There’s a questionable notion floating around out there in the numerous discussions over heritable human genetic modification.
This idea goes that if germline human gene editing goes awry for any number of reasons, scientists could simply reverse it by applying genetics again.
The reversal notion does not fit with the reality of science as we know them today and could be harmful in giving false reassurance of the safety of genome modification.
To put it another way, you can’t retract a designer baby or its genetic modifications if they are later proven to be problematic.
If human modification were done in the germline (sperm and eggs or in a 1-cell embryo), then for better or worse every one, barring chimerism, of the trillions of cells of the resulting genetically modified (GM) baby would have that genetic modification. How would you effectively reverse an unexpectedly deleterious hard-wired change in all of those cells? The reality is that it would be impossible. Trying to do so would also raise the very real possibility of introducing yet more problems as well.
If the reversibility notion of human genetic modification is meant instead in a broader population sense such that within the larger human population that accidentally harmful genetic changes could be reversed or at least their transmission stopped, what would that entail? Forcing people who carry such unexpectedly “bad” genetic changes not to reproduce? We need to consider social justice issues.
Or is reversibility only implied in the context of gene drive-based genetic modification introduced into organisms in a natural ecosystem rather than humans? Even there I’m doubtful reversal attempts would work and others are also skeptical.
Overall, scientists and others should use greater caution in discussing the notion of reversibility of genetic modification. It would not be as simple as portrayed sometimes. Other notions such as genetic “off switches” for modifications in organisms (while elegant systems in the laboratory setting) could also prove in the real world to be impractical amongst heterogeneous cells in an organism within a population of organisms.
This doesn’t mean that people should stop working on or thinking about reversal strategies or conditional approaches to genetic modification. Quite the opposite as that work is important and should continue, but the notion that one could “simply” reverse an introduced genetic problem is misleading and downplays legitimate concerns over safety. It also potentially exaggerates human control of genetics in the real world.
As some of you readers know, I’ve written a new book on human genetic modification including on possible use of CRISPR in people. In the book I discuss the potential upsides and risks of CRISPR’ing people. The book is called GMO Sapiens. In it I discuss something called “reproductive quarantine” where humans with unexpectedly negative genetic outcomes from modification attempts are prevented by governments from reproducing.
While CRISPR’ing people would be an experiment, if something goes wrong with it then unlike a bad experimental outcome in a test tube or in a dish, or even a profoundly flawed paper that can be retracted, I don’t see how you undo the harm at the very least to individuals.
More broadly this raises the point that in these kinds of hypothetical human genetic experiments, the person becomes the experiment, necessitating a higher level of discussion that includes bioethical and social justice considerations.