- This argument for why the human individual doesn’t come into being at conception is interesting because it doesn’t depend on modal1 arguments from twinning2, though twinning is mentioned.
- There’s considerable overlap between this paper and Chapter 5 “In the Beginning: What's going on in there?” of "Kazez (Jean) - The Philosophical Parent: Asking the Hard Questions About Having and Raising Children". Indeed, this paper is how I discovered that book.
- Kazez begins by admitting that she first encountered the argument that our lives couldn’t have begun at conception in "Ford (Norman) - When Did I Begin: Conception of the Human Individual in History, Philosophy and Science", a surprising source because the author is a Jesuit3. Ford’s view is that none of us existed as a single-celled zygote4 “and onwards”.
- Given our current scientific understanding, we should now realise that conception is an impossibly early onset for our lives, and so we can avoid all the hand-wringing consequent on the disposal of IVF left-overs. If the superfluous embryos5 are not “future people” then their disposal should cause us no more concern than that of the left-over sperm and eggs.
- The argument is that in the first few days there’s no unified individual. The rapidly-multiplying cells are like “marbles in a bag (the zona pellucida)”. Because the cells don’t yet work together, they aren’t part of a multi-cellular organism. We’re referred to "Smith (Barry) & Brogaard (Berit) - Sixteen Days", which points out that at that stage there’s no defence against cells simply being removed.
- It seems the “marbles in a bag” model is a bit too simplistic – there is some unity, but not enough. The morula “has the spatial unity of a flock of birds, not the functional unity of an organism”. Each of the cells in the morula is equally “special” in that it can result in a separate individual.
- What about later on? Up to day 5, the conceptus – now a blastocyst – is constrained in size by the zona pellucida, so cell multiplication leads to smaller and smaller cells. There is differentiation into the 100-celled trophoblast and the 12-celled embryoblast6. But on day 5 the blastocyst hatches and immediately starts growing, with the trophoblast becoming the placenta, amniotic sac and other support structures and the embryoblast7 becomes the fetal body. On day 6, implantation occurs.
- Because only 15% the blastocyst will develop into the fetus8, Kazez doesn’t think you can trace yourself back that far. But, what about the embryoblast9? Not that either, as it’s incompletely differentiated and not all of it will develop into the fetus10. But, is it possible that we once had a placenta and amniotic sac as proper parts, which were subsequently shed like dead skin? Not common sense, but possible?
- We can be traced back to the fetal part of the 14-day-old embryo11, when the primitive streak develops and differentiation into fetus12 and support structures is complete.
- So, there are two coherent stories to tell:-
But, there is no coherent story for saying we began to exist before day 4.
- We began around day 5 with support structures as temporary parts, which were subsequently lost.
- We began around day 14 as an implanted embryo13, and never had support structures as parts.
- Some argue that our lives began much later14, but even if we grant an earlier start – but not one before day 4 – most of the IVF worries disappear.
Footnote 3: Footnote 14:
- There’s a quotation from David Copperfield where it is assumed that our lives begin at birth.
- Kazez does not reference the work of Elselijn Kingma who considers that we were once a proper part of our mothers. See also "Finn (Suki) - Bun or bump?".
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2018