The Science of Abortion: When Does Life Begin?

In a recent interview, Senator Marco Rubio (R-FL) declared it is a scientific fact that “human life begins at conception.” He also said that “leaders on the left” who “wag their fingers” about the “settled science” of global warming are hypocrites when it comes to science, and someone should ask them if they accept the “consensus of scientists that says that human life begins at conception.”

Going further, the senator added, “I’d like to see someone ask that question. It’s never asked. And that’s not even a debatable thing, we can actually see that happening. I mean, that is a proven fact. And yet that’s a scientific consensus they conveniently choose to ignore.”

In the wake of these remarks, MSNBC reporter Irin Carmon and Washington Post blogger Philip Bump pushed back at Rubio, asserting that:

  • he made a “scientific blunder on abortion.” (Carmon)
  • “conception” and “life” “aren’t scientific terms.” (Carmon)
  • “the scientific experts we spoke with didn’t offer any consensus” on when life begins. (Bump)

However, as documented below, the facts of science support Rubio’s point and reveal that the claims of Carmon and Bump are scientifically baseless.

Science shows that life begins at conception
Contrary to Carmon’s allegation that “conception” and “life” are not scientific terms, both of these words are clearly defined in science dictionaries and widely used in scientific literature.

To cite just a few examples, the American Heritage Science Dictionary defines “conception” as “the formation of a zygote resulting from the union of a sperm and egg cell; fertilization.” (For reference, a zygote is the first stage of a human embryo.)

Likewise, the entry for “life” in the American Heritage Dictionary of Science states that life is “the form of existence that organisms like animals and plants have and that inorganic objects or organic dead bodies lack; animate existence, characterized by growth, reproduction, metabolism, and response to stimuli.”

Rubio’s statement that “human life begins at conception” is consistent with both of these definitions, because human zygotes display all four empirical attributes of life:

  • Growth—As explained in the textbook Essentials of Human Development: A Life-Span View, “the zygote grows rapidly through cell division.”
  • Reproduction—Per Human Sexuality: An Encyclopedia, zygotes sometimes form identical twins, which is an act of “asexual reproduction.” (Also, in this context, the word “reproduction” is more accurately understood as “reproductive potential” instead of “active reproduction.” For example, three-year-old humans are manifestly alive, but they can’t actively reproduce.)
  • Metabolism—As detailed in the medical text Human Gametes and Preimplantation Embryos: Assessment and Diagnosis, “At the zygote stage,” the human embryo metabolizes “carboxylic acids pyruvate and lactate as its preferred energy substrates.”
  • Response to stimuli—Collins English Dictionary defines a “stimulus” as “any drug, agent, electrical impulse, or other factor able to cause a response in an organism.” Experiments have shown that zygotes are responsive to such factors. For example, a 2005 paper in the journal Human Reproduction Update notes that a compound called platelet-activating factor “acts upon the zygote” by stimulating “metabolism,” “cell-cycle progression,” and “viability.”

Furthermore, the science of embryology has proven that the genetic composition of humans is formed during fertilization, and as the textbook Molecular Biology explains, this genetic material is “the very basis of life itself.”

In accord with the facts above, the textbook Before We Are Born: Essentials of Embryology and Birth Defects directly states: “The zygote and early embryo are living human organisms.” This may be controversial from a political perspective, but the sciences of embryology and genetics leave no doubt as to when human life begins.

ACOG is not an objective scientific authority
Bump’s article is entitled, “Marco Rubio demanded people look at the science on abortion. So we did.” Yet as far as the article reveals, the entirety of Bump’s “scientific” research consisted of speaking to a single organization: the American College of Obstetricians and Gynecologists, or ACOG.

While Bump’s article clearly shows that ACOG avoided the question of when life begins and attempted to change the subject, Bump did not articulate this to his readers. Instead, he used ACOG’s non-answer to conclude that life “is something of a philosophical question,” and “the scientific experts we spoke with didn’t offer any consensus” on this issue.

That is not “looking at science,” as Bump claims he did. Rather, it is cherry-picking the opinions of selected scientists and uncritically relaying them. It also presumes that the chosen scientists are unbiased and incontestable authorities on this issue, which is demonstrably not the case with ACOG’s leadership.

For instance, when a debate over partial-birth abortion was raging during the Clinton Administration. ACOG prepared a statement disclosing that a “select panel convened by ACOG could identify no circumstances under which this procedure, as defined above, would be the only option to save the life or preserve the health of the woman.”

Yet instead of releasing this information to the public, ACOG faxed it to the Clinton administration with a header that stated: “CONFIDENTIAL, NOT FINAL, DO NOT COPY, DO NOT DISTRIBUTE.”

This document came to the attention of a White House lawyer and policy advisor named Elena Kagan (later appointed by President Obama to the Supreme Court). She was displeased with ACOG’s conclusion and wrote a memo warning that its release would be a “disaster,” especially since ACOG opposed banning partial birth abortions.

Kagan then proceeded to edit ACOG’s statement by adding that partial-birth abortion “may be the best or most appropriate procedure in a particular circumstance to save the life or preserve the health of a woman….” Those words did not reflect the thrust or scope of ACOG’s findings, which Kagan clearly understood because she had detailed them in a previous memo.

Nevertheless, ACOG adopted Kagan’s words as its own, thus using the rhetoric of a Clinton administration lawyer in place of its own medical conclusions. Those are not the actions of an objective scientific authority but of an organization that is willing to place politics over science.

What is science?
There is a lot of posturing about science in the world of politics, but some of what is reported as “science” is actually just the claims of selected scientists, which happen to be at odds with the facts of science.

Science, in the words of Webster’s College Dictionary, is the “systematic knowledge of the physical or material world gained through observation and experimentation.” Notably, this does not entail parroting the assertions of someone with scientific credentials.

In the realm of science, what matters is facts and logically inescapable conclusions that flow from them—not opinions, no matter who voices them or how prevalent they are. A classic example of this is Galileo, who wrote that when it comes to the sciences, “the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.”

In this instance, Rubio is that man, and Carmon, Bump, and ACOG are substituting their ideology for science in the public debate over abortion.

 Editor’s note: This essay first appeared June 10, 2014 on Just Facts and is reprinted with permission.

James D. Agresti


James D. Agresti is the president of Just Facts, a nonprofit institute dedicated to researching and publishing verifiable facts about public policy.


    Life begins at conception. That which is conceived is so small that the most powerful microscope in the world can’t see it, but it begins to grow.

    And – if it’s growing it’s ALIVE.

  • Sign

    Apparently the Pelvic Left needs “experts” to point out the obvious.

  • john

    Your last point–that what counts as “science” in public discourse is just as much a product of power as objective research–is really the most important one. It gratifies us to know that there is a natural order to the universe and that abortion violates it, but Americans’ pretentions to rationalism notwithstanding, the policies around abortion will not be made more just as a result of science. On the other hand, like all other battles worth waging, it is still an important tool in the rhetorical struggle,which may bear fruit in concert with the Holy Spirit…

  • Though it is not absolutely certain either just what constitutes a scientific consensus or
    settled science or that any given scientific consensus or settled science will
    remain such, Rubio and the author do make a powerful point: we should not
    choose to ignore scientific consensus or settled science. This is so when the scientific
    consensus or settled science bears on the question of whether human life begins
    at conception. But it is also so when it bears on that of whether we are witnessing
    global warming induced by human activity.

    • James Blazsik

      Richard, common sense tells us that life begins at conception. This is an every day occurrence, concurrent with everyone.

      Global warming caused by human activity is not. There isn’t any actual scientific proof of it, just computer models. The size and complexity of the earth and ecosystem is such that any prediction that goes, say a 100 years in the future, is human conjecture and not science.

      The global warming thing is the stuff of politicized science and nothing else.

      • Well, at least you’re not ignoring the scientific consensus; you’re dismissing it outright.

        • Augustus

          No, he’s appealing to the hard science, rather than those who believe in man-made global warming based on faith. There has been no consistent warming of the planet in the last 15+ years. Growth in Co2 does net necessarily correspond to warmer climates. There is plenty of evidence to show that the sun is the determining factor in the earth’s climate. Honestly looking at the evidence with clear eyes is not ignoring or dismissing the so-called “scientific consensus.”

      • Louise

        Yes, there is a scientific “conspiracy” worldwide fudging the facts on climate change. Get real.

    • michael susce

      “Though it is not absolutely certain….. that any given scientific consensus or settled science will remain such”. What wisdom!. We cant be absolutely certain if the earth revolves around the sun or whether the earth is round…..whether blacks are equal to whites….. whether the holocaust occurred or not….if the universe exists…..And I am so glad that you are absolutely certain that there cannot be absolute certainty in any settled science……

      • I will happily grant that my opening clause does not give full expression to a comprehensive understanding of science. But my actual point was that one should not ignore [or simply dismiss] scientific consensus or settled science when it points in a direction you are uncomfortable with, even as you appeal to scientific consensus or settled science when it points in a direction you are comfortable with.

  • Michael Rzeppa

    I knew this in High School before abortion was legal. Back then there was no question on the beginning of life it is only when abortion was legal that it’s cheerleaders try to spin it into something plausible.

  • Julie

    This a great article and it does justice to Rubio’s comments. However, pro-abortion people know that unborn are living and it is life in the womb, but they state that the woman’s life is more important. It doesn’t matter what her reason for deciding to abort. Their consensus is she has the power to decide to murder her child. Pray they listed to the Holy Spirit and turn from their sin.

  • tamsin

    Amazing to read about Elena Kagan’s involvement in this, editing the ACOG statement and helping to redefine the goal of partial-birth abortion away from the fact of killing a child in utero, towards “preserving the health” of a woman who finds herself in “a particular circumstance.”

    • Sign

      That anyone can genuinely believe her propaganda is sad.

  • Son of Stonega

    ACOG and “science” should not be uttered in the same breath. “Conception” had always been accepted to mean the moment of fertilization (even by ACOG). When IUD’s were ready to burst on the scene, ACOG changed the definition of “Conception” to be the time of implantation. This allowed the manufacturers of IUD’s to deny the reality that their devices caused abortion of very early children because the new definition meant these children were not even “conceived”.

  • hombre111

    Pretty well done.

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  • David Kenny

    Re. Richard Hennessey’s comments. There is no consensus of scientists on global warming. There are about 70 scientists who are actively pushing this concept and who also have significant influence in placing research grants and who benefit from personal recognition. The 2000 scientists often quoted are researchers whose grants and recognition depend on the support of the key 70. The famous liberated e-mails from the British and US climate centers show clearly that those who control the publications use isolation, threats and discrimination in placing grants, approval for publishing and journal representation to force researchers to follow their lead (particularly the UN IPCC) in setting the theories and conclusions regarding climate research. Any knowledgeable engineer in aerothermodynamics will soon recognise that the concept of man made global warming is utterly unsupportable by basic physics.

    • Louise

      What planet are you on? There IS a consensus on climate change. You just don’t want to acknowledge the facts. What is it with all you (religious) conservatives and your head-in-the-sand position?

      • David Kenny

        Replying to Louise. Perhaps you could quote some facts and logic to support your accusations against me. It is impossible to have a rational dialogue with emotional comments and ad hominem attacks. Attacking me personally is not an argument but it is an attempt to shut me up. How do you know whether I am a (religious) Conservative; I didn’t say that. I AM an aerospace engineer with 40 years experience and a depth of knowledge in aerothermodynamics and physics and an in-depth knowledge of the facts having studied the physics and data for the past 10 years. Obviously you didn’t read what I said, where I pointed out that there is no consensus on anthropomorphic global warming because only 70 scientists actually promote this concept. You obviously have done no research or reviews on the subject, particularly the physics analysis. If you don’t do this, you are simply repeating what someone else claims and accepting it as true with no factual basis.

        • Louise

          Stop embarrassing yourself.

  • Stephanie

    I think everyone knows that a new human life begins at conception. People deny it because they want unrestricted sex and know that abortion is needed as a backup for when contraception fails, because no matter what some people try to tell you contraception is never 100% effective. The sad truth is that some of them would rather murder the child than raise him/her or place him/her for adoption. Others are being pressured into abortion and need help to carry the child to term.

    • Louise

      Yes, “life” begins at conception. So what? That is entirely different from saying a zygote has the same rights and personhood as the woman carrying the zygote. The woman’s life takes precedence over a zygote. If you want to debate at what stage “on-demand” abortion becomes problematic that is fine. However, if the woman’s life is in danger, a late-term abortion should be permitted.

  • Judie Brown

    Agresti has avoided defining the fact that there are also human beings who begin their lives in an asexual manner including monozygotic twins. In this sense and for the sake of accuracy the word “conception” is inaccurate. Let’s take care not to leave a single pre born human being behind.