Tree of Souls - An Avatar Community Forum

As it looks that in the past there were no species that reached a level of manipulating intelligence as humans do now (see the "ancient aliens" thread ;) ), I dont think it is a "niche" that has to be filled. In fact some biologists argue that it may actually be a dead end in evolution because it leads to what is now called the "sixth mass extinction". That does not say anything on other ways of intelligence. Manipulative intelligence (e.g. a form of intelligence that allows the species to completely shape their environment) may be only one form of intelligence among many possibilities. Maybe other beings memory or their ability to memorize songs or to dream may be a lot stronger.
But in terms of manipulative intelligence, I'd also be inclined to either other primates, though I give them little chance if we are talking about a human extinction scenario because that most likely would affect them as well (e.g. if climate change makes mammal life impossible in many parts, if a virus kills humans and other primates, if humanity blasts the planet with nuclear bombs). Many of these things also affect the oceans, but still aquatic life is somewhat shielded from some of the dangers (though ocean acidification, pollution, overfishing, eutrophication,... are also killing oceanic species). So I'd also give the cephalopods a fair chance - they even have good potential to actually develop the ability to go terrestrial. If extrinction event is large enough, all bets are off though - who would have thought that when the great reptiles were wiped out, that some rodent sized animals called mammals would rule the world some millions of years later. This is by the way the minimum timescale we'd be looking at in terms of this topic: millions of years...