Now why is it people are assuming that humans made them?
Because there is no other known process by which that a structure like that can occur. As soon as there is evidence suggesting otherwise, they will investigate that.
Why aren't scientists coming up with theories on how natural processes made it?
Because in all of history and observation, there is nothing to indicate that is likely or has ever happened.
A bunch of earthquakes and things could have caused the stones to get carved up, and then landshift and earthquakes cause them to get filled up and buried, etc.
Very true. It also could have been caused by your sister that you might not have even know you had traveling back in time in a TARDIS just to mess with you. But, since there is zero evidence that either of those things can, does or has ever happened, there is no investigation into it.
Anyway, how life first began, that is life on this planet, looking into intelligent life vs random as part of all possibilities then your claim that then one must look at a rhino made of pigs is a ridiculous comparison. One would consider the possiblity where any sort of intelligent life is responsible for life on this planet, whether biological alien scientists, God, a rhino of pigs, etc.
Well, first of all, it's not "random". Secondly, since there is no evidence of intelligent life outside of humans, one cannot assume what form it would take. You simply don't know. Therefore, if you claim that, to be scientific, one must look at ALL possibilities, that must be included. For all you know, God is a rhino made of pigs and that is what spirit is made of, pigs. All means all.
Anyway the scientific process doesn't mean that all hypothesis that life originates on this planet and by random chance and that is the only possibility that is considered and investigated.
No one said it did. You clearly didn't understand what you said, my response or the implications of either.
If that is what you believe then your as close minded as you were when you were a JW.
I don't believe it. Only and idiot would and only someone who doesn't understand the scientific method or basic logic would derive that from what I said.
The basic problem with "all" is that first, it's a logical impossibility. Even if you want to include only broad topics as "all", you can't ever know if there is something you don't know, therefore you can't say you've investigated "all", ever. Period. Full stop. Do not pass go.
Secondly, there are some topics that are outside investigative possibilities. You say "god may have done it and we should investigate", but there is no way to do that. God is invisible, made of undetectable stuff that no one can describe, able to perfectly hide from detection and, according to Christian scripture, will cause death just by even looking at him. It's a perfectly un-investigatable explanation. There is no way to move forward. There is no evidence that ANYTHING was every cause by an invisible undetectable intelligence made of unknown stuff.
Why should anyone investigate that?