Note: This blog touches on a hugely controversial topic and is not meant to persuade anyone to change their minds but is rather meant to discuss the various factors in people's understanding of the issue and ethical/legal conclusions that they draw from said understanding.
One of the seemingly toughest questions that is actually one of the easiest questions in the world today is, "When does life begin?" It's one of the several questions that surround the "What is the meaning of life?" conversation, which also includes what happens when you die, why you're born, and what you're supposed to do, be, or learn while you're here on Earth. Of course, there is an unanswerable spiritual element (for those who believe) of when your spirit inhabits your body as well as agreed-upon ethical questions regarding human rights, their origin, and the attributes that give you them. But out of all of those tough questions that cross the biological, physical, and non-physical realms, "When does life begin?" is the easiest one of them all.
You are a living organism that started as a fertilized egg in your mother's womb (or, if you're reading this years in the future, maybe an artificial womb!) where a sperm and egg came together to form a new, unique genetic sequence. It is scientifically, absolutely true that your life began at that moment. You stay in the womb for nine months for one simple reason: you couldn't survive outside of it. Ironically, you can't survive immediately after you're born either, but that is unique to species of organisms with birthing limitations such as humans whose birth canal cannot fit a fully developed human body and brain (complete with a giant skull) through it.
So why do scientists obfuscate this simple fact? The ethical implications. If a person admits that life begins at conception, then one feels pressured to conclude that intentionally ending that life before birth is "killing" or, using the legal term, "murder". It basically gives people with the political viewpoint of making pregnancy termination illegal the moral and legal high ground. So, no matter how much of a proposed "person of science" someone claims to be, he or she will knowingly state the falsehood that "Scientists don't know when life begins." All the discussions about heartbeats, consciousness, feeling pain, and viability are ethical lines for when ending its life would seem barbaric, not scientific definitional lines of when the life began. Organisms are not like buildings where you don't say the building is a real thing until the ribbon-cutting ceremony (see what I did there with the reference to umbilical cord-cutting?).
But this is not a post telling you what ethics you should hold. Instead, we'll explore why it's an ethical issue and then come back to truth vs. ethics in life and its beginnings.
People search for ethical lines to draw for a very specific reason: human life begins within another human being. Because of that, there is a conflict of two competing ethics:
Clearly, pregnancy creates a conflict between these two ethics: it’s one body growing inside of another body, so if someone wanted to remove this organism growing inside of her (as the first ethic would allow you to do), she would have to violate the second ethic (because it would end the life of a human organism). This is the ultimate form of ethical conflict, surpassing the great debates of human history such as territorial and religious conflicts in the Middle East and giving people the right to vote without the responsibility of conscription.
The interesting thing about this debate is that if humans could grow in an artificial womb or a woman could "turn off" their ability to reproduce, then the debate would be over: you wouldn't be able to kill a person because there is no competing ethic to violate. You can't just kill a fetus in an artificial womb because it's not inside a woman's body where the woman would need autonomy over it. If someone could only get pregnant through consciously choosing to, then accountability would fall on the person who made the choice. Combine the two, and now you have an organism that was deliberately created and is not infringing on anyone's liberty by existing, thus having 100% protection from the day it's fertilized. The ethical thing to do in every circumstance would be to not kill the fetus.
But we don't live in a world (yet) where those two conditions are completely true. Because a woman has to carry the child and because she can't choose whether or not she conceives on-demand (because forcible sex is always possible and impermanent prevention methods are not 100% effective), there are situations where the ethics are not as obvious as "don't kill people" without any reason for doing so. As most people know, the three main legitimate reasons given for ending a fetus's life are rape, incest, and the life of the mother. The ideas here are those two conditions manifesting in three ways: the woman did not consent to having her egg fertilized, the child might have genetic defects that make him or her unviable, and the child-bearing process might pose health risks to the mother who should be able to put her health before her responsibility to give birth to the child.
Because of these two competing ethics and these various conditions that put liberty in direct conflict with life, the legal system has to draw a line as to when one ethic supersedes the other so they can write a law that they can enforce. Effectively, which ethic is more important at any given time. This is the real reason for the lines as to what people falsely claim are "when life begins"—it is really when the liberty ethic should no longer trump the life ethic. There are six primary lines that people draw:
Note that each line drawn is based on a different logical perspective of the ethical dilemma: life trumps all; a person is legally alive when his or her heart starts until it stops; it becomes ethical to hurt things that perceive or feel pain; "I know it when I see it"; it can survive on its own; it's out. Each of the arguments have a logic to it, and each one is about figuring out whether the life has progressed enough where it's more important to keep it alive than protect individual liberty.
Two final points on the ethics of when life begins: legality and logical consistency (i.e., hypocrisy). Remember that the line being drawn here is a legal and not ethical one. Everyone would agree that a dead fetus is a negative outcome. Everyone would agree that having to carry a consequence of rape for nine months is a negative outcome. So it's not about good or bad when it comes to the courts; it becomes about agreeing to what the law needs to be so that you can enforce behavior. This is why arguments such as "safe, legal, and rare" exist.
As for the logical consistency, you can probably tell that you can make any line seem logical but then also show inconsistency across other situations. For example, if someone chants "my body, my choice" as an argument and then want to force others to take a vaccination, then they don't really believe that brief statement in its literal meaning (i.e., if you could do whatever you wanted with your body, you could refuse to inject it with a chemical). People on that side of the political debate also have a list of scenarios where they want to protect people from themselves, such as people being restrained if they're suicidal, homicidal, or practice self-harm—unless it's for an abortion, in which case that rule doesn't apply. On the other side, the argument is that they care about unborn children but don't want to provide healthcare and also support the death penalty (note, however, that this isn't technically an inconsistency since not killing an innocent person is different than guaranteeing that it receives services or punishing a guilty party for committing a crime—it would only be inconsistent if they shouted, "your life should always be sustained," which they do not). In that case, however, they are choosing to punish the victim of the crime to protect the new innocent life that would be a second victim if terminated.
There are many aspects to the legal part of the rule: personhood and protection under the law become clear and definitive at birth because the organism is separate. The criminal justice system would get more complicated and difficult if every miscarriage and stillborn child had to be investigated and ruled a natural death or murder, so there's a pragmatic element to it as well. Additionally, teenage rape victims might have to carry a rape baby to term or be jailed for murder; alternatively, a law only allowing exceptions for rape might lead to thousands of false claims and imprisoned innocent men. The ethics in the lawmaking go far beyond the direct impact and cover enforcement and the societal consequences. That's why the "when life begins" argument is yet one of many factors that go into the ethics and legal ramifications of pregnancy termination.
Seeing all of those complications and complexities, you can now see why the objective, scientific reality of when life begins is obfuscated: it would give more credibility to arguments moving the line closer to conception and, therefore, leading to more women who are legally obligated to bring an unwanted pregnancy to term. While technology is getting better over the years and pregnancies are more preventable in ways that are near-universally acceptable (e.g., contraception, Levonorgestrel), there is still majority acceptance of first trimester terminations that are long past the point at which it objectively is a living organism. In psychology, it is called "cognitive dissonance" in that a person would consider themselves a monster if they killed human life, so rather than move the bar and prevent women from hurting the fetus they dehumanize it (e.g., "clump of cells", "not a person", "parasite", and "it's not a baby; it's a fetus"). Despite the fact that one could make an argument that the ethical line of life is at conception and the legal at birth, it is difficult for humans with competing arguments to hold complex, somewhat conflicting ideas at the same time and so they often simplify things down to one argument and one line.
Therefore, while we might never know what happens when you die or why you came here (i.e., the intent—if there is one), we do know definitively when life begins. That does not mean that the ethics are clear, as they are definitely not. In a perfect world, there would be no terminations of pregnancies...but there would also be no rape, no health complications during pregnancy, and no genetic problems causing a child to not survive for very long. Because those things all exist, there is now a societal agreement/compromise that has to be struck about how to handle this situation in the court of law. What rights do mothers have, unborn children, and even fathers (imagine a scenario, for example, where both parents want to have a child and a mother changes her mind for non-health reasons at the last legal second—there are two parties negatively impacted by that decision).
The problem with ethics is that they only manifest into rules based on what the humans that set them can agree upon—there is no magical set of universal, perfect ethics that exist for us to find. That's why laws need to change over time: ethics change over time. Regardless of how the ethics of this situation shape up, however, one thing is certain: you as a living organism began once that egg was fertilized and you became your own unique DNA sequence. There might be a spiritual answer that is different (e.g., your spirit comes in midway) or a philosophical or ethical one that is different (e.g., consciousness is required for the action to be immoral), but those will never be definitive. There might also be a day that comes where we can make reproduction such a deliberate act that ending it would be clearly, objectively immoral and deserving to be illegal; until then, we'll have to deal with the ethical conflict and, therefore, the definitional obfuscation at the societal level as well.
Note: If you wonder why people who claim to be truth seekers would obfuscate the truth, I will recite a line I use over and over again in my writings: people don't care about truth; they care about outcomes. If the truth prevents them from attaining a desired outcome, they will believe what benefits them instead.