Human moral systems are ultimately biological: they are generated by brains, and brains are composed of mechanisms that evolve by standard Darwinian natural selection. Like all biological adaptations (such as hearts, uteruses, and hands), these mechanisms solve problems related to individual survival and reproduction. The moral judgments of individuals can generally be regarded as the primary products, or else as the by-products, of these mechanisms. Disgust about mating with one’s next-of-kin, for example, is probably the primary product (that is, the product that evolution “intended”) of a mechanism designed to avoid inbreeding. The tendency to condemn gratuitous harm to animals, on the other hand, is most likely the by-product of mechanisms that function primarily to enable empathy with humans, and to advertise one's kindness to other people. (Note that to regard a trait as a by-product as opposed to a primary product implies nothing at all about its social value).
Some psychological adaptations for morally-relevant behavior solve problems that exist in virtually all human environments (for instance, the problem of avoiding inbreeding). Others are solutions to problems that are more severe in some environments than others, and this is a major reason why—despite the fact that human nature is fundamentally the same cross-culturally—some aspects of moral systems vary significantly across cultures. For example, in environments in which access to resources depends especially heavily on success in war—such as among the tribal communities of highland New Guinea, or the fiefdoms of medieval Europe—people are relatively likely to endorse military virtues like fierceness and valor and to disparage cowardice.
Human psychological adaptations can also create innovative value systems that solve problems in a wide range of adaptive domains. Values that promote scientific inquiry, for instance, help solve problems related to subsistence (agricultural science), survival (medicine), trade (industrial production), and many other domains. This human ability to design innovative moral systems is another reason why morality varies across cultures, and researchers like biologist Richard Alexander and anthropologist Robert Boyd have suggested how this cultural variation can lead to moral evolution. Humans are biologically adapted to compete in groups, and an important advantage that one group can have over another is a moral system that better promotes competitive success. If features of a society’s moral system (such as values that promote scientific progress) advantage that society in intergroup competition, then the moral system can be favored by “cultural group selection” (not the same thing as biological group selection, which is a process whereby individuals evolve to benefit their groups at the expense of their own genetic survival, and which appears unnecessary as a distinct explanation for human behavior; for details see Steven Pinker's article or my book review). Historically, groups with relatively empowering moral systems have tended to supplant groups with relatively enfeebling moral systems, and also to be imitated by weaker groups who wish to emulate their success. Through these processes, winning moral formulas have tended to spread at the expense of losing ones.
From this perspective, the crucible of intergroup competition plays a key role in determining which moral systems flourish and which ones perish. This view does not necessarily imply anything cynical about morality: there’s no reason at all from biology that this competition must be violent (and indeed, Pinker argues persuasively in his recent book that it has become much less violent over time), and nonviolent, productive competition can lead to a rising tide of benefits for humanity in general. What this view does imply is that morality ought to be less about passionate expressions of outrage, and more about designing a value system that will enable societal success in a constantly changing and eternally competitive world.
(A version of this article will appear as the author's "Natural Law" column in the banking magazine Global Custodian).
Copyright Michael E. Price 2012. All rights reserved.