Yeah, that's more of a heuristic for determining the health of an infant. An algorithmic approach would give you a definite yes-or-no for all baby inputs.

And the analogy breaks down here because the online ecosystem adapts very fast. It would work if there was some sort of gene that led to premature births plus high Apgar scores (the equivalent of a malicious website that ranks well).

That's why search is so tough: search engines and gaming have coevolved to the point that in plenty of areas, search quality would go down if people weren't trying to game the algorithm.