The unscientific nature of the concept that “human life begins at fertilization,” and why it matters

 The unscientific nature of the concept that “human life begins at fertilization,” and why it matters

Volume 107, Issue 3, Pages 566–567


Richard J. Paulson, M.D.


We live in a time of unprecedented scientific progress. This is not a remarkable statement, as it could easily have been made anytime during the preceding millennia of cultural evolution. Information grows exponentially, and each era not only has access to more information than the preceding era, but also adds more new discoveries and data. Additionally, the present time has given us unprecedented access to information and rapid communication. Unfortunately, one unintended consequence of our near instantaneous communication is the rapid proliferation and dissemination of misinformation and outright disinformation.

Read the full text here.


Go to the profile of Ana Maria Dumitru
over 5 years ago
Very respectfully, I would like to suggest that Dr. Paulson may have confused two distinct topics here: one is the scientific observation of the biological characteristics of the human embryo, and the other is the philosophical question of when human "personhood" begins. Science allows us to observe the cell biology, and, as Dr. Paulson points out, both the sperm cell and egg cell are living cells, as is the zygote formed from the fusion of the sperm and the egg. So the science tells us that as far as when the zygote is considered "living," it is a living cell from the beginning. However, much of the debate about the topic of "when life begins" is actually about determining when the developing human embryo should be considered for personhood. A landmark article from Magdalena Zernicka-Goetz and colleauges, published in Nature Cell Biology in 2016, demonstrated that it is possible to culture human embryos from pre- to post-implantation in the absence of maternal tissue, and that the pre-implantation human embryo exhibits what they refer to as "embryo-autonomous" behavior; remarkably, they find that the human embryo is able to organize and differentiate in culture past the implantation stage. This is purely scientific evidence of the developmental continuum of the human from fertilization onward. The remaining issue up for debate is thus whether the published literature on the autonomous behavior of the human embryo is sufficient to give the human embryo personhood status.
Go to the profile of Alexander Quaas
over 5 years ago
Thank you for this important and timely rebuttal of the concept that "life begins at fertilization". The answer to the question when an embryo becomes a "person" is difficult, and attempts to establish a definitive time point are bound to be arbitrary- similar to the (also arbitrary) "14-day rule" in human embryo research: As you point out, the scientific community has a duty to vet and promote "good" information, and to adamantly discredit and oppose the dissemination of "fake" science.
Go to the profile of Evelin Lara-Molina
over 5 years ago
Thank you Dr Paulson for this brave and rigorous reflection.
Go to the profile of Justo Aznar
over 5 years ago
Rarely have we found such a short text with so many scientific inaccuracies as the "Inklings" published recently in Fertility and Sterility (1), in which the author states that the concept that human life begins at fertilization is an argument more religious than scientific, if not solely religious. Let us look at some of the statements made in this article. 1. “One observation that has been attributed to scientific consensus—one that is highly relevant to our field—is the concept that ‘human life begins at fertilization.’ This statement is commonly offered by religious organizations and is often cited as the basis for so-called personhood amendments, but the assertion that it is scientifically sound is incorrect.’’ It is evident that research aimed at trying to define the beginning of human life can only be approached from a scientific perspective. Another matter is whether it can or cannot be done. We believe that the vast majority of experts in this field today accept that the life of the human embryo begins at fertilization. Basing this claim on religious beliefs is at least unfounded. Religion has a spiritual, not biomedical, mission. Its arguments run along paths different to those of the experimental sciences, and in no way can the idea that life begins at fertilization be attributed to a religious concept. 2. “It has profound ramifications for the treatment of infertility, particularly for in vitro fertilization (IVF)”. Clearly, determining when human life begins very directly affects assisted reproduction practices, particularly IVF, so it does not seem incongruent to try to eliminate the biological reality that human life begins at fertilization, because if this is so, any manipulation of that preimplantation human embryo would have objective ethical repercussions. 3. “We fertility doctors take extreme care to protect and nurture the preimplantation embryos in our incubators and cryotanks”. Obviously, it would be very hard to accept that doctors working in assisted reproduction clinics would not want to be as respectful as possible with the embryos they handle, although it seems evident that it would be difficult to justify the care they take of them if they are considered clusters of cells. This appears to us a new and inexplicable contradiction. 4. “We realize that in almost all cases these aggregates of cells represent the best chance for our infertile couples to realize their dream of building their families”. Calling the preimplantation human embryo an "aggregate of cells" is a statement lacking any scientific basis. That single-celled human being, the zygote, is a structured being, just as the biological organism generated from its division will be. There is abundant evidence that confirms this scientific reality, which we cannot list here, although we have done so in depth in a previous article (2). Moreover, recent studies confirm the existence of self-organization in the cells of the embryo, without any outside influence, even in the preimplantation phase (3). 5. “However, handling an embryo with the potential to produce a pregnancy is not the same as handling a human life”. This is, once again, an unfounded statement. The evolutionary stage of the embryo does not change its biological nature, any more than the phenotypic differences between the neonate and the adult alters their status of human being. 6. “If harm to a preimplantation embryo were to be considered the same as harm to a human being, then the demise of a preimplantation embryo—a not infrequent event in vivo, as well as in the IVF laboratory—might well be treated as a human death, perhaps with manslaughter charges brought against the embryologists”. Harming a preimplantation human embryo is effectively harming a human life, because we cannot find any biological reason to distinguish both realities. We believe it is precisely this that the author seeks to eradicate: the negative ethical judgment derived from the harm that can be done to preimplantation human embryos by dispossessing them of their intrinsic human nature. 7. “What is scientifically incorrect about saying that human life begins at fertilization? First, it is a categorical designation in conflict with the scientific observation that life is a continuum. The egg cell is alive, and it has the potential to become a zygote (a single-celled embryo) if it is appropriately fertilized and activated by a live sperm. If fertilization is successful and the genetic complement of the sperm is added to that of the egg, the resulting zygote is also alive”. Herein lies one of the major contradictions of this article. The zygote is indeed an individual of the human species that presents a "continuum" in its evolution, until its natural death, with no interruption or change in its nature. The change between the nature of the egg and that of the zygote is objectifiable, both genetically and in its development program, which is non-existent in the egg and evident in the zygote. Confusing a cell, such as the egg, with a living human being, such as the zygote, is an unacceptable scientific error. The egg is clearly a living cell and the zygote is a living human being. A single living cell can never give rise to a human being capable of developing and reproducing. It may give rise to another cell, but nothing more. Two living cells are required to generate the zygote, the egg and the sperm, which after joining their genomes, will result in a living being different to its progenitor cells. 8. “The zygote has the same size as the egg; other than for its new genotype, the cell (comprising the cytoplasm and the rest) is nearly identical to the egg cell. From a biological perspective, no new life has been created”. Trying to define the similarity or dissimilarity between the egg and the zygote by size is an inadmissible scientific gaffe. We do not believe that size defines the ultimate condition of being, but is only an expression or characteristic of this; above all, it is even more unacceptable to state that if it were not for the genotype, both cells would be practically identical. Clearly, the genotype is what will define the identity of that new human being. 9. “Second, ‘human life’ implies individuality, which is also not consistent with scientific observations. In the clinical practice of IVF, we often speak of preimplantation embryos as individual entities, with distinct qualities like a specific genotype (mosaicism notwithstanding), and morphologic and developmental characteristics. But at the same time we realize that each of the totipotent cells that comprise these embryos is, at least theoretically, capable of producing a complete new individual”. Here, another error is introduced, in our opinion scientifically unacceptable; to us, equating indivisibility with individuality is scientifically grievous. It is obvious that at a certain time in our biological evolution, human beings are divisible, to the 8-cell embryo; later, however, we pass to another stage in which we are not divisible. There are many divisible individuals in nature, for example amoeba, so divisibility is not counter to the individuality of the being. 10. “The preimplantation embryo is essentially an aggregate of stem cells, which has the potential to produce a pregnancy, including placental and fetal tissues, assuming that it successfully implants in a receptive endometrium”. The author again repeats here that the preimplantation human embryo is an aggregate of stem cells, which has the potential to produce a pregnancy. Some time ago, Zernicka-Goetz (and we will not cite further examples although there are others) demonstrated in a paper published in Development (4) that the zygote, after dividing into two cells, assigns each of them very different specific functions. This led Helen Pearson, in an article published in Nature (5), to state that our destiny is defined from day one. This is science; what you state in your article is pure lucubration. The preimplantation human embryo is, essentially, a human being endowed with its own autonomous genetic identity and development program. Furthermore, it is made up of stem cells, but this is not, as the author says, the essence of its nature. 11. ‘‘Life begins at fertilization’ may certainly be considered a religious concept; because religious ideas are based on faith, no further proof is necessary. It is pointless to use science as an argument against faith-based dictums”. As previously mentioned, the author's earlier statement that human life begins at fertilization is considered a religious concept is lacking any scientific basis. Requiring evidence that allows a zygote or early embryo to be identified with a human being is clearly a scientific, not religious, task. 12. “If we do not object, our silence will be interpreted as scientific validation of this wholly religious, entirely unscientific conclusion”. As you say, if we do not argue against your article, our silence could be interpreted as a validation of what you state, in the sense that to affirm that human life begins at fertilization can only be justified on religious grounds, when we really believe that its demonstration must be based exclusively on biological grounds. Mixing science and religion is to have no idea of what science is and what religion is. Fortunately, the vast majority of the scientific community who have addressed this issue, including those who defined the "pre-embryo" in the past, recognize the strength of the arguments that confirm the human nature of the zygote and the early embryo. Even judicial decisions of international courts back that evidence. References: 1. Paulson RJ. The unscientific nature of the concept that “human life begins at fertilization,” and why it matters. Fertility and Sterility. 2017; 107: p. 566–567. 2. Aznar J, Bellver V, Casanova G, Torres MJ. The status of the human embryo according to Michael Sandel. Therapeia. 2012; 4: p. 69-82. 3. The Rockefeller University. New method allows first look at key stage of human development, embryo implantation. [Online].; 2017. Available from: 4. Piotrowska K, Wianny F, Pedersen RA, Zernicka-Goetz M. Blastomeres arising from the first cleavage division have distinguishable fates in normal mouse development. Development. 2001; 128: p. 3739–3748. 5. Pearson H. Developmental biology: Your destiny, from day one. Nature. 2002; 418: p. 14-15.
Go to the profile of Thomas W. Hilgers, MD
about 5 years ago
Thomas W. Hilgers, MD I once read a definition of rationalization which said that it is made up of “apparently good reasons in the place of real reasons.” In fact the short letter on “The Unscientific Nature of the Concept that ‘Human Life Begins at Fertilization’ and Why it Matters” published in the March 2017 issue (Volume 107, pgs. 566-567 by Richard J. Paulson, MD) fits that definition perfectly. In this article, the author suggests that the statement “human life begins at fertilization” is a form of “misinformation and outright disinformation” comparing it to “fake” news. Dr. Paulson suggests that such statements suggest “apparent scientific contradictions and that the reader or listener may develop a skepticism about the scientific method, and concludes that science, like news media, is not a reliable source of information.” It should be noted that scientific journals are often replete with editorial and political spin, but this article does not appear to recognize this. Of course, Dr. Paulson relies on the well-worn refrain that this “is commonly offered by religious organizations” and adds that “the assertion that it is scientifically sound is incorrect.” He offers a concern for the work that he is involved in the treatment of infertility and in vitro fertilization. He then suggests that fertility doctors take “extreme care to protect and nurture the preimplantation embryos.” It is only, however, because they represent “the best chance for infertile couples to realize their dream of building their families.” While this is an “apparently good reason,” it doesn’t deal with the reality of the phrase “human life begins at fertilization.” He seems to be mostly concerned about the doctor being exposed to “manslaughter” charges. I don’t recall that that’s ever happened. In justification for his thoughts, he specifically says that, “It is in conflict with the scientific observation that life is a continuum.” This is one of the same arguments that the Supreme Court in Roe v. Wade used, so it sounds very familiar. Certainly in a generic sense, life is a continuum, but nobody’s ever been talking about life as a generality, but rather the beginning of the life of an individual who never previously existed. His reasoning is based upon “the egg cell is alive” and has the potential to become a “zygote if it is appropriately fertilized and activated by live sperm.” And if all of this happens, then “the resulting zygote is also alive.” He tries to gain some strength in his argument by suggesting that “the zygote has the same size as the egg other than for its new genotype, the cell … is nearly identical to the egg cell. From a biological perspective, no new life has been created.” It is truly difficult to take this argument seriously. I know for myself that I’m not a grown-up oocyte nor am I a grown-up sperm. In fact, the genotype means everything to the individual human person and the fact that the size of the zygote is about the same size as the egg cell is irrelevant. It defies the reality of the newly formed, never again to be duplicated, individual human life. It seems to me that to prove his thesis, he could report on his study and evaluation of in vitro fertilization pregnancies with special reference to all of those babies that were gestated and eventually delivered when the time from fertilization up to implantation is purposely excluded (or destroyed). I know of no such study that’s ever been done, nor can I expect that it will be done. It is a little bit like saying that the first 10-15 cell divisions of an ovarian cancer are not really ovarian cancer. Dr. Paulson does make a stab at the idea of “individuality” of these human lives by suggesting that “multiple individuals can arise from the implantation of a single embryo, as in the case of identical twins.” Identical twins occur in 1 out of 270 births or 0.3% of the time. So in 99.7% of concepti, individualization does occur at the time of conception or fertilization. The mere fact that on rare occasions, these things can happen does not mean that the whole of that process should be redefined because of a minority occurrence. It is an old argument that has lost a significant amount of substance over the last 40 or 50 years. Dr. Paulson appears to try to get through this by referring to them as “totipotent cells” or even “stem cells.” But you need to show me that a stem cell has ever developed into a human being. Yes, human tissues such as the liver, kidney, thyroid, teeth, etc. etc., but none of those are human persons. The personhood is the whole of the individual, not just its parts. So then he ends up by saying “life begins at fertilization may certainly be considered a religious concept; because religious ideas are based on faith, no further proof is necessary.” However, in my religion, faith enlightens reason and reason enlightens faith. The two are not completely separate from each other, although they do have different foci. There is definitely one group within the population however, who have a significant antithesis to religious faith. These individuals have little idea what it means to have faith and they have persisted in their attempts to force their idea of morality on the rest of us. Many years ago, I remember a noted gynecologic surgeon who testified that when he looked under the microscope at a human embryo, he could not see a human soul. At that he kind of chuckled because he felt he had a “gotcha moment!” But nobody said you could see the human soul no matter how hard you looked. What I would suggest is that eventually as we look more and more at the act of human fertilization we will identify biochemical or other stimuli inherent to the zygote that moves it in the direction of either an individual or identical twins. But of course, we don’t have that information yet, but to call this only religious is frankly ludicrous. It’s a kind of semantic gymnastics that frankly our science does not need along with being highly judgmental and prejudicial. Incidentally, my practice is devoted to patients who have infertility and our success rates are legitimately good by just looking for the underlying causes and treating them effectively. More on this will be coming over the next several years. But the IVF doctors have given up on looking for the causes of infertility and they rarely deal with that reality. I see so many patients who have previously been through either failed IVF programs or IVF programs in which they were treated like someone on a conveyor belt. The time will come when more and more women and couples begin to realize this and see that there is an alternative, and then they may very well look back on this article that suggests that “human life begins at fertilization” is an unscientific proposal and the whole picture will begin to come back together again. Thomas W. Hilgers, MD Pope Paul VI Institute for the Study of Human Reproduction
Go to the profile of Andrei Mirovan
over 2 years ago

Regarding dr. Richard J. Paulson's  note entitled „The unscientific nature of the concept that ‚human life begins at fertilization,’ and why it matters”:

Its intention to clarify, amend, and educate is most commendable. Nevertheless, its self-confident tone starkly contrasts with the inaccuracies and confusions that occur in the text.

Against the widespread assumption that human life begins at fertilization, Paulson offers two central arguments:

First, that „the scientific observation” shows “that life is a continuum”: the gametes (the sperm and the egg cell) are already alive, before merging together into a zygote;

Second, that „’human life’ implies individuality”, but that „the preimplantation embryo is not actually an individual”, because one single embryo can develop into multiple individuals (the case of identical twins).  “It is only after implantation – states Paulson -- that the early embryo can further differentiate into the organized cell groups that enable the developing conceptus to progress further in embryonic and eventually fetal development.”

However, both these arguments are objectionable:

The first one speaks of “the beginning of human life”, without further qualifications. This is strange, given the finding that, below in his letter, dr. Paulson proves he is totally aware that at stake is not human life in general, but individual human life. And the case can be made that a new individual human life (more precisely: a new human individual) appears, biologically, no earlier than the moment of fertilization. Even dr. Paulson does not say otherwise. So, the fact that, in the pre-fertilization phase, the gametes are alive, although correct, is simply irrelevant for the discussed topic.

The second argument that Paulson mounts against the idea that a new individual human life begins at fertilization has its own problems, beside the equivocation already pointed out. To see why, it should be mentioned that, in his comment, Paulson also refers to the abortion controversy. However, for the abortion debate, it is not enough to establish when a new human individual is created, but rather in what developmental stage does the new human individual become a person – or at least a morally relevant entity.

Therefore, neither the assertion that the pre-fertilization gametes are alive, nor the contention that individual human life begins, biologically, only with implantation do, as such, help one answer this latter question.

Nonetheless, dr. Paulson tries to contribute to the abortion debate, by writing the following:

”We fertility doctors take extreme care to protect and nurture

the preimplantation embryos in our incubators and cryotanks.

We realize that in almost all cases these aggregates

of cells represent the best chance for our infertile couples to

realize their dream of building their families. However,

handling an embryo with the potential to produce a pregnancy

is not the same as handling a human life [my underlining – A.M.].

If harm to a preimplantation embryo were to be considered the same

as harm to a human being, then the demise of a preimplantation

embryo—a not infrequent event in vivo, as well as in

the IVF laboratory—might well be treated as a human death,

perhaps with manslaughter charges brought against the embryologists.”


It is, indeed, cogent to admit a big difference between an embryo and a fully developed human adult. However, dr. Paulson also suggests that it’s less morally grave to harm a pre-implantation embryo than to harm a post-implantation one. Probably, that’s because, according to his position, the individual human life only begins at implantation. This notwithstanding, quite the opposite argument can be made: precisely insomuch as, before implantation, the human embryo can develop into multiple human individuals, it is all the more graver to harm a pre-implantation embryo, because a greater human potential lies in it.

Hence, despite the difference between a human embryo and a human adult, it’s still not at all evident that induced abortion is (with some exceptions) morally acceptable; and dr. Paulson’s confused letter is powerless as ammunition for the pro-abortionist camp.


Go to the profile of Samuel Jennings
over 2 years ago

I appreciate the Doctor’s choice to open his article with a statement of gratitude.  He reminds the reader of the technological innovations of the past few hundred years that improve the quality and length of human life.  The doctor credits breakthroughs in medical technology with allowing many infertile couples to realize their goal of raising biologically-related children.  In his discussion his compassion is evident.  Moreover, trying to discover a material-biological foundation for individuality is fascinating if anything is.  Finally, the Doctor articulates the mainstream of his field’s finding on the fertilization process that is comprehensible (or so we think!) to the lay reader and allows for an appreciation and wonderment at the process.   

But this is not the strongest element of the Doctor’s article.  The strongest part of the article decries the abuse of academic science—often involving a misreading of the evidence—for lay political arguments.  The result is not only widespread lay misinformation about the results of a particular study or body of studies, but a mistrust of scientific endeavors generally.   That leveraging putatively scientific arguments is the only way our society allows itself to have moral, legal, political, and philosophical arguments illuminates a cultural poverty and stupidity that is as regrettable as it is ubiquitous.   Often enough, as in the example he cites, this is a cover for other kinds of arguments.  One suspects that it results from intellectual laziness, an inferiority complex, or both.  One needs hardly look around to see examples-- “science says eat ____ to live longer,” “bio hack your way to happiness,” “Global Warming will DESTROY everything!,” or my favorite--“studies show Christians have better sex!!”  Grifters and ignoramuses abound—and always have a pet scientific study to “back them up.”   

And yet, this piece needs some more serious work. 

First, the Doctor ignores how scientists themselves created the state of public discourse wherein only putatively scientific arguments count as evidence.  Radical polemicists like Richard Dawkins abuse the parameters—and limitations—of their own discipline to make arguments well beyond their purview.  This of course has deep roots—19th century race science/ phrenology, the entire conceit of Marxism,  positivism, and eugenics all purported to obviate the need for public discourse rooted in anything other than their own findings and horizons—limited as they were by a reductionism.   Politicians (at least in the United States) accepted these propositions by default unless consciously choosing the opposite. Given the radical activist-scientists' success in bullying other methods of reasoning out of large segments of the public square, can we blame people for wanting to couch their supposedly unscientific claims in scientific evidence?  

His second and more serious flaw involves his terse characterization of religion and/or faith as fundamentally unaccountable and/or unresponsive to evidence, logic, and reason.  He passes briefly enough over the topic to depict a monolithic and unthinking religion that operates mainly as a foil for science.  It’s a straw man argument that would be laughable among serious observers of religion if it was not precisely the kind of mischaracterization that bothers him about popular and/or political uses of science.  The idea that religion and faith either cannot or will not engage in conversation with logic/reason /science is an old polemical trick from the eighteenth century—and should stay buried with its proponents.  Intellectually and historically, it is as simplistic and unfounded of an idea as one is likely to come across.  Religion, at least in the three great monotheistic traditions of Western Culture, always operated under the directive that, in the words of Augustine, “faith seeks understanding.”  Practically, this meant that faith and religion, as arguments about the nature of reality and humans’ place within it, participated in the production of scientific knowledge.  Luminaries such as Avicenna, Aquinas, Augustine, Newton, Mendel, and others stand as obvious examples that these traditions stand in constant conversation with logic, reason, and science. 

Hopefully the Doctor is merely ignorant of both the larger history within which contemporary science is embedded as well as the multifaceted and complicated history of religion, religious belief, and practice.  I look forward to better informed work in the future. 

Sam Jennings 

Oklahoma State University