Take a look at current Japanese culture for example. Basically in a nutshell, the land is maxed out, they have entered a deflationary spiral of sorts, the Socialism experiment has failed,
(But has it ever begun?)
the central Bank of Japan owns something like 65% of all corporate debt, and the people work at corporations that exist basically just to pay off the interest on their corporate debt --- so basically "zombie" banks and corporations. So the young people, overburdened with an old world social structure that's no longer working, and overburdened with personal/corporate debt, lack of advancement opportunities, etc. are no longer dating, marrying, reproducing and having families. The majority of guys aren't even interested in the girls, just interested in themselves (preening, socializing, hanging with their guy friends, etc.). Sounds pretty depressing, huh?
There used to be a social pact of sorts until the 70's-early 80's whereby a big corporation, after sucking the parent's blood for a lifetime, would employ the child on the elder's retirement. This pact has been broken with the crisis of the 80's, and never resumed thereafter. So the frail socio-economic cohesion of Japan is going to the dogs. Socio-cultural cohesion is still quite strong, though. Maybe it's an island thing.
This made me think of something I had read a while back about a mice experiment conducted in the 1960's by John B. Calhoun.
I didn't know about that. I read up a bit. Very interesting.
Half way down the Wikipedia page you can read about it, especially about the male mice that came to be known as "the beautiful ones". The similarities between his experiment conclusion and what is happening now in Japan is uncanny.
https://en.wikipedia.org/wiki/John_B._CalhounYes! The grass eating kids, or "vegetarian men" as it gets translated into English. And as Ibian points out further down,
this at least is not an "island thing."