Many underestimate the abilities of ancient man, throughout human history man has been capable of remarkable accomplishments.A better question would be how did we make the huge mental leap forward all of the sudden? And why haven't any other animals gotten smart?This fails as an appeal to ignorance fallacy.Again why we're the Egyptian's building pyramids around the same time the Aztecs were?
They were separated by oceans
And why did they abandoned the practice?
That you don't know why the Egyptians were building pyramids around the same time as the Aztecs doesn't mean the 'answer' is 'god.'
Then it turns out dolphins may in some ways be smarter than us and dogs are getting smarter living along side us. Who knows in 1000 years dogs might talk. If that happens they'll say its a miracle but its actually science.