Why would you rule out a manufactured item (a r...

Why would you rule out a manufactured item (a remnant of an ancient civilization)?

Why would you rule out the mummified (freeze-dried) remains of a creature that once lived, but is now dead?

You have taken the stance that if it doesn't walk... it must be a... rock... or wait, not even a rock, an optical illusion of a rock formation? Why are these the only options you consider, Sarl?