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Probably the biosphere was simpler (fewer extant species at any given time). Being highly intelligent seems to be biologically expensive: the human brain burns

Probably the biosphere was simpler (fewer extant species at any given time). Being highly intelligent seems to be biologically expensive: the human brain burns a huge amount of calories, and as to the demands of being an upright species with a large head:body mass ratio, ask any mother. Lots of species are intelligent - not just the mammal kingdom (dolphins, apes, elephants), but also birds (corvids) and even molluscs (octopus), but nothing else has shown any tendency to develop the sort of runaway intelligence (and corresponding brain development => biological demand) that humanity has. Seems likely that the average intelligence of animals was quite a lot lower in the Mesozoic, and that while high intelligence is evolvable, it takes a long time to evolve - whereas isolated island species do evolve radically large or small body sizes over a few thousand generations, change their diet substantially, and some certainly become _less_ intelligent, there aren't any examples of an island species evolving significantly higher intelligence to occupy a new ecological niche.

sudhirj 4y ago
That seems much more convincing, that intelligent life evolves easy and often enough, but the level of intelligence required to observe or signal other planets is completely unnecessary for survival, so there’s no pressure to evolve to that level. There’s a joke in Hitchhikers Guide that says dolphins are the most intelligent species on earth, to which the response is how can that be, all they do is happily swim around all day… … yes, exactly, they’re the most intelligent species on the planet.
- Ancapistani 4y ago
  > the level of intelligence required to observe or signal other planets is completely unnecessary for survival, so there’s no pressure to evolve to that level. Ah, but humans today are fully capable of guiding our own evolution toward whatever goal we desire as a group, regardless of "fitness". Perhaps there is a threshold of intelligence that, once reached, allows the possibility of that species becoming more intelligent and capable over time.

sudhirj 4y ago

That seems much more convincing, that intelligent life evolves easy and often enough, but the level of intelligence required to observe or signal other planets is completely unnecessary for survival, so there’s no pressure to evolve to that level. There’s a joke in Hitchhikers Guide that says dolphins are the most intelligent species on earth, to which the response is how can that be, all they do is happily swim around all day… … yes, exactly, they’re the most intelligent species on the planet.

Ancapistani 4y ago
> the level of intelligence required to observe or signal other planets is completely unnecessary for survival, so there’s no pressure to evolve to that level. Ah, but humans today are fully capable of guiding our own evolution toward whatever goal we desire as a group, regardless of "fitness". Perhaps there is a threshold of intelligence that, once reached, allows the possibility of that species becoming more intelligent and capable over time.