Carrier’s cosmic sperm bank hypothesis to deal with Paul’s claim that Jesus was made from the sperm of David, usually just meaning that he came from David’s bloodline (the old testament talks about God forming people in the womb).  How would Paul’s readers have been able to understand Paul’s claim in a mythicist way?  Carrier tries to resolve the difficulty by saying there is a vaguely similar case of preserved sperm in Zoroastrianism.

Interestingly, Price does something very similar.  Regarding Jesus’ baptism, Price writes:

• The scene in broad outline may derive from Zoroastrian traditions of the inauguration of Zoroaster’s ministry. Son of a Vedic priest, Zoroaster immerses himself in the river for purification, and as he comes up from the water, the archangel Vohu Mana appears to him, proffering a cup and commissions him to bear the tidings of the one God Ahura Mazda, whereupon the evil one Ahriman tempts him to abandon this call. (Price, New Testament Narrative As Old Testament Midrash)

To which Ehrman responds:

• Zoroastrianism?  Vohu Manu?  Ahura Mazda?  These were the influences that determined how the story of Jesus’s baptism were told?  … Even if it is not historical, the story of Jesus’s baptism must go back to the very earliest Christian communities in Aramaic speaking Palestine.  How many Aramaic speaking Palestine Jews were influenced by accounts of Zoroaster’s initiation in the presence of the archangel Vohu Mana (Ehrman, Did Jesus Exist, 203-204) 

And we see this method problem again and again from Carrier.  He explains the James the brother of the lord passage in Paul by saying James was not a real brother but a non-apostle baptized Christian.  But, Ehrman points out in 1 Cor 9:5 Paul seems to be saying Jesus’s brothers took their wives on their missionary trips.  Similarly, Carrier has a complicated figurative explanation of Paul saying Jesus was “born of a woman,” which may be right, but also carries the straightforward sense of human, such as when the gospels say John the Baptist was born of a woman.