An attempt was made, in Matthew 1:22–23, to justify the virgin birth story by referring to Isaiah 7:14 where is written:

Behold a virgin shall conceive and bear a son, and they shall call his name Immanuel.

Though Matthew interprets this as a messianic prophecy it is not—it is part of a warning Isaiah is giving regarding events of that time—and indeed it is absurd even in the gospel because Matthew’s angel has just directed Joseph to call the child “Jesus”, not “Immanuel!” Nevertheless, Matthew’s reading of it as a messianic prophecy is the sort of thing that Essene pesharists did. Matthew even uses the pesharist’s formula, “which being interpreted is”. In their books of commentaries, Essenes would take parts of the scriptures and reinterpret them in ways that suited them. That Christians freely did the same indicates their common roots—and they still happily call Jesus “Immanuel” though that was never his name.

The word translated “virgin” employed in the Greek version of the Jewish scriptures was “parthenos”, but a reference to the original Hebrew yields the word “almah”. Both “parthenos” and “almah” did not necessarily mean a virgin as we understand it, a woman who had never had intercourse. In Greek, it could mean youth, the state of unmarriage, or even a person who is first married. In Hebrew, it could mean, beside the usual meaning, an immature girl who could not conceive because she had not yet started to menstruate. The Hebrew word for “virgin” is “bethulah” and would surely have been used in Isaiah if “virgin” was the meaning the author intended.

Young girls were betrothed to their future husbands until they could legally marry at the age of twelve and a half—menstruation usually started later. A married virgin could therefore conceive—in Joel 1:8 a virgin’s husband is mentioned. Mary was described as betrothed to Joseph implying that she was a minor under the age of twelve and a half—Joseph might have broken the law by having sex with a minor, and pretended he was surprised at the outcome to protect himself. Matthew 1:25 is at pains to refute any such thought by stating that Joseph “knew her not” till she brought forth her first born son—the euphemism “knowing her” meaning having sex with her. In any event, the virgin Mary could have given birth with no miracle involved.

The idea of a virgin as a premenstrual girl allows her to have children and still be a virgin. If she were to conceive from her very first ovulation, she would not have menstruated but would be a mother and still a virgin. If she conceived at the first ovulation after the birth, she could be a virgin mother of two children of different ages. Since Jewish girls often married before menstruation, “virgin” mothers were not unusual, explaining the case in Joel 1:8. Mary was a minor who could become Joseph’s wife when she reached the age of twelve and a half. Thus the “virgin” Mary could have given birth.

If she did, the truth was misunderstood in the gentile world of the Roman Empire, and indeed beyond, where it was de rigeur not only for gods but also great men to be born of virgins. Ra, Hatshepsut, Amenophis III, Cyrus the Great, Julius Caesar, Pythagoras, Alexander, Augustus and others, were thought to have been born miraculously. Plato was born of Paretonia, begotten of Apollo, not Ariston, his father, according to one authority. Perseus, Apollonius of Tyana, Fu-Hsi, Lao Kium, Zoroaster and Attis all came of virgin mothers according to their believers.