But after a fashion, much of archaeology and the anthropology based on it is speculation. We can come up with well documented cases for civilizations with a lot of surviving records. Egypt left a lot of stuff buried where wave upon wave of believers with hammers and matches didn't have access to it, so we discover they had a lot of gods, and even have information about what many of them were about. Other cultures which didn't have as many, or as durable records, we end up having to use records of other competing civilizations about, and get only the propaganda left over from the "winners" who survived, which are a touch biased.
For instance, just read up in the bible about the city states that were destroyed by God's holy rollers. Heathens and sinners and idolators to the last, and all killed for God's divine judgment, plan, chosen people, etc.
So, yes, the fish could be unrelated, and yes, the fish could be related. The evidence for womb/fish being 'the same word' (Delphos) in Greek (and Christianity has a lot of Greek influence), the presence of Greek gods and demigods predating the savior on a stick which have more or less the same story as him, the use of fish symbols in Roman pagan artifacts, and heavily used in Egyptian religion (which influenced the Greeks when they conquered Egypt 300 years before 'God Jr.') all of that (admittedly circumstantial) evidence could be totally unrelated to the 'fish' being adopted by Christians. Of course, all we have is "No it's not! How dare you even imply it?" as evidence from the Christians that the fish was
uniquely and 'divinely' inspired to them.
Anyway, all
comparisons between Christianity's symbols and other cults that used them provokes outrage, and really, provoking that sort of
mindless outrage from an innocent little hypothesis is worth backing it up a little research to produce more comparisons, and it's unfortunate that so many sites don't cite where they did any of theirs, and yet more is in copyrighted/printed materials that are as yet still awkward or impossible to access on the internet.
It doesn't really matter
where the fish they tacked on their car came from. (A plastic mold in a factory, actually.) It only matters that it is such fun mentioning it to them and comparing them.
Here are a few of the sites I visited with background info.
(Cool fishy amulet for Hathor)
http://www.duke.edu/~jls26/egypt.html
(The Greek Pantheon)
http://www.theoi.com/Pantheon.htm
(An interesting article about surviving documents)
http://scriptorium.lib.duke.edu/papyrus/texts/rule.html
(Alexander the great - on a free encyclopedia)
http://www.wikipedia.org/wiki/Alexander_the_Great
(The holy database of all known gods! But apparently, their (beta) search engine is broken....)
http://www.godchecker.com/database/all_egyptian_gods.html
and were choked in the sea.