Yes, in The Blank Slate I argue that Homo sapiens has much to be modest about. We are prone, to varying degrees and in various circumstances, to ethnocentrism, violence, adultery, ambition, superstition, and self-deception, among other vices. As one reviewer put it, we are not stardust, we are not golden, there is no way we're getting back to the garden—get used to it.
So, does this mean we should all take poison now and be done with it? Not yet. In many ways The Blank Slate is an optimistic book. Limits to pessimism can be found at three levels.
The first consists of philosophical reflections on our condition. Should we rue the fact that we belong to such a sorry species—like Woody Allen when he said, "My one regret in life is that I am not someone else"? In fact our flaws are double-edged, and we might not accept the offer of a demon to trade them in for something else.
Take the kin-selected limits on altruism, which tempt us to form dynasties, hire our relatives, spend money on luxuries for our children (orthodontics, summer camp, expensive educations) that we could have used to save the lives of unrelated children in the developing world, and bequeath our estates to our heirs—one of the biggest impediments to economic equality. Unjust, perhaps. But our close relatives have a special place in our hearts because the place for everyone else is, by definition, less special. Would we really be better off if our relationships with our parents, siblings, and children were not uniquely precious?
Or take romantic love, with all its perfidy and heartbreak. Donald Symons has pointed out that if people belonged to a species in which each couple was marooned on an island for life, the absence of romantic rivals would not select for lifelong bliss; it would select for no consciousness at all. There would be no falling in love because there would be no alternative mates to select from, and falling in love would be a huge waste. Nor would there be pleasure in sex, which would be done for reproduction and would provide no more feeling than the release of hormones or the production of gametes. The richness and intensity of the emotions in our minds are evolutionary testimony to the preciousness and fragility of our relationships in life.
The second level is the one of practical social improvement and hopes for moral progress. Here, too, human nature should not be cause for lamentation. The human mind is a complex system of many parts. It may have temptations toward greed or violence, but it has much else besides. It has cognitive faculties that can learn the lessons of history and take a long view of the future. It has faculties of combinatorial reasoning that can come up with new solutions, just as our combinatorial language faculties come up with new sentences. It has a moral sense and a capacity for sympathy which, granted, might be applied by default only to our clan, but which can also be expanded to include the tribe or species. As Bob Wright showed in Nonzero, this expansion can be driven by our capacity to enjoy gains in trade, making other people more valuable alive than dead; it can also be expanded by cosmopolitan forces (history, journalism, realistic fiction) that make it easier to project ourselves into other peoples' lives.
Finally, we get to the level of individual decisions on how we live our lives. We all know that identical twins reared apart are highly similar in their intelligence, personality, and temperament. That is one of many discoveries suggesting that some of the differences among us come from differences in our genes. But here is a sobering fact. Identical twins, even when they are reared together, are nowhere near being perfectly correlated. Up to half of the variation in psychological traits is not explained by genes, families, or any of the other usual suspects. I believe Marty has some interesting things to say about this.