In Orthodox Judaism there is a saying:  "The previous generation is to the next one as angels are to men; the next generation is to the previous one as donkeys are to men."  This follows from the Orthodox Jewish belief that all Judaic law was given to Moses by God at Mount Sinai.  After all, it's not as if you could do an experiment to gain new halachic knowledge; the only way you can know is if someone tells you (who heard it from someone else, who heard it from God).  Since there is no new source of information, it can only be degraded in transmission from generation to generation.

Thus, modern rabbis are not allowed to overrule ancient rabbis.  Crawly things are ordinarily unkosher, but it is permissible to eat a worm found in an apple—the ancient rabbis believed the worm was spontaneously generated inside the apple, and therefore was part of the apple.  A modern rabbi cannot say, "Yeah, well, the ancient rabbis knew diddly-squat about biology.  Overruled!"  A modern rabbi cannot possibly know a halachic principle the ancient rabbis did not, because how could the ancient rabbis have passed down the answer from Mount Sinai to him?  Knowledge derives from authority, and therefore is only ever lost, not gained, as time passes.

When I was first exposed to the angels-and-donkeys proverb in (religious) elementary school, I was not old enough to be a full-blown atheist, but I still thought to myself:  "Torah loses knowledge in every generation.  Science gains knowledge with every generation.  No matter where they started out, sooner or later science must surpass Torah."