Those things do show an intergenerational evolution of complex techniques, though, if only by trial and error. Certainly at some level they must have understood the tumor to be the cause of a malady, for instance. Even now we know of drugs whose biological pathways are poorly understood. Scientific understanding often follows rather than precedes the discovery of a technique. Which is fine! Someone, somewhere, makes a discovery or an incremental improvement to a technique that works in practice. Eventually someone else comes along and tries to reason about how that works. Both add to the body of knowledge. I dsiagree that something can only be characterized as "advanced" if it is fully understood. Advancements also build upon practical knowledge.

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