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Evolution & Morality: Explanation vs. Justification

Neo-Darwinian evolutionary theory tries to explain everything that it tries to explain about the behavior of organisms in terms of "inclusive fitness": if a gene influences the behavior of its host organism in such a way as to increase the number of copies of itself in future generations of related organisms, then it, and the behaviors it encourages, will tend to spread.

Among the behaviors that neo-Darwinian evolutionary theory tries to explain in these terms are various human moral prescriptions & proscriptions.

For example, the aversion to and prohibition of incest between close family members - especially between parents and children, and between brothers and sisters: since the offspring of such unions suffer from elevated levels of genetic diseases, a gene that influenced its host to feel averse to sexual relations with parents, &/or children, &/or siblings would tend to spread.

In due course, feelings of aversion to such relations would become prevalent. The prevalence of such feelings would in turn lead to the adoption of moral rules prohibiting such conduct.

Personally, I find this, in outline, a fairly persuasive explanation for the ubiquity of traditional moral rules forbidding incest between close family members.

But is it - could it ever be - a justification for such rules?

Imagine a father and daughter (of the age of consent), in lust with one another, who argued as follows:

The prohibition of father-daughter incest is a product of primitive conditions that no longer obtain. We have no intention of producing any offspring. I've had a vasectomy, and she's on the pill. Moreover, in the unlikely event that she still managed to conceive a child, we could always have it checked before birth for genetic defects, and abort if necessary. So what's the problem?

Could a neo-Darwinian evolutionary theorist, qua neo-Darwinian evolutionary theorist, make any effective rebuttal to such an argument?

I don't think so.

More generally: while I think that neo-Darwinian evolutionary theorists can offer all sorts of interesting explanations for traditional moral judgments, I do not think that they can justify any moral judgments whatsoever.

Comments (17)

Well, if you murder your wife, it is hard to have children with her. Her is a case where the explanation and the justification overlap.

The Chicken

Should be:

Here is a case where the explanation and the justification overlap.

Steve, I'm very pleased to find you saying that--about not being able to provide a justification. That is one reason (among others) why sociobiology is so unsatisfactory. Almost the only way to make it morally interesting is to turn it into a form of determinism: "Don't blame people for doing X or for feeling strongly that Y should be proscribed. They can't help it; it's in their genes." Which is, like all determinism, profoundly unsatisfying.

"Don't blame people for doing X or for feeling strongly that Y should be proscribed. They can't help it; it's in their genes."

This statement is true in every species up to, but not including, man. Sociobiology is nothing but warmed over Thomistic notions of instinct dressed up in DNA language. Sociobiologists should really read St. Thomas's discussion on how man differs from animals (the whole rational soul thing). Only man can make moral judgments (and not simply instinctual ones) that transcend DNA because he, alone has a part of him that transcends DNA - his rational soul.

Sociobiology cannot really answer questions of like people like hula hoops one year and not the next. They really can't show how fads can come into existence, vanish, and return. They really can't explain how some societies can go from being charitable and reasonable to becoming vile and irrational and then return to charity by the action of a single individual. In other words, they can't explain lynch mobs and their sudden conversions or St. Joan of Arc. I was reading a history book once that was talking about the fracturing of France in the 1200's and 1300' when the book just stops and starts a new paragraph that was one sentence long: Then came Joan of Arc. When sociobiology can explain Joan of Arc, I might listen to them.

The Chicken

Isn't this exactly what the materialists want? That no morals can be justified, therefore nothing is immoral? I thought this was understood.

I dunno, DmL. True story (as told to me): Some years ago some people who challenge Darwinism were talking to some guys at an ostensibly conservative think-tank. I can't remember which one it was, so I won't make something up, but it was a name I had heard of. And they were told (paraphrasing), "We really aren't interested in your material and don't want to do anything with it, because Darwinian sociobiology is the best defense for our conservative political values, and we will undermine that if we question Darwinism as a scientific theory."

To me, that certainly sounds like these were people who believed they could get real moral mileage out of Darwinian scientific theory.

True. If there is no God, it is still essential that we act like our evolved notions of morality and ancenstral customs are in fact divine law. That is why delving into the question of the existence of God is so dangerous. Some people intuitively sense that God is not there, but they don't understand that they might best need to be quiet about it. They are in the unfortunate position of not being able to tell the truth without potentially introducing chaos. But the cat is out of the bag.

Personally, I find this, in outline, a fairly persuasive explanation for the ubiquity of traditional moral rules forbidding incest between close family members.

I really wonder about one aspect of this analysis, Steve. According to Judeo-Christian tradition, all humans are descended from Adam and Eve, and there was perforce a lot of marrying between brothers and sisters, at first, then first cousins, and finally second cousins, before we could have gotten to the point of intra-family sexual taboos beginning.

Stepping away from the Bible and Genesis, I was under the impression that gene analysis of the current population strongly indicates that all present-day humans are descended from a single woman at some point in the past. So that the suggested sociological conclusion is that in that woman's immediate descendants, there were no effective constraints about marrying your blood relations.

Although I don't put a great deal of stock in this suggestion, I wanted to pass it along: Some Christians propose that Adam and Eve had perfect genetic code in the Garden of Eden. After their sin, they were no longer preserved from damage to their genes, but they would have passed along to their kids nearly perfect genetic codes as well. Successive generations would gradually have more damage, so that by the time many generations had passed, there would be the observable reality that brother and sister marrying would have a much higher likelihood of a genetic disorder springing up - but this observable situation would not have been present in early generations.

Finally, I would strongly object to a notion that this "instinct" against marrying one's sibling or cousin arose by natural forces of evolution after man attained a rational nature and a culture, and calling this anything other than a simple embodiment of a cultural choice, not an evolutionary "instinct". Which raises an important side-question: is this "instinct" found generally in other animals, like other vertebrates? other mammals? other primates?

This instinct is found in other species in nature, though it is not an insurmountable one. After all, selective inbreeding has been used upon domesticated animals for thousands of years. Even so, the gross genetic diversity of the human race is much narrower than that of most mammals. It is therefore less risk for two rat siblings to have offspring with serious genetic flaws than two human cousins.

Also, consider the energy put into raising a child. On average, a woman will give birth to a single child, with an outside possibility for twins. A woman is less likely to ovulate until the previous child is weened. Then adding in disease and famine, a stone age woman may require years before she can compete numerically with the rat's first litter (and its even worse for modern, contracepting women).

As such, the odds are against humans, the stakes are higher, so the instinct must be made stronger.

As for why some conservatives may utilize Darwinian theory, consider that the Marxism demands that humanity can achieve a Utopian paradise. This is, of course, absurd without the belief that humanity evolved to fit within a biological niche of Utopian paradise. Now the survivability of a slow, awkward biped bereft of fangs, claws, or protective fur in the African Savanna during the Late Pleistocene, is best described as very difficult. As such the only way such a primordial paradise for said awkward biped to evolve is by divine intervention. You all knows what happens next.

Hi, Steve

Personally, I find this, in outline, a fairly persuasive explanation for the ubiquity of traditional moral rules forbidding incest between close family members.

In would say that evolutionary theory can offer only a persuasive explanation for a behavioral tendency to not engage in incest. Most animals share the same behavioral tendency, but don't appear to have a moral imperative against it. Likewise, we have a behavioral tendency to breathe when we need oxygen, and to avoid food that tastes bad, but we do these things automatically and don't really require a moral obligation to do them.

There is a huge logical leap in going from a behavioral tendency to do or not do something to a moral sense that you should or should not do that thing. For one thing, the sense that you ought to do something is case of representation - ie intentionality. That is massive explanatory chasm that is simply being skipped over whenever Darwinians make arguments of the sort "X is bad for survival and would be selected against, therefore natural selection explains the moral injunction against X".

Two things that I think should be clarified. First, the distinction between a norm being justified for a society, and an individual's obligation to follow that norm. Steve Burton argues in his example against the latter justification, but the biosocial justification (when offered seriously) generally seems to be for the former. The former biosocial claim is less trivial to shoot down in this case: that is, the claim that if a society is to flourish, it ought not approve of incest. For some traits of human nature this justification works - a society has to respect humans' natural loyalty to kin - and for some it doesn't - a society does not have to respect a natural tendency to rape. So this sort of society-wide justification has to be considered norm by norm, society by society, concentrating on all the contingent cultural and natural details, rather than by some general argument.

Second, Burton's whole argument seems to apply not only to putative biosocial justifications, but to all modern, "scientific" theories of natural law, like Hobbes for instance. With respect to any of these theories the individual can say, as in Burton's example, "Yes, this societal norm is justified on the principle of human flourishing, but why should I follow it in this case?" So I think evolution is a red herring here.

These taboos were hard wired into human cultures at a time when we were too few as opposed to our present situation which tends to skew us towards sentimentality when we look backwards.

We plains apes lived on the edge for most of our existence. Exogamy brings allies and willing hands. Endogamy not so much and incest not at all.

There were immediate benefits to marrying out. Those benefits associated with a broadened gene pool would only work out over generations. We should also consider that the strength of in-law incest taboos argue against genetics as the primary driver.

Like polygamy, incest seems to inevitably lead to unhealthy social dynamics (homeless teens in St. George, Chinatown). Back in the day this would have threatened group survival.

We plains apes...

Speak for yourself, Koko.

If your blogging colleague Ed Feser has judged it poor form to promote his fine recent book again in your comment column, then—since I do not know Ed and have no interest in his book's royalty—may I now promote the book? Sections 4.2 and 5.4F of The Last Superstition make a rather neat colloquy with your article.

I will say that I have seldom spent a better 27 dollars than on Ed's book. The book is heartily recommended to all your readers, and doubly to readers whom your article's topic interests.

not much to be said, if say, men, prey on their daughters or nieces what line remains to be crossed. Morality isn't an act specific restriction, it is a overarching series of proscriptions, a nebulous but real and important series of hindrances and prejudices, born through time of the fears, legitimate fears, of people who relied on an imperfect custom to maintain to order in ages less subject to an Authority both dominant, distant, and in it's essence, amoral but ambitious.
Darwinism is, if taken too seriously, a bad joke. Now as learned folk, sinecured, fat, and loose from memory as folk rarely have been in in the past, blessed by the benedictions of relativism,take to flight in the fancies of narrow imagination, and in the willful and selective reading of a cannibalized history, the god, Will. as never imagined by Schopenhauer, nor I dare say, by Freud, achieves an unhindered & unlettered freedom. A Self, grounded in a libertine and necessarily ignorant base, one that congratulates itself on it's blindness, becomes definitional in a society that holds a type of person that reads from idiot cards before movie cameras directed by vulgarians of a particular affluent but distinctly odious type.

I said, "not much to be said". Best to close. In a world of ignorance pleasure is King, more so when borders are absent and the manacles of self discipline gone.


But is it - could it ever be - a justification for such rules?

What would you consider sufficient to be justification? Once the rule is established, it is either enforced or exceptions are made.

This topic reminds me of a good passage from the book The Way the World Is by John Polkinghorne, which I'll quote in full because I have nothing better to do at the moment:

"At this point my socio-biological colleague taps me on the shoulder. He has the explanation of these moral convictions of mine. They are genetically programmed into me because altruism is an aid to group survival in the struggle for existence. Let us recognize that remark for what it is. It is no scientifically demonstrated fact, but an ingenious suggestion. Caution is all the more necessary because our friend is using a key which appears to open nearly every lock. There is a line of argument which runs: men (or animals) possess property X; they have survived; therefore property X must be an aid to survival and that is all that need be said about it. If altruism is just an aid to survival, it is surprising that those selfish genes have not been more efficient in creating it. The quintessence of our moral experience is that what we recognize that we ought to do, is so often in fact what we do not do. The picture of human evolution is of the rise of a tribe of killer apes who war on their own kind... It has not been shown that the human story is just a saga of genetic self-perpetuation, and quite frankly it strikes me as preposterous to suppose so."

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