Image by Maria Oswalt

Intro to Embryos

At the moment of sperm-egg fusion — i.e. fertilization or conception — a genetically distinct, whole, living organism is produced. Because the product of a same-species reproduction is always a differentiated member of that same species, in human reproduction, it is a human organism. In the early stages of development, this human life is referred to as an “embryo.”


Embryonic life, like all human life, deserves to be free from aggressive violence. Unfortunately, embryos are often seen as disposable, material to be used for research purposes, or tools for achieving pregnancy. Below we explore the use of embryonic human life in assisted reproduction and stem cell research.

Assisted Reproduction and the Discarding of Embryos

In Vitro Fertilization (IVF) is the most common assisted reproductive technology. In order to perform IVF, mature eggs are collected and fertilized in a lab, and one or more of the fertilized eggs are transferred to a uterus where, ideally, they will implant in the uterine lining and develop normally. 


Although IVF does not have to involve the taking of life, the discarding of embryos is an incredibly common part of the process. IVF procedures often involve forming multiple embryos for multiple attempts at pregnancy, and as a result, there are frequently embryos left over. Parents can choose to freeze these embryos to be implanted at a later date, destroy them, or donate them for research. In addition to this, doctors generally inject multiple embryos into the uterus to give a better chance of at least one successful implantation, and if multiple embryos implant, physicians often recommend “selective pregnancy reduction” — in other words, aborting one or more of the children. 


These choices — which embryos to destroy, which to perform research on, and which to save — are not random. Embryos are tested for genetic abnormalities before implantation, and  those that are not considered normal are either discarded or saved “to model genetically inherited diseases” for developing new drugs.


In the law these embryonic human beings are often described in property language, as “material” or “products” of conception, as something that can be “donated.” This implies that they are an object owned by another rather than an individual human life with their own rights and inherent dignity. Nowhere is this more clear than in custody disputes during divorce cases. In the case of a couple who had stored their embryos for nine years before deciding to separate, for example, the court ruled that the embryos were “marital property” rather than human beings with constitutional rights.

Human beings should never be considered property.


If assisted reproductive technology is not conducted in a way that protects life (i.e. only creating as many embryos as one plans to inject and carry to term), it ends up objectifying these prenatal humans. Embryonic lives are weighed against each other, some chosen as having the correct potential to be allowed to continue developing, others judged as material for research. 


Embryos and Stem Cell Research

Stem cells are a basic building block of the human body: they have both the ability to develop into more specialized cells, such as heart muscle cells, brain cells, or blood cells, and the ability to divide indefinitely, making them extremely important in cell repair and human development.


Stem cells are often used for regenerative medicine, such as producing new cells to replace diseased cells in people with spinal cord injuries, Alzheimer’s, or Parkinson’s. In some cases, stem cells can even be used to grow new tissue for use in transplants. Stem cells are also used in many types of research: they can be programmed to act like diseased cells that will be targeted by a drug, so that the drug can then be tested on the cells. Stem cells are also used for studying the development of cells, diseases, and, in the case of embryonic stem cells, people.


The derivation of the usable human embryonic stem cells begins with the growth of the human embryo to the blastocyst stage, at which time there is an inner cell mass (ICM) surrounded by an outer layer of cells (trophectoderm). The ICM is removed from the embryo to allow for experimentation on the HES cells, thereby killing the embryo. Embryology reveals that a human embryo is in fact a distinct human organism, not just a “clump of cells.” Embryonic stem cell research, therefore, necessitates the intentional deaths of thousands of tiny, embryonic human beings — it cannot be done without violence. 


“If human embryonic stem cell research does not make you at least a little bit uncomfortable, you have not thought about it enough.” 

These are the words of Dr. James Thomson, the scientist who first extracted stem cells from human embryos. Dr. Thomson, himself uncomfortable with the ethics of research using embryos, worked to develop an ethical alternative, hoping that the use of embryos would become “a funny historical footnote” rather than a common research tool. At first, many saw adult stem cells as unrealistic alternatives because they are found in small numbers (while blastocysts have many stem cells) and because they did not have the potential to develop as many types of specialized cells as embryonic stem cells. But in 2006, Dr. Thomson’s team discovered a way to induce adult stem cells to be “pluripotent,” or have the ability to develop the same types of cells as embryonic stem cells. These induced pluripotent stem cells (iPSCs), then, are able to be used in similar ways to embryonic ones, but they do not have the same ethical problems associated with them.


“Isn’t it great to start a field and then to end it?” Dr. Thomson said in an interview with the New York Times in 2007. Although he sees the field as closed, many still consider embryonic stem cells as ethical research subjects, and embryonic lives continue to be destroyed for research purposes.

Nonviolent Alternatives: Adult and Placental Stem Cells

Adult stem cells show great promise in research — in fact, they are considered by some to be the “gold standard in regenerative medicine.” Research into the use of induced pluripotent stem cells (iPSCs) is increasing at a much faster rate than research with embryonic stem cells, and some researchers predict that this rate will continue, as iPSCs are easier to derive than embryonic stem cells. Collecting adult skin cells only requires a simple biopsy, “about as painful as a blood draw,” and a large number of cells can be drawn from a comparatively small amount of tissue. As Dr. David Prentice writes, iPSCs “have distinct advantages compared with embryonic stem cells because they can be made from virtually any person or tissue, healthy or diseased, more cheaply and efficiently than embryonic stem cells...” iPSCs can also be patient-specific, made from the patient’s own skin cells, and therefore they are more likely to be accepted by the patient’s immune system. 

In addition to this, stem cells taken postnatally from the umbilical cord and placenta have shown great promise and are both “low-cost” and “pain-free.” In fact, parents can choose to donate cord blood to a blood bank for use in transplants or curing serious diseases — and no life is lost or endangered in the process. The utilitarian reasons for using embryonic stem cells are becoming fewer and farther between.

iPSCs have been used to study the Zika virus and lissencephaly, and studies on cells derived from bone marrow and cord blood show promise that they can promote cardiac regeneration and repair. Adult stem cells have been used to help treat neurological conditions like Multiple Sclerosis. They hold great promise, and their derivation does not involve the destruction of life — which cannot be said for embryonic stem cells.

Closeup of a Petri Dish

Addressing Common Arguments

Below we address some common arguments about the ethics of embryo destruction and embryo research.


"An embryo may be alive, but an embryo is not a person."

Some argue that “personhood” is what makes a life worthy of protection. Embryos, the argument generally goes, are not persons, because they do not have the correct level of rationality, sentience, or development.


At Rehumanize, we advocate for human rights for all human beings. If there could ever be a category of “living humans who are not persons,” then personhood, at best, is a useless attribute. At worst, it is discriminatory and deadly. Humans still in their embryonic and fetal stages deserve the same rights as humans in their neonatal, toddler, child, adolescent, and adult stages.


Wanted versus unwanted embryos

Others argue that the permissibility of destroying embryos comes from the embryo’s condition of being either wanted or unwanted. Proponents of this argument might see destroying or performing research on embryos that are intended for IVF as immoral, but only because the embryos are wanted by someone who has a stronger “claim” on them. In this view, it is the consent of the “owners” who no longer desire the embryo that confers the morality of the destruction of embryonic life, and it would be simply wasteful to not use unwanted embryos for research.


This argument becomes ridiculous when placed in any other context. We would not say that a friend’s right to live free from violence is dependent on their being wanted, or that our grandparent’s value is constructed by our valuing them. So why would we make such a dangerous exception for embryos? Unwantedness cannot be the justification for violence against another human. Worth cannot be based on whether or not we are wanted.


"Embryonic lives aren’t even grievable."

Some point to high miscarriage estimates to argue that embryonic lives can’t have much value if so many die every day. After all, if those lives mattered, wouldn’t we grieve them? 


The strange thing about this argument is that it completely ignores the experiences of the people who do grieve the loss of embryos, and it only helps to reinforce the stigma surrounding the grief that many experience after miscarriage. Grief over embryo loss affects those who conceive naturally and those who use assisted reproduction, and, contrary to popular belief, the length of pregnancy does not seem to be connected to the intensity of grief. People who make the choice to destroy embryos they no longer want to use or can no longer afford to freeze are often surprised by the mourning that comes after the decision. In the cases where laboratories have had freezer malfunctions that resulted in the loss of thousands of embryos, people have spoken out about the devastating loss and families have come together in their grief, holding services and building memorials for the lost lives.


"It would be better to save thousands of lives through new treatments than to save a couple embryos."

Some argue that the potential for lifesaving cures outweighs any moral issues with experimenting on embryos, even going as far as to say that refusing to experiment “would be morally equivalent to killing” the people who might benefit from this research. Let’s examine the moral claims here and then take a look at what the research has told us thus far.


These claims are based on utilitarian calculations that do not recognize the inherent dignity and value of every life, instead seeing them as having measurable levels of value. The Consistent Life Ethic has no room for this type of thinking. It is imperative that medical ethics reject this utilitarianism as these ethical frameworks — which treat individual lives as disposable in the pursuit of scientific advancement —  have led to deplorable human research studies we have seen throughout history. The belief that refusing to take the life of embryos is doing violence against others comes from a grave misunderstanding of what aggressive violence is; respecting the dignity of a vulnerable group and refusing to use them for our own ends is the antithesis of violence. 


In addition, embryonic stem cell research has not been as groundbreaking as previously expected. When research began on embryonic stem cells, they seemed to many people like a research subject sent from heaven. Journalists gushed over the possibilities ahead for curing disease, and ethical objections were swept to the side as mere obstacles in the way of medical progress. 

But stem cell therapy has progressed much slower than predicted, and early excitement led to exaggerations in public discussion about the rate at which stem cell research has already progressed. In fact, this exaggeration of potential stem cells, and the accompanying assumption that “the only problem is the evil physicians and government, who want to separate people from lifesaving therapies,” as Dr. Charles Murray, co-director of the Institute for Stem Cell and Regenerative Medicine at the University of Washington, put it, has led to an unwarranted and dangerous assumption that experimental treatments will lead to unprecedented cures. After fifteen years of evidence to the contrary, it is time to stop destroying human lives for the sake of experimentation.

Learn More

White Paper on the Medicalization of Violence

Fetal Cells in the Cosmetics, Food, and Medical Industries

Designing Humans to Be Destroyed

What Is Embryonic Stem Cell Research?

Embryos: Persons or Property?

Citations from embryology textbooks

Note: the terms "zygote," "embryo," and "fetus" are all references to stages of development — just like the words "infant," "adolescent," and "adult." Calling someone an adult doesn't negate the fact that they are a human being. Similarly, referring to children in the womb by their stage in development doesn't negate their humanity, either. "Human development begins at fertilization when a sperm fuses with an oocyte to form a single cell, the zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual."
[Moore, Persaud, Torchia. The Developing Human: Clinically Oriented Embryology, 10th edition. Philadelphia, PA: Elsevier, 2016, p. 11.] "Almost all higher animals start their lives from a single cell, the fertilized ovum (zygote)... The time of fertilization represents the starting point in the life history, or ontogeny, of the individual."
[Carlson, Bruce M. Patten's Foundations of Embryology. 6th edition. New York: McGraw-Hill, 1996, p. 3] "Development of the embryo begins at Stage 1 when a sperm fertilizes an oocyte and together they form a zygote."
[England, Marjorie A. Life Before Birth. 2nd ed. England: Mosby-Wolfe, 1996, p.31]
"Human development begins after the union of male and female gametes or germ cells during a process known as fertilization (conception).
"Fertilization is a sequence of events that begins with the contact of a sperm (spermatozoon) with a secondary oocyte (ovum) and ends with the fusion of their pronuclei (the haploid nuclei of the sperm and ovum) and the mingling of their chromosomes to form a new cell. This fertilized ovum, known as a zygote, is a large diploid cell that is the beginning, or primordium, of a human being."
[Moore, Keith L. Essentials of Human Embryology. Toronto: B.C. Decker Inc, 1988, p.2]

"Embryo: the developing organism from the time of fertilization until significant differentiation has occurred, when the organism becomes known as a fetus."
[Cloning Human Beings. Report and Recommendations of the National Bioethics Advisory Commission. Rockville, MD: GPO, 1997, Appendix-2.]

"Embryo: An organism in the earliest stage of development; in a man, from the time of conception to the end of the second month in the uterus."
[Dox, Ida G. et al. The Harper Collins Illustrated Medical Dictionary. New York: Harper Perennial, 1993, p. 146]

"Embryo: The early developing fertilized egg that is growing into another individual of the species. In man the term 'embryo' is usually restricted to the period of development from fertilization until the end of the eighth week of pregnancy."
[Walters, William and Singer, Peter (eds.). Test-Tube Babies. Melbourne: Oxford University Press, 1982, p. 160]

"The development of a human being begins with fertilization, a process by which two highly specialized cells, the spermatozoon from the male and the oocyte from the female, unite to give rise to a new organism, the zygote."
[Langman, Jan. Medical Embryology. 3rd edition. Baltimore: Williams and Wilkins, 1975, p. 3]

"Embryo: The developing individual between the union of the germ cells and the completion of the organs which characterize its body when it becomes a separate organism.... At the moment the sperm cell of the human male meets the ovum of the female and the union results in a fertilized ovum (zygote), a new life has begun.... The term embryo covers the several stages of early development from conception to the ninth or tenth week of life."
[Considine, Douglas (ed.). Van Nostrand's Scientific Encyclopedia. 5th edition. New York: Van Nostrand Reinhold Company, 1976, p. 943]

"I would say that among most scientists, the word 'embryo' includes the time from after fertilization..."
[Dr. John Eppig, Senior Staff Scientist, Jackson Laboratory (Bar Harbor, Maine) and Member of the NIH Human Embryo Research Panel -- Panel Transcript, February 2, 1994, p. 31]

"The development of a human begins with fertilization, a process by which the spermatozoon from the male and the oocyte from the female unite to give rise to a new organism, the zygote."
[Sadler, T.W. Langman's Medical Embryology. 7th edition. Baltimore: Williams & Wilkins 1995, p. 3]

"The question came up of what is an embryo, when does an embryo exist, when does it occur. I think, as you know, that in development, life is a continuum.... But I think one of the useful definitions that has come out, especially from Germany, has been the stage at which these two nuclei [from sperm and egg] come together and the membranes between the two break down."
[Jonathan Van Blerkom of University of Colorado, expert witness on human embryology before the NIH Human Embryo Research Panel -- Panel Transcript, February 2, 1994, p. 63]

"Zygote. This cell, formed by the union of an ovum and a sperm (Gr. zyg tos, yoked together), represents the beginning of a human being. The common expression 'fertilized ovum' refers to the zygote."
[Moore, Keith L. and Persaud, T.V.N. Before We Are Born: Essentials of Embryology and Birth Defects. 4th edition. Philadelphia: W.B. Saunders Company, 1993, p. 1]

"The chromosomes of the oocyte and sperm are...respectively enclosed within female and male pronuclei. These pronuclei fuse with each other to produce the single, diploid, 2N nucleus of the fertilized zygote. This moment of zygote formation may be taken as the beginning or zero time point of embryonic development."
[Larsen, William J. Human Embryology. 2nd edition. New York: Churchill Livingstone, 1997, p. 17]

"Although life is a continuous process, fertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed.... The combination of 23 chromosomes present in each pronucleus results in 46 chromosomes in the zygote. Thus the diploid number is restored and the embryonic genome is formed. The embryo now exists as a genetic unity."
[O'Rahilly, Ronan and Müller, Fabiola. Human Embryology & Teratology. 2nd edition. New York: Wiley-Liss, 1996, pp. 8, 29. This textbook lists "pre-embryo" among "discarded and replaced terms" in modern embryology, describing it as "ill-defined and inaccurate" (p. 12}]