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Senator Rubio is Right – Human Life Does Begin at Conception

Trent Horn

Last week senator Marco Rubio said on the Sean Hannity show that “Science is settled . . . human life begins at conception.” While some people who support legal abortion might scoff at the senator’s remarks, the fact is that all the evidence stands firmly behind what he said.

Now, science can’t prove a valuable human being, or a person, or someone with an immortal soul begins to exist at conception because concepts like “the soul” “value” or “person” are immaterial and are therefore outside the realm of science (even thought they are still real concepts). Instead, science shows us that biological human beings begin to exist after sperm and egg successfully unite to form a zygote, or a one-celled human organism.

Make Your Case

Pro-life advocates should avoid making simplistic claims such as “Abortion kills a life” or “Life begins at conception.” This leaves them open to a rebuttal such as this one from atheist Carl Sagan:

Despite many claims to the contrary, life does not begin at conception: It is an unbroken chain that stretches back nearly to the origin of the Earth, 4.6 billion years ago. Nor does human life begin at conception: It is an unbroken chain dating back to the origin of our species, hundreds of thousands of years ago.[1]

While it is true that living cells or human cells have a long history, the same is not true for individual human beings. Sagan’s criticism is overcome if we drop the assertion “Life begins at conception” and say instead “A human organism begins to exist at conception” or “The life of an individual human being begins at conception.” This may seem like semantics, but it is important to use this vocabulary with pro-choice advocates who may think an embryo is alive in the same sense that sperm and egg are alive.

This mistaken set of assumptions may cause the pro-choice advocate to think that an embryo’s life never really began at conception. He might instead think that at conception life in the form of sperm and egg was rearranged and became life in the form of an embryo. For them, the newly formed embryo might have the same value as egg or sperm until it “becomes a human being” later in pregnancy.

When it comes to defending the claim that an individual human being begins to exist at conception, I don’t recommend only making appeals to authority such as “Science says life begins at conception” or “All scientists agree life begins at conception.” The members of your audience may simply not believe you, or they may think the authorities you are citing are simply wrong.

Instead, I recommend using a simple argument that shows that at conception two body parts (sperm and egg) recombine and form an entirely new body that is a living, whole, human organism who is growing and developing into adulthood. After making this argument, it is then helpful to cite authorities which show humans begin their lives at conception (or twinning in the case of identical twins).

A Ten-Second Apologist

My favorite argument for the humanity of the unborn is based on Stephen Wagner’s “10-second pro-life apologist.”[2] Steve was once flustered that he could not defend his pro-life beliefs in a conversation that took him by surprise, so he went home and crafted a 10-second sound bite that goes like this:

  • If it’s growing, isn’t it alive?
  • If it has human parents, isn’t it human?
  • And human beings like you and me are valuable, aren’t we?

Sometimes, Steve’s sound bite will do the trick, and the person with whom you are talking will accept that the unborn are biological human beings. Other times you may have to use more evidence to prove that the unborn are (1) alive, (2) human, and (3) whole organisms.

Clearly, the unborn are alive, because they are receiving nutrients from the woman that cause the fetus to grow via cellular reproduction. And they are human because they came from human parents and have human DNA. Some critics will say in response to this, “Yes, the fetus is alive and human, but every cell in my body is alive and human. Is every cell in my body a human being?”

Not Just Any Cell

But this false argument confuses parts and wholes. Saying, “A fetus is alive and human. Sperm and egg are alive and human. Therefore, a fetus is a body part like sperm and egg” is as fallacious as saying, “A truck is made of metal. Nuts and bolts are made of metal. Therefore a truck is a car part like a nut or a bolt.” Because two things have traits in common does not mean they are the same kind of thing. Sperm, egg, and other body cells are parts of a human body. In contrast, a fetus, embryo, or even a one celled zygote that exists after conception is a whole human body that is able to develop itself over time.

The unborn are not mere tissue or body parts like sperm, egg, or skin cells. They are also not like cancerous tumors that can grow and even sprout body parts such as hair or teeth but have no potential to develop into an adult human.[3] Instead, an unborn child, when given time, nutrition, and a proper environment (i.e., not outside the uterus) will develop into a mature human being if he does not die prematurely, which is not true of sperm, egg, or body cells. Embryologist E. L. Potter says,

“Every time a sperm cell and ovum unite, a new being is created which is alive and will continue to live unless its death is brought about by some specific condition.”[4]

The fact that some embryos and even other born children die before they become adult humans does not negate the fact that they are human beings. They still are human beings because they have the intrinsic capacity to develop into a mature human being even if their development is tragically cut short.

Pro-choice bio-ethicist Peter Singer agrees:

“[T]here is no doubt that from the first moments of its existence an embryo conceived from human sperm and eggs is a human being,” he says, “and the same is true of the most profoundly and irreparably intellectually disabled human being, even of an infant who is born anencephalic—literally, without a brain.”[5]

Call in the Experts

Once you have defended the claim that from conception the unborn are biological human beings by using the ten-second pro-life apologist, it is more than appropriate to augment that argument with appeals to relevant authorities. For example, in Planned Parenthood v. Rounds (2008), the Eighth Circuit Court of Appeals found that requiring abortionists to say that the fetus is a “living, separate, whole human being” does not force an abortionist to espouse an unconstitutional religious viewpoint. The court ruled that this statement was a biological fact that even physicians affiliated with Planned Parenthood accept![6]

Distinguished scientists and philosophers also back up the court’s opinion. The standard medical text Human Embryology and Teratology states, “Although human life is a continuous process, fertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed.”[7] (Among embryologists, the preferred term for the beginning of life is fertilization instead of conception).

Keith Moore and T.V.N Persaud’s textbook The Developing Human states, “Human life begins at fertilization” and Langman’s Medical Embryology also states that, “Development begins with fertilization.”[8] The fourth chapter of Scott Gilbert’s textbook Developmental Biology is simply titled, “Fertilization: Beginning of a New Organism.”[9]

Finally, David Boonin, the author of A Defense of Abortion, writes, “Perhaps the most straightforward relation between you and me on the one hand and every human fetus on the other is this: All are living members of the same species, homo sapiens. A human fetus after all is simply a human being at a very early stage in his or her development.”[10]

Case Closed

The fact that an individual member of the species homo sapiens, or a human organism, begins to exist at conception (a.k.a fertilization) is, as philosopher Robert George once said, “A stubborn fact of science.” But science can only tell us what something is, not whether it is valuable or has any rights. At this point you should ask your pro-choice friend, “Is there anything wrong with saying that all human organisms, no matter how old or young they are, should have the same basic rights and be treated equally with one another?”

Now you’re on the right track to make a powerful “case for life.” To learn more about how to make such a case, check out my DVD, “Making the Case for Life” available from Catholic Answers.


[1] Carl Sagan. Billions & Billions: Thoughts on Life and Death at the Brink of the Millennium. (Random House Publishing: New York, 1997) 201.

[2] Stephen Wagner. Common Ground without Compromise: 25 Questions to Create Dialogue on Abortion (Stand to Reason: San Pedro, CA, 2008) 69.

[3] These tumors are called teratomas which comes, not surprisingly, from the Greek word for “monster.”

[4] E.L. Potter, M.D., and J.M. Craig, M.D. Pathology of the Fetus and the Infant (3rd Edition). (Year Book Medical Publishers, Chicago, 1975)  page vii.

[5] Peter Singer. Practical Ethics. (Cambridge: Cambridge University Press, 1993) 85-86.

[6] The court ruled: “Planned Parenthood’s evidence at the preliminary injunction stage does not demonstrate that it is likely to prevail on the merits. . . . The State’s evidence suggests that the biological sense in which the embryo or fetus is whole, separate, unique and living should be clear in context to a physician. . . . Planned Parenthood submitted no evidence to oppose that conclusion. Indeed, Dr. Wolpe’s affidavit, submitted by Planned Parenthood, states that “to describe an embryo or fetus scientifically and factually, one would say that a living embryo or fetus in utero is a developing organism of the species Homo Sapiens which may become a self-sustaining member of the species if no organic or environmental incident interrupts its gestation.” Planned Parenthood Minnesota, North Dakota, South Dakota; Carol E. Ball, M.D vs. Mike Rounds, Governor, in his official capacity; Larry Long, Attorney General, in his official capacity” United States Court of Appeals for the Eighth Circuit No. 05-3093 Section I Filed June 27, 2008.

[7] Ronan O’Rahilly and Fabiola Müller. Human Embryology and Teratology, 3rd edition.(New York: Wiley-Liss, 2001) 8. The full quote reads, “Although human life is a continuous process, fertilization (which, incidentally, is not a “moment”) is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte.”

[8] Keith L. Moore and T.V.N. Persaud  The Developing Human: Clinically Oriented Embryology, 9th edition. (Philadelphia, PA: Saunders, 2013). 2. The full quote reads, “Human development begins at fertilization, approximately 14 days after the onset of the last normal menstrual period.” T.W. Sadler. Langman’s Medical Embryology. 11th edition. (Williams & Wilkins: Baltimore, 2010) 13. The full quote reads, “Development begins with fertilization, the process by which the male gamete, the sperm, and the female gamete, the oocyte, unite to give rise to a zygote.”

[9] Scott F. Gilbert. Developmental Biology. 10th edition (Sinauer Associates, Inc: June 30, 2013).

[10] David Boonin. A Defense of Abortion (Cambridge University Press: Cambridge, 2003) 20.

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