First of all: One very viable option in science is to say that we don't know. If we don't know, we simply don't know, there is no point in making stuff up. That

First of all: One very viable option in science is to say that we don't know. If we don't know, we simply don't know, there is no point in making stuff up. That does not mean that people might not form hypotheses as a first step to eliminating that lack of knowledge, but as long as we don't have some serious evidence, it's just a hypothesis, not a claim of knowledge, and we continue to simply not know, even if we might be speculating wildly as to what the explanation might be, and in some cases it might be that we never will know, and that is perfectly fine. In this context you should also note that simply positing an intelligent designer does not actually gain you anything. Explanations can be recognized by their ability to predict future observations. Positing an intelligent designer does not allow you to make any predictions whatsoever. There is nothing necessarily fundamentally wrong with positing an intelligent designer - it's just not an explanation - so, if you want to have an explanation, you are still on square one. You essentially just have given the thing you lack knowledge about a name, namely "intelligent designer", but you haven't gained any knowledge about it. As for your sand castle example: Well, I don't really have a clue how a geologist or an archeologist would go about that, but presumably one could try and determine the structure of the castle, such as the form of the grains, and how they stick together, and find other instances of similar structure to try and figure out what kinds of processes might be able to form such a structure? But as always: When in doubt, we simply don't know. Also, I smell the Boeing from the junkyard argument for creationism. In case I am right there, you urgently should educate yourself about what natural selection is and in particular how natural selection is not random, and how evolution without natural selection would not work.