“It is in our view wrong to create something with the potential for becoming a human person and then deliberately destroy it” Despite that dissent by three members, the Warnock Committee recommended the British Parliament allow research on human embryos for the first 14 days after fertilization. It had lasting knock-on effects on how embryos are regarded or discarded.
To call a fertilized egg or a microscopic embryo a “potential baby” is proverbial for anyone who sincerely believes it is immoral to destroy them. But does it stand up to reason or biology? The expression is used as grounds for attacking IVF (see the post Alabomination) and this week the HuffPost reported on a GOP congressman who accused fertility treatment of killing more children than abortion.
Baroness Mary Warnock avoided the adjective when we discussed IVF legislation at her home in 2019, a few months before she died. The meaning of “potential” has been weighed in philosophy classes and found wanting ever since Aristotle strode the Lyceum. Contemporary moral philosophers from Peter Singer to Monika Piotroska (though not all) call it wishy-washy and too hollow for valid debate. Philosophers offer more scholarly critiques, but this is my attempt to strike a blow using an example to chime with the times.
John Doe is an ordinary American citizen who aspires to be the next President of the United States. He fulfills the three conditions for a candidate, all rather trivial compared to his current job. Unfortunately, the odds are against him, like tossing a ball into a spinning roulette wheel with millions of pockets and only one winning number. Nevertheless, he continues to call himself a potential president because the wild gamble has a greater chance than zero.
Luck isn’t enough to win the White House. He can’t start without the drive to succeed and self-belief. He won’t get traction without being adopted by a political party. He must avoid falling ill or exposing an embarrassing personal history. He needs generous donors to fund his campaign. Then, he must beat better-known candidates at a primary election. And when he finally faces an opponent in a federal election, adverse political winds can blow a polished presentation off-course. A theoretical chance of winning crashes against the reality of obstacles beyond his control. A successful election is contingent on circumstances and conditions. In other words, it depends.
The Australian philosopher Stanley Benn used nuts as a metaphor. He pointed out that acorns have the potential to become oak trees, but acorns are not trees. Hence, he said, “a potential U.S. President is not on that account the commander-in-chief of the Army and Navy.” And Aristotle, a higher authority, held that potentiality is not actuality or real in the fullest sense. To vest the same rights in a fertilized egg as a viable fetus or liveborn person seems too nonsensical to mention, except some people hold it as a creed.
Although every egg or embryo is in theory a potential baby-in-waiting, its fortune depends in reality on more than raw probability. It must negotiate hurdles it cannot control. To have agency, it must start with a competent genome and cytoplasm, then be transported and nourished on its journey through the fallopian tube before embracing the juicy uterine epithelium. Its progress will stall unless it can alert the mother’s physiology to adapt and cooperate to make a placenta. Outside of her nurturing environment, an embryo cannot actualize its potential and has no agency alone in a dish or freezer.
To the best of my knowledge, the Jesuit priest Richard A. McCormick is the originator of the widely observed 14-day rule for human embryo research. He served on the Ethics Advisory Board of the U.S. Government when it reviewed the implications of Louise Brown’s birth. At that time, the ethical care of embryos seemed academic because the U.S. Supreme Court had settled the latest date for abortion at the stage of viability in the Roe. V. Wade case (no longer since 2022). Unlike the U.K. and some other countries, a rule for embryos never became law in the U.S.A. Recent calls to extend the deadline are likely to meet more resistance than when the Warnock Committee settled it based on the latest time that embryos can split to form separate individuals.
We have seen a blastocyst splitting to make a pair of embryos. The sporadic event occurs more often in vitro than in the body, judging by twin births. Trophectodermal cells squeezed out of a herniated zona pellucida by rhythmic contractions became pinched off into a second sphere. A pair has the makings of genetically identical (monozygotic) twins if both contain some of the inner cell mass. Twinning can occur for several more days but not after gastrulation when the primitive streak generates germ layers for a future body. If personhood is indivisible, it must begin no earlier than about two weeks after fertilization when two separate individuals (or souls) can still emerge from a single zygote.
Besides the principle that guided the Warnock committee, there are more reasons to deny the humanity of early embryos. However, I hasten to add that scientific reasoning should not undermine a certain kind of respect they deserve if hard to define. Patients often call their embryos “babies” and the stakes are huge for laboratory staff who care for them.
Fertilization is a shibboleth for a fundamentalist view of embryology. It is undeniable that a new and unique genetic entity emerges at the union of egg and sperm, presented in classical embryology as a precise event, but more accurately viewed as a process.
Lawmakers and official regulators throw up their hands when science muddies the waters that used to look transparent and denies arbitrary divisions. Laws and rules require clear-cut definitions. The German Embryo Protection Act (1990) fell into a trap when it restricted clinical embryology practices based on an outdated view of fertilization. It defined fertilization as the merger of male and female pronuclei to form a zygotic nucleus, granting it human “dignity” (whatever that means for a single cell). I wonder when people conflate a zygote’s genome with core personhood if they realize it implies reductionism, a materialistic philosophy I suspect many would disavow on other terms.
Science never stopped acknowledging sperm as the only cell type able to create a viable embryo with an egg (setting aside cloning). And yet, other agents can trigger eggs to grow—the prick of a sharp needle, a drop of ethyl alcohol, and other chemicals that elicit a calcium current across the membrane. A parthenone is hard to distinguish from a real embryo up to the blastocyst stage and may even have a diploid genome (strictly maternal, of course). Parthenogenesis looks like embryogenesis: appearances are deceptive.
Molecules synthesized before ovulation kick-start development at fertilization, so the embryo depends entirely on its maternal inventory until the new genome switches on a couple of days later. The genome remains silent while epigenetic marks on the egg and sperm’s DNA are edited for the transition to embryo progenitors of all body parts and some of the placenta. Since fertilization is a process, it is moot to ask when a new individual begins life. If gamete fusion is like a comma in a sentence, necessary but insufficient on its own, does switching on the zygote’s genome after fertilization qualify as genesis, or should we choose the earlier date when key molecules are synthesized? Fertilization as a continuum makes it harder to hold one moment more momentous than another.
Likewise, embryogenesis follows a hazier path than the rigid program depicted in textbooks. The egg still looking like a homogeneous blob after activation is roused to intense biochemical activity and starts dividing to make progressively smaller cells, like slicing a cylindrical “truckle” of hard cheese. The slices make a mosaic assigned for future body parts or supporting tissues, although the bifurcation of lineages is not obvious until the late blastula stage. Since frogs and toads don’t have a placenta, every cell in their embryos is destined for the body.
Human embryos arrive in the uterus after a journey lasting three days in the fallopian tube (as long as Jonah in the belly of a whale). From 8 to 16 cells, they hollow out to make blastocysts in two days. This is slow progress but necessary in mammals for the ovary to switch hormone production and delay a blastocyst in the tube where it could threaten an ectopic pregnancy. The same stages in amphibians gallop through early cell divisions to reach the gastrulation stage only 12 hours after fertilization. Tadpoles emerge two days later from their jelly coat.
This striking difference between life in a womb (viviparity) or a pond or nest (oviparity) led British and American scientists to simultaneously coin the word “pre-embryo” for free-floating embryos. Although an apt description, it failed to defuse an ethical debate about embryos, the only word we used in lectures and textbooks before IVF. I understand if critics complain that casting pre-embryos is all smoke and mirrors. Embryology is better defended by research that shows it is more plastic than we once knew.
We discarded a baseless belief that DNA is discarded when no longer needed after cells develop and specialize. All cells except red blood cells still possess a complete and duplicate set of genes, so they can turn into different types in theory. This theory is confirmed by reproductive cloning and induced pluripotent stem cells which show the arrow of time is not strictly irreversible from the totipotential zygote to highly differentiated cells like nerves and muscle (cancer is a kind of exception). Technology can turn the genome of mature somatic cells back to an undifferentiated state from where it can be steered to another destiny. In a sensational series of experiments, Japanese scientists generated fertile gametes from mouse skin cells. Thus, germ cells have been dethroned from their absolute role as conveyers of the chain of inheritance because “proletarian” cells can serve the same role with the helping hand of science. The implications of this revelation are still sinking in.
I began discussing the “potential” of embryos to make babies and now close on a note about their “interests.” It is another oily word, more often heard in a courtroom than in biology and reproduction. At the risk of sounding bizarre, I think every cell in a dish has interests whereas a chip off an inanimate rock has none. From an amoeba or alga to a honeybee or human, living organisms have a common interest in survival, growth, and reproduction as their raison d’etre. The interests of the simplest creatures are protoexistential (nothing to do with existentialism) whereas the lives of advanced animals have more meaning, freedom, and sex. And yet, the interests of a fertilized human egg cannot be aligned with an amoeba despite both being unicellular. I pleaded earlier for embryos’ special status based on parental interests.
The flow of reproductive interests is bidirectional in a triangular relationship between mother, father, and offspring that is mostly cooperative and occasionally conflicted. Women conceiving naturally are oblivious of the first days after fertilization until it is disclosed days after implantation and gastrulation with a test or from a missed period or even later from feeling fetal “quickening.” Maternal impulses then kick in to love, protect, and nurture a new life within.
How different for a couple receiving fertility treatment! The currents of sentiment start flowing immediately after a laboratory report of conception in a dish. It holds the tentative promise of fulfilling a dream after a long journey with infertility toward hope. Childbearing and rearing always stirred powerful emotions, though generally out of public view and at later stages of pregnancy or after birth. We now know the same emotional drama is stirred by a microscopic speck of protoplasm that was never seen, known, or loved in history at that stage before IVF. People mourn the death of embryos in private unless a rare laboratory accident gets into the news. Divorcing couples fight over the custody of embryos in court, not like other matrimonial property but every bit as intensely as if they were children. Specks matter. That’s why in society and by law embryos are given a special status, not based on their biological “potential” but because of their value to the people who conceive them.
Illustration: A blastocyst floating in a green wood (source: the author by generative AI)
Wonderful! I enjoyed the presidential candidate analogy near the beginning - thank you for another beautifully written piece.