There is no intelligence where there is no change and no need of change
It is a law of nature we overlook, that intellectual versatility is the compensation for change, danger, and trouble. An animal perfectly in harmony with its environment is a perfect mechanism. Nature never appeals to intelligence until habit and instinct are useless. There is no intelligence where there is no change and no need of change. Only those animals partake of intelligence that have to meet a huge variety of needs and dangers.
So, as I see it, the Upper-world man had drifted towards his feeble prettiness, and the Under-world to mere mechanical industry… Apparently as time went on, the feeding of the Under-world, however it was effected, had become disjointed. Mother Necessity, who had been staved off for a few thousand years, came back again, and she began below. The Under-world being in contact with machinery, which, however perfect, still needs some little thought outside habit, had probably retained perforce rather more initiative, if less of every other human character, than the Upper. And when other meat failed them, they turned to what old habit had hitherto forbidden. So I say I saw it in my last view of the world of Eight Hundred and Two Thousand Seven Hundred and One. It may be as wrong an explanation as mortal wit could invent. It is how the thing shaped itself to me, and as that I give it to you.