I agree that we must distinguish "heritable" (varying genetically within in a population) from "evolutionary" (being explicable in terms of phylogeny or adaptation) from "genetic" (a direct or indirect product of the genome) from "unchangeable." But your reasonable advice that people not strive to pole-vault themselves to a level of happiness outside their inherited range seems to assume that there is some connection between them—that at least in this case, what is heritable is also difficult to change. The connection may not, in fact, be far-fetched. For example, opinions on many controversial topics are partly heritable—as Gilbert and Sullivan wrote, "Every boy and every gal that's born into the world alive is either a little liberal or else a little conservative"—and studies have shown that the more heritable an opinion is, the more resistant people are to changing it.
You suggest that my students who would rather be happy pigs than sadder-but-wiser humans bespeak an American hedonistic take on happiness. Is there an alternative explanation: sheer age? Could an orientation toward a good and meaningful life be a hard-won lesson that sinks in only in adulthood or even middle age? One thinks of teenagers' penchant for drugs, casual sex, reckless driving, extreme sports, and romantic infatuation, and of adults' reflections on which decisions in their lives gave them lasting satisfaction. Is turning toward a good and meaningful life just part of growing up? Cross-cultural data would be relevant. Are there cultures in which adolescents are no more hedonistic than adults?
Danny Kahneman speaks of aggregating pleasurable and painful moments, though he also distinguishes the desire to maximize this tally from the desire to have experiences that fall into a satisfying autobiographical narrative (as when we make an arduous trip to an interesting event to be able to say that we have done it). When people ask me, "Do you enjoy writing?" I give them the old author's reply, "I enjoy having written."
Beauty is an interesting case (see Nancy Etcoff's Survival of the Prettiest: The Science of Beauty). Many evolutionary psychologists argue that there couldn't be "beauty genes" for particular facial features, because if there were, they would have been selected to fixation many generations ago, and everyone would now be equally beautiful. If there are beauty genes, they express themselves in the brain of the beholder, not the face of the beholdee. We are attracted to features of anatomy that index a person's health, fertility, and absence of developmental defects.
I'd like to return to my own (and Bob Wright's) question about human nature and optimism at the level of politics and social organization. In The Blank Slate I point out that the image of the mind as a tabula rasa is not as rosy as it sounds. It invites totalitarian dictators to try to fill up the slates with the right kind of inscriptions rather than leaving it to chance. It emboldens them to base their authority on a moral superiority to their rivals and to imagine that their repressive governments are temporary measures that will some day wither, allowing a "new man" to live in harmony. Democracy, in contrast, is based on a jaundiced theory of human nature and calls for permanent checks and balances to control human ambition and self-deception. Mao said, "It is on a blank page that the most beautiful poems are written." Madison said, "If men were angels, no government would be necessary; if angels were to govern men, no controls on government would be necessary." In societies no less than individuals, acknowledging our limitations may ultimately be more humane than denying them.