To assume that this informs us at all about non-human designers does not even remotely follow, however. Sure, we can spot things that humans have designed reasonably reliably, but we also have lots of experience with human-designed things. It's not some innate ability we have, spotting man-made things - it's a learned skill, gained by experience with man-made artifacts, and subsequently drawing inferences based on that experience.
That being said, where's your baseline for non-human designers? Where's your collection of known products of non-human designers, from which you can draw inferences about unknown artifacts? Hate to say it, but the answer is: you don't have one, and hence it's of a wholly different nature than spotting signs of human designers.
True. This leaves open the very real possibility that any "designer" tests I define in terms of known processes may be doomed to fail.
OTOH, the means by which a particular physical process can be harnessed are probably fairly constrained. It certainly seems reasonable to base scientific tests on the assumption that there will be commonality. If that assumption turns out to be incorrect, then gosh, I guess my tests didn't support the hypothesis: which is exactly how it's supposed to go.
What would be bad science would be to simply assume we couldn't recognize non-human design, and not try to test it at all.
That being said, where's your baseline for non-human designers? Where's your collection of known products of non-human designers, from which you can draw inferences about unknown artifacts? Hate to say it, but the answer is: you don't have one, and hence it's of a wholly different nature than spotting signs of human designers.
Actually, we do have a collection of known products of non-human designers. For example, it's known that crows and other animals invent and use tools. True, they're not terribly sophisticated tools. If we take sticks as an example, we find that animals use them in the exactly same way you or I use sticks as tools. The point being, the evidence points (weakly) to there being a likelihood of commonality in human and non-human design.