[WildUtah]

There are people, even in Japan, that want a whole mess of children. That preference is heritable. Each generation has more of these people because they're the ones that reproduce.

Eventually those fertile and natal enthusiasts will dominate the population and exponential growth resumes. The current situation is a temporary response to an external shock, specifically to reliable contraception. But Malthusian conditions will return; Darwinism requires it.

[kbutler]

Statistics suggest your view of Darwinism is incorrect.

http://www.infoplease.com/ipa/A0884238.html shows avg household size has been declining since before contraception, and it doesn't look like contraception changed the slope.

[b_emery]

I respectfully disagree. Your assumption about the preference being heritable is questionable.

[wolfgke]

Couldn't it not be a gene but a meme that is inherited, instead?

> Each generation has more of these people because they're the ones that reproduce.

I.e. each generation has more of these people since people who see having children as something positive reproduce and teach these values to their children.

Being a memetic instead of genetic factor would have the advantage that it is easier to "unprogram" it, i.e. by having rules/incentives in the society that discourage reproduction or by education.