Wow, yet another amateur article.
I already gave the Carrier essay on virgin birth which gives numerous examples as well as motivation. But even if it was actually invented in the gospels, so what? Do you think every invention in all mythologies is real? Do you realize that every concept in Lord of the Rings and all other fiction is made up? People can make stuff up? For a myth to be influenced by another myth it does not have to be identical.
Was West Side Story identical to Romeo and Juliet?
"This is, of course, false. Ra is born of a virgin mother, was not conceived sexually, and predates Christian mythology (by a lot). Perseus, too, is born of a virgin mother, was not conceived any more sexually than Jesus was (both Perseus and Jesus involve magical fluids impregnating their respective mothers), and also long predates Christian tradition (and was even acknowledged by early Christians themselves as doing so). Hephaestus was also in popular conception born of a virgin (albeit a magically reinstated virginity), was not conceived by any material means at all, and again in a tradition well antedating Christianity."
as to motivations:
"So the notion that the virgin birth was not a lift from paganism is highly improbable. The idea is obviously a Jewish adaptation of a popular motif in surrounding cultures. There is no other credible explanation for why it ever became important to claim such a thing of Jesus. Just as “our God must be able to do things your God can” led to syncretistic innovation within Judaism (whereby, for example, the Jews suddenly “discovered” their God would resurrect them, at oddly the very same time they learned the Zoroastrian God would), so “our godman must be as awesome as your godmen” had the same effect. Thus, Jesus couldn’t be sexually conceived, because that was gross, and yet he had to be a pre-existent being inserted into a woman’s womb to reify prophecy. A conundrum. But as soon as Jews saw how the pagans solved this problem for their godmen, they would obviously have stolen the very same solution. This is how all ideas and technologies proliferate from one culture to another. “Well if pagan gods can directly create fetuses just with their divine
pneuma, then so can ours, damnit!”"