Many evolutionary psychologists, including Steven Pinker, professor at Harvard, claim that our minds at birth are not a blank slate, and further, that evolution has endowed humans with a "moral instinct". In other words, we have evolved an instinct to act often from motives beyond narrow self-interest, and to make value judgments like right/wrong, just/unjust, etc.

This seems reasonable to me. We appear to be a complex mix of nature and nurture. But what is the relationship between our evolutionary programming and our everyday morality? Can a science of the moral instinct explain human morality? Or does the realm of culture and experience muddy up the waters too much?

First of all, it is worth noting that the moral instinct, like other instincts, is only a driving force; it is amoral by itself—just as our instinct for power is distinct from an act of power, instinct for storytelling distinct from stories, instinct for sex distinct from a sexual act. Morality comes into play when value is assigned to an act or idea, for e.g., robbing a rich landlord and calling it just, or declaring torture wrong. Our moral instinct, quite unbidden, simply drives us to weigh the impact of an act on others and assign to it a value. (Anthropological data suggests that, in addition to this moral instinct, certain aspects of our morality, i.e., the value we assign to an act, may also be universal and could be innate.)

Let's compare the moral instinct with another human instinct, say, hunger. When hunger kicks in, it wants to be assuaged. How it is assuaged generally varies by taste—snakes and strawberries could both satisfy, since both are nutritious, chewable, etc. Likewise, the moral instinct can be "assuaged" in multiple ways, a fact evident across space and time in the range of human moralities, which nevertheless share some common ground and bounds. The idea that a science of the moral instinct (or "moral sense") can explain human morality—perhaps even become the basis of a "scientific morality"—seems to me about as persuasive as the idea that a science of hunger can explain "taste". We can learn many facts about hunger, but can they explain the many "tastes" around the world (likewise for the musical instinct)? This simple distinction is often ignored, including, it seems to me, by Pinker, who believes that "much of what makes you you resides in your genome." *

To the question—Can a science of the moral instinct explain human morality?—Pinker wants to say yes, but cannot find conclusive evidence. And like many good scientists, he refuses to give up—his voluminous writings reveal his unbending faith. While he admits that "Morality ... is still something larger than our inherited moral sense, and the new science of the moral sense does not make moral reasoning and conviction obsolete," Pinker, I suspect, secretly wishes it would. It is one thing to distrust reason and conviction (both consciously realized and often deployed retroactively to dignify an instinct), another to minimize even the subconscious conditioning of culture and experience on our morality. Instead, Pinker has tried to explain all kinds of morality using evolutionary psychology alone.

It is worth noting here that our evolutionary psychology was forged during and before the Pleistocene era. In evolutionary terms, humans haven't changed much since. What's changed radically is our environment. It is not easy to estimate the explanatory power of evolutionary psychology in our own day and age, suffused as it is with novel notions of "the individual" and "the autonomous self", history and progress, science, technology, modern medicine, migration and travel, markets and advertising, organized religions, high-rise living, etc. Perhaps it can explain a lot, but the evidence is not forthcoming. For now, Pinker's oeuvre has more in common with self-help books than defensible works of science. Some of my own thoughts on his popular appeal are captured in this review on Amazon.com.

Some scientists have employed a more rigorous approach to human morality. Jonathan Haidt, for instance, has identified five distinct types of moral instincts that underlie the vast diversity of moralities. It is a compelling classification which, among other things, explains the differences between conservative and liberal worldviews. Notably, Haidt himself attempts no more than a classification of moral instincts and resists explaining morality through specific combinations of genes, subconscious acculturation, and conscious reasoning. Pinker accepts Haidt's thesis in toto, as in this recent NY Times article, but also aims a lot higher:

The only other option [besides religious morality] is that moral truths exist in some abstract Platonic realm, there for us to discover, perhaps in the same way that mathematical truths (according to most mathematicians) are there for us to discover. On this analogy, we are born with a rudimentary concept of number, but as soon as we build on it with formal mathematical reasoning, the nature of mathematical reality forces us to discover some truths and not others. (No one who understands the concept of two, the concept of four and the concept of addition can come to any conclusion but that 2 + 2 = 4.) Perhaps we are born with a rudimentary moral sense, and as soon as we build on it with moral reasoning, the nature of moral reality forces us to some conclusions but not others.

Moral realism, as this idea is called, is too rich for many philosophers’ blood. Yet a diluted version of the idea — if not a list of cosmically inscribed Thou-Shalts, then at least a few If-Thens — is not crazy. Two features of reality point any rational, self-preserving social agent in a moral direction. And they could provide a benchmark for determining when the judgments of our moral sense are aligned with morality itself.

This is classic Pinker: comparing morality with math, lurching towards a "moral realism" that is "too rich for many philosophers' blood" but perhaps not his own. His search for a benchmark to determine "when the judgments of our moral instincts are aligned with morality itself" betrays his belief in a "high" morality that awaits discovery through reason, like rules in mathematics. This seems very much in line with Pinker's previous works. In his lucid review of Pinker's The Blank Slate, evolutionary geneticist H. Allen Orr notes that "Pinker champions a Darwinian psychology of human beings. But the proposition that we can build a Darwinian science of mind is distinct from—and more ambitious than—the proposition that the slate isn't blank." Orr goes on to say:

Pinker has a habit of making things seem simpler than they are and of doing so in a way that just happens to make his claims more secure and his conclusions more inescapable than they really are ... there are good reasons for not going as far as he'd like you to. Pinker's tendency to make things too easy leads him into three kinds of problems. One is scientific, one historical, and one ethical.
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Pinker's fondness for "evolutionary psychology" will come as no surprise to those who remember How the Mind Works. But it is surprising to see how extreme he has become. Pinker seems never to have met an adaptive tale he doesn't like...
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Now there's no reason to think that Pinker's psychology-as-adaptive-tale is inherently hopeless. A Darwinian approach to mind may be no more impossible than a Darwinian approach to mammaries, and an evolutionary psychology might well reveal something about human nature. Indeed any or all of Pinker's adaptive tales could be true. But there are grounds for worry. One is that, despite Pinker's confident tone, the evidence for his stories varies wildly and some of his tales are sheer speculation. There is, for example, little or no evidence that either human neonaticide or self-deception is genetic. These cases are in fact symptomatic of a serious problem with evolutionary psychology: its research program shows a curious tendency to invert itself. You might think that convincing evidence that a particular form of behavior is inherited usually leads to attempts to explain how and why it evolved. But often what happens is the reverse: the fact that we can conceive of an adaptive tale about why a behavior should evolve becomes the chief reason for suspecting it's genetic. Why, after all, does Pinker think human neonaticide might be genetic? Where are the twin studies, chromosome locations, and DNA sequences supporting such a claim? The answer is we don't have any.

... evolutionary psychologists sometimes forget a hard truth: a Darwinian story is not Mendelian evidence. A Darwinian story is a story. And the accumulation of such stories has an important consequence. The slate may seem to get less and less blank in part because evolutionary psychologists keep scribbling more and more tales on it.

Pinker has compared the moral instinct with the language instinct. He claims that humans possess a moral grammar similar to Chomsky's "universal grammar"—"we are born with a universal moral grammar that forces us to analyze human action in terms of its moral structure, with just as little [conscious] awareness" of the rules in play. Perhaps. But what takes us from the "universal grammar" to Othello?

PS: Also check out Louis Menand's critique of Pinker in the New Yorker.