[hn_throwaway_99]

Given that fertility rates are currently plummeting worldwide, the principles of natural selection would dictate that humans are currently undergoing very high selection pressure for specific traits.

Basically, any genetic trait that causes people today to think "You know, I think I'm going to remain childfree" is specifically selected against, and any trait that causes people to want more children will be selected for. I'd argue that the invention of reliable birth control was that biggest change in human selective pressures in history. Evolution made sex highly pleasurable and desirable because it often resulted in passing on your genes. That's no longer true with reliable birth control, and with such a huge environmental shift natural selection will act on other avenues that cause people to have children.

[thomassmith65]

Evolution is surprising and complicated enough that that might not be the full picture.

People have relatives and relatives have many genes in common.

If there are genetic traits that predispose people to remaining childless, it could wind up that populations with those genes end up with larger branches on their family tree.

It's been a while since I read the Selfish Gene, but its central point is that natural selection is about genes, not individuals.

[thrance]

Why did you just assume there are genes that predict "not wanting children"? It's happening uniformly all around the world, and is much better predicted by things like wealth and freedom than anything else: cultural reasons, not heredity.

[eudamoniac]

It is safe to assume pretty much any proclivity has some, however minor, genetic basis. Separated twin studies have shown enough similarities in basically every aspect of personality that it's a plausible bet.

All over the world, some groups are deciding not to have kids and some are. Globally declining fertility rate says nothing about genetic proclivity to want children unless fertility rate goes to zero.

[hn_throwaway_99]

I think you've misunderstood my point. To clarify, there was strong selection pressure in the past to "make sex desirable" (and obviously I'm oversimplifying a lot here, but the premise still holds) because that was enough to ensure that passing on your genes was the result a large percentage of the time.

Now, though, birth control has broken that connection between "having sex" and "making babies", so now "making sex desirable" no longer is enough of a trigger that results in passing on your genes. So, in that sense, the environment in which humans reproduce has changed drastically, in a short period of time. So now there should be strong selection pressure for people to have children beyond just making sex enjoyable. Whether that shows up in a stronger innate desire for children themselves or whatever I won't speculate on - I'm just making the point that widespread birth control is a huge change to humans' environment to which natural selection should act on, by definition. What I am not saying is that "not wanting children" currently is the result of some fundamental genetic difference between sub-populations.

[thrance]

I think my point still stands? For selective pressure to select anything, there has to be preexisting genes that predict how much someone wants kids. And again, cultural and material factors are so much more important than genetic ones on the matter, that I don't believe the latter has any quantifiable effect.

[dachris]

True, and here's an interesting twist: as you wrote, this is mainly happening due to "I think", so it's primarily on a memetic level. Humans also pass on lots of thought/behavioral aspects to their children (memes). Therefore I'd expect that selection on the behavioral level is happening much faster than on a genetic level.

Idiocracy's "stupid genes win" likely won't happen, my theory is that selection will remove memes (behavioral/thought/cultural patterns) that cause childlessness from the meme pool much faster.

Could also well be that natural selection will rear it's ugly head again first. I previously thought that people rejecting the evolutionary theory (creationists etc) were just backwards and anti-science. But I've realized since that this is a too simple judgement. The ethical implications of evolution are dark. Humans have had a word for selection since the dawn of language - "death".

A bit sad that paraphrasing Paul Watzlawick in this context fits very well: one cannot not participate in evolution.

[skissane]

> my theory is that selection will remove memes (behavioral/thought/cultural patterns) that cause childlessness from the meme pool much faster.

The sociologist Eric Kaufmann wrote a book Shall the Religious Inherit the Earth?, arguing that traditionalist religious groups (such as ultra-Orthodox Jews and the Amish) will become demographically dominant in the long-term (decades and centuries) due to their greater fertility and high retention rates (>80% of their children stay in the group as adults)

[_nalply]

I think the possiblities that a minority can leave the group is an important escape valve for them. Now assume that in the future they are going to be not such a minority anymore like today, then what happens? Maybe some oscillation like for Lotka-Volterra situation, perhaps a bit different?

[skissane]

The possibility of defection to mainstream society actually increases the selective pressure against defection-promoting alleles/memes, compared to if that possibility didn’t exist; the mainstream acts as a genetic/memetic sink to absorb those alleles/memes, reducing their prevalence in the next generation.

I think the fact that in e.g. the United States there are multiple such high fertility traditionalist religious minority groups coexisting makes it unlikely any one of them will end up completely dominant in coming centuries. More likely, I think, conservative religious groups will ally together across confessional boundaries to attain shared policy objectives (e.g. government funding of private religious schools). As such, I don’t think the possibility of defection to secular society will disappear; secular people will still exist, just numerically and politically weakened compared to today.