The first part of this question may be most directly approached by a brief consideration of the text of
Mt 1:16. The text upon which the Revised Version (British and American) is based reads: "And Jacob begat Joseph the husband of Mary, of whom was born Jesus, who is called Christ." Beside this there are two readings, one contained in the so-called Ferrar group of manuscripts, and the other in the Sinaitic which, differing among themselves, unite in ascribing the parentage of Jesus to Joseph. This has been seized upon by negative critics (see for list and discussion Machen, Princeton Review, January, 1906, 63; compare Bacon, HDB, article "Genealogy of Jesus Christ," Am. Jour. Theol., January, 1911, who long ago gave in his advocacy to the supposition that the evangelists could easily reconcile the supernatural birth with the actual paternity of Joseph) to support the idea of a primitive Christian tradition that Joseph was the father of Jesus. Of this contention Zahn leaves nothing, and concludes his argument with this statement: "The hope of finding indications in old manuscripts and versions that the authors of lost Gospels or brief writings which may have been worked over in our Mt and Lu regarded Joseph as the physical father of Jesus, should at last be dismissed. An author who knew how to make even the dry material of a genealogy to its least detail contribute to the purpose of his thought concerning the slandered miracle of the Messiah's birth, cannot at the same time have taken over statements from a genealogy of Joseph or Jesus used by him which directly contradicted his conception of this fact. Any text of Mt which contained such statements would be condemned in advance as one altered against the author's interest" (op. cit., 567). It is interesting to note that Allen (ICC, "Matthew," 8), starting from the extreme position that the Sinaitic form of statement, of all extant texts, most nearly represents the original, reaches the same conclusion as Zahn, that Matthew's Gospel from the beginning taught the virgin birth.