Many people, laypeople and scholars alike, assume that the kinds of dispositions that inevitably prevail in the process of biological evolution must be selfish and immoral, rendering humans and other animals bad by nature. Such people reason that selfish genes (that is to say, genes that design mechanisms that enable them to produce replicas of themselves) produce selfish individuals. However, this idea is misguided because there are significant differences between selfish genes and selfish individuals. The kind of individual selfishness that is an enemy of morality differs from genetic selfishness in several significant ways, and selfish genes may increase their frequency in populations by disposing individuals to cooperate with others and to behave altruistically toward those who possess copies of their genes, especially their blood relatives and members of their groups. Updating Darwin's early ideas on the evolution of the moral senses, I explain in The Origins of Morality: An Evolutionary Account how dispositions to behave in moral ways could evolve, and I offer evidence that such dispositions have evolved in humans and other species.
Viewing morality from an evolutionary perspective can contribute to our understanding of its nature by encouraging us to ask how the forms of conduct we consider moral and the mental mechanisms that dispose us to make moral judgments originated, and what functions they served in early human environments. People possess beliefs about morality for a reason. The key to understanding what morality is lies in understanding what it is for-how moral beliefs and moral behaviors contribute to people's welfare; how they help them adapt to their environments. A general definition of morality can be derived by considering what the behaviors and states of being that people consider moral have in common. I conclude that the essence of morality lies in dispositions to uphold social orders that help individuals survive, reproduce, and propagate their genes-morality is a set of ideas about how people should behave in order to reap the benefits of cooperative relations with others.
People from all cultures consider five main types of behavior moral-respect for authority, self-control, altruism, fairness, and honesty. Precursors of all five types of behavior have been observed in other animals. Dispositions to behave in these ways have evolved in many species because it is adaptive for individuals to show deference to more powerful members of their groups, to resist the temptation to engage in self-indulgent behaviors, to help their friends and relatives, to sustain systems of reciprocity, and to fulfill their commitments. Even though these behaviors may entail short-term losses in personal profit and pleasure, they are equipped to foster individuals' long-term biological and genetic interests by helping them avoid punishment, lead healthy lives, induce others to like them, reap the benefits of social exchanges, and uphold the groups and people on whom their welfare is dependent. Evidence that such dispositions have evolved in many species and that they stem from primitive, emotion-producing structures in the "old brain" indicates that we must attend to sources other than uniquely-human "new brain" processes such as reason or culture to achieve a full understanding of morality.
It is important to note that sources of morality such as moral reasoning, learning, and culture that are featured in psychological theories of morality stem from biologically-evolved brain mechanisms. Even when these mechanisms give rise to such maladaptive behaviors as genetically-costly forms of justice and care, their forms and functions are still products of evolution. Viewing morality from an evolutionary perspective offers a framework for situating, refining, and revising psychological theories of morality.
Although humans are similar to other animals in their dispositions to behave in prosocial ways, they also display species-specific forms of conduct. No other species donates to charity, helps animals it will never meet, debates moral issues with others, or invests mental energy in weighing the pros and cons of various moral decisions. To account fully for the evolution of morality in the human species, we must attend to the roles played by higher-order mental mechanisms such as those that endow humans with advanced linguistic, perspective-taking, and moral reasoning abilities.
We must attend to these mechanisms, but we should be careful not to idealize them or to overestimate their influence, as many social scientists and philosophers have. Although sophisticated forms of moral reasoning endow people with the potential to make sophisticated moral decisions, these forms of reasoning are often corrupted and overridden by more primitive cognitive and emotional processes. Furthermore, ironically, the mental mechanisms that endow people with the capacity to make moral judgments probably evolved in the context of strategic social interactions as tools designed to enable members of groups to manipulate others into behaving in ways that benefit them. To understand the roles played by these mental processes in the moral behavior of contemporary humans, we must attend to the goals that people use them to achieve in their everyday lives. Although people sometimes take the perspective of others, engage in moral reasoning, and debate moral issues to make the best possible moral decisions, they more often invoke these processes to manipulate others, to persuade others that they are right, to defend their friends and relatives, to allay their guilt, and to justify self-interested behaviors. Evolutionary perspectives on human morality encourage us to be on the lookout for the self-serving, nepotistic, and group-upholding goals that people use moral judgments and moral behaviors to achieve.
In closing, I argue in "The Origins of Morality" that evolutionary perspectives on moral behavior and moral sentiments may have implications for philosophical debates about cardinal principles of morality. If moral prescriptions evolved to induce members of groups to behave in ways that advance their long-term biological interests by upholding the social orders of their groups, then it makes sense to evaluate principles such as "act in a manner that produces the greatest good for the greatest number," "treat people as ends, not means," and "do unto others as you would have them do unto you" in terms of the capacity of such principles to fulfill these ends.