To an extent I think it's still true if you're on foot/boat (i.e. the way people travelled in the olden days). You could probably travel all of Africa and all

To an extent I think it's still true if you're on foot/boat (i.e. the way people travelled in the olden days). You could probably travel all of Africa and all of South America without ever showing a passport, and even between the two with a boat. It would require some deliberate approaches but I think it would be possible without playing mission impossible. The informal economies in both continents are large enough I would wager someone could travel between and among those two continents for life and get by without ever having a passport. For the most part, rigid passport control can really only exist at airports, controlled ports, possibly some 'choke-points' in roads, and some exceptionally closely guarded borders. If you're in bumfuck nowhere in the third world absolutely no one has time to mess with deporting you unless you did some dumb shit to make it worth their while. Watch some documentaries on people trying to immigrate (illegally) to EU or America. You always see the stories about people working from country to country all though Central/South America and Africa and when they get stuck at the border absolutely no one has the money to deport them all the way back to their home country. There are tons of people like this that get stuck somewhere like Mexico, Brazil, Argentina, Chile with no papers and somehow their life just.... continues on. Eventually their children are born wherever they get stuck and there's a good chance after 1-2 generations their family are <new country> nationality.