In making this argument, I disagree with those many critics of sociobiology who assume a nature/history dichotomy in claiming that the biological study of animal nature cannot explain human history. One of the first critiques of Ed Wilson's Sociobiology was Kenneth Bock's Human Nature and History: A Response to Sociobiology, first published in 1980. The central argument of this book is "that explication of social and cultural differences is a primary task of the human sciences and that such explication is best sought in comparison of human histories, not in human biology or comparative ethology" (ix). Human biology or comparative ethology can study the biological nature that human beings share with other animals. But Bock insisted that "animals other than man do not have histories" (198). Animal behavior is determined by the biological nature of each species, which can be studied by biologists. But human history in its contingency and diversity shows a human freedom from nature that transcends human biology, Bock argued, and this human history can be studied by historians, but not by biologists.
Bock does admit, if only in passing, that sometimes changes in an animal's environment can give rise "from time to time and from place to place to activities in one population of a species that were not there before and are not present among other populations of the species," and thus these animal populations might be said to have "histories," and those who study human history should be interested in this as possibly illuminating the character of historical phenomena (147-48).
Here Bock was referring to some of the early evidence for animal cultural history. And now we have much more evidence that many animals do indeed have cultural histories, so that animal groups of the same species develop distinctive behavioral traditions that distinguish one group from another. We can see this, for example, in the different chimpanzee groups in Africa. Jane Goodall's Chimpanzees of Gombe is a political history of the chimpanzees in Gombe National Park in Tanzania, who have a unique suite of cultural traditions.
Goodall's political history of the Gombe chimps includes political biographies of the individual chimps who shaped that political history. She gives all of the chimps names, and she records the stories that display their unique personalities. When she went to Cambridge University to work on her Ph.D. in ethology (animal behavior), she was told that this was all wrong--that speaking about animals as having individual personalities is an anthropomorphic projection of uniquely human traits onto nonhuman animals. To be truly scientific, she was told, she needed to reduce chimp behavior to general patterns of data without trying to explain the personal histories of individual chimps.
Similarly, John Hibbing, who is a leading proponent of the biological study of political behavior, has said that biopolitics must be limited to studying the "bedrock dilemmas of politics" that are universal to all political communities (Hibbing 2013). While biology can illuminate "cross-polity commonality," biology has no application to variable traditions of political culture or to the biographical history of individual political actors. Thus, like Bock, he assumes that human cultural history and individual history transcend nature. When I refer to the biographical history of Lincoln's decision to issue the Emancipation Proclamation as a necessary part of a biopolitical science, Hibbing says that this is bringing in "non-biological factors" that cannot be studied biologically. But if one includes the science of animal behavior within biology, and if one sees that the biological study of animal behavior includes the study of particular events in the political history of animal groups shaped by unique cultural traditions and unique individuals, then any biopolitical science must include political history and political biography.
For a long time, many biologists were not interested in the evolution of animal personalities, because they assumed that evolution would shape a species typical psychology shared by all individuals of the species with little heritable variation. Evolutionary psychologists (like Leda Cosmides and John Tooby) have concentrated on human universals as evolutionary adaptations shared by all human individuals (Nettle 2006).
But in recent decades, the biological study of animal personalities has become one of the hottest topics in biology (Carere and Maestripieri 2013; Pennisi 2016). Actually, this is a rediscovery of what Aristotle explained in his biological works. He recognized that "in a number of animals, we observe gentleness or fierceness, mildness or cross temper, courage or timidity, fear or confidence, high spirit or low cunning, and, with regard to intelligence, something equivalent to shrewdness" (History of Animals, 8.1). In his Generation of Animals, Aristotle distinguished between three levels of inherited traits among animals. An animal species, including the human species, shows generic traits shared with some other animals, specific traits shared with members of the same species, and temperamental traits that differ among individuals of the species. Thomas Aquinas adopted this biological idea from Aristotle as showing three levels of natural law corresponding to generic nature, specific nature, and temperamental nature.
In the recent biological studies of animal personality, personality designates behavioral and physiological differences among individuals of the same species, which are stable across time and across different situations. An individual personality is a consistent pattern in how an individual feels, thinks, and acts. Some researchers have used different terms for this--such as temperments, behavioral syndromes, and predispositions.
Extensive empirical studies of animals in the wild and in laboratories have shown personalities across animal taxa--including invertebrates, fish, birds, and both nonhuman and human primates. One of the most commonly observed traits of personality arises from the distinction between the active, risk-taking, aggressive, and bold personality, on the one hand, and the passive, risk-averse, nonaggressive, and shy personality, on the other hand. Jerome Kagan has shown that human infants from an early age can be seen as showing either a bold and uninhibited personality or a shy and inhibited personality, and that as adults these differences in personality remain. He also showed that these behavioral traits were correlated with distinctive neuroendrocine activity.
This same continuum of behavioral traits from extreme boldness to extreme shyness can be found in other animals. For example, among the great tits, a common Eurasian bird, some individuals are aggressively bold in their foraging for food, while others are less aggressive and more shy. One might think that the aggressive individuals would always win out over the unaggressive individuals, but that's not true. In one study, 541 individuals were tracked for 4 years. It was found that when bird populations were low, and resources were abundant, aggressive individuals had higher rates of survival and reproduction. But when bird populations were high, and resources were scarce, competition for territory and food sharpened, and the aggressive individuals wore themselves out by getting into too many fights, while the less aggressive individuals were more likely to survive and reproduce.
One of the most extensively studied models of human personality among psychologists is the Five Factor Model that describes human personality differences across five domains--Openness to Experience, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (OCEAN). Each domain corresponds to an axis running from high to low. So, for example, those individuals high in Agreeableness tend to be helpful, trusting, and cooperative with everyone. Individuals lower in Agreeableness tend to be less helpful, more suspicious of others, and more competitive than cooperative.
This same Five Factor Model can be applied to the study of nonhuman animal personalities, using the same methods as are used in studying human beings. Four of the factors appear in many animal species. But Conscientiousness seems to appear only among chimpanzees and human beings. One possible explanation for this is that Conscientiousness requires a high cognitive ability for making plans and controlling impulses in executing those plans, which requires the large frontal lobes found only in chimps and humans.
The five factors of personality have been found to be highly heritable and thus genetically influenced. But these factors also vary according to environmental experience, particularly the environment of early experience, which influences personality throughout life. So personality seems to arise from genetic predisposition, from environmental learning, and from the interaction of genes and environment (including the cultural environment). Through experimentation with animals in the wild and in laboratories, scientists can make testable predictions about the genetic and environmental causes of personality.
They can also study the correlation of these personality traits with distinctive neurobiological and physiological substrates. For example, the low neurotransmission of serotonin and the high neurotransmission of dopamine are associated with novelty-seeking and risk-taking. Consequently, psychotropic drugs that alter this neurotransmission can have profound effects on mood and behavior.
It might seem strange that adaptive evolution by natural selection has not eliminated these differences in personality. If natural selection is selecting for the optimal adaptation of a species to its environment for survival and reproduction, why wouldn't all or most individual animals of the same species show that same behavioral propensities, as suggested by evolutionary psychologists like Cosmides and Tooby?
One possible answer, as argued by David Nettle, is that there often is no optimal solution to the problems faced by animals, because they face trade-offs between different fitness costs and benefits, where there is no unconditionally best behavioral strategy. We should consider the possibility that each personality trait in the Five Factor Model has evolutionary costs and benefits, and whether the benefits exceed the costs depends on contingent and fluctuating circumstances. If this is so, then we should expect to see individuals showing alternative personality traits that are sometimes better and sometimes worse for the animal.
So, for instance, being high on Agreeableness might be beneficial for an individual in being attentive to the mental states of others, in enjoying cooperative relationships with others, and in being a good coalitional partner. But that same personality trait of Agreeableness might also be costly for an individual who is too trusting in being exposed to social cheating and failing to maximize one's selfish advantage.
It is possible that the cultural evolution of the bourgeois virtues in modern liberal societies depended on an evolutionary history favoring personality traits like high Agreeableness and high Conscientiousness. The evidence from cross-cultural economic game experiments that show that being integrated into market exchange is correlated with a greater sense of fairness might support this conclusion.
Carere, Claudio, and Dario Maestripieri, eds. 2013. Animal Personalities: Behavior, Physiology, and Evolution. Chicago: University of Chicago Press.
Hibbing, John. 2013. "Ten Misconceptions Concerning Neurobiology and Politics." Perspectives on Politics. June 2013.
Nettle, Daniel. 2006. "The Evolution of Personality Variation in Humans and Other Animals." American Psychologist 61: 622-31.
Pennisi, Elizabeth. 2016. "The Power of Personality." Science 352: 644-47.