In case of Japan, there might be another heuristic at work: “the place is overpopulated, high population means low resources, low resources means less healthy offspring, therefore it might be a good idea to hold off reproduction until I find a less populated place.”—I vaguely remember reading something along these lines about mice, but can’t cite the source.
(Of course I’m not talking about restricting reproduction to conserve resources ‘for the group’).
If you are interested in the topic, there’s a fairly detailed analysis of the origin of the “demographic transition” in the book “Not by Genes Alone”. They mostly finger human culture.
In case of Japan, there might be another heuristic at work: “the place is overpopulated, high population means low resources, low resources means less healthy offspring, therefore it might be a good idea to hold off reproduction until I find a less populated place.”—I vaguely remember reading something along these lines about mice, but can’t cite the source.
(Of course I’m not talking about restricting reproduction to conserve resources ‘for the group’).
If you are interested in the topic, there’s a fairly detailed analysis of the origin of the “demographic transition” in the book “Not by Genes Alone”. They mostly finger human culture.