If you were new to earth, and you were discovering animals for the first time, would you look at a Chihuahua and a Saint Bernard and think to yourself, those are the same animal? We turned dogs into chihuahua's and Saint Bernards in 200 years of selective breeding. If it were to continue, what...
From what I can tell, no god's have been come into existence on Earth yet, so by your logic, it would still be unreasonable to believe that a god would have come into existence somewhere else.