From about 80 CE, Christianity has taught that Jesus was conceived by his mother, Mary, when she was still a virgin. This was believed to have happened through the power of the Holy Spirit, without an act of sexual intercourse. This phenomenon is known as the "virgin birth", although "virgin conception" would be more accurate.
This is the way it was supposed to have happened... At the critical moment of conception, when "God the Son" entered Mary's unfertilized egg, the Holy Spirit prevented Mary from passing on to the fetus her sin nature. The process of conception, pregnancy and birth manifested a sacred and sanctified mystery.
It is precisely because of the virgin conception that Jesus was born without the stain of original sin. Jesus could not sin because it was not in his genes.
Catholics have also taught the doctrine of "perpectual virginity", meaning that Mary lived, gave birth to Jesus, and died a virgin. They have also taught that Mary also without original sin -- the doctrine of the "Immaculate Conception". In 1854, Pope Pious IX pronounced and defined that Mary "in the first instance of her conception, by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved exempt from all stain of original sin."
The virgin conception story is found in the Gospel of Matthew... "Behold, a Virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel." (Matthew 1:23)
The was apparently foretold by the prophet Isaiah, according to the Septuagint (the first translation of the Hebrew Scriptures into Greek).
Isaiah 7:14 reads "Therefore the Lord himself shall give you a sign; Behold, a Virgin shall conceive, and bear a son, and shall call his name Immanuel."
The problem is that the verse was mistranslated into the Greek.
The verse in the original Hebrew reads... "Hinneh ha-almah harah ve-yeldeth ben ve-karath shem-o immanuel".
The Hebrew words ha-almah mean simply the "young woman"; and harah is the Hebrew past or perfect tense, "conceived", which in Hebrew, as in English, represents past and completed action. Were the verse to have been properly translated, it would read... "Behold, the young woman has conceived (... in other words, is with child) and beareth a son and calleth his name Immanuel."
Almah means simply a young woman of marriageable age, whether married or not, or a virgin or not. The word "virgin" in Hebrew is always expressed by the word bethulah. But in the Septuagint translation into Greek, the Hebrew almah was mistakenly rendered into the Greek parthenos, which means virgin.
So what does all of this mean? Well, IF the story of the virgin conception is a fantasy, THEN one could quickly move to assume that Mary had a normal human conception (and birth). THEN, one would have to assume that Joseph or someone else was the father of Jesus. THEN, one would have to assume that Jesus did inherit original sin. THEN, one would start to question Jesus' divinity (since he could sin like anyone else). Of course, original sin is a "doctrine" of the Church, not a fact...
This is the problem with poor or inaccurate translations of the Bible... they lead to the creation of stories, dogmas, and doctrines that become so ingrained in the belief systems of Christians over hundreds of years that we lose sight of the inherent instability of the basis of these beliefs.
It seems like so many core Christian beliefs have been built like a house of cards... pull one card out and the whole thing comes tumbling down. That is why so many give little importance to the acurracy of the translations, and dismiss it as irrelevant since the Bible is the "Word of God" and therefore we must have faith that it is perfect, consistent, inerrant.
Faith is not based on logic. I accept that. I also accept that one sometimes has to be flexible (as well as creative) with regard to the process of scriptural interpretation. However, the stories on which our faith and interpretations are based should at least be based on correct translations. That's surely not too much to ask.