The problem I have with using the creation of Adam and Eve is that Adam was not born in the story, so it really doesn’t hold water in my opinion. For example, Adam was created, presumably from the earth, so it wasn’t that Adam’s body was needed to be formed but that Adam’s body didn’t exist (one can’t be human without a body).
I don’t think that is the case with infants. Although a zygote or embryo etc. aren’t entirely formed (in the physical appearance of a human) it is entirely formed in the substance of another human in that a zygote should only be developed to the level of a zygote, an embryo as an embryo etc. For example, when an infant is born, they are born with a brain, but the neural connections in their brain still do not exist (it is the function of the brain to develop the connections). So in the same way it is the early cells of a zygote or an embryo’s function to continue to develop into the rest of the body. Although it physically may not look like it has a fully formed body, it does in that it is fully formed to the level it should be formed, and it is performing the function that it should in its level of prenatal development.
The only problem with my own theory is that by appearance I am wrong, as typically we think of a human as a human being with arms and legs etc. But that brings up another question, If one bases the human substance or identity on functionality and appearance, what about those who are born not functional in some way. For example, if a child were born without a fully developed digestive or reproductive system, and then they are fully human without the typical appearance or functionality. So the only way to rationalize these cases would be that its human life (spiritually) either begins after a particular function or after consciousness, but then another question arises when an infant is born unconscious.
Of course, then one must consider evolution. If a human species, in Adam and Eve, developed from a different species and at one point they became a new species of their own, they had the DNA of the new species and the capability to develop into the new species at conception. So then they were an animal in the womb until after birth when they became human, in that the human species must have a soul. Of course, to accept that one has to accept my first premise.
I am thinking as I write this, so I am sure I will read it later and find flaws, so everyone feel free to correct anything.