Bill Moyers once quipped, “Civilization is a thin veneer of agreeable behavior stretched across the passions of the human heart.” Among the most persistent of these dark passions is ingroup favoritism. Christian versus Muslim, black versus white, liberal versus conservative – anywhere one group outnumbers the other, we typically see the minority get snubbed, insulted, or physically attacked by the majority. Psychologist D.B. Krupp and mathematician Peter Taylor of Queen’s University in Ontario recently published a theoretical model of how strife tends to develop between unequal groups. Their work supports the controversial claim that prejudicial violence is at least partially rooted in behavioral genetics. If correct, this provides one explanation for the persistence of ethnic conflict – not an excuse for intolerance.
D.B. Krupp heads the Program in Evolution and Governance at the One Earth Future Foundation. He explained to me via email, “I develop theory about the evolution of cooperation and conflict and test it in humans, both with laboratory and ‘real world’ data.” Krupp and Taylor’s recent paper is a compelling elaboration on famed evolutionary theorist W. D. Hamilton’s inclusive fitness theory. Inclusive fitness quantifies the obvious: there is an evolutionary benefit to assisting one’s close genetic relatives, even at a cost to oneself. For example, if a man dies saving three sons, half of his genes survive in three virile packages. Hamiltonian spite works on the same principle: if the martyr takes a genetic competitor down with him, his sons are that much safer.
Scaling up to the net social effect, inclusive fitness provides a persuasive explanation for altruism toward ingroups and spite toward outgroups. According to Krupp: “[A]symmetrical relatedness takes our understanding of altruism and spite further by showing that [these behaviors] can be patterned in ‘ethnocentric’ – or, really, ‘phenocentric’ – ways that depend on the phenotypes (e.g. physical appearance, accent, clothing, beliefs) of our neighbors.”
In other words, people tend to help those most like themselves and to hinder those who are different. Krupp and Taylor explore the wider phenotypical neighborhood’s influence upon this exclusionary tendency, particularly when one group outnumbers another. The authors’ work is an analytical model – purely theoretical, not empirical. The action occurs on paper, bound by rigorous mathematics. They begin by imbuing abstract entities with numerical values, then proceed to let them evolve, thus testing their elaboration on Hamilton’s inclusive fitness equation.
In effect, Krupp and Taylor construct a hypothetical population of self-cloning organisms that resemble singing insect colonies. As with humans and many other animals, these organisms detect genetic relationships through “phenotype matching.” Rather than establishing kinship through inherited odors or color patterns, phenotype matching relies on learned signals such as shared gestures or vocal patterns. Sameness becomes a proxy for relatedness. Imagine one group performing the Muslim adhan to indicate that they’re “family,” while the other chants the Nicene Creed.
Although it’s typical for such signals to be passed down within families, they can also be mimicked by nonkin, making the ingroups potentially fluid. An example would be a xenophobic family that speaks with a peculiar dialect. They adopt a child with very different physical features. Although the family may still treat other outsiders with suspicion, the adoptee’s shared dialect is sufficient to override any negative response that physical dissimilarity might trigger. This sort of flexibility can extend out a few city blocks, or across the global canopy of a world religion.
As Krupp and Taylor’s hypothetical organisms begin reproducing, some groups break off and settle in the other’s territory, creating native majorities and migrant minorities – or “common” and “rare” phenotypes. Eventually, these two groups strike upon evolutionarily stable strategies that should be familiar to anyone living in a multicultural society: social organisms with the ability to recognize kin exhibit “phenocentrism,” helping their own and hindering the Other. But Krupp and Taylor’s number-bots also develop an interesting variation:
- “Rare” migrants were highly altruistic toward their own kind, but only mildly spiteful to their majority hosts.
- “Common” natives were moderately altruistic toward each other, but developed intensely spiteful behaviors toward minority rare types. Due to their dominance and security, majority individuals could easily absorb the costs of spiteful behavior.
- The greater the proportion of common-to-rare types – i.e., the more predominant the majority – the more these strategical differences were magnified.
Krupp and Taylor’s most important contribution is their breakdown of asymmetrical costs and benefits. Majority groups can afford to snub and persecute minority groups, whereas minorities must pay a heavy price for revolting. Also, individuals in the majority can get away with minimal altruism toward their compatriots, while minorities are under pressure to be exceedingly loyal to those in their group.
Turning attention back to the messy real world, the authors correlate these findings with observed animal behaviors, most notably Argentine ants. When placed together in an arena, “individuals drawn from genetically homogeneous colonies are more aggressive towards conspecifics drawn from heterogeneous colonies than the converse, often with fatal results.” To put it another way, these Argentine ants don’t take kindly to strangers.
Their paper concludes by comparing this evolutionary model to human behavior. As in the simulation, human preference for close relatives can be hijacked and directed toward a variety of learned phenotypical signals. For instance, whether zealots congregate in temples, churches, or mosques, they take care of their “brothers and sisters.” Unfortunately, heretics and infidels are perceived as non-relatives. Krupp and Taylor engage the brutal side of this instinct, citing “ethnically motivated hate crimes” in America and the UK. These generally show regional majorities attacking ethnic minorities in greater numbers. The examples in the UK are particularly relevant to religion, as hate crimes disproportionately target Muslims there.
Statistical correlations aside, we find abundant historical accounts of tribal totems being used to harness “Hamiltonian spite” against weaker minorities. The Roman Empire brutally executed Christian martyrs; centuries later Catholics did the same to heretics. The 20th century saw neo-pagan Nazis attempt to exterminate their Jewish minority. In a similar fashion, anti-theist Communists slaughtered “enemies of the people” by the millions, many for being Christians, Confucians, or Buddhists. Although the 21st century has suffered less mass violence thus far, today we see enormous spite toward Islamic immigrants coming to the West. We also see Christians being murdered by Muslim majorities in Syria and Libya. History is a continuous saga of dominant co-ethnics squashing the odd man out
Krupp and Taylor’s analytical model suggests that the persistence of intergroup violence has a genetic basis. This idea is largely suppressed by social scientists committed to the “nurture hypothesis” and political egalitarians who fear that biological explanations will somehow justify cruel behavior. Both of these approaches assume that instinctive behavior is somehow intractable. But if you acknowledge that people are naturally inclined to be greedy, does that justify raiding someone’s bank account? If children tend to bully each other – not because they are infected with memes for meanness, but because mammals tend to play rough – should we cease to urge them toward fair play?
Peace and stability will only be possible if we are realistic about the root causes of violence. Certainly, social inequality and violent rhetoric have long been recognized as sources of injustice. However, as more and more evidence points toward evolved psychological biases, these should also be considered alongside the other factors driving ethnic and religious strife.
For more, read “Social evolution in the shadow of asymmetrical relatedness“ in the Proceedings of the Royal Society.