He set out to walk around the world. After 27 years, his quest is nearly over

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.

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.

One must distinguish between "classical" communism (Stalinism, which is dead except in North Korea) and the modern variety, which is alive and well and I think is what you mean.

There are many that think themselves "cosmopolitan", when it is a delusion and coping mechanism about being a parochial hicklib. A chip on their shoulder that makes them especially fervent acolytes of liberalism (as in: Obama flavoured, not the other kind), hoping it offsets their humble origins after moving to the big city, so folks won't get the idea that they are flyover country chuds that vote the wrong way.

A cosmopolitan, as in one that truly knows the different cultures and people of the world because he has deep first hand experience, or has read so much that it allows to draw some independent form of conclusion, is either a strong proponent of borders or a fool.

The core tenet that makes this communism-adjacent is the denial of differences: everyone is equal, "no one is illegal" etc pp. Ignorance of history and the nature of man is a must to take this position.

A group of men crossing the border into another country was (usually) automatically considered invaders if its size exceeded a certain number.

Eg Iberian Peninsula (Reconquista and later): Foreign parties >10 armed men could not cross without permission between christians and muslims.

Chinese frontier zones, Scythians, Huns, Mongols, Turks etc all had similar rules. If you want to go back further, then Assyria, Egypt, Hittites, Greece had such limits.

You are correct that there are many examples of border control mechanisms, in different levels and ways. Maybe even usually the vast majority for many levels and ways.

Some nations, countries or groups, or other levels, did play with some of those mentioned ideas of less border control mechanisms in some ways or levels, also going back thousands of years.

Countries that were not successful with border control mechanisms, sometimes ceased to exist.

But there are many different levels and ways, and the whole topic is, to put it very mildly, extremely complex.