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Four Problems with Naturalistic Evolutionary Ethics

by Paul Rezkalla


Gargan, the caveman, lived for only one purpose: producing offspring. His sole purpose in life was to propagate his DNA by any means necessary. Brutality and selfishness are simply the tools of the trade to accomplish the life mission bestowed upon him by natural selection, making Gargan a mean character with no regard for any creatures, human or otherwise, around him.

This caricature of evolutionary morality is becoming increasingly outdated as new methods of observing and studying mammalian behavior shed light on behavioral tendencies. Humans are social mammals, and as such, we depend on each other’s cooperation to survive. Thus, there is a kind of proto-morality that can be observed even among chimps, bonobos, and other primates. Some species of primates understand and live by the laws of reciprocity and fairness, engaging in tit for tat and giving favors in exchange for future favors. Frans deWaal points out that Chimpanzees “build a social economy of favors and disfavors to food to sex and form grooming to support in fights. They seem to maintain balance sheets and develop expectations, perhaps even obligations, hence their negative reaction to broken trust” (The Bonobo and the Atheist, 129). This complex system of interaction is interesting scientifically, but it suffers from some deep problems when applied to conversations about morality and normative ethics.


  1. Naturalistic Fallacy

Defining that which is “good” as that which is “natural” commits what G. E. Moore called the naturalistic fallacy: “To argue that a thing is good because it is natural or bad because it is unnatural…is therefore certainly fallacious: and yet such arguments are very frequently used.” “All that the Evolution-Hypothesis tells us is that certain kinds of conduct are more evolved than others” and what this leads to, say some, is the “definite view that better means nothing but more evolved; or even that what is more evolved is therefore better.” Once we collapse “goodness” into “naturalness,” we have no standard by which to measure the moral status of human behavior. In order for human behavior to be subject to evaluation, “goodness” has to mean something more than merely “that which is natural.” Moore also points out that: “The value of the scientific theory, and it is a theory of great value, just consists in showing what are the causes which produce certain biological effects: whether these effects are good or bad it cannot pretend to judge.” A recent study has demonstrated a link between the genetic mutation that inhibits the production of Monoamine Oxidase A (an enzyme that catalyzes dopamine and seratonine) and both lower levels of empathy and higher levels of aggression. Another study has shown that males with less white matter in their brains are more likely to experience and express pedophilic tendencies. If “goodness” and “naturalness” are synonymous, then it would follow that male aggression and pedophilia are good, but we all agree that this is not the case. We subject human behaviors and tendencies to moral scrutiny by a standard that exists beyond human behaviors and tendencies (we do it no other way!).

  1. Is-Ought Fallacy

The evolutionary sciences only tell us what is the case about evolutionary history, primate behavior, human psychology, etc. They do what science is meant to do: describe the natural order of things. Hence, by virtue of what science is, it merely describes behavior, but it cannot prescribe behavior. As David Hume pointed out, there is an epistemic and normative gap between that which is the case and that which ought to be. Deriving an ought from an is seems difficult, if not impossible. Science, the careful, methodical observation of the world, can only describe human behavior. It cannot prescribe moral behavior. While scientific results and discoveries can offer interesting and even relevant insight into ethical questions, science is not the arbiter of ethics. And as with the naturalistic fallacy, we run the risk of endorsing immoral oughts simply because we observe some immoral behavior that simply is. A recent anthropological survey of human ancestors in the Pleistocene era has suggested that male-on-female rape was exceedingly common. Due to various factors, females began to recognize and implement their role as sex monopolizers, and this in turn led to an increase in rape. This detrimental exchange of behaviors was soon phased out by natural selection, but for some time it was the norm. It still goes without saying that rape, whether then or now, is morally reprehensible regardless of circumstances. If it is true (and it is) that rape is, always has been, and always will be wrong, then we can condemn natural states of affairs that favored rape and concede that we cannot derive an ought from an is.

It is also interesting to note that humans seem unique in that there is a moral dimension to our behavior. Rape among humans is not merely forcible copulation. Forcible copulation takes place regularly in the animal kingdom with ducks, sharks, dolphins, and bedbugs. Bedbugs and other invertebrates actually practice what is known as “traumatic insemination” as the ordinary means by which they copulate. With human beings, forcible copulation is termed “rape” because we recognize that human behavior is saturated with moral status, whether good or bad. Male lions sometimes kill cubs, but they do not murder. Fighter ants use aphids as forced laborers, but they do not practice slavery. Young bottlenose dolphin males have been known to corner a single female and take turns forcibly copulating, but they do not commit rape. Murder, slavery, and rape are immoral acts that are only possible among humans because of the unique ability of human actions to carry moral status.

  1. Arbitrary Moral Values

The values and tendencies that humans hold are contingent upon the specific kind of social mammals that we are. Had the tape of evolutionary history been rewound and played once again, we might have a completely different set of moral values and tendencies –on what Angus Menuge calls “strong evolutionary ethics.” Darwin himself noted this conclusion: “If, for instance, to take an extreme case, men were reared under precisely the same conditions as hive-bees, there can hardly be a doubt that our unmarried females would, like the worker-bees, think it a sacred duty to kill their brothers, and mothers would strive to kill their fertile daughters; and no one would think of interfering.” Michael Ruse also paints a stark picture: “We are what we are because of contingent circumstances, not because we necessarily had to be as we are. Suppose, instead of evolving from savannah-living primates…we had come from cave-dwellers. Our nature and morality might have been very different. Or take the termites…they have to eat each other’s feces…had humans come along a similar trail, our highest ethical imperatives would have been strange indeed.”

  1. Evolutionary Science Undermines Justification for Moral Beliefs

Imagine that when you were a child, a scientist gave you a pill that caused you to believe that George Washington was the first president of the U.S.A. Imagine also that this pill caused you to forget that you ever took such a pill. Finally, imagine that the same scientist finds you again late in life and confesses to you that you were part of this experiment of which you were unaware. He tells you that your belief that George Washington was the first president was solely the product of a pill. If you had never researched the topic for yourself, you would not be justified in continuing to believe that George Washington was the first president, right? The only reason you had that belief was the pill that was given to you. But now that you have knowledge about the pill, you cannot honestly say that you have good grounds for believing that George Washington was the first president.

The same is true of evolutionary science and what it tells us about ethics. We are learning now, more than ever, that human beings are social animals with tendencies built in to us over the course of evolutionary history that allow us to function well together in groups. We have tendencies to take care of our children, our spouses, etc. We have tendencies towards reciprocity, altruism, and empathy. The problem however is that coming to know that these tendencies are inculcated into us by evolutionary processes geared towards maximizing survivability and reproduction actually undercuts our justification for believing that these moral tendencies are true and binding for us. In the same way that once you find out that your George Washington belief is solely the product of a pill, you no longer have good reasons for continuing to believe it to be true, understanding that “morality” is merely a set of evolutionarily-ingrained tendencies also undermines our justification for moral beliefs and actions. “Morality, or more strictly our belief in morality, is merely an adaptation put in place to further our reproductive ends (Ruse and Wilson 1985)” and it “is a collective illusion foisted upon us by our genes” (Ruse 1986).


Photo: “Two apes share a moment” by Indo_girl2010. CC license. 

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