I have argued that cooperative behavior and mutual restraint — the bulwarks of civil society and liberty — arise from observance of the Golden Rule. (See this, this, and this, for example.)  There is some new evidence for the importance of the Golden Rule as a regulatory mechanism:

Despite the fact that cooperation in one-shot interactions is viewed as both biologically maladaptive and economically irrational, it is nonetheless behaviorally widespread in our species. This apparent anomaly has posed a challenge to well-established theories in biology and economics, and it has motivated the development of a diverse array of alternatives—alternatives that seem to either conflict with known selection pressures or sensitively depend on extensive sets of untested assumptions.

These alternatives all assume that one-shot cooperation is an anomaly that cannot be explained by the existence of cooperative architectures that evolved for direct reciprocity. Our main results show that this assumption is false: organisms undergoing nothing but a selective regime for direct reciprocity typically evolved to cooperate even in the presence of strong evidence that they were in one-shot interactions. Indeed, our simulated organisms can form explicit beliefs that their interactions are one-shot and, nonetheless, be very likely to cooperate. By explicitly modeling the informational ecology of cooperation, the decision-making steps involved in operating in this ecology, and selection for efficiently balancing the asymmetric costs of different decision errors, we show that one-shot cooperation is the expected expression of evolutionarily well-engineered decision-making circuitry specialized for effective reciprocity.

This cooperation-elevating effect is strong across broad regions of parameter space. Although it is difficult to precisely map parameters in simplified models to real-world conditions, we suspect that selection producing one-shot generosity is likely
to be especially strong for our species. The human social world—ancestrally and currently—involves an abundance of high-iteration repeat interactions and high-benefit exchanges. Indeed, when repeated interactions are at least moderately long, even modest returns to cooperation seem to select for decision architectures designed to cooperate even when they believe that their interaction will be one-shot. We think that this effect would be even stronger had our model included the effects of forming reputations among third parties. If defection damages one’s reputation among third parties, thereby precluding cooperation with others aside from one’s current partner, defection would be selected against far more strongly (44). Therefore, it is noteworthy that cooperation given a one-shot belief evolves even in the simple case where selection for reputation enhancement cannot help it along. It is also worth noting that a related selection pressure—defecting when you believe your partner will not observe you—should be subject to analogous selection pressures. Uncertainty and error attach to judgments that one’s actions will not be observed, and the asymmetric consequences of false positives and misses should shape the attractiveness of defection in this domain as well.

In short, the conditions that promote the evolution of reciprocity—numerous repeat interactions and high-benefit exchanges—tend to promote one-shot generosity as well. Consequently, one-shot generosity should commonly coevolve with reciprocity. This statement is not a claim that direct reciprocity is the only force shaping human cooperation—only that if reciprocity is selected for (as it obviously was in humans), its existence casts a halo of generosity across a broad
variety of circumstances.

According to this analysis, generosity evolves because, at the ultimate level, it is a high-return cooperative strategy. Yet to implement this strategy at the proximate level, motivational and representational systems may have been selected to cause generosity even in the absence of any apparent potential for gain.Human generosity, far from being a thin veneer of cultural conditioning atop a Machiavellian core, may turn out to be a bedrock feature of human nature. (Andrew W. Delton, Max M. Krasnow, Leda Cosmides, and John Tooby, “Evolution of direct reciprocity under uncertainty can
explain human generosity in one-shot encounters,” Proceedings of the National Academy of Science, Early Edition, July 25, 2011.)

The authors assume but offer no evidence that one-shot cooperation is an evolutionarily acquired trait. A stronger position  is that one-shot cooperation is a culturally transmitted trait. In any event, the authors’ findings underscore the importance of the Golden Rule to liberty. As I say in ““Evolution, Human Nature, and ‘Natural Rights,”

the Golden Rule represents a social compromise that reconciles the various natural imperatives of human behavior (envy, combativeness, meddlesomeness, etc.). Even though human beings have truly natural proclivities, those proclivities do not dictate the existence of “natural rights.” They certainly do not dictate “natural rights” that are solely the negative rights of libertarian doctrine. To the extent that negative rights prevail, it is as part and parcel of the “bargain” that is embedded in the Golden Rule; that is, they are honored not because of their innateness in humans but because of their beneficial consequences.