Humans and animals enforce their borders since millennia.
The idea that borders are unimportant is very very recent. That is to say, its commie gobbledygook.
Borders of Westphalian nation-states being relevant is recent, unlike personal and tribal territories.
I am not convinced that the idea is recent, or rather, related ideas are not recent, going back thousands of years. It can be extremely complex, to put it very mildly. How well people that put their trust in some of those ideas fare, can likewise be an extremely complex topic, and can also be political. In some cases in some ways some of them might have fared well, in some other cases in some ways, maybe less so.
Right, well we know which side of the enclosure of the commons you for some unaccountable reason assume you’d have born in.
Why do you think it's a communist thing? Communist countries (both historically and current) tend to protect their borders fervently.
I'd say no-border cosmopolitanism is more of a classic liberalism thing.
In practice, communist countries have always put a lot of effort into keeping their citizens in.
> enforce their borders since millennia.
In English it's "have enforced their borders for millennia"; the phrase "since [length of time]" is almost always grammatically incorrect and a giveaway that someone's not a native English speaker.