The more likely explanation—related to tech—is that we don’t need kids anymore

While that’s certainly a contributing factor worldwide, I think the data contradicts it quite a bit. Japan, as an example, has the elderly heavily rely on their children as a retirement plan. Far more so than countries like the US that has a higher birthrate. Also include that while undeveloped countries like Kenya have some of the highest birthrates in the world, it’s far less than similarly developed countries had 100 years ago

that’s a much lesser concern because I seriously doubt humans of the past thought that hard about such things when living to 40 was considered amazing

There is a bit of a misconception there with average life expectancy. Once you made it to adulthood, your life expectancy was far higher than would be expected from an average life expectancy of ~40. It was brought down heavily by all the young deaths

Now we have birrh control and—in Western societies—stability/safety is much more likely if you don’t have kids. We’ve basically flipped the script on our evolution.

I don’t doubt this is a strong factor, but if it were the largest factor, wouldn’t we expect countries with strong social programs like Norway to have much higher birth rates? I suppose those social programs would tend to correlate with birth control