sharing opportunities and challenges that laws designed to share resources are particularly well-attuned to address. Successful big game hunting requires balancing individual and cooperative interests. A legal regime limiting the private property claims of individual hunters could encourage cooperation and might be quite helpful in this context. Moreover, our ancestors’ ability to “solve” the meat-sharing problem by defining what constitutes communal property and what constitutes private property might have provided a pathway to develop a broader tendency to use a generative normative system to “solve” resource-sharing problems.

Divvying up transaction surplus

Another insight from exploring resource-sharing laws as a window into law’s roles in the maintenance of a cooperative society is that this line of inquiry helps to explain aspects of the nuanced relationship between prosociality and transactions with strangers in market transactions. There are well-established competing hypotheses about the link between participation in market transactions and prosociality. As Albert Hirschman observed, on the one hand, there is the “doux commerce” thesis that commerce is “a civilizing agent of considerable power and range.” On the other hand, there are concerns that “capitalist society … exhibits a pronounced proclivity toward undermining the moral foundations of any society” (Hirschman, 1982, Rival interpretations of market society: Civilizing, destructive, or feeble?)

Largely absent from this debate is the question of how parties to market transactions divvy up any gains from trade. Gains from trade present the kinds of resource-sharing challenges that resource-sharing laws are designed to address. This insight generates testable hypotheses. The ability to successfully divvy up transaction surplus might moderate the relationship between participating in market transactions and prosociality. If this is correct, then the relationship between prosocial attitudes and participation in market transactions should vary depending on market structure. Where there is one price at which all transactions take place, there is less of a need for cooperation because the market price provides a ready-made mechanism with which to allocate transaction surplus. In contrast, in a market characterized by a series of independent bilateral negotiations the challenge of sharing transaction surplus in a fair and efficient manner needs to be addressed each time a transaction is consummated. As a result, at least some amount of prosociality may be helpful or even generated when participating in a bilateral negotiation.

Work by Armin Falk and Nora Szech shows how an experiment could shed light on this hypothesis by exploring whether market structure moderates the relationship between prosociality and participation in market transactions. Falk and Szech did not find a statistically significant difference on their measure of moral values between treatments in which transactions were executed by bilateral trade and in which transactions took place at a pre-set price. Their work does, however, suggest ways to further explore the hypothesis that divvying up transaction surplus explains at least some part of the nuanced relationship between prosociality and participating in market transactions.

These ideas and others in the article Evolutionary psychology and resource-sharing laws show how considering resource-sharing laws in the context of evolutionary psychology generates a variety of insights as to how and why law may have played a pivotal role in the emergence of human sociality.

Read the article: Guttentag, M. (2023). Evolutionary psychology and resource-sharing laws. Evolution and Human Behavior, 44(3), 264-271.

This article is part of a special issue of Evolution & Human Behavior on Evolution, Justice, and the Law, edited by Debra Lieberman & Keelah Williams.