> Other events (if in the next decades) that might kill billions of humans:
>
> - meteorites.
No asteroid large enough to kill billions of humans is likely to impact Earth in this century. After that, it's likely that humanity will be so advanced that it'll be able to either mitigate or deter an impact of any magnitude.
An overlooked possibility imho would be a catastrophic population decline[1]. Basically women not having children anymore. Japanese style, only worse.
It's difficult to imagine it leading to extinction, since there will always be groups, at the very least religious groups, who will keep having babies. But still, it wouldn't take much of a cultural change for it to expand to all women.
Not saying it's plausible, but to me in terms of population dynamics it's at least as much of a concern as climate change (by this I mean that I believe reproductive behavior will have more impact on demography than climate change).
There is _massive_ evolutionary pressure going against this. To the extent that not wanting to have children is at all genetic, it will disappear from the gene pool within a few generations.
That the desire to "not want to have children" (especially among women) exists at all is caused by the sexual revolution (contraceptives), which changed who had children from "people who desired sex" to "people who desired to have children."
Maybe contraceptives are a dead-end against which evolution can't do much.
Maternal instinct exists : it pushes a woman to keep her offspring alive at all cost. I suppose it also makes women yearn for having a baby to take care of. But apparently, having just one is enough for them. Maybe two, but they seem to be content with no more than that.
What makes a woman pregnant in the first place is the sexual impulse of the male. That sexual impulse is the primary way nature gets animal organisms to reproduce. With contraceptives, males can satisfy that sexual impulse without creating new offspring. How will nature induce highly-intelligent animals to make an offspring if the sexual intercourse is no more sufficient? It's hard to imagine how genes could intervene high enough on cognitive functions to induce a thought such as "I must have intercourse with this women without contraception because I want children".
Well, no rule is written in stone. What you talk about could be a consequence of the fact that men and women are more or less built the same way after all. Kind of like why men have nipples, even if they are useless to them.
My point remains anyway : even if there was a perfect symmetry in gender roles, parenting instinct would be what makes parents desire to have at least one offspring and keep it alive at all cost, but what would drive them to have more than two would be sexual impulse.
I don't understand : we are in the middle of the biggest population explosion in the history of the world and at the back end of a century of government programs aimed at reducing childbearing...
Most of the population explosion is behind us. Many developed countries have sub-replacement fertility, and it seems to be a trend followed by developing countries.
"As of 2010, about 48% (3.3 billion people) of the world population lives in nations with sub-replacement fertility."[1]
Complex behavior can be and often is genetic. A great example of this is the vastly different behavior of the zebra and lion when in close company with zebras. The zebra will engage in herd behavior, whereas the lion will try to eat one of the zebras. No amount of socialization can alter these behavioral patterns.
I can tell you that my wife and I both knew long before we were anywhere near adults that we wanted families. You know how some people know that they want to be a fire fighter or a police officer when they grow up? I knew I wanted to have a bunch of kids. The story is more or less the same for her. And my wife and I both grew up on the left, where the attitude toward having children varies from something you do after you have your career sorted to outright anti-natalism.
> . A great example of this is the vastly different behavior of the zebra and lion
We're not zebra and lions
> knew long before we were anywhere near adults that we wanted families
peer pressure is strong in our society
family is a motivation to stay alive for many
> I knew I wanted to have a bunch of kids.
Yeah I though I knew as well, much like I thought I was going to be an astronaut
Now I'm a grown up man, in charge of his life, and I know I don't care about a family
And it's not the gene's telling me, I still think about having a legacy, a mini me persisting my DNA but I know that it's just a legacy from the past where a man without a family to support wasn't a real man.
That's it, education and culture
If reproducing was such a strong genetic trait, men on heart would have been billions centuries ago
The truth is kids are family support, the more societies get rich, the less people make children
It's scientifically proven, poor need kids not for reproduction but for elderly support
Poor also make a lot of children because in poor societies kids die more easily
For all of human evolution except the last 50 years, so 6,997 out of the last 7,000 generations, the drive to have sex was synonymous with the drive to have children. Then we invented birth control. Now evolution will select for people who have a desire to have children, separate from their desire to have sex.
The idea that complex behavior can be caused by genes in animals, but somehow not in humans is incorrect. People point to culture as if it is some magical force that makes people do things, but the human ability to create and interact with culture is itself the result of genes. After all, zebras and lions don’t have culture.
And you missed my point: I grew up in a culture that did not value having children. Having children was considered an after thought, something to be done after you had attended to your career. Growing up, I only knew one family with 4 children. They were considered the weird religious family. Yet I have known since I was 12 or 13 that I wanted to have a large family, even though I grew up in a culture that would look down their noses at a family of 4 or more children.
And the argument that poor people have lots of children for financial reasons doesn’t hold up any more. It did when most people were farmers, but the poor in the developed world are no longer farmers and I don’t think there’s any way to argue that children are a net financial benefit to them.
Citation needed - obviously culture and education have an enormous impact on how humans live, but given that other animals are driven to reproduce, it shouldn't be a surprise that we are also.
> There is _massive_ evolutionary pressure going against this. To the extent that not wanting to have children is at all genetic, it will disappear from the gene pool within a few generations.
This is only the case if the selection pressures which humans in the developed world are facing stay the same. Since they seem to be tied to our technological development, I think there is a good argument to be made that these selection pressures will intensify as we breed resistance to them. My personal theory is that the increasing addictiveness (see the PG essay on this[0]) of modern life is why people are having less children. I don't see that trend changing.
I do think there's a good chance that technological renunciation and voluntary cultural isolation of some sort are the best solution to this problem for people who are naturally susceptible to the addictiveness of modern life.
Based on what I've read, pre-agricultural people nursed their children until the age of 4 or 5 when they could keep up with the tribe on foot, which limited the birth rate. The explosive growth in population we have had for the last few thousand years dates to the agricultural revolution, when we settled down in one place which allowed women to wean their children sooner and have more. So in a sense the absence of birth control is the new and unusual phenomenon here. If you look at ratios of sexual activity to pregnancies human beings are extreme outliers- we clearly are evolved to use sex for bonding first and reproduction second, so the idea that birth control is going to change our behavior through selection pressure seems wrong.
I can not imagine that lack of babies could ever become a problem for humanity until humans decide to build humans so that the "natural human species" dies out.
The solution for the aging population:
- Automation.
- Biochemical solutions and genetic engineering to remain/become capable. Replacement of natural body parts by machine body parts.
Worrying about overpopulation is short-sighted. Also, no matter what kind of problems overpopulation brings, it's hard to imagine how that could lead to extinction, which is what we were discussing.
Overpopulation is frequently the cause of steep popuation decline (90+%) in ecology due to input resource depletion and the building of toxins that are the end products of that species metabolism.
Pollution and resource scarcity are the obvious limits that can send population numbers off a cliff.
I would view the comfortable lives of humans in the developed world as a very peculiar circumstance, not as something which will persist as the norm. Life expands to consume all available resources. Humans are part of the lineage that we call life. That we are poorly adapted to modern life is just a temporary state of affairs. Though many people are opting out of large families, not all are. And the people who aren't are the future of the species.
No asteroid large enough to kill billions of humans is likely to impact Earth in this century. After that, it's likely that humanity will be so advanced that it'll be able to either mitigate or deter an impact of any magnitude.
An overlooked possibility imho would be a catastrophic population decline[1]. Basically women not having children anymore. Japanese style, only worse.
It's difficult to imagine it leading to extinction, since there will always be groups, at the very least religious groups, who will keep having babies. But still, it wouldn't take much of a cultural change for it to expand to all women.
Not saying it's plausible, but to me in terms of population dynamics it's at least as much of a concern as climate change (by this I mean that I believe reproductive behavior will have more impact on demography than climate change).
1. https://en.wikipedia.org/wiki/Population_decline