Theology and Evolutionary Psychology, Chapter 4: God's Plan for Sex and Marriage

Why do we marry? For Christians, why is God so keen on marriage? And even more specifically, why does God restrict sexual activity to marriage?

I'd like to start addressing these questions by first discussing the leash principle.

I believe the leash principle was first articulated by E.O. Wilson. The basic idea is this:

A. Does culture have human nature on a leash?

B. Or, does human nature have culture on a leash?

If it's A we have the notions of the blank slate and behaviorism where culture pulls human nature, shaping it as we would silly putty. But if it is B, then many of the cultural systems we see around us actually exist to accommodate the demands created by a pre-existing human nature.

For example, let's look at marriage. Is marriage a cultural innovation that shapes human nature? Or is marriage a response to human nature?

I deploy the leash principle here as it gives us interesting questions to ask as we approach topics where human nature and cultural institutions (like marriage) interface.

But let's back up and look at current religious conversations about sex and marriage.

In the Judeo-Christian tradition, sex is reserved for marriage. Oftentimes people ask, why is this so? Two responses typically follow. First, there is the answer from Divine Command: God just says so. Fine, but WHY does God link sex and marriage? What is His reasoning?

In response to this second question we typically get what I'll label the harm narrative. The harm narrative is this: If you have sex outside of marriage you'll be psychologically harmed. The harm isn't physical, but if you have sex outside of marriage something is "broken" inside you that never can be recovered and the integrity of your personhood is damaged or compromised.

Now, the reason the harm narrative gets deployed is that, for most Christians, there has to be something damaging about sex outside of marriage. Otherwise, why would God be so keen to prohibit it? In short, sex has got to be not just bad, but bad for you. That is the harm narrative.

Let's look a little more closely at the harm narrative:

First, given the role of sex in our adaptive history the harm principle seem dubious on the face of it. We are sexual creatures and modern American marriage rituals are relatively new in evolutionary history. Thus, it is a tall order to claim that sex outside of current American marriage rituals is psychologically harmful. Such a claim willfully ignores 3.5 million years of sex.

Second, the harm of sex might actually be due to the harm narrative. That is, it could be argued that the shame, guilt, loathing, and sense of brokenness related to amartial sex is a product of telling people that they SHOULD be screwed up if they have sex outside of marriage. If so, it might be the Christians who are harming people.

Third, given the data, I don't think the harm narrative is true (this follows from #1). This creates the following predicament: Non-Christians begin to suspect that Christians tell lies to get people to conform to Christian values.

So we return to the question: Why marriage? Why sex within marriage? I've just suggested that the harm narrative is not a good answer to these questions. Worse, the harm narrative might actually be causing the harm. Worse still, the harm narrative might make Christians look like liars. But if the harm narrative is shelved is there another rationale for "Why marriage?" and "Why sex within marriage?"?

Evolutionary psychology gives us one: Sexual rivalry and jealously.

Evolutionary psychology suggests that sex is like food. It is a finite resource that people compete for. The biological imperative is to reproduce ("Be fruitful and multiply!"). If so, how do you coordinate the sexual marketplace? Enter the leash principle. That is, human nature (the imperative creating a volatile sexual marketplace) creates an adaptive problem for human societies. How do we allow mating to occur without competition escalating into violence?

Because violence due to sexual rivalry is THE problem of sex. The problem isn't psychological harm; it's the possibility of social disintegration. For example, as I've blogged about before, homicidal fantasies are intimately tied up with sexual rivalry and jealously. As another data point, sexual jealously is the number one cause of domestic violence.

The point, then, is this: Marriage (and binding sex to marriage) is a cultural innovation to reduce communal violence (due to sexual rivalry and jealously).

With this notion in hand we see why the marital diversity in the bible (the OT patriarchs were polygamous) and across cultures makes sense. The goal of marital rituals is not to find God's "ideal plan" for a man and a woman. God's plan is to inhibit human violence. And there are many different kinds of ways that one might use to regulate the sexual marketplace. Take an anthropology course and you'll see what I mean. Overall, marital customs regulating the sexual marketplace are probably the greatest non-violence innovation in human history. Thus, the issue isn't HOW you regulate the marketplace but that it IS regulated in some fashion.

What I'm suggesting is that God's plan for marriage might be less about the couple and more about the entire community. Marriage is a sociological intervention, it's not a psychological intervention.

If this is correct then the theological conversation about sex should move away from the harm narrative ("Sex is bad for you") to sociological issues of envy, jealously, covetousness, "using people," harm, and communal violence. Marriage is about these issues. It's not about protecting you from sex.

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27 thoughts on “Theology and Evolutionary Psychology, Chapter 4: God's Plan for Sex and Marriage”

  1. Richard,

    As I have said for some time: God's first command given to male and female is to have sex early and often ("Be fruitful and multiply and replenish the earth." Genesis 1:28, 9:1). Sex has never been a problem for God. It is, as you says, a question of how we deal with it so as not to--ahem--screw everything else up.


    George C.

  2. That's, of course, assuming that it's God (and not certain religious humans) who actually wants to restrict sexual activity to marriage.

    I'd suggest that limiting sex to marriage, similar to your second point (the harm of sex might actually be due to the harm narrative), could also be the cause of much of the sexual rivalry and jealousy out there as well. The idea of limiting sex to marriage might have actually made sense at one point (might being a key word here as I'm not 100% certain that it ever actually did), but I'm not convinced that it does today, at least in the west.

    I've been involved in polyamorous relationships in the past and my experience is that jealousy, even sexual jealousy, is a learned (and unnecessary) behaviour. If society stopped teaching (and believing) that a person "owns" the rights to their partner's body when it comes to sex then a lot of the issues with sexual jealousy would just go away.

  3. Richard,

    There is a very helpful review of matters your posts are dealing with in the most recent issue of The Chronicles of Higher Education. See this URL:

    If that won't do it and you don't have access to The Chronicles, the review can be accessed through the Arts & Letters website.


    George C.

  4. I wonder if there is any research on the "swinging" phenomenon that began in the 50s. Is jealousy and rivalry a problem within swinger communities? Surely there must be some data on this by now.

  5. I have a quick follow-up question. You talk about marriage and sex in regards to the benefit of the society, which seems to make sense. But, from a psychologist's perspective, is there any benefit for the couple in keeping sex within marraige? In other words, does marriage help diminish the "violence" of sex for the two parties involved or only in regards to the society as a whole?

  6. That was wonderful post Richard!

    I agree with your well written analysis and your conclusion. Preservation of community is the basis for all OT teachings. The 10 commandments and the rest of the Torah echo this fact. Do not kill, covet, commit adultery,etc. are all commands to prevent violence from jealousy.

    The same argument could be made about the commandment to honor the sabbath which is the first form of "workers rights" focused on fair treatment of workers aimed to maintain order and preserve a healthy community relationship in contrast to the oppressive community forced on them in Egypt (making bricks 7 days a week). This most important command as well as commands about land ownership and limits to slavery and generational wealth (jubiliee) was an attempt to install justice and prevent a breakdown in community through unfair treatment and unjust distribution of wealth.

    I feel it is clear that the purpose of religion as highighted in the OT is the preservation of community.

  7. Danutz! Good to see you here. Great minds migrate to the same blogs I guess (although it's undoubtedly quite presumptuous to label this gray matter of mine 'great'). :-)
    Richard, I think that your critique of appeals to the harm principle suffice to establish the ethicality of non-marital sex, but of course, certain elements are lacking from your analysis. Sexuality goes to our very core, and so I don't think it'll do to reduce the 'harm' of promiscuous sex to a societal phenomenon. We are embodied beings, and relationality is wired into our sexuality--certain forms of sex can therefore be detrimental to particular individuals, as well as to the societies they inhabit.
    The crux of the issue for me however, is that the call of Christians isn't merely to avoid that which is wrong and (when possible?) to do what is good. No. We are called to a higher standard which involves acknowledging God's sovereignty (viz. embodying the Kingdom). Biblically speaking, this means adhering to broad brushstrokes of the biblical narrative, of which Genesis 1 and 2 are inalienable components.
    So while unequivocal condemnation of non-Christians having extramarital sex might be silly (or rather, simplistic), that cannot be the end of the discussion for those who claim allegiance to the Creator (I do think there is some flexibility as to how this works out, but I just wanted to point out that mere 'morality' is never the basis for Christian living).
    My two cents.

  8. I really like this post.

    I think you are still telling, in a sense, a harm narrative (it is a broad, sociological one rather than a narrow, individualistic one). However, I think it is much more sensible than the harm narrative that I hear from mainstream evangelicalism.

    I also think it can be more readily defended in terms of the text of the OT AND NT. Just think of all of the situations where non-monogamous sexual conduct results in violence of some sort - David being the prime example.

    Likewise, Jesus' concerns relating to sexuality and divorce in Mt. 5-7 seem to be focused on issues of justice and love with respect to the treatment of women (the violence he's concerned about may not be immediately felt - like an assault - but its real nonetheless).

    Another side note - some writers in the field of jurisprudence (a field of study that relates to the hows and whys of a system of justice) during the last few decades have similarly argued that the justice system's main value is not that it intrinsically does something that is "good," but merely that - by providing a community-sanctioned system for dispute resolution - it keeps people from taking to the streets with their grievances against each other...

  9. Hello Everyone,
    Great thoughts all around. Just a few clarifications.

    I don't want to say that couple-level or person-level analyses of sex and marriage are illegitimate or that God is not working on those levels as well. I'm just mainly pointing out that the sociological level, which may be the most important level of analysis, often gets ignored and that focus on this level changes in the conversation in interesting ways.

    Sometimes I wonder about the following. They say that "romantic love" and marrying for love is a new development in the history of the world. That in times gone by, marriage functioned more like what I've described in this post: A way for the community to get along. That is, marriage was communally functional but, perhaps, individually unfulfilling (particularly for women). Given the rise of romantic love what now is happing? Clearly, it seems God is working in this trend. I consider the love I have for my wife one of the greatest goods in my life. But this trend can also make us ego-centric, susceptible to Cinderella syndromes. The trend seems good yet problematic. I wonder about all this.

  10. I wonder if binding sex to marriage is still necessary as a cultural innovation to reduce jealousy and rivalry. I looked up my own question about swinging on the great wiki, and interestingly "research" shows that only 6% of people engaged in this lifestyle experienced extreme jealousy. I was amazed to find that there are over 4 million people practicing this kind of extreme sex sharing. Are these communities getting torn apart by jealousy and rivalry? I don't have any first hand accounts, unfortunately, but after reading the wiki article this seems not to be the case. Perhaps for most people, provoking jealousy requires both deliberate deception and adultery. Or maybe culture is just changing thanks to technology, women's lib, etc.

  11. Hi Pecs,
    As a social scientist I don't know if I'd feel comfortable generalizing from the swinging community to the general population. To swing practically requires an attenuation of jealousy so it's not surprising to not find it there. If proneness to jealousy is normally distributed in the general population than we would naturally find people on the lower end of the continuum. Also, we would need to see any research on swinging in a good peer reviewed journal (and hopefully replicated) as "data" on swinging is bound to be tied up in group interests (either for it or to discredit it).

    My hunch is this: Free or swinging love as a general cultural norm is an impossibility. Human nature just can't handle it. There have been no documented human cultures who have wholesale "deregulated" the sexual marketplace. That's not a coincidence. Sexual jealousy and rivalry is deeply embedded in the human psyche.

  12. Yeah, I was thinking as I wrote that about "Kinsey" which I watched recently. The frequent and free sex among that academic group seemed to have had the kind of detrimental effects stemming from jealousy. Perhaps the swingers are the exception, and sexual jealousy is so embedded that no amount of cultural or technological revolution will change things.

  13. Perhaps the swingers are the exception, and sexual jealousy is so embedded that no amount of cultural or technological revolution will change things.

    I'm still not convinced that this is the case. I suspect very strongly that sexual jealousy is based on a combination of personal insecurity and a mindset of ownership of one's partner. If a society were to make any effort at all towards combating both of these factors, based on my own personal experience I believe that there's a strong chance that sexual monogamy as a norm could easily become a thing of the past. Either way neither I, nor anybody else, has any ontological right to tell a partner what to do with their body as long as they're not harming us with their choices (yes, I believe the harm factor is the best measurement for sexual activity, but I bypass the problem of your point #2 because I don't believe that God cares if we have premarital or non-monogamous sex so I'm not telling others not to) as we don't own the rights to our partner's body (perhaps we would legally in some countries, but ontologically speaking we really don't).

  14. C. H.,

    It seems to me that "God cares" about sex in that God made us sexual beings. I am dubious of such facile phrases as "no one has the right to tell us what to do with our bodies as long they are not harming us with their choices." I don't think any of us individually is wise enough to determine what short- or long-term
    harm our actions, sexual or otherwise, might produce.

    However, I incline to agree with you that pre-marital and monogamous sexual relationships is "largely" learned social behavior developed [adaptationally?] to protect women from exploitation by testosterone-ladened males. I say "largely" because I believe that most social prohibitions develop because of ontological needs and realitites. Despite modern individualistic ideologies, we are, as Aristotle stated it, social, contextual creatures to the core. None of us is a wolfboy (or girl) even though we may have wolfish (or randy)behaviors.


    George C.

  15. Hello Ricardo,

    I must point out what I feel is one very weak argument in your post (did you expect less--ha):

    . We are sexual creatures and modern American marriage rituals are relatively new in evolutionary history. Thus, it is a tall order to claim that sex outside of current American marriage rituals is psychologically harmful. Such a claim willfully ignores 3.5 million years of sex.

    The fact that it's been happening for 3.5 million years does not argue against the idea that it's inherently damaging; the rest of your argument is based on this assumption, which I find dubious.

    So, I'd like you to comment more, if you'd like, on how you're certain non-marital sex is not psychologically damaging. This is what I've heard all my life, and to argue against it is pretty paradigm-shifting to me.

  16. CH,
    I often think people camp out as either Rousseauian (optimistic) or Hobbesian (pessimistic) regarding human nature on these issues. I'm Hobbesian on this issue. I think sexual jealousy is innate to human nature and not the product of cultural norms. I think you'd disagree with that.

    I'd like to flip this if I may, as it is hard to prove a negative.

    You're making the positive claim: Amaritial sex is harmful.

    If so, there should be clear (i.e., empirical) , universal (i.e., cross-cultural), and consistent (across the millennium) damage caused by amartial sex. Correct? If so, I'd like to see the evidence for why you believe this.

  17. My claim is not to have proof of such harm, though I believe it to be true from conversations I've had with others.

    My objection here is that 3.5 million years of practice does not prove that harm is not happening. See what I mean?

  18. I think I understand. Okay, let's start from scratch then. Question to debate: Have people been being harmed by amarital sex over the last 3.5 million years?*

    My position (the negative claim): I see no evidence of harm.

    Your position (the positive claim): I see evidence of harm.

    Great, what is your evidence?

    *Note that genus Homo was not around that far back, so were talking about Australopithecine sex for a million or so years:-)

  19. Cole,
    Just to clarify, my prior comment was meant to be playful. I'm being playful because you'll NEVER give me the satisfaction of agreeing with me:-)

    I guess what I'm saying is this: I don't see dramatic evidence that the harm narrative is true. People have been having amartial sex for thousands if not millions of years and I just don't see the psychic scars. And if I don't see the scars (as a person sympathetic to the Judeo-Christian ethic) what must skeptics see? They see a bunch of religious people trying to scare teenagers, using fear as a means of behavioral control.

    Now maybe harm is being done. If it is, the case should be easily made with good evidence. No fear, just the facts. But, per my comments to you above, I don't see the strong case for the harm narrative. And, to be people of intellectual integrity, should we not have the facts in hand before we go scaring people?

  20. Now, Richard, I often agree with you; I find your arguments very compelling at times. I am disgusted by dung-shaped brownies, for instance.

    I am going to invoke C. S. Lewis here, though I can hear the GSTs eye-rolling from here. He states (in many places, but Mere Christianity and Surprised by Joy most famously) that we are governed by an unspoken, God-given moral compass (in essence) that transcends time and culture. In all cultures, for example, we know that it's wrong to murder because...well, because "we feel it" for lack of a better term. There is a moral standard that accompanies being human beings.

    So, I would, by extention, say look at how much pain must be dealt with because of amarital sex--attachment bonds that impede future relationships, primarily. Your argument will be that we have culturally created both the romantics bonds that go with sex, as well as that amartial sexual attachment pain, but I would side with Lewis that these are inherent to our compass, though I have no proof. But neither does anyone have proof that such pain is "merely" cultural. I suppose it's a conundrum.

    Except I think I have this on my side: can't we argue that all cultures value sexual conservativsm? Not just for the survival reasons you've stated, but for "moral" ones as well? How many liberal (or "progressive") dads eagerly await the day their young daughter loses her virginity to a roving young man so that she can experience the fun of it?

    Now, I realize it's up to me to convince you that all cultures value monagamy over other sexual practices, but I'm sure there are cultures that value sharing sexual partners moreso. I know that Hawaiians sent their women in outriggers to visiting ships in order to hospitably service the sailors. But that doesn't mean the women wanted it, were not harmed by it, or that such sexual practices bolstered their moral compasses.

    That's all for now.

  21. Cole,
    We probably agree more than disagree, but let me clarify what I mean by "sex" in this post in contrast to your examples.

    When I talk about sex and the harm narrative I'm talking about two consenting people who have sex because they genuinely love each other. Thus,
    I'm assuming that these two people have a strong emotional bond. Sex, in this situation, doesn't seem psychologically harmful (regardless of the marital status of the couple). Now, harm can occur if someone pretends to love another just to have sex. That is, they violate trust just to get sexual access (men usually do this to women, stereotypically speaking). The harm here, I contend, is not due to the sex but due to the lies and broken promises. Sure, the person in hindsight might regret having sex with the slimeball, but its not the sex per se that is causing the harm. It's the emotional violation that makes the sex toxic (in retrospect).

    Now, it seems to me that God knows all this, that sex is risky not due to the sex but due to the fragility of human commitment. Thus God, in his wisdom, binds sex to marriage. But again, God's intervention has less to do with sex and more to do with human promise-keeping. Breaking promises is harmful. Sex is neutral, sometimes good and sometimes bad given the nature of relations between the two people.

    So, going back to your C.S. Lewis example. I can agree with Lewis that inside all people our moral compass tells us that breaking promises is a bad thing. I think there is strong evidence that all people share this moral law. But I don't think all people feel that sex is intrinsically harmful. In fact, I know that not to be the case.

  22. Maybe I'm showing my own cynical bent here, but isn't your last comment here kind of begging the real question?

    Theologically-speaking, it seems that the notion of sinful humanity, as a doctrine of the Christian faith, states that ALL human beings, whether they realize it or not, at some point WILL "violate trust just to get sexual access." Our fallen nature violates trust. The debate among Christians is how much of our nature is bent that way: all of it, or only a part?

    But either way, the bent is there. Even in the very best relationships, violation of trust will happen due to human fallen-ness. I realize that's a bit depressing, but it does seem to be the key point: Does sin really affect all of us, in ways that damage us whether we realize it or not? If it does, then the "harm narrative" seems to retain some of it's value, even if the way it's been interpreted contains flaws.


  23. Geoff,

    It seems to me that "human fallen-ness," as you put it, is less a Biblical idea and much more a Manichean notion mediated through Greek thought through Augustine, radicalized even more by Luther, Calvin, the Puritan divines and writers like John Milton. The Genesis story speaks of expulsion or exile, not fall. Sin is associated with behavior, not ontology. Adam and Eve sinned because they did something, not because of their "nature."

    Richard, "Fallen humanity" or the "Fall" might be a topic you might want to take up.


    George C.

  24. Hi George,

    Although I see your point, I think you'd have a hard time making the case that Scripture does not strongly imply an ontological element to sin (though I'd be interested in reading further on the subject!). The overwhelming witness of Scripture is that everyone is guilty of sin, and this is not a surprise. The assumption is that everyone WILL fail, and salvation through Christ is necessary because of human inadequacy.

    Perhaps this is not explicitly ontological, but if something is guaranteed to be the case for every single person, I think we would be safe to say that such a pattern indicates something deeper than mere behavior. There is something at work which has brought about this behavior in every human being that has ever existed, except, evidently, for Christ. So, I guess the question is: what is that "thing" which dictates behavior?

    Manicheanism, as I understand it, is primarily concerned with Gnostic dualism, in which the "body" is bad, and the "spirit" is good. This may have been improperly emphasized in some of Augustine's thought but don't think the doctrine of "the fall" relies primarily on such a dualistic notion of reality. The issue is not that there are two worlds of light and darkness fighting for ultimate control. It is, rather, that darkness has been defeated, but for some reason we keep returning to it anyway.


  25. Geoff,

    Let's discuss the "Fall" off-blog. My email address is Contact me there and we can dialog further.


    George C.

  26. Hey George, I emailed you... just checking to see if you got it. thanks.


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