How many generations until evolution drives the birth rate goes back up?

[Bohandas]

On the short-term yes, but in terms of the actual fitness of the ancestor peacocks (or if modern peacocks were coexisting with those ancestors) then the modern ones would be out-reproduced by the ancestral ones. The effect of runaway sexual selection created a population-level environmental effect which in turn closed off otherwise biologically-possible options to have more offspring.

So in essence, the peacock-genes all have to voluntarily have less kids than they in principle could, in order to have any kids at all.

Total population isn't strongly selected for regardless

[poppy]

I like this sequence...
1. An apocalyptic event

2. A somehow non-apocalyptic massive war.

3. Space Colonies.

[Beleriphon]

Know what we know about the human genome I'm willing to say how many generations will it take to genetically encourage a high birth rate? Probably so many the population isn't recognizably human any more. Modern humans have existed for around 80,000 years, give or take a millennia. That is to say an average generation being 20 years, so 4000 generations we might see a change in as many generations forward at a genetic level. Even then I don't think we will since families are driven by necessity and desire, neither of which are defined by our genes. Those things are cultural, a desire for comfort might be genetic but the process by which we get there isn't.

If we were to compare Khufu to you (and that means any of you reading this, unless you aren't human for some reason), genetically you are identical. There is no genetic difference between you and him, despite nearly 4500 years between your births, or over 200 generations. Even Rameses II who lived into his 90s and reportedly had several hundred children isn't genetically different between you or any other human. His desire for children was a function of 1) being the Pharoh 2) have several dozen (hundred?) concubines with access to birth control and 3) no particular reason NOT to father that many children (it basically guarantees he'll have an heir).

[deuterio12]

Even then I don't think we will since families are driven by necessity and desire, neither of which are defined by our genes. Those things are cultural, a desire for comfort might be genetic but the process by which we get there isn't.

It's both. Our bodies crave food and water and human contact, and indeed every culture is built around satisfying those human primal urges one way or the other. No sane parent wants to see their children go hungry nor thirsty.

And if your culture can't give people food and water and skinship in some way, then it's gonna collapse pretty fast.

[Paleomancer]

I believe global birth rates are actually declining all over the world. The issue is more that we have a lot of people and thus even a smaller number of children per person still equals a massive population increase.

Perhaps the biggest reason any organism has lots of offspring is in situations where only a few of said offspring will survive to adulthood, due to environmental threats that increase risk of mortality. However, evolution as applied to humans can be tricky, because tool use and transmission of information through culture and language have dramatically impacted human genetic changes throughout history. No other organism has anything close to our ability to alter local environments to our will. Since most humans retain the ability to have lots of children if they desire, we’ll only likely see an increase in birth rate also involving culture, personal choice, and/or high mortality rates. Impossible to predict how fast, though given humans can be smart, we’d probably figure it out within one-two generations, natural selection need not apply.

[Themrys]

But the runaway sexual selection has made it so that not making the large colorful tail causes it to be more difficult to find a mate now. So even if the species as a whole could have more kids by dropping the tail, there aren't any continuous moves which get there from here without going through an intervening lower-fitness state.

Interesting that you mention that.

I think the decline of birth rates has two reasons. One is, of course, the fact that it is very expensive to raise kids in industrialized countries, and sensible people don't want more kids than they can afford.

The other reason is most probably that after hundreds of years of patriarchy, the human male has, with the lack of evolutionary pressure, become so boring that many females just aren't able to find one that is sufficiently attractive to keep them interested for long enough to conceive children. Basically the opposite of the peacock. The human male excels at earning money and competing against other males (which in patriarchy was sufficient to spread his genes) but is rather boring to look at, all in all.


It might only take one generation for the governments to evolve a solution to the problem that having children gives women a strong financial disadvantage.

As for the evolution of the human male, well, we'll see. That's going to take a lot longer. Though we might see immediate effects - teenage boys have been known to learn how to play the guitar in order to impress girls. With feminism increasing evolutionary pressure, perhaps we'll see more boy bands.

[halfeye]

natural selection need not apply.

Wrong.

The thing about natural selection is that it is everything and anything. When humans select artificially, that is also natural selection, it's being adapted to our needs, but it is still actually having a real effect on real populations.

The problem with the idea of humans breaking free from natural selection is that we are part of the feedback loop. We can do anything we like to e.g. dogs, because we are not dogs. However, we are human beings, and anything we do to the human species affects us, the actors (as in the people performing the actions) too. The control of a feedback loop being affected by the actions of the loop necessarily changes the performance of the loop in unpredictable ways, it is no longer a controlled feedback loop.

e.g. cats could control human evolution, if they were completely free from human breeding control. However, they are not free of human breeding control, so if they somehow tried, the loop would do funny things, because we control their selection (to some extent, if not totally) and so their attempts to control our selection and our attempts to control theirs would enter into a broken feedback loop, and the results would be unpredictable, and would become more severe and unpredictable with passing time.

[Rakaydos]

I wouldnt be suprised if the trend toward less children as conditions improve is an Epigenetic (non-DNA based inherited trait) safeguard against population overrun.

The evolutionary logic being that in previus population overruns, the populations (human or human genetic ancestor) that pigged out on excess resources were less able to handle the shortages afterward than the populations that moderated their birthrate in low-stress times.

[halfeye]

I wouldnt be suprised if the trend toward less children as conditions improve is an Epigenetic (non-DNA based inherited trait) safeguard against population overrun.

The evolutionary logic being that in previus population overruns, the populations (human or human genetic ancestor) that pigged out on excess resources were less able to handle the shortages afterward than the populations that moderated their birthrate in low-stress times.

Could equally be genetic, if it raises long term survivability, genes can be for it.

[AMFV]

Interesting that you mention that.

I think the decline of birth rates has two reasons. One is, of course, the fact that it is very expensive to raise kids in industrialized countries, and sensible people don't want more kids than they can afford.

The first part is probably true, the second part is... maybe less true.

For some people the financial side of things doesn't necessarily play as key a role in their decisions as it does for others.

The other reason is most probably that after hundreds of years of patriarchy, the human male has, with the lack of evolutionary pressure, become so boring that many females just aren't able to find one that is sufficiently attractive to keep them interested for long enough to conceive children. Basically the opposite of the peacock. The human male excels at earning money and competing against other males (which in patriarchy was sufficient to spread his genes) but is rather boring to look at, all in all.

I'm fairly sure this is wrong. Humans because of how our reproduction works can have one or two males fertilize fairly large groups of females the same way that Gorillas or Chimps do. So even if there's only suitable male to every five or six ladies that's still enough to keep things going at least in theory.

Also I pretty categorically reject the "men are boring now" argument. I don't think that the spread of career women has drastically changed what women find attractive. I mean I'm not terribly attractive and am only moderately financially successful and I was not when I met my wife, and I have had very few problems finding partners, when I was so inclined. I mean I usually found the same subset of ladies that were attracted to qualities I had. But if I can I imagine many other guys could as well.

Now what I think there are is a larger group of guys (although still nowhere near a majority, except for maybe in Japan) that are simply choosing to not pursue women and that is negatively affecting things. Although maybe not enough to have a major effect on a statistical scale, except for possibly in Japan where supposedly it's a crisis (although I haven't been there to be sure).

It might only take one generation for the governments to evolve a solution to the problem that having children gives women a strong financial disadvantage.

Many, many career minded women have chosen to have children, in the past 30 or so years. Even giving that there is some disadvantage to it. I imagine that the women who are likely to beg off child-rearing for financial reasons probably were less likely to be the women wanting to have children in the first place.

As for the evolution of the human male, well, we'll see. That's going to take a lot longer. Though we might see immediate effects - teenage boys have been known to learn how to play the guitar in order to impress girls. With feminism increasing evolutionary pressure, perhaps we'll see more boy bands.

Guys learning guitar to impress girls predates the widespread of feminism. In fact that probably extends to the invention of the guitar. Teenage boys have always done things to impress women for all of recorded history. Now what exactly those things are has changed (although less than you might think), try going into a mixed gender group of highschoolers and see if you can get two guys to have any kind of physical competition, it may surprise you.

[Rockphed]

Guys learning guitar to impress girls predates the widespread of feminism. In fact that probably extends to the invention of the guitar. Teenage boys have always done things to impress women for all of recorded history. Now what exactly those things are has changed (although less than you might think), try going into a mixed gender group of highschoolers and see if you can get two guys to have any kind of physical competition, it may surprise you.

My memory from high school was that you could get a physical competition going regardless of the presence of women. Women being around just raised the stakes from intense to life-or-death.

[halfeye]

Women being around just raised the stakes from intense to life-or-death.

lol, truth.