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Evolutionary Perspectives on Ethics M Hourdequin, Colorado College, Colorado Springs, CO, USA

ª 2012 Elsevier Inc. All rights reserved.

Glossary Group selection Natural selection at the level of

groups.

Kin selection A process by which altruistic behavior

toward relatives can evolve due to genetic relatedness;

by helping relatives, an individual perpetuates copies of

shared genes.

Moral error theory A meta-ethical view according to

which everyday moral thought and language are

erroneous, because the true nature of morality does not

support the presuppositions of moral thought and

language. Typically, moral error theorists hold that

everyday moral language presupposes the existence of

mind-independent moral values and/or objective,

universal moral obligations, although no such values or

obligations exist.

4

Moral realism A meta-ethical view according to which

moral properties are objective, moral claims can be true or

false, and the truth or falsity of moral claims is not relative

to the views of individuals or particular social groups.

Natural selection An evolutionary process by which

those traits that confer on their possessors a greater

likelihood of survival and reproduction tend to increase

in a population over time (through generations), while

those traits that confer on their possessors reduced

likelihood of survival and reproduction tend to decline in

prevalence.

Reciprocal altruism A process by which altruistic

behavior can evolve through the exchange of assistance

over time, which allows individuals to achieve benefits

greater than those they would achieve in the absence of

such cooperation.

Introduction

With the publication of On the Origin of Species in 1859, Charles Darwin introduced to the world the theory of evolution by natural selection. In doing so, Darwin revolutionized biological thought, and his theory remains at the core of modern biological science. As twentieth-century geneticist Theodosius Dobzhansky famously observed, ‘‘Nothing in biology makes sense except in the light of evolution.’’ Yet the implications of Darwin’s theory extend far beyond biology. Darwin held that all living things are part of a single tree of life, and hence that humans evolved through the same basic processes as other organisms. Moreover, evolution by natural selection has shaped not only human anat­

omy and physiology, but also our thought, behavior, and even our moral capacities.

Understanding how evolutionary theory can be used to shed light on the nature and origins of human morality is a challenging and multidisciplinary endeavor. The inquiry relies on scientific understanding, but also requires philosophical analysis to untangle the ethical implications of an evolutionarily informed conception of human beings. Evolutionary approaches to ethics there­

fore involve the interplay of scientific and philosophical thought.

Philosophical work in evolutionary ethics utilizes biological theory, empirical science, and philosophical tools such as conceptual analysis to understand the

relation between evolution and morality. At the center of the study of evolution and ethics is the theory of evolution by natural selection. Since Darwin’s time, evolutionary theory has been updated to reflect con­

temporary understanding of the mechanisms of inheritance and the role of genes and DNA in trans­

mitting information from one generation to the next; nevertheless, the core features of Darwin’s original the­

ory remain intact. The key elements of the Darwinian evolutionary the­

ory are the following:

1. Variation: Organisms vary in observable traits (phenotypes). These traits may be physiological, anatomical, developmental, or behavioral.

2. Heritability: Some of this phenotypic variation is biologically heritable: that is, through biological repro­

duction, resemblance in certain traits is passed from one generation to the next.

3. Natural selection/differential reproductive success: Some traits better enable their possessors to survive and reproduce than others, and organisms possessing these fitter traits tend to survive and reproduce more success­

fully than those possessing other, less fit traits. As a result, the frequency of traits in the population as a whole tends to change over time, with fitter traits increasing in prevalence.

To illustrate, imagine a population of deer that vary in their swiftness and, hence, in their ability to evade

Evolutionary Perspectives on Ethics 235

predators. If speed and the associated ability to escape predation are heritable traits, and if swifter deer tend to survive and reproduce more successfully than those less fast of foot, then swiftness will tend to increase in succes­sive generations of deer, while slowness will decline. Successive generations will have a higher proportion of swift deer and a lower proportion of slow ones, and the mean swiftness of deer in the population will increase. Natural selection thus explains changes in the character­istics of populations over time.

As soon as Darwin articulated the basic theory of evolution by natural selection, puzzles began to arise regarding its implications for human and animal behavior. Darwin himself avoided much discussion of humans in On the Origin of Species, but he clearly believed that the theory applied to human beings, and his later book, The Descent of Man, contains a chapter devoted to the evolution of human morality. The ideas developed there are remark­ably prescient, and theoretical developments since Darwin’s time have made his speculations appear increas­ingly plausible.

For many readers of On the Origin of Species, the theory of evolution by natural selection posed a problem for understanding morality. Moral behavior typically is thought to involve altruistic acts grounded in genuine other-directed concern. However, Darwin describes nat­ural selection as a winnowing process that works through a competitive struggle for existence. How can helping behavior in animals or altruistic and moral behavior in humans survive this evolutionary struggle? The problem is this: The more energy and time an organism spends assisting others, the less energy and time it has to invest in its own survival and reproduction, hence the less likely it will be to produce a large number of robust offspring. If helping behavior is heritable, then an altruist’s offspring will be similarly inclined to assist others rather than to focus on their own survival and reproduction. Thus, help­ing seems like a behavioral strategy doomed to evolutionary failure. From the point of view of evolution­ary survival, the best strategy would seem to be to invest all one’s energy in one’s own survival, reproduction, and offspring care. Individuals that adopt such a strategy should be evolutionarily successful and proliferate at the expense of other, more ‘altruistic’ individuals. Over the long term, one would expect altruists to decline to extinc­tion as ‘selfish’ individuals come to predominate.

Following this logic, some scholars, such as nine­teenth-century biologist Thomas Henry Huxley, believed that, indeed, evolution fosters selfishness. Huxley therefore held that the development of human morality requires opposition to our natural evolutionary tendencies. Others, such as the Social Darwinists of the late nineteenth and early twentieth century, believed that ethics and social policy should allow natural selection to take its course: If the strong survive and the weak perish

(or fail to reproduce), society will be better off in the long run. By contemporary lights, both views are overly sim­plistic. Nevertheless, the puzzle to which they respond is an important one, and one that contemporary theories in evolutionary ethics must address: How can moral com­mitments and moral behavior endure over generations, if evolution by natural selection favors those who focus on their own survival and reproduction at the expense of others?

Reconciling Evolution and Altruism

Over the course of the twentieth century, biologists iden­tified two important mechanisms that alleviate the conflict between evolution and altruism. Both mechan­isms work by showing how apparently altruistic behavior can be recharacterized as individually advantageous from an evolutionary perspective. As biologists William Hamilton and Robert Trivers explained in their respec­tive work, aid to kin and assistance to nonrelatives can – under certain circumstances – enhance individual fitness.

Kin selection explains how altruism can evolve among genetically related individuals. One intuitive way to think of kin selection is by extending the logic involved in parental care. At first glance, one might think that the struggle for existence would favor a narrow focus on one’s own survival. However, from an evolutionary perspective, survival is only one part of the equation. Because the evolutionary process is intergenerational, long-term evolutionary success requires the production of offspring who, too, survive and reproduce. Investing in the survival of one’s off­spring is therefore consistent with the basic strategy of promoting one’s own reproductive fitness, since fitness is measured by the number of descendants one leaves in subsequent generations. But if it is fitness enhancing to assist one’s own offspring, might it not be fitness enhancing to assist other close relatives, who share a similar genetic makeup, particularly if such individuals are of reproductive (or pre-reproductive) age?

The answer is yes, albeit with some limitations. As the genetic relationship between the helper and the helped attenuates, it becomes less advantageous to invest in help­ing. For example, it would be more fitness enhancing for an individual to lay down her life for a son than for a cousin. In 1964, biologist William Hamilton formalized an account of the conditions under which it is fitness enhancing to assist a relative. He showed that one would expect ‘‘altruistic’’ behavior (where one assists another at a cost to oneself) to evolve when the costs of such behavior are less than the benefits to the recipient, discounted according to the reci­pient’s genetic relatedness to the donor. As the relationship becomes more distant, the ratio of cost to benefit must decrease if helping is to be evolutionarily favored.

236 Evolutionary Perspectives on Ethics

Formally, altruistic behavior can be selected when C < B � R, where C is the fitness cost to the donor, B is the fitness benefit to the recipient, and R is the coefficient of relatedness.

Thus, in the case of one’s full sibling, where the coefficient of relatedness is 0.5 (siblings share, on aver­

age, 50% of one another’s genes), it is evolutionarily advantageous to endure a cost C if by doing so one can confer a fitness benefit greater than 2C on the recipient. The general prediction of Hamilton’s theory of kin selection is that helping behavior can be evolutionarily favored, but such behavior should be targeted toward close relatives.

Not all examples of altruistic behavior occur between close relatives, however. This led biologist Robert Trivers to suggest another mechanism by which altruism could evolve: reciprocal altruism. Trivers’s theory of reciprocal altruism suggests that under certain circumstances, conditional helping beha­

vior can be evolutionarily stable. The circumstances that favor such behavior can be identified using iterated game theoretic models. In a one-shot prisoner’s dilemma, noncooperators will always earn higher pay­

offs (i.e., have greater fitness) than cooperators. But if the game is repeated, then an individual who coopera­

ted and was bilked in the first round can retaliate against the defector. It turns out that in a game with many rounds in a population containing a variety of strategies (some defectors, some cooperators, some con­

ditional cooperators, etc.), the strategy ‘tit-for-tat’ – where an individual begins by cooperating, but then responds by doing whatever the opponent does – can be highly successful, and can beat out the strategy ‘always defect.’ The intuitive explanation for this is that reciprocal altruists enjoy the benefits of coopera­

tion when paired with cooperators or other reciprocal altruists, while they avoid being seriously taken advan­

tage of by defectors by refusing to cooperate in subsequent rounds. Defectors, on the other hand, never get taken advantage of, but they also fail to enjoy any of the benefits of cooperation.

Theoretical models of kin selection and reciprocal altruism go a significant distance to dissolving the tension that Huxley identified between evolution and ethics. There are limitations, however. For one, the models are behavioral and not psychological models. They offer no explicit insight as to how moral motivation evolved, although to show that altruistic behavior – a type of behavior often associated with moral behavior – is com­

patible with evolution certainly makes it more plausible that ethics as we know it could be the product of natural selection. Kin selection and reciprocal altruism both sup­

port the idea that natural selection and altruism need not be diametrically opposed.

Nevertheless, a number of scientists and philosophers believe that kin selection and reciprocal altruism alone are insufficient to account for the moral behavior and moral psychology of human beings. According to these scholars, one of the most fundamental limitations of kin selection and reciprocal altruism is that they cannot pro­vide a full explanation of human ultrasociality, which involves cooperation in large, unrelated groups to which individuals have significant loyalties and for which indi­viduals are often willing to make serious sacrifices.

Darwin, interestingly, noted this feature of human social life well over a century ago (although he did not label it ultrasociality), and in The Descent of Man, heproposed a mechanism to explain it. Darwin emphasized the importance of certain emotions – such as courage, sympathy, and loyalty – as a foundation for social life and moral behavior. These emotions, suggested Darwin, evolved by the very same evolutionary mechanism that is at work in so many other contexts: natural selection. However, the evolutionary struggle that generates emo­tions such as courage is not a struggle between individuals, but rather the result of competition between different human groups. Darwin argued that those groups that possess a greater prevalence of cooperative, loyal, and courageous individuals will prevail over those groups full of selfish individuals, because lack of social concern inevitably leads to internal strife.

The mechanism of selection Darwin outlined in rela­tion to the moral emotions is group selection. For many decades, group selection was disfavored by biologists for a variety of reasons, including the fact that it was not clear exactly how this mechanism could work in nature. In particular, the conditions required for group selection were thought rarely to be obtained. Recently, however, group selection has experienced a renaissance as biolo­gists and philosophers have disentangled conceptual problems and adduced plausible mechanisms and empiri­cal examples of this process. In relation to human moral capacities, group selection has the potential to account for aspects of human psychology and behavior – specifically those involved in human ultrasociality – that kin selection and reciprocal altruism seem insufficient to explain.

In the view of this author, a full explanation of the origins of human morality will appeal to natural selection at multiple levels as well as to processes of cultural evolution through which ethical norms are elaborated. Recent research suggests that cultural and biological evo­lution interact both to stabilize ethical behavior and to facilitate change in ethical norms over time in response to changing social and environmental conditions. Because scientists are still exploring the frontiers of multilevel selection theory, cultural evolutionary theory, and the interactions between cultural and evolutionary processes, few evolutionary ethical theories have fully integrated these ideas.

Evolutionary Perspectives on Ethics 237

The Relationship between Evolution and Ethics

Scientific and philosophical work addressing the compat­

ibility of evolutionary theory with human moral thought and behavior comprises one part of the task of under­

standing the relationship between evolution and ethics. However, philosophers are interested in many further aspects of this relationship. For example, while a descrip­

tive account of how morality evolved is an important component of research on evolution and ethics, tradi­

tional philosophical theories have emphasized the justification of moral beliefs and behavior rather than their explanation. Some critical questions for evolution­

ary approaches to ethics, then, are these: What is the relationship between evolutionary explanations and phi­

losophical justifications of human morality? Does the knowledge that we are evolved creatures make any dif­

ference to our understanding of morality? Should an understanding of evolutionary theory change the way we think about ethics, and if so, how?

Replies to these questions typically fall into one of three camps that conceive an evolutionary explanation of morality as (1) neutral, (2) justifying, or (3) under­

mining in relation to substantive ethical claims. In the first camp are those who deny any deep relevance of evolution to ethics. A second group argues that evolu­

tion acts as a standard that can support normative ethical judgments (judgments about what we ought and ought not to do). According to the third view, a thorough understanding of the evolutionary processes that produced human beings ‘explains away’ ethics, or at least undermines its fundamental presuppositions, supporting skepticism about the existence of objective moral truths. Theories that defend one of these three positions are, at least in part, meta-ethical. They are theories that tell us something about the nature of morality and, more specifically, about the nature of the relation between evolution and ethics. Often, argu­

ments for each of these three positions rest on further claims about the nature of morality, some that are informed by evolutionary explanations of it, and others that are informed by more fundamental conceptual or philosophical arguments. For example, those who defend the neutrality of evolution with respect to ethics typically appeal to philosophical arguments asserting the lack of derivability of prescriptive claims from descriptive ones, while those defending the third posi­

tion may argue that an evolutionary explanation of morality shows our moral concepts to be confused and to involve us in commitments to the existence of entities (such as moral facts) that seem dubious in light of a scientific account of how and why we think, talk, and act in moral terms.

Evolution Is Neutral: The Autonomy of Ethics

Proponents of the neutrality view include most Kantians, who hold that ethics is autonomous and independent of the particularities of human nature. Eighteenth-century philosopher Immanuel Kant argued that the fundamental principle of ethics depends on just one feature of human beings: our capacity to reason. Reason is necessary to discern the requirements of morality; without it, ethics would be impossible. In Kant’s view, morality has the same structure for all rational beings: there is nothing especially unique about human reason that influences the structure of morality in relation to us. Thus, to take one example, although we may learn through the study of evolution how we came to have certain emotions and desires, the nature of human emotional life reveals noth­ing about the general form of morality. In fact, what morality requires of us, according to Kant, is to overcome our desires and inclinations, and to act instead out of respect for the moral law.

The view that an evolutionary explanation of ethics is neutral with respect to normative ethical theory draws support from two important claims in the history of Western moral philosophy. The first claim is that norma­tive facts are not reducible to ordinary natural facts, and that any naturalistic analysis of an ethical term such as ‘good’ is bound to fail. Twentieth-century philosopher G. E. Moore argued for this claim in his Principia Ethica, where he held that all attempts to define moral terms naturalistically involve the naturalistic fallacy: They attempt to define an indefinable nonnatural property. Moore supported this view with his well-known open question argument. The central idea of this argument is that for any naturalistic definition one offers of an ethical term such as ‘good,’ it is always an open question whether the natural property identified in the definition really is good. To illustrate, we can imagine a perfectly intelligible conversation in which one person asserts that goodness is pleasure, and another replies, ‘‘Well, sadomasochism is pleasurable to the sadomasochist, but is sadomasochism good? ’’ This type of question may be asked in response to any analytic naturalistic definition of ‘good,’ held Moore, thus no definition can close the question of what consti­tutes goodness with the force of conceptual necessity.

Moore’s argument has been criticized in a variety of ways, but perhaps the most important conclusion to be drawn from these discussions is that the open question argument applies only against a certain approach to show­ing the relevance of evolution to ethics: Specifically, the argument applies against evolutionarily informed attempts to define moral terms naturalistically. Moore’s objections do not apply directly to nondefinitional accounts that assert the relevance of evolution to ethics.

On this latter count, a second claim, most famously articulated by eighteenth-century Scottish philosopher

238 Evolutionary Perspectives on Ethics

David Hume, holds greater sway. Hume held that pre­scriptive claims (‘ought’ claims) cannot be derived from purely descriptive ones (‘is’ claims). In an evolutionary context, Hume’s law, as it is commonly known, seems to imply that a descriptive account of the way in which human morality evolved is insufficient to underpin a prescriptive, or normative, ethical theory. Scientific fact and moral value are fundamentally distinct, and the latter cannot be wrung from the former.

Hume’s law raises a number of difficult philosophical questions, and not all philosophers accept that ‘is’ and ‘ought’ are as distinct as Hume made them out to be. Even if one accepts the is/ought distinction as unproble­matic, however, it seems unlikely that an evolutionary understanding of human beings can be dismissed as alto­gether irrelevant to normative ethics. For example, it is widely accepted that normative conclusions may be informed by descriptive premises. More specifically, descriptive facts may make more precise the nature and extent of our moral obligations. To illustrate:

P1. One ought not cause animals pain gratuitously (nor­mative premise)

P2. Trophy hunting causes animals pain (descriptive premise)

P3. Trophy hunting is gratuitous (normative premise; ‘gratuitous’ is an ethical term)

P4. Trophy hunting causes animals pain gratuitously (based on premises 2 and 3) C: One ought not engage in trophy hunting (based on premises 1 and 4).

Here, the descriptive second premise adds content to our moral obligations by specifying the relationship between trophy hunting and animal pain. Notice that this argu­ment does not derive fundamental moral principles (e.g., one ought not cause pain gratuitously) from descriptive claims. A defender of the neutrality position therefore might concede that descriptive facts (about animal pain, human evolution, or anything else) have the potential to fill in details about the nature and extent of our moral obligations while remaining committed to the view that such facts are neutral with respect to morality’s funda­mental principles.

From a contemporary perspective, one might think of the autonomy of ethics position as one on a continuum. It is widely agreed that empirical information can add con­tent to our moral obligations, and many defenders of the autonomy of ethics agree that normative moral theories should respect the dictum ‘ought implies can.’ Thus, if evolutionary science tells us something about the limits of human ethical capabilities, these insights should be taken into account. Nevertheless, defenders of the autonomy of ethics reject the idea that fundamental moral principles could be derived from or grounded in facts about human evolution, and they further reject the idea that an

evolutionary account of morality could succeed in show­ing our most fundamental moral commitments to be false.

Evolution Justifies Ethics: Evolutionary Moral Realism

In contrast to those who defend the autonomy of ethics, some philosophers hold that evolution can ground moral theory and justify fundamental moral claims. The Social Darwinists, for example, believed that human social sys­tems should be constructed so as to allow the struggle for existence to proceed unimpeded. There are many ways to object to this view, but suffice it to say that one of Social Darwinism’s most basic problems involved an elision of ‘is’ and ‘ought’ (i.e., of the descriptive and the prescrip­tive), for which little argument was provided.

More recent efforts to ground ethics in evolution typi­cally take a more sophisticated approach that is informed by an acute awareness of Hume’s law. Such positions are versions of evolutionary moral realism: They hold that moral facts exist, moral claims can be true or false, and that the truth or falsity of moral claims and the existence of moral facts are grounded in facts about human evolu­tion (perhaps along with additional facts about human psychology, culture, etc.).

Some defenders of evolutionary moral realism focus directly on the is/ought problem, attempting to explain how it can be overcome. Robert Richards, for example, argues that the move from evolutionary description to normative prescription is bridged not by unstated norma­tive premises, but by inference rules that would be endorsed by persons possessing ordinary moral capacities. These inference rules reflect widely shared, intuitive moral judgments – judgments that are themselves the product of our evolved moral sense. William Rottschaefer and David Martinsen suggest a different strategy for grounding evolutionary moral realism: They hold that values are ‘‘emergent natural properties’’ that supervene on nonmoral natural properties. Human survi­val and reproduction is an objective value that emerges from the evolutionary process, and it is a basic value, because other values – such as the cultural values of science and art – depend on survival and reproduction for their realization.

Other evolutionary moral realists, such as William Casebeer, take an Aristotelian approach. Aristotelian approaches ground ethics in a distinctive human nature that determines what it is to live a good human life. Aristotle thought that the capacity to reason distinguishes humans from other animals, and that the highest good, or telos, for human beings involves the full exercise of prac­tical and theoretical reason. Evolutionary accounts that follow in the Aristotelian vein develop an account of the human good that is informed by our evolutionary history and evolved psychology: Such accounts develop a

Evolutionary Perspectives on Ethics 239

naturalistic and evolutionarily grounded account of human flourishing. One important feature of Aristotelian accounts is that they blur the distinction between acting ethically and acting in one’s self-interest. In the Aristotelian view, the best kind of life for a human being – both objectively and subjectively – is a life that fulfills the human telos. Those who live this kind of life flourish; they lead fulfilling and meaningful lives. In Aristotelian terms, they achieve eudaimonia. Thus, one part of the Aristotelian evolutionary moral realist’s response to the challenge of Hume’s law turns on the idea that normativ­ity is built into the kind of creatures we are. Morality is about fulfilling one’s human potential, and the potential of human beings is determined by our biology. Whereas Aristotle’s own account of the human telos relied on a natural teleology that aligns poorly with modern scientific understanding, contemporary evolutionary Aristotelian theories typically draw on notions of function that figure in modern evolutionary biology and underpin claims such as, ‘‘The function of the heart is to pump blood.’’ Proponents of this approach believe that the evo­lutionary function of human beings is one that fits reasonably well with our intuitions about what it is to live a good human life. Opponents are suspicious, holding that that an ethics grounded in an evolutionary teleology reduces goodness to what conduces to survival and repro­duction, and that this misidentifies the fundamental point of ethics.

For its proponents, Aristotelian theory appeals in part because of the way it blends the descriptive and the prescriptive. What is morally right is grounded in the kinds of creatures we are, and what is morally good is also what enables each person, as an individual, to flour­ish. If this is right, then the problem of moral motivation is less stark than many modern moral theories suggest. (Aristotelian moral realists nevertheless acknowledge var­ious ways in which moral motivation can fail, including failure to recognize the good and failure to be motivated by what one recognizes as good.) Moreover, the human evolutionary story helps to explain why a eudaimonistic view – one centered on individual human flourishing – does not collapse into narrow egoism. Because we are deeply social creatures, to live good and satisfying lives requires that we participate in reciprocal social interac­tions, form friendships, care for others, and so on. Objectors may hold that the Aristotelian strategy makes ethics contingent on the existence of a certain motiva­tional structure, such that ethical imperatives do not apply and cannot motivate those who lack this structure; but the evolutionary Aristotelian may not see this as a serious concern. Although the motives that guide human beings are products of contingent evolutionary processes, they are motives that we, as human beings, have, and in this sense, they are quite secure (even if not always fully reliable!). A fully developed Aristotelian-style

evolutionary ethics would incorporate an account of moral development to explain how a virtuous character can be reliably developed in creatures like ourselves.

Evolution Undermines Ethics: Moral Error Theory

Rather than denying any deep relevance of evolution to ethics, or conversely, attempting to derive a normative moral theory from the structure of the evolutionary pro­cess, defenders of the undermining view think that there are fundamental tensions between our everyday ethical commitments and an evolutionary genealogy of morals. Those who argue that evolution undermines ethics typi­cally are error theorists: They believe that our everyday moral concepts and commitments are erroneous because they fail to fit with an evolutionary explanation of how and why these concepts and commitments arose.

Evolutionary moral error theorists follow in the foot­steps of J. L. Mackie, who argued that a careful look at the structure of morality simply fails to support the realist point of view that is embedded in our moral language. Mackie supported his error theory with arguments from disagreement and queerness. Why, asked Mackie, is there so much persistent moral disagreement, if there is a single true morality? He acknowledged that disagreements arise in other areas of inquiry, such as science, but he noted that in science, there are objective ways of settling controver­sies, whereas in ethics, there are not. Thus in the scientific case, but not in the ethical one, we are warranted in concluding that there exists an underlying, discoverable truth. Unlike scientific facts, ethical values are projected onto the world by us. Mackie offered further backing for this view with his argument from queerness, according to which moral properties are both epistemically and onto-logically queer. They are epistemically queer because unlike garden-variety natural properties like solidity and length, goodness and rightness cannot be detected with the five senses. Moral properties are also ontologi­cally queer, because unlike ordinary natural properties that are motivationally inert, moral properties are sup­posed to be intrinsically action guiding. Rather than accept the epistemic and metaphysical oddity of moral properties, thought Mackie, we should take their queer­ness as a reason to doubt their existence.

Like Mackie, evolutionary error theorists offer argu­ments that undermine what they take to be certain basic presuppositions of morality, such as its objectivity and mind-independence. Error theorist Michael Ruse has argued that our moral beliefs are merely the products of individual-level selection for greater survival and repro­duction, hence objective morality is an illusion. Morality is not composed of objective commands that are built into the fabric of the world; it is merely a mechanism devel­oped through natural selection that spurs individuals to

240 Evolutionary Perspectives on Ethics

cooperate with others in order to secure certain benefits for themselves. In Ruse’s view, once we explain our nor­mative beliefs as the result of natural selection at the individual level, little room remains for questions of ulti­mate justification. Morality cannot be objectively justified.

Error theories typically do not support or debunk particular normative claims; instead, they call into ques­tion the status of normative claims in general. Thus Ruse has argued that while moral claims can be distinguished from ordinary, garden-variety statements of desire or preference, their justification goes no deeper. Although moral beliefs make a greater claim to interpersonal authority and objectivity, they are no different from straightforward preferences in provenance. Our commit­ment to morality has the same fundamental origin as our desires for food and sex: moral commitment made a difference to individual reproductive success and was naturally selected. Many widespread moral beliefs bear the marks of their Darwinian ancestry, according to Ruse. For example, the strong obligations human beings typi­cally feel toward their children or close relatives are most likely the product of kin selection, while a tendency and felt obligation to reciprocate is the result of evolutionary processes favoring reciprocal altruism. The upshot of these evolutionary explanations for the basic human moral outlook is that once we see the causal origins of human moral beliefs as rooted in natural selection, the ideas that our moral beliefs originate from God or are intuitions about objective, nonnatural moral properties begin to look gratuitous. A parsimonious explanation of human morality can dispense with the idea of objective foundations.

To those who maintain that a moral realist position is compatible with or can be grounded in an evolutionary account of human morality, Richard Joyce argues in The Evolution of Morality that none of these accounts can deli­ver the ‘‘practical clout’’ to which our moral language commits us. More precisely, such accounts cannot vindi­cate the inescapable authority that moral claims are supposed to have. According to Joyce, our use of moral imperatives presupposes that these claims are inescapable (they apply to everyone, regardless of their ends) and authoritative (they would be irrational to ignore). Joyce finds that prominent attempts to defend evolutionary moral realism offer not the robust normativity that char­acterizes our everyday moral language, but rather a weaker, more contingent normativity, where the force of moral judgments depends on some kind of connection between the moral judgment in question and the ends of the agent to whom they are addressed. Thus, putative evolutionary vindications of morality fail to provide the kind of normativity that moral language presupposes. Furthermore, an evolutionary understanding of morality strongly suggests that this robust normativity is, in fact,

undeliverable, and that our everyday moral language therefore implicates us in false views about the objectivity of morality. Joyce’s own suggested response to this condi­tion is that we acknowledge the problematic commitments of moral language while continuing to use it. Under this new regime, we would treat morality as a ‘useful fiction,’ something that helps us get around in the world and get along with one another, despite the fact that our moral beliefs do not track any kind of objective moral truths (because there are no such truths).

Whether error theorists are correct in their diagnoses turns on two distinct issues: (1) the nature of our everyday moral commitments, particularly the extent to which our moral language really does presuppose robust objectivity and practical clout, and (2) whether an evolutionary story truly undermines the commitments of our moral language and concepts (whatever those may be). Those who reject evolutionarily based moral error theories can respond to the error theorist’s position with respect to (1) and/or (2).

A moral constructivist, for example, might reject the idea that moral discourse depends on a robust, mind-independent account of objective moral value and con­clude on this basis that an evolutionary account of morality is not as debunking as the error theorist suggests. Constructivist views hold that there are moral facts; how­ever, such facts are in some sense socially constituted. According to the constructivist, moral facts and norms are grounded in that to which rational agents would agree under certain conditions. At least some moral con­structivists take the view that an evolutionary genealogy of morals is compatible with or can serve as the basis for a constructivist moral theory. Following along these lines, one might hold that humans evolved the ability to reg­ulate their societies through moral norms, and that such norms are the result of agreements (tacit or explicit) among reasonable people with the aim of living coopera­tively together. A constructivist might go on to endorse this evolved practice of morality, arguing that conduct that is morally permissible is that which people who share an interest in living cooperatively together would accept. Scott James defends this kind of view.

A related, but distinct, line of reply to the error theor­ists comes from noncognitivist moral theorists, who hold that moral claims express attitudes or emotions rather than beliefs. As such, moral claims are not truth-apt: they cannot properly be evaluated as true or false. There is, therefore, no error revealed by an evolutionary genealogy of morals that calls into doubt the existence of moral facts. Noncognitivists bear the burden of explaining why our moral discourse strongly resembles discourse concerning facts, however. Allan Gibbard offers such an explanation in his 1990 publication Wise Choices, Apt Feelings. There he develops a norm expressivist view, which analyzes moral statements as expressions of the acceptance of certain norms. Gibbard’s complex account

Evolutionary Perspectives on Ethics 241

attempts to retain a place for moral criticism and correc­tion, and in this way, to do justice to features of moral discourse that pose problems for earlier noncognitivist accounts. Gibbard draws on a broad evolutionary story in support of his analysis.

In sum, the fate of evolutionary moral error theory turns on (1) clarification of the presuppositions of every­day moral language, (2) details of the evolutionary account of morality, and (3) the relationship between moral language and the evolutionary account. Controversy exists surrounding each of these issues, and recent philosophical and empirical work illuminating them has made evolutionary moral error theory the sub­ject of lively debate. What we should do if error theory is true – for example, whether we should embrace moral fictionalism – is a question also in need of further discussion.

Evolution and Applied Ethics

In recent decades, evolutionary approaches to ethics have focused primarily on how evolution may shed light on the nature of morality and the possibility of a naturalistic ethical theory. The implications of evolutionary theory for our understanding of issues in applied ethics have garnered less attention, perhaps in part because of the criticisms levied against those who have attempted to justify certain social policies (such as the laissez-faire policies of the Social Darwinists) or behaviors (such as infidelity among men, based on an evolutionary explana­tion of male philandering) by appeal to evolution. Although the relationship between evolutionary biology and applied ethics raises difficult and contentious issues, there are a number of ways in which evolutionary per­spectives on morality are relevant to practical ethical questions. For example, if moral error theory is true, then it would seem that there is no objective, mind-independent foundation for moral judgments and the assignation of moral responsibility. Insofar as certain kinds of legal responsibility hinge on an objective con­ception of moral responsibility, error theory has the potential to raise problems for our current legal system. Evolutionary theory also may be relevant to discussions of genetic manipulation and human enhancement: if mor­ality is grounded in human nature, and we alter human nature in significant ways, what are the implications for morality? Third, growing evidence of proto-moral beha­viors and sophisticated emotions in nonhuman animals, along with an understanding of morality as an evolved phenomenon, may change conceptions of what we owe, morally, to nonhuman animals. Lastly, if an evolutionarily informed account of morality helps us understand the extent to which morality is objective, subjective, or cul­turally relative, it may open up new lines of thought with

respect to the management of moral disagreement, within and across cultures.

Conclusion: Further Issues and Future Directions in Evolutionary Ethics

Evolutionary approaches to ethics have experienced a renaissance in recent years. These new approaches respond to difficulties with earlier theories, such as Social Darwinism, and take seriously the challenge posed by Hume’s law. Realist evolutionary moral theories have grown more sophisticated, while at the same time, moral error theorists have worked to show how an evolutionary genealogy of morals helps to vindicate J. L. Mackie’s views. On the descriptive side, empirical work and theoretical developments are enriching the dialogue between evolutionary science and ethics and providing provocative new results for philosophers to integrate into their ethical theories. For example, primate studies have strengthened our understanding of the potential evolutionary precursors to human morality, and some theorists have argued that we should recognize chimpanzees, monkeys, and other primates as proto­moral creatures. How this research should affect our thinking about the nature of human morality and our obligations to nonhuman animals is a topic in need of substantial further study.

Other developments have occurred through the use of evolutionary game theory and experimental game theory. Evolutionary game theory facilitates the modeling of inter-actors with various behavioral strategies; these models associate strategies with various payoffs that affect their survival in future generations. Evolutionary game theorists therefore can examine what kinds of behavioral strategies are stable over time, and how different combinations of behavioral strategies lead to different evolutionary out­comes. Evolutionary game theoretic models have revealed, for example, that various altruistic strategies can be stable over time, but that the stability of particular strategies depends on initial conditions (the distribution of different kinds of strategies in the original population). For example, altruistic strategies may be unstable in a population domi­nated by selfish strategies, but stable in an initial population that is more mixed. This kind of theoretical modeling has been complemented by experimental tests with actual human subjects. Such tests have revealed fascinating results, such as significant deviations from the predictions of eco­nomic models of rational self-interest in the direction of prosocial behavior and equitable distribution. Joseph Henrich and his collaborators have found that the results of such experiments vary across cultures, however, raising questions about the biological and cultural roots of prosocial behaviors and the degree to which prosocial behavior is shaped by upbringing and cultural contexts. Similarly,

242 Evolutionary Perspectives on Ethics

neuroscientific studies of human ethical decision making have led to speculations about innate ethical intuitions and their evolutionary basis (in particular, the work of Joshua Greene), but additional research is needed to connect neu­roscientific findings with the evolutionary basis (if any) for certain patterns in human moral judgment. The best current research on the biology and psychology of human moral thought and behavior indicates that a descriptive, scientific understanding of human morality will be complex and rely on research from diverse scientific disciplines. A full evolu­tionary account likely will need to incorporate traditional biological evolution and cultural evolution, as well as selec­tion at multiple levels. Recent work on biocultural evolution, such as that of Peter Richerson and Robert Boyd, is of particular relevance here. Because our understanding of the evolutionary basis for human morality is itself evolving, evolutionary approaches to ethics, which attempt to provide an integrated account of human morality as well as to under­stand the philosophical implications of this account, comprise a challenging, yet exciting, field of inquiry.

See also: Aristotelian Ethics; Darwinism; Egoism and Altruism; Game Theory; Kantianism; Theories of Ethics, Overview.

Further Reading

Boniolo G and De Anna G (2006) Evolutionary Ethics and Contemporary Biology. Cambridge: Cambridge University Press.

Casebeer W (2003) Natural Ethical Facts: Evolution, Connectionism, and Moral Cognition. Cambridge, MA: MIT Press.

Darwin C (1981) The Descent of Man and Selection in Relation to Sex [1872]. Princeton, NJ: Princeton University Press.

DeWaal F (2006) Primates and Philosophers. Princeton: Princeton University Press.

Gibbard A (1990) Wise Choices, Apt Feelings: A Theory of Normative Judgment. Cambridge, MA: Harvard University Press.

Greene JD (2003) From neural ‘‘is’’ to moral ‘‘ought’’: What are the moral implications of neuroscientific moral psychology? Nature Reviews Neuroscience 4: 847–850.

Henrich J, Boyd R, Bowles S, Camerer C, Gintis H, McElreath R, and Fehr E (2001) In search of Homo economicus: Experiments in 15 small-scale societies. American Economic Review 91: 73–79.

James SM (2009) The caveman’s conscience: evolution and moral realism. Australasian Journal of Philosophy 87: 215–233.

Joyce R (2006) The Evolution of Morality. Cambridge, MA: MIT Press. Mackie JL (1977) Ethics: Inventing Right and Wrong. New York:

Penguin. Richards R (1986) A defense of evolutionary ethics. Biology and

Philosophy 1: 265–293. Richerson PJ and Boyd R (2005) Not by Genes Alone: How Culture

Transformed Human Evolution. Chicago: University of Chicago Press.

Rottschaefer WA and Martinsen D (1990) Really taking Darwin seriously: An alternative to Michael Ruse’s Darwinian metaethics. Biology and Philosophy 5: 149–173.

Ruse M (1986) Taking Darwin Seriously: A Naturalistic Approach to Philosophy. New York: Basil Blackwell.

Sober E and Wilson DS (1998) Unto Others: The Evolution of Altruism. Cambridge, MA: Harvard University Press.

Relevant Websites

http://plato.stanford.edu/entries/morality-biology/ – FitzPatrick W, Morality and evolutionary biology.

http://www.emory.edu/LIVING_LINKS/dewaal.html – DeWaal F, Living Links.

http://www.sciencemag.org/multimedia/podcast/#20080216b – Science Magazine, 16 February 2008, Scientific perspectives on the evolution of morality [MP3], Science Podcasts.

http://www.templeton.org/darwin200/ – Templeton Foundation, Darwin 200: Evolution and the ethical brain.

Biographical Sketch

Marion Hourdequin (Ph.D., Duke University) is an Assistant Professor of Philosophy at Colorado College. She specializes in naturalistic and evolutionary approaches to ethics, environ­mental ethics, and comparative (Chinese and Western) philosophy. She has published in a number of journals, including Environmental Ethics, Studies in History and Philosophy of Science, and the Journal of Chinese Philosophy.