One of our most able and informed scientific journalists, William Saletan, astutely summarizes the pioneering contribution of the dissident evolutionary psychologist Jonathan Haidt:

Social conservatives see welfare and feminism as threats to responsibility and family stability. The Tea Party hates redistribution because it interferes with letting people reap what they earn. Faith, patriotism, valor, chastity, law and order — these Republican themes touch all six moral foundations, whereas Democrats, in Haidt’s analysis, focus almost entirely on care and fighting oppression. This is Haidt’s startling message to the left: When it comes to morality, conservatives are more broad-minded than liberals. They serve a more varied diet.

This is where Haidt diverges from other psychologists who have analyzed the left’s electoral failures. The usual argument of these psycho-­pundits is that conservative politicians manipulate voters’ neural roots — playing on our craving for authority, for example — to trick people into voting against their interests. But Haidt treats electoral success as a kind of evolutionary fitness test. He figures that if voters like Republican messages, there’s something in Republican messages worth liking. He chides psychologists who try to “explain away” conservatism, treating it as a pathology. Conservatism thrives because it fits how people think, and that’s what validates it. Workers who vote Republican aren’t fools. In Haidt’s words, they’re “voting for their moral interests.”

One of these interests is moral capital — norms, prac­tices and institutions, like religion and family values, that facilitate cooperation by constraining individualism. Toward this end, Haidt applauds the left for regulating corporate greed. But he worries that in other ways, liberals dissolve moral capital too recklessly. Welfare programs that substitute public aid for spousal and parental support undermine the ecology of the family. Education policies that let students sue teachers erode classroom authority. Multicultural education weakens the cultural glue of assimilation. Haidt agrees that old ways must sometimes be re-examined and changed. He just wants liberals to proceed with caution and protect the social pillars sustained by tradition.

Another aspect of human nature that conservatives understand better than liberals, according to Haidt, is parochial altruism, the inclination to care more about members of your group — particularly those who have made sacrifices for it — than about outsiders. Saving Darfur, submitting to the United Nations and paying taxes to educate children in another state may be noble, but they aren’t natural. What’s natural is giving to your church, helping your P.T.A. and rallying together as Americans against a foreign threat.

How far should liberals go toward incorporating these principles? Haidt says the shift has to be more than symbolic, but he doesn’t lay out a specific policy agenda. Instead, he highlights broad areas of culture and politics — family and assimilation, for example — on which liberals should consider compromise. He urges conservatives to entertain liberal ideas in the same way. The purpose of such compromises isn’t just to win elections. It’s to make society and government fit human nature.

The hardest part, Haidt finds, is getting liberals to open their minds. Anecdotally, he reports that when he talks about authority, loyalty and sanctity, many people in the audience spurn these ideas as the seeds of racism, sexism and homophobia.

So some take-away points:

Liberals are too reckless about dissolving moral capital.  That's why they should take seriously conservative positions as reasonable defenses of the perennial moral interests of members of our social species.  It goes without saying that both liberals and conservatives should compromise, and both liberals and conservatives mistakenly believe that their ideological principles are more reasonable than they really are.

The conservative passion to defend legitimate personal authority, loyalty, patriotism, personal responsibility, sanctity (or sacred duty), and the family correspond to genuine insights about who we really are.  So conservatives aren't simply or mainly unreasonable when they vote in support of such indisepnsable and admirable moral virtue against those who are vainly exaggerate the possibility and goodness of individual liberation or "autonomy" in a most un-Darwinian way.

Conservatives often go too far, forgetting our personal interests in freedom.  But that doesn't mean that what they say and do does nothing but mask "racism, sexism, and homophobia."  "Politically correct" liberals distort reality and angrily fight against reason when they reduce the moral doctrines of the past to pointless or pathological oppression.  Conservaties aren't simply or mainly patriarchal rednecks in the thrall of superstitious fundamentalism.

Haidt, of course, surely exaggerates how Darwinian many conservatives really are.  The Tea Partiers, after all, are really big on individual rights and the tiny government they associate with our Founders.  And Christian virtue—such as charity—is intensely personal as well as merely social.  The City of God, of course, includes all human beings or not just Americans or those we've successfully assimilated into our tribe.

And Haidt acknowledges, but sometimes seems to underplay, the social virtues or social responsibility of many liberals, who, after all, sometimes really do care about the well-being (and even the souls) of the unfortunate.  Unregulated or overly intrusive "capitalism," as Haidt says, erodes moral virtue too.