Immaculate Fertilization?

I believe the virgin birth stories in Matthew and Luke are intended to demonstrate the special character of Jesus. I do not believe that God provided the sperm that fertilized the egg in Mary’s womb. I have often heard that when Matthew writes, “All this took place to fulfill what the Lord had said through the prophet: The virgin will conceive and give birth to a son, and they will call him Immanuel (which means “God with us”),” he mistranslates the word ‘alma’ from Isaiah 7:14 because he used the Greek Septuagint as his source. According to someone on the internet, that is ridiculous because the Septuagint available to Matthew only included the Torah. The Septuagint we talk about today has the whole Hebrew Testament, but it was written by Christians much later. Also, I’ve read other places that alma refers to an unmarried young woman–which frankly, in ancient civilization seems to me to be pretty synonymous with physical virgin given how young people married. So, I don’t know.

Anyway, from Plutarch’s biography of Numa Pompilius we have Numa’s response to those who would want him to be king. He says, “Yet Romulus had the advantage to be thought divinely born and miraculously preserved and nurtured. My birth was mortal; I was reared and instructed by men that are known to you.” At some point I’ll start thinking about Numa, but note that Romulus was “divinely” born. For me, the fact that another first century biographer notes that a tremendously important, foundational figure is divinely born bolsters my notion that Luke and Matthew were making it clear to the readers that Jesus was every bit as much an ordained leader of the world as these Romans. I’m not sure what the claim means to those who believe that God literally impregnated Mary.

Is it impolite to suggest God provided sperm to fertilize the egg in Mary’s womb? First, I don’t see why that would be the case. If you believe in literal virgin birth then at some point Jesus has to have human physiology, and it seems conception would be a natural place for that to take place. Second, if you think that is impolite, consider this: Could a human man fertilize an egg to grow in God’s womb? Plutarch didn’t address the conception part of this question, but seemed to think it is ridiculous to think gods could only have sex with mortal women:

And this in particular gave occasion to the story about the goddess, namely, that Numa did not retire from human society out of any melancholy or disorder of mind, but because he had tasted the joys of more elevated intercourse, and, admitted to celestial wedlock in the love and converse of the goddess Egeria, had attained to blessedness, and to a divine wisdom. . . . Though, indeed, the wise Egyptians do not plausibly make the distinction, that it may be possible for a divine spirit so to apply itself to the nature of a woman, as to imbreed in her the first beginnings of generation, while on the other side they conclude it impossible for the male kind to have any intercourse or mixture by the body with any divinity, not considering, however, that what takes place on the one side must also take place on the other; intermixture, by force of terms, is reciprocal.

Hence, the question: Is immaculate fertilization possible?