When do we Truly Twin?

Many use twinning as an argument that life does not begin at conception/fertilitzation/gamete fusion.

Although what we do know of the inner workings of cells is tantalizing and beautiful, cells are still black boxes. The single-celled human zygote is the blackest (and most interesting) of these boxes. We have known for decades that there is early asymmetry in the zygote that later shows up in the division of the inner cell mass (ICM) and the trophectoderm.

We also know that intracellular components are moving as soon as sperm affects egg (cortical reaction, pronuclear migration events, etc). There is a great deal of mechanical action taking place, by which this tiny organism's body is quickly building infrastructure by which it will direct the rest of its development. Such organized activity promoting the development of a single organism is directed, like all operations of a living body, by a soul. This indicates (for those who don't realize this), that ensoulment occurs "at conception" (in non-scientific language), during fertilization, or at/around sperm-egg fusion.

But what about twinning? Complete twinning cracks a complex, tiny body into two between days 0 and 13 of life. Depending on when the cleavage occurs, the twins share zero, one or more tissues.

Twinning is a natural and normal process. We can tell this because a) it occurs frequently, and b) there is a falling-short of it--conjoined twinning.

What causes twinning? I propose that infusion of two souls occurs at conception/fertilization/sperm-egg fusion. These two organizing principles begin directing development of a single zygotic body. There are too many cooks in the kitchen, leading to an unstable union, perhaps because the processes directed by the two new souls don't place adherent components (e.g. desmosomes) where single souls would. This results in fracturing of the conjoined body (a process disrupted by some defect in the material in the case of conjoined twins).

Technology probably won't allow to see the difference between the intercellular workings of single-soul-driven and multiple-soul-driven zygotes for many years. Nevertheless, we can observe the end effect (what appeared to be a single body breaking in two parts and surviving, forming two complete sets of parts) and work back to the presence of two directing principles working from the outset on their completely totipotent cell.