Did the story of the virgin birth of Jesus have its origin in older religious beliefs, like Buddhism?

A while ago I started chipping away at a blog entry on the claim that the virgin birth of Jesus is just a copy cat tale used by the early Christian church. The idea is that Christians borrowed this fictional element of the life of Christ from countless other myths. The view, although not well attested in scholarly literature, gained some popularity with online sceptics with the release of the sensationalist but error-ridden documentary Zeitgeist. This claim circulates at so-called sceptic websites and forums, rather than in serious scholarly critiques of religious belief. Unfortunately, such online forums are often teeming with a credulous audience who devour conspiracy theories and tales of coverups, with very little actual scepticism. I’ve decided not to write one long blog entry. Every now and then I’ll blog on one of the figures that the virgin birth Jesus was supposedly copied from.

(So please do not waste your time replying by saying “sure, THAT connection might not exist, but what about this OTHER myth that Jesus was copied from?” I’ll do them one at a time.)

Candidate #1: Gotama (Gautama) Buddha