“If I had a son, he’d look like Trayvon.”
— Barack Obama on Trayvon Martin
It generally is taken as a given that the United States must become more Hispanic and less Anglo as a matter of demographic inevitability, but that assumption rests largely on the continuation of current patterns of immigration, which itself is predicated on ignoring the question: Does greater diversity serve the greater good? Glenn Loury once observed that the essence of conservatism is the belief that “human nature has no history.” Even as we hope to live up to the best of our natures rather than down to the worst of them, the evidence counsels a measure of pessimism on the subject — and not only for Republicans concerned that the demographic deck is stacked against them in the long term. Progressives who dream of a Nordic-style welfare state will find themselves challenged by the costs of greater diversity, as will those of us who hope, perhaps naïvely, for a politics and a culture that is more humane and individualistic, and less regimented along racial lines. We’ve been told that diversity is our strength, but the unhappy truth may be something closer to the opposite.
Since the time of Charles Darwin, evolution theorists have puzzled over the question of altruism. The remorseless logic of evolutionary selection suggests that individuals should be very selfish, but, in fact, they often are not. Vampire bats share food, primates groom one another, birds put themselves at risk by issuing warning calls when a predator is detected, and so on. In theory, evolution should weed out behavior that puts an individual at a relative reproductive disadvantage, however slight. Darwin himself, considering the question of sterile insect castes (e.g., the worker ants, which never reproduce but serve the colony queen, which does), thought that it was potentially “fatal” to his theory. He settled on the idea that the solution to his dilemma probably was in family relationships, and evolution theorists of subsequent generations developed that into the theory of “kin selection,” an evolutionary strategy by which we pass on our genes both by reproducing and by supporting our relatives — those who share genes with us — an example of what is known as “inclusive fitness.”
The human brain is a shrewd investor: We may be inclined to share and to cooperate, but we are much more inclined to share and to cooperate with those who are closely related to us, and with those who reciprocate. The evolutionary psychologists Leda Cosmides and John Tooby have demonstrated that the brain contains a specific mechanism, probably in the limbic system, to detect cheaters — people who derive benefits from social exchange without satisfying social requirements. Human beings are not especially good at detecting rule violations — but in the context of social exchange, we are remarkably good at it, a fact that holds true for people of different backgrounds and in different cultures.
Reciprocity is intensified by relatedness. You don’t treat your old friend from high school the way you treat your children, and you probably wouldn’t be as apt to donate a kidney to a stranger as to a brother. As with cheating, the human brain is good at judging relatedness, through facial cues and, very probably, through other mechanisms as well. (Wasps detect relatives via pheromones; so might we.) We tend to have more faith in people who look like us, as Lisa M. DeBruine of McMaster University put it in the title of her 2002 paper “Facial resemblance enhances trust.” (But it doesn’t necessarily make us more trustworthy: “Resemblance to the subject’s own face raised the incidence of trusting a partner,” DeBruine writes, “but had no effect on the incidence of selfish betrayals of the partner’s trust.” We’re kind of an awful species.)
We are more inclined to share and to cooperate with people to whom we are related, and we are most likely to trust faces that look like our own. When President Obama noted that if he had a son, that son would look like Trayvon Martin, he was giving voice to a natural inclination, perhaps a more powerful one than he understands. (Nearly 200 Latino men have been murdered in Los Angeles County in the past twelve months, but they don’t look like President Obama.) I’ve always had some contempt for the idea that Mae Jemison wouldn’t be an astronaut if she hadn’t seen Nichelle Nichols playing Lieutenant Uhura on Star Trek, but perhaps I am understating the power of identification. Jamelle Bouie points to a disturbing study in which white subjects were more likely to support harsh criminal-justice measures when they were given the impression that prison populations are even more disproportionately black than they actually are.
How wide we draw the circle of kinship and how we think about its boundaries are cultural issues, true, but our habit of scrutinizing and categorizing, and of adapting our behavior accordingly, is as much a natural part of us as our blood and bones.
The obvious and unfortunate flip side of this is that we are less inclined to trust and share with people who are less like us. This has been a well-established fact in social-science literature for a long time: Ethno-linguistic diversity imposes costs on societies by reducing trust and undermining social cooperation. It isn’t a linear relationship, because diversity has real value, too. There are very happy homogeneous societies and miserable homogeneous societies; there are rich diverse countries and poor diverse countries. Quamrul Ashraf and Oded Galor, economists at Williams and Brown, respectively, have argued that there is in effect a point of diminishing return for diversity, finding that excessive homogeneity has held back the economic performance of Native American populations but excessive diversity has hobbled development in Africa. Their position is a controversial one, but research from around the world has produced similar results: Peter Thisted Dinesen and Kim Mannemar Sønderskov surveyed Danish municipalities from 1979 to the present and found that increasing diversity was correlated with diminished social trust. The effect seems to be general, at least at some level.