March 16, 2005
Twins Study Finds Adult Religiosity Heritable

University of Minnesota at Minneapolis psychology graduate student Laura Koenig and other U Minn researchers have found in a twins study that religiousness becomes more genetically determined as we age. (same article here)

Environmental factors, like attending religious ceremonies with family, affect our religiousness as children, but genes most likely keep us attending and believing as we become adults.

A study published in the current issue of Journal of Personality studied adult male monozygotic (MZ) and dizygotic (DZ) twins to find that difference in religiousness are influenced by both genes and environment. But during the transition from adolescence to adulthood, genetic factors increase in importance while shared environmental factors decrease. Environmental factors (i.e. parenting and family life) influence a child’s religiousness, but their effects decline with the transition into adulthood. An analysis of self-reported religiousness showed that MZ twins maintained their religious similarity over time, while the DZ twins became more dissimilar. “These correlations suggest low genetic and high environmental influences when the twins were young but a larger genetic influence as the twins age” the authors state.

Participants for this study were 169 MZ and 104 DZ male twin pairs from Minnesota. Religiousness was tested using self-report of nine items that measured the centrality of religion in their lives. The twins graded the frequency in which they partook in religious activities such as reading scripture or other religious material and the importance of religious faith in daily life.

If any of the Minnesota researchers see this then what would be extremely interesting would be to collect fertility data on these men. Are the more religious men reproducing at higher rates than the less religious? Are genes for religiosity being selected for? I'm guessing the answer is Yes!

The questioning was conducted on male twins in their early 30s.

The twins, all male and in their early 30s, were asked how often they currently went to religious services, prayed, and discussed religious teachings. This was compared with when they were growing up and living with their families. Then, each participant answered the same questions regarding their mother, father, and their twin.

One of the biggest unanswered questions about the human race's future is what choices will people make once they can control the genetically controlled attributes of their offspring. Will people choose to make their children be more or less spiritual than they are? My guess is that the mild to moderately religious may choose to make their kids even more religious while those who are not religious at all will choose genetic variants that ensure their children will not be religious. Therefore the mildly religious and the people who are lukewarm to religious belief will become a smaller fraction of society while the emphatically religious and the emphatically not religious both increase in number.

Will splits over questions of religious belief widen in the future due to widening genetic divergences between the religious and non-religious? If so it will fit into a larger pattern that I'm predicting: "Children Of The Future May Be More Genetically Determined".

Also see my previous posts "On Religious Belief And Germ Line Engineering" and "Genetically Engineered Minds And Religious Experience" and "Serotonin Receptor Concentration Varies Inversely With Spirituality"

Share |      Randall Parker, 2005 March 16 04:07 PM  Brain Spirituality

Kurt said at March 16, 2005 5:53 PM:

i have always thought that religious belief was genetic. I seem to encounter hostility when I have said this, even in enlighted places like Even when I have made it clear that I intended no pajorative meaning, whatsoever.

Some people seem to need religion, others do not. Kind of like music or the arts. Some people don't care, other cannot live without it. Whenever you have a "thing" that some people are into and others are not, and there is no obvious explanation for it, you can usually bet that there is a geneitc explaination for it.

The tendency for religious belief is not linked to IQ. Lots of high IQ people are into christianity or other religions. There are psychological explanations for why people believe in religion, but they do not correlate perfectly, nor do they provide an actual mechanism for why people are into religion and others are not. Also, I have never been attracted to any of the religions, nor do they seem to provide any "answers or solace" to me. I think that I am one of these people who simply do not identify with "religion".

Hense, its got to be genetic. Why this is controversial is completely beyond me.

We accept the fact that some people are into the arts and music and others are not, and think nothing of it. Why can't we have the same societal attitude towards religous belief?

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michael vassar said at March 17, 2005 12:27 AM:

Armand Leroy's new "Edge" article makes me wonder whether these sorts of selection questions are of much long-term relevance. If he's right that we have a strong selective bias in favor of low mutational load, and if it will be possible in fifty years or so to eliminate essentially ALL of the mutational load, then it seems entirely plausible that given continued sexual liberalism and consequent enhanced reproductive skew, before long men modified in this manner will be fathering close to ALL of the children except possibly for the children of a few highly religious women. People with no mutational load and a healthy upbringing would, by hypothesis, be about 19SD more attractive than the baseline! Any thoughts on this?

David N. St. John said at March 17, 2005 12:57 AM:

"Participants for this study were 169 MZ and 104 DZ male twin pairs from Minnesota."

Randall, I would be very curious to see this experiment repeated with a statistically significant population of MZ and DZ FEMALE twin pairs. Would their attraction to religious belief be stronger or weaker than the male pairs? And would the heritablity of attraction to religious belief be stronger, weaker, or about the same as the male pairs?

David N. St. John

Robert Silvetz said at March 17, 2005 9:17 AM:

I don't share with RP such a certainty that the trait will go bimodal. Here's why: At it's root, religious thought is an inability to percieve the world as it is -- e.g. it's a perceptual-to-conceptual cognitive failure. The brain model of ideas is out-of-synch with reality. The concept of faith outlines this perfectly "believing something you have NO REASON to believe". Competitive behavior and the ability to succeed requires a thorough acceptance of reality. As parents select superior competitive genes for their kids I bet dollars-to-doughnuts we will see religious thought drop to zero with time.

Nor is the fact that some high IQ folks have deep religious feelings an issue. The tail of the distribution is undoubtedly there. Not that you can't breed such a population -- there is a subset of jews which clearly falls into such category. But if you look worldwide and do a rough guesstimate of successful individuals vs religous belief you will notice a couple billion humans mired in religious belief going nowhere in their lives.

And lastly there is always the "fear of death" factor which is where religion ultimately springs from. What will happen to religious thought in a world where one doubling of the lifespan to 150 years will probably buy SENS and virtual immortality for most people alive today?

My usual 2cents with a grain of salt.

James Collie said at March 17, 2005 11:19 AM:

>"Competitive behavior and the ability to succeed requires a thorough acceptance of reality."

I think you're attributing to much value to the acceptance of reality.

Competitive behaviour has absolutely no need for acceptance of reality. In contrast, I think competitive people think they are significantly better than they are. This opinion can be a self fulfilling prophesy leading to success.

The ability to succeed is not nearly so much dependant on a person's skill as it is on a person's willingness to deal with failure and try again. Most of those billion of people going nowhere are looking at reality and accepting it. They are not mired in religious belief, but they are people who take the world as they see it, or are fed it, and have no vision. Vision is seeing what can be instead of what is. Vision is making a reality instead of accepting one.

Competition and success are the result of vision, not the result of a sense of reality. Vision can be generated by a religion teaching or a variety of other things like personal greed or a high need for acceptance. Vision, greed and religion are all dependant on and by-products of creative thinking. Creative thinking does not require acceptance of reality.

Acceptance of reality is still important. It is what separates useful thought from nonsense. If a creative idea disagrees with your definition of what is real, it is useless.

Randall Parker said at March 17, 2005 11:43 AM:

Robert Silvetz, I have to agree with James Collie. I've known people who are extremely reality-oriented in, say, bond trading or in practicing medicine. But then get them to talk about religion or politics and they are suddenly in fantasy land. People become reality-oriented when they benefit directly. But when there is not a very direct corrective feedback loop punishing their incorrect views they can maintain big misconceptions and believe very false things about the world.

Still, your point about rising IQ increasing religiosity is correct, all else equal. The question in my mind, though, is what wil people do to their children on the non-IQ genes that affect perception and affect how we experience reality. I certainly think it will be possible to code up genes to produce high IQ but deeply religious offspring. How many people will choose to do that? I don't know.

Lono said at March 17, 2005 11:46 AM:

Well as a Scientist and a fudamentalist Christian I think that these results may be an oversimplification.

For instance I am an extremely curious person - and this behavior is controled by the synergistic effects of many genes which caused me to research both the sciences and world religious teachings.

Therefore it may be that the Genes that lead to increased religiousosity also are related to how one learns and thus related to a wide variety of social behaviors.

I therefore cannot imagine that one could easily select for increased religious disposition without affecting a wide range of behavioral traits.

And as we become more sophisticated at genetic engineering I think we will shy away from tampering with genes that influence behavioral traits due to their inherent complexity and potential side effects and instead focus on correcting diseases, incresing physical characteristics, and stabilizing or ending the normal aging process.

Behaviors will likely be more influenced through more efficient uses of media and medicine, since these mechanisims are not permanent and can be changed dynamically over relatively short periods.

As for those who think that religisosity is merely a side effect of vestigial genes (like in the Sci Fi novel Childhoods End) I couldn't diasagree with you more and you really shouldn't let your personal beliefs (or lack of them) unduly influence your interpretation of this particular study.

Garson Poole said at March 17, 2005 11:56 AM:

I suspect that “religiousness” is not a coherently defined phenotype. There are a remarkably wide variety of “religious” belief systems. Monotheistic religions such as Judaism and Christianity differ dramatically from Buddhism. Indeed, even the term “Buddhism” signifies a cluster of diverse religious beliefs. The paper by Koenig et al measured “religiousness” in a single population of US men. The researchers used a “self-report of nine items” to assess “religiousness” and that is a rather crude methodology in my opinion. Yet, the work is interesting preliminary research.

To illustrate the difficulty of defining “religiousness” as a phenotype I suggest visiting the website of Oxford philosopher Nick Bostrom and reading about the simulation argument. Bostrom argues that “there is a significant probability that you are living in computer simulation”. Indeed, with some reasonable sounding assumptions he argues that “we are almost certainly living in a computer simulation”. The arguments Bostrom presents are not religious in character. Instead, they are “computational”, “rational” and “materialist”; however, if we are living in a simulation then one might say that the creators and executors of the simulation have godlike powers over us, the denizens of the simulation. Also, it is quite natural to identify “the godhead” with the entity or entities that are running the simulation.

So, are the believers in the simulation-argument displaying high-levels of “religiousness” or are they displaying high levels of “scientific rationalism”?

Joshua Allen said at March 17, 2005 11:39 PM:

Silvetz; you sound like someone who is firmly anchored in the material, so I wonder how you can be so confident in your assessment of those more spiritual than yourself. As someone who has been intensely spiritual since the youngest age, I have always been puzzled by anyone who seems so certain of reality. I could make equally negative characterizations of these materialists (self-delusional, desperate to convince themselves that they control something, arrogant, pitiably defective and damaged, etc.) but it's probably better to just say they are different.

I would argue strongly that spirituality is not opposed to reason. The two are completely complimentary, and a blind faith in reason is irrational. Reason is a tool with its own limits. Spirituality also has its place, and its limits.

IMO, spirituality is highly corellated with intuition and empathy. When we see people with severe aspergers, who can master complex logic but cannot empathize with another human, we pity them -- because they have raw mental horsepower with no intuition. People who severely lack intuition and empathy cannot relate to others, while people who lack just a bit can never be spiritual.

I'm not opposed to materialistic explanations though. One theory might be that people with particular serotonin characteristics are more likely to have episodes of deep depression, and are forced to confront and explore spirituality as a way to find some respite. In other words, a certain level of inner tummult that causes them to choose a more spiritual path. This I would buy -- that the genes expose a weakness for which the people are forced to cope and compensate through spirituality. If you keep kids lobotomized on ritalin and prozac, I predict a much lower level of spiritual development as adults.

I also would buy an explanation based on over-developed ability to rationalize intuitively. I think the psychopath's detachment from reality is a side effect of the ability to rationalize automatically without interference from the conscious mind; and possibly the spiritualists detatchment comes from the same source.

Kurt said at March 18, 2005 1:31 PM:


Thats an interesting and useful way to describe the spiritual/materialist dicotomy. Materialism applies to the real physical world, spiritualism applies to interpersonal relationships. Even though I am a hard core materialist like Silvetz, I can certainly relate to this way of thinking.

As we know well. much of interpersonal relationships defy reason and rationality, especially the dating game. Biochemicals and neurotransmitters do corelate with general emotional states to some extent. However, the corrlation is not exact and I don't think that it can ever be a deterministic predicter of future behavior of any given individual, not to mention specific tastes and desires that people have. Given this, perhaps we should just accept each other for who we are and, as long as we don't step on each others toes, allow people the freedom to live and let live.

bobhenr said at March 19, 2005 12:12 AM:

Spirituality puzzles me, and always has. I decided on my own, without even knowing about atheism, that there was no god when i was 11. I had gone to church most every Sunday since I was 6 or 7, and though I assumed the stories to be true when I first heard them, it didn't take long for me to see them as shams (my take on it, I'm not by any means insisting I am right here).

I for one am not the least bit certain of reality. I'm just far less certain of spirituality. I do not claim to know the truth. I consider the real world interesting, not known. To me, religion is an unnecessary diversion, one that wants to remove me even further from the unknown by forcing the obviously untrue on me as truth. Again, this is my perception. It seems to be correct for me. I understand that others disagree. Whether or not there is a genetic component involved is relevant scientifically. However, I have absolutely no reason to think that only genes determine an individuals position in this matter.

Genetics might play a part. Both of my brothers are also atheists, though one is semi-spiritual and attends his local Unitarian Universalist church. On the other hand, my paternal grandfather was a very fundamentalistic christian who died of a heart attack while yelling at a Jehovah's witness who had come to the door. He was also a tyrant, bullying all of his children in the name of god, and not one of them became a practicing christian, so nurture, positive or otherwise, may well play a role too. (You bullying christians keep this in mind. My grandfather had 6 children, 11 grandchildren, and 20 great-grandchildren. His kids hated him. At our last family reunion we all discovered that not one of us (my UU brother excepted, barely) has ever attended church as an adult, and my brothers and I were the only ones that attended as children.)

Europeans, as a group, are far, far less religous than Americans. Yet the majority of us have European genes. I suspect something else is going on here.

This study seems a bit too small and the study group too limited to be meaningful. The results are perhaps interesting enough to warrant further study with a more diverse group, but even if proof positive existed, many would deny it. I'm pretty sure they would say "Its just a theory..."

Kurt said at March 19, 2005 11:30 AM:

Supposedly, the purpose of spirituality and religion is to provide some sort of explanation that when you die, you don't really die. You go on to live in non-physical form or another dimension or something like that. In otherwords, spirituality is supposed to be about immortality. The problem is that "spirituality" does a half-asred job of living up to its bargain. Most people who claim to be spiritual or religious are still afraid to die. They do not act or talk like they view death as simply a doorway to a new life, the same way that a HS senior considers graduation as the doorway to his or her new life.

There is also the whole prohibition against suicide and assisted suicide. If these people really believed that death is simply a doorway or a phase transition (like puberty or HS graduation), then they should have no hang up with suicide, assisted or otherwise. Since you don't really "die" when you die, the body is no more special than a car. If it gets old and beat up, you get rid of it.

Since the "spiritual' people don't subscribe to this line of reasoning, even though it is logically consistant with the concept of surviving physical death, I must conclude that the religous or spiritual people really do not believe that human consciousness does not survive physical death. Does this not make the whole "spiritual" thing completely meaningless? At least as far as being an effective "immortality strategy".

This is one of the two principle reasons why I came to reject religion and spiritual stuff when I was in college.

The other reason why I cam to reject religion is the notion of individual autonomy (the "libertarian" argument against religion).

If spirituality does not offer an effective "immortality strategy" and it requires you to give up a certain measure of individual autonomy and self-determination, then what good can it be?

Are some of you begining to see why I don't like "spirituality"?

lkj said at March 20, 2005 7:28 PM:

So what if you don't like spirituality Kurt?

Dowlan Smith said at July 27, 2005 3:29 PM:

Robert Silvetz states, "At it's root, religious thought is an inability to percieve the world as it is -- e.g. it's a perceptual-to-conceptual cognitive failure. The brain model of ideas is out-of-synch with reality. The concept of faith outlines this perfectly "believing something you have NO REASON to believe".

Of course this is begging the question. If there is a spiritual dimension (ie God/gods etc), then a purely materialistic world-view would be " inability to percieve the world as it is..." Also he mischaracterizes faith as "believing something you have NO REASON to believe." Many people of faith would see their faith as based in reason, experience, and reliable authority. Of course there are unthinking religous dogmatics, but there are unthinking dogmatics of many other stripes.

boris said at December 18, 2006 2:50 PM:

What is religion?

Simple. Religion is like USB. An instinct provided data port for culture to download useful adaptations too recent and too complicated to be incorporated into instinct directly. It's a live update channel for natural selection to operate at the cultural level rather than the biological.

Of course individuals with good religious USB ports will adapt more readily to an environment controlled by culture. Remember that natural selection is not "intelligently designed" hence the measure of fitness is not determined by what should be true and logical in a scientific sense but rather what actually works to advance the species and the culture.

For that religion works better than science. For one thing science is too easily coopted by charlatans and most individuals lack the skill to seperate the junk from the true.

DWPittelli said at December 19, 2006 5:05 AM:

Robert Silvetz: "At it's root, religious thought is an inability to percieve the world as it is -- e.g. it's a perceptual-to-conceptual cognitive failure.... Competitive behavior and the ability to succeed requires a thorough acceptance of reality."

Most religions, in this country, anyway, don't make any claims about the current physical universe, and make increasingly few claims about the prehistoric past. (Due, yes, to centuries of embarrassment at the hands of science.) As such, with religion mostly about the nature of an objective morality, and/or what happens to us after death, there are few practical costs to following a religion, apart from time spent in church or praying, and money donated to the church (rarely even as much as the 10% suggested historically) -- costs not dissimilar to that of many other hobbies or forms of entertainment, such as watching pro sports or gambling (and tax-deductible in the case of religion). Most of us have the time and the need to do something quite different than our work, and to belong to a stable community, and practising religion fits the bill for many people. Further, regardless of newsworthy failures of some churches and ministers, a religious community is more likely to come to your aid in difficult times, such as during money troubles or in old age, than is a casino or hobby group.

Further, most religions (in Minnesota like the US overall, weighted primarily to Catholicism and various Protestantisms) have essentially optimistic views: man is important, God loves us, right and wrong are clear, we have eternal souls, good is rewarded and evil punished. I think it is harder to bring children into the world believing that man is insignificant, God does not exist or is indifferent to us, morality is made up, and evil people who are seen to prosper on Earth in fact are not punished. (I concede that I am a counterexample, having two children.) I suspect that the connection between religiosness and childbearing is real, and is deeper than the opposition to birth control of some churches -- but either way, religion is "fit" in the Darwinian sense.

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