Field of Science

Why are religious people so fertile?

On average, religious people have more children than non-religious people. Now, that's a sweeping generalisation, of course. However, statistically it seems to hold good, to different degrees, for all the societies that I've seen examined.

But why? It's an important question. A common answer is that this is evidence that religion is evolutionarily advantageous. The idea here is that religious belief in some way facilitates having lots of children (perhaps by making you a nicer, trustworthy person), which gives you a head start in the race to pass on your genes to the next generation.

It's a view that I think is plain wrong.

I think the link is not with religious belief and fertility, but rather with conservative family values and fertility. And, crucially, I think that link is a recent innovation.

Here's some new research to back that up.

Markus Jokela, at the University of Helsinki, has analysed the changing relationship between personality traits and fertility in people living in the USA who were born in the decades 1920 to 1960 - a period of huge cultural innovation, especially with regard to women's rights.

He looked at the conventional "5-factor" model of personality, which rates individuals on their extraversion, neuroticism, agreeableness, conscientiousness and openess.

He found that three of these traits (extraversion, neuroticism, and agreeableness) were consistently related (either positively or negatively) to fertility over time.

However, conscientiousness, and in particular openess, were linked to lower and lower fertility rates as the decades rolled by. That was the case for both men and women.

What this means is that the declining fertility rates seen in the younger groups of people was largely driven by dwindling fertility among people who were highly open to new experiences (as Wikipedia says, these people are "inventive/curious vs. consistent/cautious").

So cultural conservative were more likely to retain high fertility but - and this is the crucial bit - this is a new phenomenon. Among people born in the early part of the 20th century, fertility was no higher among cultural conservatives than among the inventive/curious.

So, while high fertility among the religious may have implications for the future distribution of 'religion genes' (if such a thing even exists), it does not explain the current genetic distribution.

There's another recent paper that backs this up, albeit in a somewhat more tangential way. Joseph Stanford and Ken Smith, at the University of Utah, have shown that, among Mormons, what we have come to regard as a 'normal' link between higher income and lower fertility is reversed.

In other words, Mormons with high income actually have higher fertility than Mormons with lower income. To me, that's surely a sign that cultural conservatism, which restricts the employment options for women, is a core reason explaining the modern link between religion and fertility.

In the past, of course, everyone was old-fashioned. And so everyone, religious or not, had high fertility rates!

Of course, most children back then died young, but that's a different evolutionary process at work...
Jokela M (2012). Birth-cohort effects in the association between personality and fertility. Psychological science, 23 (8), 835-41 PMID: 22722269

Stanford JB, & Smith KR (2012). Marital fertility and income: moderating effects of the Church of Jesus Christ of Latter-Day Saints in Utah. Journal of Biosocial Science, 1-10 PMID: 23069479

Creative Commons License This article by Tom Rees was first published on Epiphenom. It is licensed under Creative Commons.


  1. I'd been thinking along similar lines for a while. It is good to see evidence supporting what had been a hunch.

  2. Part of the problem here is applying the darwinian view to this - as a darwin skeptic, I am not surprised that the darwinian interpretation fails to shed light on this.

    I can tell you how evangelicals view this - it is a difference in worldview and values.

    Many liberals have bought into what some call a belief in scarcity - that we have severely limited resources, and in a Malthusian way, think that they are doing something ethical and good by limiting their progeny.

    Evangelicals, looking for a reason to justify their belief in filling the world as per the command to Adam and Eve (and Noah), would retort that (a) malthusian predictions have failed, because they (b) ignore the role of technological innovation in changing our resource usage, and (c) underestimate the actual plentitude of resources.

    So that is the primary world view difference - a liberal belief in scarciity, and a lack of faith in or understanding of the role of technology in resource uses and provision.

    Another darker proposed motive of liberals, rooted in darwinism, is the idea that man is just another animal, perhaps even a parasite on earth whose selfish numbers NEED to be reduced.

    The value difference (again, that proposed as a general answer by Evangelicals) is that conservatives value family and children much more highly - highly enough to be horrified by abortion, and highly enough to want mor than one or two.

    The modern liberal desire for less children is also viewed as indicative of our individualistic, selfish pursuit of self and pleasure and leisure in American culture. Biblically speaking, this is the typical worldly value system described by the Apostle John in 1 John 2:16 - that satisfaction is errantly found in possessions, power, and pleasure.

    So evangelicals would see the liberal desire to have less children as an indicator of having bought into the worldly value system.

    To sum up, we would explain this difference, not in darwinian terms, but in terms of:

    a. Scarcity v. abundance views
    b. Valuing humanity over nature v. valuing humans and nature equally
    c. Seeing fulfillment primarily in family rather than in self-development and self seeking
    d. seeing more children as a greater blessing, not a greater hindrance to our own goals

  3. Actually, this is not so complicated. Basicly conservatives do not think about economic issues or welfare of the family. They believe god will give eventually if they do everything right. on the other hand, liberals or non religious people try to plan and want to offer the maximum welfare and education etc to their child. so when conditions not suitable they wait ot don't have children at all. I believe it can be also true that there are plenty of conservative or religious people who just think "they" must outnumber the "others"

  4. Dgsinclair, it's not that strange to see darwinian views failing on humans. We've evolved to the point where we're beyond basic natural selection in many ways.

    We're a unique species due to our intelligence and as such don't really follow the natural rules anymore.

    As for severely limited resources; if you take a chart of population of the world over time and keep in mind that our resources either stay about the same or go down (in case of fossil fuels) you will see a probably very scare image.

    I'm not going to look it up for you, it's easy to find and it works better if you look at it through curious eyes. I hope you still have those.

  5. Natural selection has not failed to shed light on it. The point is that the environment has changed, and as a result selective pressure have changed, and with them optimal strategies. This is Darwinian evolution in action!

    To put it more plainly, in the past you needed to balance gaining material security against ghigh birth rate. As a result, people are driven to achieve social standing and material wealth.

    In the modern environment, women have to (or, perhaps, are now able to) choose between children and social status/wealth. Many choose social status.

    But, in the modern environment, material security is no longer strongly related to infant survival. So those individuals disposed to a high birth rate without worrying too much about achieving wealth and status (who might have been evolutionary failures in the past) are now evolutionary success stories.

  6. >> ANON: conservatives do not think about economic issues or welfare of the family.

    Oh yeah, that's it. Conservatives don't care about their kids. I would post as anonymous too if that's all i had to share.

    >> ANON: As for severely limited resources; if you take a chart of population of the world over time and keep in mind that our

    You make my case, and repeat the limited perspective of Malthusians. While the actual amount of fossil fuels may be fixed, what is not fixed is:

    a. Our ability to find more of it (huge new stores of natural gas are regularly discovered)
    b. The ability of technology to extract more fuel from existing stores (think fracking)
    c. The ability of technology to more efficiently use fuel, and
    d. The move to new fuels gives us incredibly more capacity - just as we moved from wood to coal to oil to nuclear, we may move to hydrogen and solar. If and when we become better at solar capture, there may be no energy limit at all.

    Now, food may not respond the same way, but the doomsday predictions of anti-population liberals are part of the reason that liberals have less kids - we just believe that they are chicken littles.

  7. >> TOMAS: But, in the modern environment, material security is no longer strongly related to infant survival.

    Well, that's some interesting post hoc reasoning, but it has naught to do with Darwinism.

    Sure, the need for children as monetary security has changed, and that may influence the number of children people have, but how is that selective pressure? There is no genetic component at all.

    And if liberals are still having less children since children are not needed for survival, their views are being selected *against* by having fewer progeny.

    But back to the question at hand - why do conservatives have more children? Why are they and their attitudes being selected FOR, as shown by their greater number of children?

    It's not about selection, it's about values and perspective, not genetics.

    The veneer of Darwinian phrases is merely an unnecessary explanatory myth, not a real source of understanding, as is the case in trying to apply it to science and medicine.

  8. The first study clearly supports Fauceir Theory's proposition that humans are enslaved by their masters, human societies that among others exert demographic control (

    By the mid 20th century infant mortality doped dramatically in all developed countries. At the same time life expectancy rose dramatically. Thus societies realize a pressing need to halt population growth.

    Probably inadvertently, that study also demonstrates that such demographic control is maintained through ideology. Those people who nowadays have less children are characterized by conscientiousness and openness. Two terms that are not neutral but clearly have positive connotations. Our ruling ideologies define terms and connotations. In ideologies that stem from societies that want more children, those people may be characterized by cowardice and egoism.

    Unfortunately, ideological pressure to curb population growth made negative selection for more intelligent and successful people, a tendency that is sharply criticized in two recent German books by Sarrazin ( and Weiss ( I'm glad to hear that the Mormons buck the trend.

  9. >> MATO: Probably inadvertently, that study also demonstrates that such demographic control is maintained through ideology.

    Yes, which is how the communists were manipulated into preparing the one child per family solution. Openness and gullibility are sisters. Some who are not as open may be exercising the virtue of skepticism, and conservatism (holding on to what has proved itself to be valuable).

    But my beef is that the cause and effect here was couched in Darwinian terms, which add little value except the comfort of a well worn myth. It annoys me that so called intellectuals can paint all of their arguments with such baloney when standard science and logic answer the questions without it.

  10. I have found much the same thing on my blog. The personality element demonstrates that it is a certain mindset of people, people who highly "traditional", especially in the social realm and respect to sex, that are today the most fecund.

    Expectations and reality: a window into the liberal-conservative baby gap « JayMan’s Blog

    fertility « JayMan’s Blog

    The trait openness to experience, which itself is correlated with IQ (the only one of the Big Five that is so correlated), is essentially the defining characteristic of liberal-minded people. I have speculated that this trait is itself a fairly unique evolutionary product of Northwest Europeans and their special evolutionary path (or, at least, has become far more prevalent among them).

    In this case, it is clear fertility appears to be a product of a certain mindset of people, perhaps people who feel sex is for procreation and not necessarily recreation.


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