

The upstart queen can replace the main queen if she dies, yeah. Queens produce a pheromone that triggers the killing of upstart queens. In the absence of a queen, an upstart queen can survive and take over.
The idea with cancer being selfish comes from an idea of organisms functioning at different levels of organization. Single-celled organisms, colonial microorganisms, multicellular life, social animals, larger societies, civilizations, ecosystems, the whole planet.
Perhaps one day we may colonize other planets and form yet another, higher level of organization. How it will function is still to be discovered but I think selfishness of individual units is always a potential.
No, we needed culture and the technology to make warm clothing, fire, and insulated structures to be able to survive. Losing fur did not help us survive cold climates at all.
Where’s the evidence that authoritarian states have been less stable over the last 5000 years? There have been plenty of authoritarian empires which lasted for thousands of years, far longer than western democracies have even existed. We are currently in a period of increasing popularity of authoritarianism. Liberal democracy may turn out to be a blip in an otherwise authoritarian-dominated history (over the next ten thousand years).
And I wouldn’t say liberal democracies have thrived at all, evolutionarily speaking. We’ve essentially destroyed our own desire to reproduce. That’s the opposite of thriving.