IN Jane Schaberg's commentary on Luke's Gospel, found in The Women's Bible Commentary she says:
In contemporary New Testament scholarship the tendency is to find the virginal conception asserted in Matthew and less clearly (if at all) in Luke. It has been claimed that Luke 1 can be read as not about a virginal conception. Read in and for itself, without the overtones of the Matthean account (so the argument goes) every detail of it can be understood as referring to a child to be conceived in the usual human way. Gabriel appears to Mary who is at that time a virgin and tells her she will conceive a son. Her question in 1:34 stresses that she and Joseph are in the period of betrothal and not having sexual relations. The question gives Gabiel an opening to speak about the character of the child to be born. Gabriel's statement in 1:35 about the Holy Spirit "coming upon" and "overshadowing" Mary is a figurative way of speaking about the child's special relation to God not implying the absence of human paternity (cf Gal 4:29 where Isaac is called "the child who was born according to the Spirit.").
Conception with Joseph as the biological father is an idea not expressly denied in Luke 1 or 2, however,it is denied in 3:23: Jesus is only the "supposed' child of Joseph. The reader who understands Luke 1 to be about a normal conception is thus faced with another alternative, the biological fatherhood of some unnamed person and the illegitimacy of Jesus. It is possible that both evangelists inherited a tradition of the illegitimacy of Jesus and transmitted it very differently. Both evangelists it must be pointed out, stress the Messiahship and holiness of the child (Matt, 1:21, 23; Luke 1:31, 35), in spite of or perhaps because of his origins.
When Luke's account is viewed as preserving and working with a tradition of Jesus' illegitimacy, several of its details fall into place. For example, in the dialogue between Gabriel and Mary, Gabriel's response (1:34) is not an explanation of how the pregnancy is to come about but is a statement of reassurance, urging trust. The verbs "come upon" and "overshadow" promise empowerment and protection (cf. Acts 1:8, Luke 9:34). These verbs have no sexual or creative connotations. Mary's question "How?" is sidestepped and remains unanswered. This scene echoes aspects of the commissioning or call or prophets. But Mary is commissioned to be a mother, not a prophet. Her response is to consent freely to motherhood (1:38). With this expression of her consent in faith Luke creates the positive portrait of Mary as model believer.
Jane Schaberg goes on with a deep and critical commentary on Luke presenting Mary as "a passive character, the antithesis of a liberated woman," from a point of view I can't imagine coming from any but the most astute of male commentators, and I doubt any of those have had such insights into the account. See what I said about why I've come to respect Scripture commentary over just the kind of ignorant reading a novice like me can bring to it. And I came with a predisposition to be open minded on the things I believe and don't believe about it, many readers already have their mind made up before they start. I don't have to find everything that a scholar like Ms. Schaberg says believable but I'm not stupid enough to discount informed commentary on it. I do think that Luke's account can well be read as Mary being more than "just" a mother. From Luke you have to conclude that she was the first to act as a Christian priest, bringing the body and blood of Jesus into the world and as the first preacher of the good news. For me, arguing with opponents of Catholic Women Priests, I've said that in a more profound way than any male priest, Mary, by the very doctrine and tradition of Catholicism, must have been the first Christian priest.
But the idea of an "illegitimacy tradition" concerning Jesus is one I not only find interesting, it's clear there was one from early in the history of Christianity - it is well documented in pagan debunkery of Christianity and it is attributed by them to "the Jews" - and it's certainly one you can imagine the opponents of Jesus probably made hay out of during his lifetime. Having lived in a small town all my life, I know how easy gossip about women and speculation about the "legitimacy" of their children is to create and once told, it spreads far easier than assertions of virtue. I doubt that was not the case in small towns and large around the Mediterranean basin back then.
The only person who could know if Mary was a virgin when Jesus was conceived would be Mary, as the Luke narrative has her saying, she'd never had sex with a man when the angel told her she was pregnant, maybe she did say that. Whether or not she remained a virgin is certainly not revealed anywhere in the Bible I know of, that was a development of later speculation, especially as the Middle Ages wore on and an ever more elaborate cult of the Virgin grew in Catholicism and to an extent Orthodox Christianity. The Mary of the Gospels is hardly to be found in it.
I'm not interested in the virginity of Mary or the possible human father of Jesus - I maintain that the improbability of earliest Christianity getting anything out of telling the story leads me to conclude that it was widely believed by them, and they were closer to it than I'll ever get - but I am interested in how the dubious nature of the story of the Virgin Birth adds depth to the teachings of Jesus and how it adds depth to the entire Jewish tradition of justice.
As I more or less started out during Advent, both the dubiousness and the scandalous salaciousness of the claims of the Virgin Birth narrative in the Matthews Gospel and its implication in the Luke Gospel would have led to a rational decision by the authors of the Gospels leaving it out.
They would certainly have known that a telling of that story would be fertile ground for their opponents to sow the idea that Mary was a tramp who slept around with Roman soldiers (as I pointed out, along with the industry in creating a cult of the Virgin, there was an opposing one creating things like a Roman father of Jesus named Panthera and many other lines of lore). The Roman Empire and Mediterranean culture was saturated in one of the more rigid forms of patriarchal forms of honor concerning the virginity of brides, their monogamous attachment to a husband (though husbands, in many cases could have more than one controlled wife) and the strict legitimacy of children as the offspring of their fathers. That was as true for Jewish culture as it was for pagan cultures, certainly the Greek culture that had so thoroughly influenced first century culture in the Middle East. It is to be noted that even with the radical transformation of the Gospels and the Epistles, that aspect of the paganism that influenced the formations of the various Christian churches was not much less malignant than it was at the time of Jesus' birth. Women thought to be or gossiped about were not treated all that much better, though they weren't as likely to get stoned to death, in many places they were likely to be murdered by their fathers, brothers or husbands. That is true today as, for example, in the United States male jealousy is one of the leading causes of violent death of women in the United States.
They knew they were telling a story that would have to have had to originally been claimed to be true by a young girl who was reportedly pregnant before she should have been, to a man she claimed to have never slept with - he'd certainly have known if that were the case, as it says in Matthew - and with an angel coming to tell her the news to start with. Who would have believed her before her son grew up to be a wonder worker and prophetic preacher? And as soon as he started to become famous, they'd have had all the more reason to bring up those old rumors about him.
I've pointed out that the implausibility of the story would rationally lead to the conclusion that unless the ones writing it down really believed in the Virgin Birth really believed it, it is one of the things they would have left out if they'd heard that claim, as possibly the authors of the Mark and John Gospels discretely did. Though it's possible they'd never heard those claims.
It wouldn't be worth repeating this if it wasn't for something else about the salacious, gossip and snark generating aspects of the story if not believed as told by the young girl who was pregnant when she shouldn't have been. No doubt a lot of people who knew her, who knew her son didn't believe it. No doubt they would be suspicious if the son didn't look like Joseph (would he have if the Virgin Birth were by the action of the Holy Spirit?) No doubt those who didn't know either but heard the story and were too wised-up to believe it for a second would say obviously Mary was a tramp and Jesus was a bastard, not the son of the guy she eventually got to marry her, even though she slept around. Celsus has her getting thrown out by Joseph for being a tramp, though as far as I know he's the only one who said that.
If Jesus couldn't have been born any lower than to have parents of the lowest economic, social and political class, born on a trip to a strange city, in what we come to think of as a barn where animals are kept - as I like to remind everyone with their manure and urine soaking any bedding that might, or might not have been there for them, flies, insects, rats, mice, put to sleep in their feed trough (seldom the most hygienic of places in even a well kept barn) put on top of that the story makes him and his mother the topic of gossip, the target of mockery and slander, certainly lower than the poorest women and children who at least had no sexual scandal and illegitimacy attached to them, in later mockery, him the son of a detested foreigner, an occupying Roman soldier of probably not much more respectable circumstances in his own milieu. Jesus would have grown up among children and adults who would not only have looked askance at his mother and him but likely would have said it, what she was suspected of a crime that might have gotten her stoned to death, maybe the reason Joseph married her - they wouldn't have found his dream revelation in Matthew much more convincing than Mary's story in Luke. Some of them might have respected Joseph as a stand-up guy, or desperate for any wife, even one who was going to present him with a Roman soldier's bastard to raise, but most of them would have seen him along the same lines as Bontsche Schweig in Isaac Loeb Peretz's rather cynical telling of the story.
Of course none of that is elaborated in the Gospels and it isn't a point I recall any early commentators pointing out. When Jesus says in that great passage in Matthew 25 that what you do for and do not do for the least among you, you do for God, he could very well have a really good idea of how least the least among us can be because it's not unlikely that even in the milieu of the lowest of the low, he may well have been lowered by the denial of the one and only thing that so many of the lowest will guard jealously, the respectability of their very person and, even more so, that of their mother.