Oddbean

People are saying that people need to have more kids to avoid population collapse. I used to think couples needed to have 2 kids, the replacement rate. But half of your kids aren't going to have kids. So you need to have 4 kids. And if you count your grandchildren that aren't going to have kids, maybe you need to have 5 kids.

I started my post with "People are saying" in order to stay rather neutral on this issue. I'm not arguing that it is true that we need to have more kids, just that if it is true, having 2 kids isn't enough. Our infrastructure and institutions were built under an assumption of continued population growth. Old people need to be taken care of, and under population decline there aren't enough new young people to do so. Infrastructure built for a certain population size becomes unmaintainable if the working population size gets too low compared to the elderly population size. And the burden on the working population becomes so great that many of them leave to other countries, causing a vicious cycle. Societal collapse accelerates and is unstoppable. Japan has this problem right now. There are tons of elderly, and the working people work every single waking hour, sleep on the train, beat themselves to death, under a sense of duty to their society. Robots might help.

A couple of thoughts triggered by that. (Not organised as a narrative.) 🧠 The population collapses are well advanced and may not be stopped. 🧠 Japan may turn out to have handled it very well, time will tell. 🧠 I hear that China may have embarked on the worst collapse yet. 🧠 In calculating kids I suggest looking at a single generation only (getting 2.1 kids though!). Betting on an unknown future may be unwise. 🧠 There is talk of ecological overshoot, I don't know enough to model and estimate that (yet), but I see counter measures in the rewilding movements. If those ideas are meaningful, then the demographic transition might save the planet. 🧠 I've seen many talk about the problem but not about plausible solutions. The automation in the Ukraine War suggests that we now have the power to automate cheaply, that will play a role. 🧠 Conventional government economics, and many "models" of society, sometimes seem intent on kicking the can down the road. (If this doesn't publish right, its my first Nostr post, I will learn!)

All good points. I can't predict the future situation and say 5 kids is right. Maybe by the time they have kids things will change a lot. I was in Japan in November and it seemed to me that there were a lot of useless jobs, people manning crosswalks or ushering people to the right part of a line. I bet they could repurpose those people if they really needed it.

You can't look at a single generation only with humans. The evidence for this is menopause and the fact that humans live as long as we do. Under a single generational model, there is no evolutionary reason for us to live so long past fertility. Populations where the older generation stopped competing for resources by dying would outcompete populations with the additional load. Thus with humans it makes sense to count descendents at the time of death. I believe the reason is because reproduction is replication of information. For most life that information is nearly entirely genetic. Or better put, molecular. Get enough molecules into a baby horse and you have an adult horse. One that can do all the horsey things. Humans aren't like that at all. Get enough molecules into a baby and you get an idiot. Humans also need to replicate all the social knowledge that allowed the parents to navigate highly complex rulesets inherent in a functional society. This takes at least 20 years of education and nurture. I believe Grandparents play a critical role in passing on the ideas and traditions that enable grandkids to make the tough choice to have children of their own that will want to have children as well. Etc. etc. Blame the invention of language for starting the evolution of a new emergent layer of life called society, humans are different in kind.