The God of the Reptile Brain

Evolution is a blind tinkerer, lacking the foresight of human engineers. Rarely, if ever, does it discard established designs and start over fresh, even when that would be more efficient. Instead, it builds on and around past adaptations, using the old as a foundation for the new. This is true throughout the biosphere, and it’s especially true of one of the most complex structures ever evolved, the human brain. The physical architecture of the mind shows, through and through, the evolutionary hacks and kludges that went into creating it.

In his book The Dragons of Eden, Carl Sagan points out that the human brain has a threefold division. The most complex and most recently evolved structure is the neocortex, responsible for rational judgment, self-control, long-term planning, and all those other characteristics we think of as most uniquely human. Below it, somewhat older, is the limbic system: shared by all mammals, producing feelings of parental love and pair-bonding. And oldest and most primitive, shared by all vertebrates, is the brainstem, which controls the instinctive drives and behaviors known as the four “F”‘s – fight, flight, feeding, and reproduction.

And if you’re feeling allegorical, you might notice a correspondence with the world’s religions. No organized religion in existence today posits a god of the neocortex. A few of the best offer a god of the mammalian brain, but even they rarely aspire to anything higher. But most – the belligerent, aggrieved, crudely literal fundamentalist faiths that command the allegiance of hundreds of millions – have gods of the reptile brain. These deities well up from the brainstem, the evolutionary remnant that sees the world as a dark palette of anger, fear, hunger and lust. Like the promptings of the brainstem, they’re concerned, more than anything else, with the lowest and most primitive animal drives: what we eat, how and with whom we have sex, whether we observe rituals and taboos relating to purity and contamination. Also like the promptings of the brainstem, the religions they preside over tend to include generous amounts of aggression, submission, and xenophobia, and inflexible rules on when these are to be displayed and toward whom.

Of course, I’m not saying that religion originates solely in the brainstem. Were that the case, we’d see distinctly religious behavior throughout the animal kingdom, which we obviously don’t. Religion requires other mental capabilities that are largely unique to humans and other intelligent mammals – social dominance hierarchies, pattern-seeking behavior, and an awareness of personal mortality. Still, it’s striking how close is the correspondence between the concerns of fundamentalist religion and the instinctive drives mediated by the most evolutionarily primitive part of our brains.

But from the rational perspective – the highest, most uniquely human perspective – it’s clear how ridiculous and morally outrageous this is. The fundamentalists believe in a supreme, universe-transcending creator whose single-minded, all-consuming focus is what people do with their genitals – a clownish, laughable notion deserving only ridicule. But even worse is the notion, held by millions of believers, that this being threatens humans: “Obey me or I’ll hurt you!” This idea is a moral depravity that could only be born from wicked minds.

Any god worthy of the name wouldn’t coerce its creatures’ obedience through fear or pain, but would set up the world so that they would all freely choose through reason to do the right thing. That would be how a supreme intelligence would create; that would be a god of the neocortex. Instead, the religions of this world are stocked with clumsy, brawling, belligerent gods of the reptile brain – gods who are constantly bewildered and enraged when their plans go astray and who can think of no better tools than violence and destruction.

Religion is supposed to bring out the best in us, we’re told by its defenders; it’s supposed to encourage the decency and compassion that human beings are capable of. And perhaps, sometimes, it does do this. But more often, it gives vent to the violent, destructive side of our nature, gives us license to express our xenophobia and violence and rage under the illusion that these qualities are endorsed by God.

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About Adam Lee

Adam Lee is an atheist writer and speaker living in New York City. His new novel, City of Light, is available in paperback and e-book. Read his full bio, or follow him on Twitter.

  • Kyle Simon

    I don’t understand, the brainstem is supposed to hold the four “F’s” but reproduction doesn’t start with an “F”? Is it a synonym for something else?
    And I never realized that the monotheistic Gods are more closely related to none neocortex abilities. Thank you for the insight.

  • Ritchie

    …the four “F”‘s – fight, flight, feeding, and reproduction.

    I actually did lol at that.

  • Katie M

    I’ve actually been thinking about this since I first read Cosmos-glad to see someone else touch on this.

  • Nathaniel

    the four “F”‘s – fight, flight, feeding, and reproduction.

    In the immortal words of the internet, i c whut u did thar.

    As always, both profound and piercing. An interesting additional thought is that humanity is mostly unique when it comes to the final f as well. There seem to be very few animals that experience pleasure during sex, but do it out of an urge similar to the one we have for defecation. And yet if you look at most religions, certainly the Abrahamic ones, the entirety of the focus is one hierarchical organization of it and to some extent ritualizing it. When it comes down to it, I don’t think the song and dance that many religions want to come before sex is all that different from the almost literal song and dance that go into many “lower” animals mating signals.

  • Nathan

    Mapping religion and its superstitious dictates onto and into primitive brain functions is speculative fiction. To the extent that religion is an artifact of consciousness, and the apparently emergent phenomenon that is consciousness, such a direct comparison goes far beyond hypothetical daring.

    It may be. Or it may not be. And I don’t think we have any tools or theories or understanding of sentience to say just how religion works or what cognitive functions it serves. Religion’s advocates have claimed that religion addresses (or at least concerns itself) with questions and concerns of ‘why are we here’ or ‘what is our purpose’ or ‘what is the meaning of life.’ But since religion so spectacularly fails to answer or address any of those concerns …

    What if it originated and fulfills some other purpose? What is religion really doing? Forget what it has socialized us to think. Consider its actual, real-world impact and effect: what is the function of religion among us humans?

  • Steve Bowen

    No organized religion in existence today posits a god of the neocortex. A few of the best offer a god of the mammalian brain, but even they rarely aspire to anything higher. But most – the belligerent, aggrieved, crudely literal fundamentalist faiths that command the allegiance of hundreds of millions – have gods of the reptile brain.

    Not to arue with the truth of this statement but you have to wonder why this should be so. After all the people who first codified these religions were as intelligent, if not as well informed, as us. They lived in complex societies and maintained complex relationships. Even if they had to resort to the supernatural to answer the fundemental questions there is no reason to imbue the creator with all the petty vengeful personality traits they chose.

  • AnonaMiss

    I think it’s important to remember that the religions we have today are the product of thousands of years of “natural selection” – most successful religions are evangelical, for example, because they out-competed their “live and let live” neighbors. I suspect where the four Fs are concerned, religion, like Hollywood, learned to cater to the lowest common denominator early on.

  • TommyP

    I really liked this post, gives me some new ideas to chew on.

  • Hendy

    This is quite interesting. I’m experiencing the severe hand of xenophobia myself as I try to establish whether the evidence supports god’s existence or not… so far my heavy leaning is toward “not.” This ‘quest’ has been going on for 7mos and it has amazed and frustrated me the entire way that religion, which professes to seek the unity of the world, seems to be the most relationally divisive force known to man.

    To take your post further, the most preposterous result of most religion’s tenants is that all expect others to consider their religion valid and ‘explore’ that they might convert… yet all have built-in guilt/shame/apologetics mechanisms to prevent anyone from actually exploring.

    The issue is further complicated as rather than presenting the jealous punishing god you present, everything is spun such that god doesn’t have anything to do with it… it’s you who choose to separate yourself from him. You reject god and therefore suffer. As someone who cares and tends toward self-doubt, it’s a real mind-f**k in contemplating… “Well, am I rejecting the evidence?” or some similar question every time a believer tries to convince me that one can’t ‘prove’ god, that I need ‘faith seeking understanding’, that the ‘transcendent’ points toward a hunger for some deity, or that I’m not ‘open-hearted/minded enough.’

    Quite the mess… It all strikes me as plausibly explained as an attempt to rationalize away anyone who rejects the beliefs of the ‘in-group’ in order to stay safe and protected. Heaven forbid that anyone had a real objection to religion that wasn’t motivated by wanting to live a licentious life or being confused about the real translation of that word from the KJV Bible in Hebrew. Then we might have a problem. But since all atheists want to do is be promiscuous and hate god and thus choose hell for themselves… we can just keep singing hymns and ignore them.

  • Wednesday

    I definitely see the connection between the reptile brain and the major monotheistic religions, and how that can lead to monotheistic religions being selected for (to take AnonaMiss’s perspective). But monotheism wasn’t a dominant paradigm until relatively recently in human evolutionary history – go back only a few thousand years and polytheism is most of what we see.

    Did the major polytheistic religions exhibit the same tendencies regarding reptile brain impulses?

  • Sharmin

    I hadn’t thought of it this way before. Thanks for giving me something to think about.

  • jack

    I agree with the essence of your post, but a few caveats should be mentioned about the so-called “triune brain”. This idea, popularized by Sagan but originating with Paul MacLean, is considered an oversimplification by most neuroscientists. It gives the impression that the reptiles get by with little more that a brainstem, which is not the case.

    As it turns out, one of my best friends was a reptile, a remarkably intelligent, adaptable and, at times, even affectionate green iguana. Sadly, she died last year after a long and happy life with me and my wife, but she taught us that there is a lot more to the reptilian brain than is commonly assumed.

    Oh, and in defense of all the other poor maligned reptiles in the world, they never kill or hate over differences in belief, they don’t go on Crusades or practice Jihad, and, so far as I know, none of them believes in an invisible, omnipotent supernatural God. If you ever find one in a church, it will probably be because some nutcase human snake-handler brought it there against its will.

  • D

    Re: Nathan (#5): In his third paragraph, Ebonmuse gives the clear caveat that he’s being allegorical and noting a correspondence. Far from being speculative fiction, it’s analogy. The value of analogies is not literal truth, but suggestive truth: getting you to think about things in different ways, rounding out your understanding. What this post does for me is to clearly highlight how religions get some of their craziest bullshit past us: by appealing to the very basest of our instincts.

    Keep in mind that religions were formed at a time when we didn’t have the internet. Almost all can trace their roots back to a time before libraries (Scientology and Objectivism are notable exceptions). Most people were illiterate, and their tribes passed down stories by word of mouth, and these went largely unquestioned because that’s what got these people to where they were back then (and of course what has worked in the past will always work just as well in the future, duh). In order for the meme to survive, the host group had to be able to maintain itself against both internal division and external conquest. Looking around at other ideas that shape the lives of people across the globe just wasn’t an option for lots of people, so they couldn’t make the sort of cosmopolitan comparison that is so often responsible for freeing our minds today.

    Evolution makes progress by finding a way to “latch on” to some point, and then branching out from there in unpredictable directions until another latching point is found (like how technology piggybacks on basic research). Think of ivy creeping up a brick wall. But people at each latching point – especially those in control and keeping things latched there – want to say that that particular point is the end-all be-all and any deviation is an abominable aberration. They want to stay where they’re latched and not risk the upheaval that may follow from branching out in unpredictable directions, the better to maintain their control (or, for us drones, to maintain the perfectly legitimate authorities who always have our best interests at heart). So to shut down one part of our nature, which is to just go and do whatever the Hell we want, they appeal to the other part of our nature, which is to worry about losing eveything by doing it wrong and stay where we are. Of course, things change no matter what, since stagnation means death – the world around us changes, and we must adapt to it or perish – so nobody’s happy because the old power-mongers keep losing control to new power-mongers, but there are always some power-mongers at the top because they keep on power-mongering. It’s a constant struggle to close the gap between entrenched cultural artifacts and the bleeding edge of our latest ethical improvements, just look at how much struggle continues to this day as we fight for race equality, sex equality, and gender equality.

    As we coexist with a power structure, it shapes us and we shape it. For the power structure to perpetuate itself – whether it’s governmental, ideological, or patriarchal – it has to keep us breeding and believing more than the other power structures hosted by other groups, whether it’s really in our best interest to do so or not (but it will tell us it’s in our best interest either way). Of course, if we could all see that it’s just a power structure that survives by running our lives, a great many would reject it (I hope!). But so many people are blind to these power structures because huge and meaningful portions of their lives are invested in their legitimacy: the idea that they are real and worth following (as opposed to made-up and primarily concerned with short-term self-perpetuation). So of course there will be a correspondence very much like the one Ebonmuse points out, as these power structures must appeal to drives so deep-rooted that they are common to all chordates, drives which we ignore at our peril.

    So what is religion “really doing”, you ask? It’s keeping its own gravy train rolling for as long as possible, at all costs: “That’s all that matters, nothing else; so help me help you help yourself.”

  • Orandat


    That was an impressive comment. Not only was it a great supplement to ebon’s original post, it also exceeded it in word count.

  • Passionate Free-Thinker

    This was an incredibly poignant post. People seem to be so afraid of offending the religious about their beliefs, however irrational they may be, that they tend to ignore the glaringly obvious fact that classical western religion is based entirely in the snake brain. This, for me, is enough to demonstrate that there are no universal truths to be found within said beliefs.

    Reading this post made me recall a wonderful part in A History of Western Philosophy, by Bertrand Russel, where he discussed how a benevolent and intelligent God would hold reason and rationality in much higher esteem than blind faith.


  • KShep

    One thing I’ve noticed about atheists here—I’ve been a regular reader for a long time—most of us don’t bother posting unless we have something to add to the discussion. The fact that this post has generated only 15 comments in 4 days time tells me that Adam has nailed it.

    Game, set, match. Thank you.