Any general theory of politics assumes a theory of human nature. A small but growing number of political scientists have been applying a Darwinian theory of human biological nature to various topics in political science. The final aim of such work would be to turn political science into a biopolitical science. These two books contribute to that end by showing how research in human biology and Darwinian theory can illuminate the study of international relations.
Although they agree on many points, Stephen Peter Rosen and Bradley Thayer disagree on the implications of a biological approach to international relations for assessing rational choice theory. Rational choice theorists assume that human beings are egoists who rationally maximize their interests. Applying rational choice theory to international relations means that decisions of war and peace are explained as rational calculations of interests by states competing with one another. Thayer believes that a Darwinian view of international relations confirms rational choice theory by explaining the human nature of rational egoism as ultimately caused by natural selection in the evolutionary competition of human beings for scarce resources. Rosen believes, however, that a biological understanding of human nature shows that rational choice theory is only partially true, because in stressing rational calculations of interest, it ignores the emotional dispositions of fear and honor as factors shaping human decisions in international relations.
In his history of the Peloponnesian War, Thucydides has some Athenian envoys in Sparta say that the imperial policies of Athens are motivated by fear, interest, and honor. Rosen says that the aim of War and Human Nature is to show “that there is a biological argument that Thucydides was right, that fear and honor play a role in human politics along with calculations of interest, but also that the other issues he analyzed, such as the nature of the political systems present in the ancient Greek world, matter as well” (p. 2). Human beings are inclined by their biological nature to be rational egoists, and so the rational choice theorists are right about this. But that same biological nature also inclines human beings to feel social emotions that make them care about others and about their status in relation to others. And so, for example, their emotional desire for honor and fear of being dishonored might move them to act contrary to their material interests. Moreover, Rosen argues, these complex motivations of human biological nature are manifested in the military and political behavior of states in international relations.
Rosen applies research in neuroscience on the complex interplay of reason and emotion in the brain and endocrine system to explain the decision making of leaders in times of international crises. Through case studies, he argues that American presidents have had to make quick decisions in complex international circumstances through emotional pattern recognition shaped by memories of emotionally charged experiences from the past. They thus employed neural pathways of information gathering and decision making shaped by natural selection in human evolutionary history.
Rosen argues that while the termination of war can result from calculated decisions about material interests, this can also result from a collapse of the will to fight among the losers, which arises from emotional distress with a neurophysiological basis. Again, his general point is that decisions about war and peace arise from the complex interaction of reason and emotion as shaped by the evolved nature of the human brain.
One prominent manifestation of evolved human nature in international relations is the natural desire for status and dominance. Those who fill the highest offices for deciding issues of war and peace tend to be ambitious people who desire dominance over others. Rosen identifies such people as mostly high-testosterone men who manifest a desire for dominance shaped in evolutionary history where men competed with one another for preeminence. People like Abraham Lincoln, Franklin Roosevelt, and Winston Churchill are moved by a desire for distinction—for honor and glory—that goes beyond any selfish calculation of material interests.
Tyrants show a similar desire for dominance. But Rosen argues that ambitious leaders like Lincoln, FDR, and Churchill do not have the tyrannical souls of people like Hitler, Stalin, and Mao. He claims that tyrannical behavior emerges from “the personal character of tyrants combined with the institutional character of tyrannies” (p. 178). Rosen's point here is somewhat unclear. But the idea seems to be that those of tyrannical temperaments will rise to the top in turbulent circumstances where there are few institutional checks or limits on the ruthless and opportunistic pursuit of power. This shows the need to channel the rivalry of politically ambitious people through an institutional structure of checks and balances so that ambition counteracts ambition.
Although he agrees with Rosen in using biological science to explain international relations, Thayer sees biological explanations as applying only to the level of ultimate causes in the genes, as distinguished from social and cultural explanations as applying to the level of proximate causes in the environment. Human behavior arises from a complex interaction of ultimate and proximate causes.
According to Thayer, evolutionary biology contributes to international relations theory by explaining the ultimate causes of war and ethnic conflict. Human beings wage war to acquire and defend resources, because this was favored by natural selection in evolutionary conditions where competing for scarce resources enhanced fitness. Human beings are inclined to ethnic conflict because in-group/out-group distinctions, xenophobia, and ethnocentrism conferred competitive advantages in human evolutionary history.
In Darwin and International Relations, Thayer repeatedly acknowledges the power of emotions in human social behavior. He speaks of the “profound emotions” of war, which include “profound love of comrades, the deepest hatred of the enemy, fear of death, and fear of disappointing the other men” (p. 191). He also refers to the “emotional depth of national identity” (p. 232). And yet he never considers how such emotions—deeply rooted in the brain and endocrine systems of human nature—might go beyond “rational choice.”
Nor does Thayer consider the moral emotions as expressions of human biological nature. He quotes Adam Smith as describing the egoism of Homo economicus, and he claims that evolutionary theory confirms this economic understanding of human nature. But he says nothing about Smith's account of the “moral sentiments” as the natural ground of moral judgment. Nor does he mention the influence of Smith over Charles Darwin's theory of the “moral sense” as rooted in human biological nature.
This is an important point because many social scientists have recently been employing experiments in evolutionary game theory that confirm the importance of moral sentiments for instilling a sense of right and wrong that motivates people to punish wrongdoers, even when this punishment requires some sacrifice of material interests. Moreover, neuroscientists are now uncovering the neural roots of these moral sentiments in the emotional-control pathways of the brain. This natural moral sense manifests itself in international relations when individuals and nations act out of a sense of justice to aid the victims of injustice and to punish those who have injured them. The tradition of “just war” arises out of such moral sentiments.
Thayer assumes that biological science cannot explain moral experience because science is concerned with factual claims rather than value judgments, and he attributes this fact/value distinction to David Hume. But Thayer misses Hume's point. Hume distinguishes is and ought in order to show that moral assessments are derived not from pure reason alone but from moral emotions. Hume believes that correct moral judgments are factual statements about the species-typical pattern of moral sentiments in specified circumstances.
Darwin saw that the ethical naturalism of Smith and Hume allowed morality to become an object of scientific study, because scientists could study the natural roots of moral judgment in the evolved moral emotions of the human animal. Recently, biologists such as Edward O. Wilson and economists such as Robert Frank have renewed Darwin's project for a scientific study of morality as founded on natural moral emotions. Thayer says that the question of whether rational choice theorists should include “moral commitment” as a factor in human behavior constraining egoism is “beyond the scope of this book” (p. 86). But a complete political science would need to explain the moral passions that drive political controversy. A biopolitical science would explain morality in politics as expressing the natural moral desires of evolved human nature.
Such a science would study not only the genetic evolution but also the behavioral and cultural evolution of human beings and other political animals. Thayer tends to reduce human biology to genetics. But biology is much more than genetics. And a purely genetic science will not explain much about politics, which depends on higher levels of complexity far beyond the genes.
DNA by itself does nothing. DNA acts through interactions at many levels of biological complexity—interactions within a cell, between cells, between organisms, and within ecological and social communities. These interactions determine the expression of genes, and the patterns of gene expression can evolve in response to behavioral and cultural evolution.
Studying the genes by themselves would tell us almost nothing about politics. But studying the genetic interaction with behavioral and cultural evolution would tell us quite a lot about politics. For example, Thayer stresses that warfare is not unique to human beings, because other animals (such as ants and chimpanzees) wage war in ways that resemble human warfare. But he does not indicate that the patterns in animal warfare show behavioral and cultural evolution. Primatologists have reported diverse behavioral traditions among various chimpanzee groups, not only in war but in other activities, and so it seems that each chimpanzee community has its own repertoire of cultural traditions. Thayer does emphasize the importance of environment or culture as “proximate causes.” But he does not clearly indicate that cultural evolution is just as much a part of biology as genetic evolution.
For a science of politics, we need a science of human nature that studies the coevolution of many causes at many levels of complexity—from genes to brains, then to behavior and culture, and finally to symbolic communication as the uniquely human adaptation. In that way, political science could become a true science by becoming a biopolitical science.
