As we approach the end of Sotah, we turn our attention to a new topic: theories of embryonic development, and compare talmudic views with those of modern science. Here is what today's page of Talmud - daf yomi - has to say on the topic:
סוטה מה, ב
מהיכן הולד נוצר מראשו וכן הוא אומר ממעי אמי אתה גוזי ואומר גזי נזרך והשליכי וגו' אבא שאול אומר מטיבורו ומשלח שרשו אילך ואילך
From where is the fetus formed? From its head, as the verse says (Ps.71:6): "From my mother's womb you pulled me out (gozi)". And it says later (Jeremian 7:29) "Pull out (gozi) your hair and throw it away.." [This second verse shows that the verb goz is used to describe the head. So the verse from Psalms must also refer to the head. According to Rashi the verse in Psalms should be read as "You formed me from my head."] Abba Shaul says that the fetus is created from its navel, and from there it sends out roots in all directions. (Sotah 45b)
Embryonic Development in Antiquity
In 1934, Joseph Needham, a British historian and embryologist, published A History of Embryology, in which he traced the history of how the embryo was thought to develop from antiquity to modern times. In this fascinating book we learn that Hippocrates (c. 460-370 BCE) believed that the fetus was formed by extracting breath from its mother, and that a series of small fires within the uterus gave rise to the bones and other organs of the embryo. Aristotle (384-322 BCE) added some details about the role of the umbilical cord. According to Needham, Aristotle understood that the role of the umbilicus was to nourish the fetus: The vessels of the umbilicus join onto the uterus like the root of a plant and through the cord the fetus receives its nourishment. Elsewhere, Aristotle claims that head of the fetus forms first. Galen (c. 129-216 CE) also used the analogy of the umbilicus serving like the root of a plant. According to Galen, the embryo grew from menstrual blood, and then from the blood that nourished it through the umbilical cord.
What Actually Happens
At its earliest stage the embryo consists of a sheet of cells, an amniotic cavity and a yolk sac. The sheet of cells develops a head (cranial) and bottom (caudal) end, and grows around most of the yolk sac. This enclosed yolk sac then grows into the gut of the embryo. The part of the yolk sac that is not surrounded by the embryo is still connected to it by a thin tube called the vitelline duct. This duct then fuses with the contained yolk sac, and forms a larger bundle of vessels we call the umbilical cord. This occurs between the 4th-8th week of gestation (calculated from the first day of the last menstrual cycle).
It is clear then, that embryo does not grow from the head or from umbilical cord. As you can see from the diagram, the fetus do not grow from the head. In fact the head develops from the early cells of the embryo as it takes on a cranial-caudal polarity, sometime around 3-4 weeks gestation, when the embryo is about 3mm in length. Neither does the embryo grow from the umbilical cord, as Abba Shaul claimed. In fact it is the umbilical cord that grows out from the early embryo, and not the other way around. (For more on talmudic embryology, see Samuel Kottek's 1981 paper Embryology in Talmudic and Midrashic Literature.)
As we will see in more detail in the winter of 2019, talmudic embryology reflected the prevailing Greek theories of the times. But those theories developed without the benefit of microscopes and the other tools later available to scientists. It was perfectly reasonable to claim that the embryo grew from its head, since even in antiquity the importance of the head for life was clear. No less unreasonable was the view that the embryo grew from the umbilical cord, for that cord does in fact sustain the embryo as it grows and matures inside the womb. But two wrong but reasonable theories does not make one correct one. Sometimes however, the rabbis of the Talmud were spot on with their embryology. For example, here is Rav Simlai (3rd century CE, and the rabbi who brought you the famous count of 613 commandments) describing how the fetus sits within the womb. Compare his words below with the famous sketch of Leonardo Da Vinci.Then answer this question: How did he know?