What evidence is there that it takes a lot of time for intelligence to evolve, in the sense of requiring very many sequential steps?
To me it seems intelligence is simply unlikely to evolve at any point of time. Roughly equally unintelligent animals may have existed for tens or hundreds millions of years before humans evolved in a few million years. (Who’s to say if the ancient ancestors of birds 100 million years ago were as smart as some birds are today?) Before that, life existed for billions of years before multicellular creatures evolved.
What evidence do we have that it takes a long time, other than that it happened late in history, which we already accounted for? My impression is that there weren’t progressively-more-multicellular forms evolving into one another over a very long period of time. The first animals lived possibly less than 700 Mya; complex Ediacaran animals appeared 575 Mya; and by 510 Mya we had ostracoderms, which were surely fully multicellular (i.e. with a germline and complex cell differentiation and organs).
That’s on the order of 100 million years for some complexity, and possibly some more tens of millions of years for more. But it’s also possible that multicellularity evolved much more quickly, and the animals just didn’t evolve larger and more complex forms for a while due to e.g. low sea oxygen levels, not having evolved eyes yet, etc.
What evidence is there that it takes a lot of time for intelligence to evolve, in the sense of requiring very many sequential steps?
To me it seems intelligence is simply unlikely to evolve at any point of time. Roughly equally unintelligent animals may have existed for tens or hundreds millions of years before humans evolved in a few million years. (Who’s to say if the ancient ancestors of birds 100 million years ago were as smart as some birds are today?) Before that, life existed for billions of years before multicellular creatures evolved.
You probably need multicellular life first, and this takes a while and does involve many steps.
What evidence do we have that it takes a long time, other than that it happened late in history, which we already accounted for? My impression is that there weren’t progressively-more-multicellular forms evolving into one another over a very long period of time. The first animals lived possibly less than 700 Mya; complex Ediacaran animals appeared 575 Mya; and by 510 Mya we had ostracoderms, which were surely fully multicellular (i.e. with a germline and complex cell differentiation and organs).
That’s on the order of 100 million years for some complexity, and possibly some more tens of millions of years for more. But it’s also possible that multicellularity evolved much more quickly, and the animals just didn’t evolve larger and more complex forms for a while due to e.g. low sea oxygen levels, not having evolved eyes yet, etc.