Are you sure we aren't specialists?
Yes, we are generalists... we live in every environment and eat anything. We are not specialized biologically.
Particularly intelligence or language specialists.
That isn't an ecological specialization. If anything that helps us not harms us as it lets us coordinate out actions more effectively for group survival.
How stable would you say our ecological niche is?
It's always dangerous to be at the top of the trophic pyramid. However, since we are such generalized critters (omnivores with no set environmental limitation) we are in good shape to stay there, even in the event of a trophic collapse. We can slide down to primary consumer (herbivore) if all else fails.
Mammoths became extinct, and elephants are generally a pretty intelligent organism. (I'd go so far as to say that elephants are the non-primate life form most likely to create a civilization) Not to mention that there is evidence that we went through a genetic bottle neck at one point and were reduced to around a thousand individuals. I'd say we're pretty sensitive to environmental changes despite our brainpower.
Elephants are specialists... Mammoths even more so. They were specalized giant herbivores dependent on particular types of plants and in particular environments. Wooly Mammoths could not survive without large areas of tundra sedge and grassland, a habitat that was all but replaced by boreal forest.
We went through a genetic bottleneck of between 3,000 and 10,000 breeding pairs... but this only counts the ancestral population, not the whole population. That means there could have been more humans who did not contribute long term to the current human gene pool. Plus, there are some serious flaws with the bottleneck hypothesis. There are ways to produce the same effect in the human population while keeping the total number of humans fairly stable. (all natural populations fluctuate up and down) and it may simply be that prior to our migration out of Africa we generally had a smaller population in the few tens of thousands.
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