> 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).

https://en.wikipedia.org/wiki/R/K_selection_theory

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"

https://en.wikipedia.org/wiki/Recent_human_evolution

> "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%+.