Exactly this. A couple of centuries from now, people will laugh about that time people thought that the population will collapse.
Most likely, there is an enormous selection pressure right now for any genes that predispose people (and in particular women) to want to have (many) kids. If those genes are as common as I believe, they should be dominant within about 10 generations (counting from approximately 1970).
And that selection pressure hasn't existed for the entire history of life? I don't think genetics have nearly as much to do with it because we are not living in a "state of nature" where genetics are the dominant factor in reproductive fitness. Even Richard Dawkins recognized this many decades ago when he coined the term "meme" to refer to the units of cultural lineage that clearly influence evolutionary fitness by altering the behavior of the people who hold them.
edit: I mean, you're not wrong, but I'd posit that there is enormous selection pressure for memes that promote fertility.
> And that selection pressure hasn't existed for the entire history of life?
Not at all. For most of evolutionary time, organisms didn't even have any kind of cognitive capacity at all (being single celled organisms). Even after brains started to develop, mating behavior was primarily instinctual. And even up until this day in humans, the sexual drive may easily overpower any desire to prevent pregnancy if people (and women in particular) doesn't have access to birth control.
Arguably, the sexual drive may have been so strong that there may have been a selection pressure favoring INHIBATION of reproductive behavior (K selection).
Especially so in females, as under some conditions, having fewer offspring and investing more in each may provide a higher number of surviving offspring than giving birth to more, but with less investment in each. Without birth control, even K-selection strategies ended up with 5 or so offspring per woman, on average, with about 2-3 surviving children on average.
With child survival rates near 100%, K-selection strategies are now strongly disfavored compared to r-selection strategies, even without birth control. (So r-selection has probably been selected for at some level for the past 150 years or so in the West). Birth control simply multiplies this effect.
> because we are not living in a "state of nature"
This, I'm sure, is a fallacy. The rate of genetic adaptation is directly linked to the strength of selection pressures, where "selection pressures" are not just survival rates, but rather the number of surviving offspring.
To quote wikipedia: "Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster than ever before"
> "meme" to refer to the units of cultural lineage that clearly influence evolutionary fitness by altering the behavior of the people who hold them.
Memes (as coined by Dawkins, not the pop culture use) are their own replicators. They code for the replication of thoughts and ideas.
Memes are not very tightly coupled to the physical fleshbags they inhabit. Like regular viruses, they often pass from host to host laterally, even though some forms are often transferred to children.
But there is no reason to think that this has limited genetic evolution (meaning adaptation, not necessarily "improvement"). This is basically orthogonal to whatever the memes are doing. (Though there is an interaction term where genes and memes form part of the natural environment of each other as replicators).
Genes may not be the dominant factor in reproductive fitness right now, but unlike for memes, the relative frequency of genes depend directly on reproductive fitness, meaning whatever variance DOES ALREADY exist in the genome for reproductive fitness are under a massive selection pressure right now.
For many, if not most memes, reproductive the reproductive fitness of the hosts has little impact on the ability of the meme to replicate. For some memes (or meme-plexes) like religions, one _could_ argue that they attach themselves strongly enough to families that they are inherited in a way similar to genes.
However, I would argue that memes can lose this power much more quickly than genes can. Just consider how quickly Christianity have been losing power over most Western linages lately.
Meanwhile, genes will continue to build up momentum for as long as the selection pressure remains. Currently, that pressure is for women to WANT to have children. While cultural effects may come and go, any genes coding directly for that will be reinforced. If these genes already exist, this will take a few hundred years. If mutations are needed, it could take 10x longer.
Eventually, though, if the selection pressure persists, having babies will have the same pull on female brains as sugar, sex or serotonin-inducing social affirmation.
At some point, though, REAL overpopulation is likely to be a limiting factor. Real, as in famine or disease will place a hard cap and re-introduce child mortality rates of 50%+.
> Memes are not very tightly coupled to the physical fleshbags they inhabit.
Which is why the most successful memes are those which induce an artificial coupling, e.g. religious beliefs that infuse culture so thoroughly that they are passed from parent to offspring essentially by default. All the major world religions do this to some extent, and it's on vivid display in the more cult-like sects.
> Currently, that pressure is for women to WANT to have children. While cultural effects may come and go, any genes coding directly for that will be reinforced.
Perhaps the fundamental disagreement here is about whether or not the extent to which a woman "wants" children is encoded primarily in genes. I have trouble believing that, on the whole, genes have anything more than a marginal influence on birth rates in the presence of freely available contraception. I could be wrong. But there's probably a reason why at least one major religion forbids the use of contraception. That looks a lot like a meme that has taken matters into its own hands, genes be damned.
I believe desire to procreate is just as much caused by environmental factors.
In particular, living in cities vs living in the country. If the organism sees "resources and space and hard to come by" (like, say, living in NYC), it will put the fertility program "on hold" until it finds sees "there is an abundance of space and resources" (for example, living in a bucolic countryside with ample food around).
The drop in birth rate since the industrial era has nothing to do with genes, and everything to do with urbanization, at least from where I'm standing. :)
Not at all. I'm merely assuming that there is a non-zero genetic component.
> The drop in birth rate since the industrial era has nothing to do with genes, and everything to do with urbanization, at least from where I'm standing. :)
I completely agree. Well, urbanization and other, related environmental factors (even farmers have fewer kids than before).
When you change environment for any species, there is a possibility that reproduction rates go down, sometimes radically. For instance, if you put cheetahs in a zoo, you're not likely to get many cubs. From a reproductive perspective, a zoo is a very hostile environment for a cheetah, even if they are guaranteed enough food, a qualified vet and have no risk of being killed by lions.
Still, over time (and unless the population goes to zero), when facing an environmental change that is hostile in the short term, the species will adapt to the new environment. When this adaptation only requires a change in relative frequency of already existing genes in the genepool, this can go very quickly. (Which is perhaps the greatest benefit of sexual reproduction.) If it requires a string of mutation, it can take a very long time.
Maybe in some places Muslims and Morons will prevent collapse. Just maybe, though, as many factors can prevent that.
In other places, like China and Japan, I don't find it likely at all that Muslims or Mormons will be allowed to do so.
Still, given enough time, genes will adapt to the new pressures of female choice and birth control. That could be a few hundred years (at most) for genes already present in the gene pool, or a few thousand if mutations are needed.
Most likely, there is an enormous selection pressure right now for any genes that predispose people (and in particular women) to want to have (many) kids. If those genes are as common as I believe, they should be dominant within about 10 generations (counting from approximately 1970).