Reading about ancient mythology, there is a lot of information based on some inscriptions. For example, there was a deity Inanna in the Sumer. As I understand, the contents of those inscriptions can be deciphered only by looking at particular words and the context they are used. How then it's possible to know how they pronounced those words?
There is also a God of heaven, named An. Is it just an agreement between researchers to assume that it was 'heaven', and not 'air' or 'sky' for example?
It seems to me that when people try to explore old religions, they are very much influenced in current religions, and in such cases, when it's not obvious what the word stands for, they take it from other religions with similar contexts, which might explain why all religions have similar aspects. If we assume that civilization was developed in many places, independently, it's strange that they have so many similar aspects.
There is another similarity which I cannot find a good explanation. I believe there really was a flood, and having no scientific knowledge, people tried to make sense of that unnatural phenomena by creating myths. What strikes me is the similarity of those myths.
In Genesis God informs Noah for the coming flood (and in some other religions, probably they are derived from one another), in China (if I remember correctly, it was from ancient eastern civilizations) a king saved a fish, then fish informed about the incoming flood to him. In another myth from another region, a king is informed about the flood from the gods, and escapes to the mountains, alone, and then starts new civilizations.
There are some 'theories' none of which seems convincing. There could be a moving society, so myths were spreading that way. Or civilizations weren't independent, although it's not clear why they would borrow myths from each other.
Or maybe all those myths are exactly the same, and they differ because the translation of them was inaccurate?