The idea thst animals can go extinct was new as hell during Rosa's time. Fucking Andrew Jackson literally thought if they looked hard enough they'd find mastodons out there cause if God wanted a species dead he wouldn't have made it in the first place. If you add the knowledge that yes, we can all die and there can be no more people ever again, the inevitability of communism is less scientific for sure. Given a long enough time span, I'm sure we would eventually get socialism but that's no longer on the table.