Ruse and Wilson in �Moral Philosophy as Applied Science� give the example of brother-sister incest avoidance as being an ethical code motivated by an epigenetic rule that confers an adaptive advantage on those who avoid intercourse with their siblings. In this discussion, Ruse and Wilson argue that moral laws disallowing incest are redundant relics of mankind's evolutionary history that provide nothing to mankind but explanations of a hard-wired evolutionary trait (179). I reject this argument. While Ruse and Wilson are undoubtedly correct in believing that mankind's capacity for moral reasoning is a result of natural selection pressure and that most ancient moral laws have an evolutionary basis, I believe that describing the genesis of moral reasoning in this way provides no information about the content of our moral beliefs now. While our capacity for moral reasoning may have evolved for the purpose of informing our otherwise unjustifiable acts with a sense of objective certitude, it is not hard to imagine that this capacity, once evolved, would be capable of much more than simply rubber stamping mankind's collective genetic predisposition. In this paper, I will use the example of an evolutionary explanation against intentional killing for personal gain to argue for the existence of a disconnect between evolutionary biology and ethics.
Ruse and Wilson might argue that human beings evolved with a genetic predisposition against murder for convenience. It is easy to see how this might be true. A person who kills others for convenience must live apart from society and apart from potential mates or else must be killed by society. This epigenetic rule �predisposes us to think that certain courses of action are right and certain courses of action are wrong (180).� These motivate ethical premises which �are the peculiar products of genetic history� and can �be understood solely as mechanisms that are adaptive for the species that possess them (186).�
I reject this notion that evolution completely prescribes ethics. Nature is amoral absent intelligent beings who make moral judgements. Once the capacity for moral reasoning is established, it does not follow that our ethical laws must necessarily mimic our evolutionary predisposition. While in the cases of selection against brother-sister incest avoidance or against murder for convenience it is easy to see how evolution can bring about an outcome that we now judge to be moral, it can just as easily effect traits that we now believe immoral. Few people would believe that man's evolutionary desire to replicate his genetic material in children would ethically justify licentiousness. Few would believe that women should be dominated by men simply because in nature males tend to be stronger and dominant. Discovering a scientific explanation for man's dominance of women in human history would not justify humanity reverting to sexism. This is a simple counterexample suggesting that discovering a scientific basis for a trait does not a priori suggest the desirability of its expression in society.
The authors do not free themselves from the naturalistic fallacy of the is-ought distinction. We may consider their argument as follows:
1. Humans tend not to murder for convenience because a naturally selected genetic trait tends to make people not murder for convenience.
2. Humans have good reason not to commit murder.
This argument seems strong. Our genetics cause us not to murder for convenience; we later conceive of an ethical code to rationalize this evolutionary preference in terms of objective truth. However, we still need an ought statement to justify statement two. In particular we need:
3. Humans have a good reason to follow their epigenetic tendencies.
Ruse and Wilson have not freed themselves from the naturalistic fallacy. They instead have a suppressed normative premise: that humans should follow their genetic predispositions. They in fact supppose an evolutionary ethics, that the proper course of action is the one we are genetically predisposed to follow. They claim that �the quest for scientific understanding replaces the hajj and the holy grail.� They have conceived of a new ethics that will supersede mankind's misplaced faith in �imagined rulers in the realms of the supernatural and eternal (86).� The new ethics is based on the simple premise that we should act according to our evolutionary nature.
This may or may not be a useful system of ethics. It will certainly lead to some outcomes, like sexism, that would seem to contradict the advice of other ethical systems like contractualism or utilitarianism. However, a follower of a system of evolutionary ethics might believe that it is the only system which allows man to act according to his genetic nature. Perhaps, by not acting according to our genetic natures, by forcing man by societal convention to maintain a monogamous relationship with a woman for example, mankind is worse off. While this may or may not be true, we have discovered that it does not follow from evolutionary biology that mankind should act in accordance with his genetic predisposition without the suppressed normative premise that mankind has a reason to follow and not ignore his genetic predisposition.
Ruse and Wilson have us sometimes ignoring our genetic predisposition and sometimes embracing it. If they believe that a proper ethical system will have us acting according to our genetic natures since moral truth is a redundant rationalization arising only after the existence of the trait, they must not talk about being �deceived by your genes (89).� If it is in our evolutionary nature to be deceived by our genes, they should not denigrate those who are acting according to their nature by believing in religion and superstition. It would seem that genetic self-deception is one evolutionarily-bred characteristic that Ruse and Wilson would like humankind to surmount. Only a normative premise could conceivably justify such a statement as ignoring our evolutionary nature. We thus see that only with an underlying system of ethics, one that believes man should act according to his evolutionary nature, can the discovery of an evolutionary explanation for behavior provide people with a reason to take their prior moral attitudes more seriously.
We will now address the question of whether or not a discovered evolutionary basis for moral behavior gives us reason to take our moral attitudes less seriously. Certainly nothing mentioned thus far would suggest this. We might however think that by uncovering a process that discourages brother-sister incest or murdering for convenience, we make deterministic and explainable what we first considered free will. We might become like the tropistic wasp Sphex, with our hard-wired responses to certain inputs (Dennett 171).
This argument commits the deterministic fallacy. Genetics only influences human behavior through interactions with the environment. For an individual person, it makes no sense to say that a certain gene compelled a person to act in a certain way because genes and our environment jointly determine our behavior. Discovering that we have a predisposition to not murder does not compel us not to murder anymore than discovering that we have a predisposition to murder compels us to murder. We might think of a rectangle with length determined by genetics and width determined by the environment. Clearly both length and width are crucially necessary to formulating the area of the rectangle, or by analogy, of our individual behavioral patterns. Finding out the length of the rectangle by uncovering our genetic makeup does not tell us what behavior will actually be expressed. Given the seemingly endless environmental conditions that can influence our behavior, it is unlikely we merely possess genetic subroutines programmed to handle any (or most) environmental eventualities. The environment and our genetics jointly lead to the expression of our behavior. Finding out we possess a genetic predisposition to an ethically damnable behavior does exculpate us as our environment, including such things as our internal reaction to finding out we have such a trait, can affect the actual expression of the phenotype.
Having established that discovering a scientific basis for aspects of our behavior does not give us reason to take our moral attitudes more or less seriously without additional normative statements, I will now argue that discovering such a scientific explanation has no relevance at all to shaping our moral attitudes.
Elliott Sober in �Prospects for an Evolutionary Ethics� argues convincingly that �An explanation for why someone believes a proposition may fail to show whether the proposition is justified, and a justification of a proposition may fail to explain why someone believes the proposition (94).� We can thus assert the following: �Evolution underlies our moral beliefs regarding murder for convenience but says nothing about why I believe that I should not murder someone.� I do not have to know that evolution occurred to explain why I do not murder people for convenience. Having knowledge of evolution, I need not believe that I do not murder someone because of an evolutionary process.
However, Ruse and Wilson believe that evolutionary biology can answer both the questions of �Why do people have the views they do concerning when it is morally permissible to kill?� and �When is killing morally permissible?� For example, in the case of brother-sister incest avoidance, we can imagine that natural selection selected in favor of people who don�t have intercourse with siblings but instead have a genetic tendency to seek oral sex with them. Over time, people could have developed different reasons to prohibit all sexual relations among siblings. Perhaps, sexual relations within a family fractures the family or perhaps parents (because of other moral reasons) could not bear to see their kids engaging in sexual relations for no point but self-gratification. In any case, evolution only sets the stage for adoption of a moral law. Discovering that evolution only selects against incestual intercourse and not incestual oral sex has no relevance at all because people have adopted entirely different reasons justifying their ethical conduct. Few people would say that the reason they do not engage in intercourse with family members is because the kids would possess genetic diseases. In the same way, most people do not say that the reason they do no kill for convenience is because they might get caught. Discovering an evolutionary basis for this conduct does not have any relevance to continuing to follow it.
In addition, Ruse and Wilson seem to commit the genetic fallacy, which states that one cannot conclude from the facts surrounding the genesis of a belief whether or not the belief is valid. By believing that evolution somehow invalidates moral arguments by explaining the existence of the capacity for moral reasoning, Ruse and Wilson argue that the genesis of the genetic predisposition not to commit murder invalidates all ethical codes related to why people do not murder for convenience.
Unfortunately, Ruse and Wilson have gone too far in assessing the cross-disciplinary potential of evolutionary biology. The fact of uncovering a scientific basis for one of our moral codes does not have any relevance on whether or not we should continue to follow them. Ethics and biology inhabit different realms; biology may be able to explain the genesis of ethics, but it cannot explain the content in any way. My parents may be able to explain the circumstances surrounding my birth, but they cannot explain my thoughts or dreams at all. They may have been responsible for my existence, but they have no connection to my decision-making process. So it is with ethics and biology.