A fetus is to a person as an acorn is to an oak. Sure, one has the potential to become the other, but is not that other in its current state. The rules governing the cutting of mature trees is not the same for gathering acorns for good reason; the potential to become something does not make you that thing.
You might counter than a baby is not an adult but both deserve the same moral treatment. Or that since the acorn and tree share the same DNA that they cannot be distinguished. Both counter arguments fail. Taking the last first, if I just died, I have my full complement of DNA. Do I deserve to continue enjoying all the benefits of a living person? Should I still collect my social security? After all, I've still got my DNA. And a baby and adult are indeed the same, simply an immature form of one to the other. A baby needs only nutrients and time to mature into an adult . An acorn is a different cycle of life; it must transform to become a tree, not just grow bigger. An acorn is not a tree as common sense would dictate.
If I have a full architectural plan to create a home, and a builder to implement those plans, nobody would say that the plans and builder are the home. Together they have everything necessary to build the house; still, they are not the house.
This is not a political issue, but a religious one masquerading as politics. Proposition 26 in Mississippi (rejected by voters) and its kin elsewhere are nothing but an attempt by Christian extremists to create a theocracy, to impose their religious views on a secular state. Other than religious zeal the effort has no justification.
Most of us would agree, left and right, that prevention, not abortion, is the vastly preferred method of family planning. Abortion is an invasive surgical technique, physically and psychologically traumatic, expensive, and potentially dangerous. Unwanted pregnancy should be exceptional rather than routine. Part of the adult responsibility commensurate with having an active sex life is prudent and careful use of contraception.
Abortion foes claim that the procedure is murder, based on the notion that a fertilized egg has the same suite of rights enjoyed by all humans. The belief that a few cells derived from a fertilized egg is a human being is a sad example of good intentions based on misguided notions of biology. The small ball of cells is potentially a human being, but so are eggs and sperm, even if to an unequal degree. All require certain conditions to realize the potential to become human. Ovulation and male masturbation would be acts of murder by the same logic that confers the status of humanness on a fertilized egg or early-stage embryo. A fertilized egg has no special status compared to an egg not fertilized. Both have the potential to become human given the right set of circumstances. The moment of fertilization is nothing but one action in a series of millions that take us from a single cell to an independently living being. Granting that moment special status is completely arbitrary and meaningless biologically.
Clearly somewhere between a just-fertilized egg and a baby about to exit the birth canal lies a distinction between potentially human and human. Because that line is difficult to draw does not mean that the line does not exist. Yes, the division between potentially human and human is increasingly difficult to distinguish with time from conception, but even later stages of the embryo pass milestones that offer important guidelines.
In the absence of a central nervous system, the embryo is incapable of any sensation. Until a brain is formed with a functioning cortex, the embryo has no ability to form any conscious thought. Neural development begins early, but the process is slow relative to other organ systems. We know from Biology 101 that the three main lobes that will become the brain form by the 29th day. About six to eight weeks after fertilization, the first detectable brain waves can be recorded, but the brain is not nearly fully formed, and the cortex is little distinguished. Before eight weeks, in the absence of any brain function, the growing embryo is little different in its human potential from a fertilized egg. Abortion at this stage is as fully acceptable as menstruation. Biologically the distinction is trivial.
Later stages of growth do not offer a sign as clear as brain development, but the fetus provides another point of determination, although one involving a higher emotional and ethical cost in the hierarchy of decision-making. Before a fetus is capable of living outside the womb at week 23, even with invasive medical intervention, the line from potential to actual human has not been crossed. Before week 23, a premature baby cannot survive. We cannot call something human that has no hopes of survival as an independent being. Again, biology speaks loudly: no human baby has ever been successfully delivered before the middle of the 22nd week. Viability between weeks 23 and 26 is uncertain, but possible. About 10% of babies born at 23 weeks survive. The Office of Science and Technology Assessment reported, too, that 10 percent of babies weighing less than 2.2 pounds born before 28 weeks survived. Lungs do not reach full maturity until week 34, and a suite of life-time medical problems can be expected for births before that milestone. Medical advances can only push this point of viability so far back toward conception, because functioning lungs, even if not mature, must be present for a fetus to survive outside the womb. No amount of medical intervention before that point of development will change this fundamental fact of biology. These undeniable facts of embryogenesis establish a second threshold for abortion at or before 23 weeks. A science-fiction scenario of an artificial womb in the far future would not change this calculation of natural development. This hard biological reality corresponds closely but not precisely to the Supreme Court's 1973 decision that states could not bar abortion until "the point of viability" which was set at around 24 to 28 weeks of pregnancy.
Note that about 90 percent of the 1.6 million abortions in the United States each year occur in the first three months of pregnancy, well within the biologically clear limit of 23 weeks.
Beyond the point of viability outside the uterus, the threshold for when an abortion is a reasonable choice certainly becomes significantly higher. Even many pro-choice advocated would agree that late-term abortions are difficult to justify, except in the extreme case of rape or incest in which the victim had no access to medical care earlier in the pregnancy.
But the moral uncertainties of late-term abortion have no bearing on the question of whether a fetus or a fertilized egg is a person. Just because we cannot define a point at which a fetus becomes a person in the spectrum of life does not imply we cannot know when we are clearly on one side or the other of that point. I know when something is green and when something is blue but I cannot tell you when one color yields to the next. Any attempt to define where one color ends and the other begins becomes arbitrary because green turns to blue across a smooth gradient of frequencies with no inherent boundaries. But we still know when something is green or blue. We also know that a fetus is not a person even if we do not know when that transition to person-hood eventually takes place. Nothing about biology or ethics compels us to call a fetus a person. The debate has plenty of gray in the middle in which honest people can disagree. However, calling an early fetus or fertilized egg a person is a religious view unsupported by fact or reason; that has no place in a secular society.
Those people who hold those views are welcome to act on them accordingly; but please do not impose your religious views on those of us who do not share them. I am not forcing you to act personally in any way counter to your personal beliefs; you have no justification to impose your views on me, to legislate my wife's or daughter's relationship with their doctor, or interfere with how they decide to deal with their own bodies. My views do not interfere with how you live your life; yet your views seek to change mine. No conservative has ever explained the ironic disconnect between the stated disdain for big government and the desire to have that very government enter my bedroom and doctor's office. So to those of you who support Prop 26 and similar pieces of heinous legislation, I offer you this advice: back off.
Jeff Schweitzer is a scientist, former White House senior policy analyst and author of Calorie Wars (July 2011) and A New Moral Code (2010). Learn more about Jeff at http://jeffschweitzer.com.