Wondering when life begins. As you do.

IVF fails more often than it succeeds. After a café conversation (following a communications meeting, rather than any really science-y stuff), I found out one of the reasons for this.

It seems it has to do with DNA methylation. For those seven people even more ignorant of science than I am, here’s the rough definition of what that is.

DNA methylation marks are tremendously important during the development of embryos. As an embryo grows, all the cells generated take on a certain cellular identity and eventually become highly specialised cells in adult life. DNA methylation marks are involved in promoting this cellular identity. Some cells generated in the developing embryo will later produce sperm or eggs. These are called primordial germ cells (PGCs). They take their DNA methylation pattern from the tissue from which they arise — the epiblast. This has to be erased so the next generation has a clean slate, ready for making a new embryo.

On the molecular level, this means DNA methylation marks are reset — or ‘reprogrammed’ in PGCs on a global scale. We don’t know about this process yet. But what we do know is that in IVF concepti, the methylation-reset switch often doesn’t work. At (typically) the 16-cell stage, when the reset switch should have worked, it hasn’t. And these little 16-cell bits of potential (and here I’m going to anthropomorphise like crazy, and unapologetically so) get confused. They don’t know what to do, because the Methylation For Dummies guide isn’t working. So they just … stop. It’s unclear whether they die, but they stop dividing, which for reproductive purposes is the same.

This is interesting in itself, but the bioethical implications are fabulous. For a long time, liberal bioethicists have countered the ‘life begins at conception’ argument with the personhood argument. The most elegant exposition I’ve found came from Norman Ford,  a Catholic priest who learned his embryology from Alan Trounson

Basically, Ford argues that foetal personhood can’t exist until the possibility of twinning has vanished. If a conceptus splits in two, which is Twin A, and which Twin B? Or does A disappear, to be replaced by B and C? Which, if any, is the original person?

But the possibility of concepti just stopping gives an interesting view of the beginnings of life, that buggers up the (I think) mistaken view that life begins at fertilisation. We frankly haven’t the vaguest idea how many fertilisations fail to continue at the methylation reset stage. We only know about the IVF ones because they’re being watched in a lab.

It might take some work to establish, but is there a viable argument that life begins at the methylation reset, rather than at the point when the most athletic sperm breaks the tape and claims its gold medal?


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