As a retired, board-certified physician trained in and living in the USA, it is with some trepidation that I am sharing my opinion as to whether human embryos are persons. But I want to point out some useful nuances.
First, if a state law says that embryos are persons for legal reasons, then I think the state has the right to define their status. However, I believe that laws should be carefully written based on facts and with a good understanding of the consequences of the language.
Secondly, a fertilized egg is on a developmental continuum. Many believe that a well-defined threshold for the onset of personhood cannot be defined and that a human embryo is a person from the moment of conception. This is the strong belief of traditional Roman Catholics. But I want to point out that the critical words “from the moment of conception” must not be used casually and without careful thought.
When a single sperm cell breaks through the egg’s wall, and the male’s DNA first enters the periphery of the cytoplasm, is the cell instantly a person? Or must we wait a few more minutes for the male DNA to closely associate with the female DNA within the egg cell before granting personhood? Or wait more time for the spherical ball of multiple cells, called a blastocyst, to appear? Or wait a week or so until the growing clump of cells flattens into a thin disc that eventually has two layers of cells, though there is then no brain or heart. The amniotic cavity will develop on one side of that disc and the rest of the placenta on the other side.
But nature has done important experiments for us that provide useful insights: monozygotic twins. These arise when an early embryo mysteriously splits, eventually resulting in babies with identical DNA. As the monozygotic twins enter kindergarten, the parents sometimes dress them alike. But ask these parents and the twins themselves. They will affirm that each twin is a distinct person. Religious people would have no trouble opining that each twin has their own soul. At what exact point did one sperm and one egg that formed a single embryo split to become two people?
Science informs us that the split did not occur “at the moment of conception;” the path to two persons occurred a little later in development. This delay will inform us of the answer to our question: Are human embryos persons? The question must be rephrased a little, though, which is vital. We should not ask if human embryos are persons, but instead, we should ask when they become persons. It seems clear that an embryo is not truly a person in the usual sense of the word on the first day if it can turn into two persons later.
The Virginia Center for Reproductive Medicine states, “Splitting of the embryo may occur at any time during the first 2 weeks after fertilization, resulting in several forms of monozygotic twins.”
The website goes on to document the following scientific facts:
“In about one third of the MZT cases, the splitting occurs within 72 hours of fertilization and the placenta will be dichorionic-diamniotic (i.e. two placentae and two amniotic sacs).
In about 2/3 of the MZT cases, the splitting occurs 4-8 days after fertilization, and the placenta will be monochorionic-diamniotic (one placenta and two amniotic sacs).
In 5% of the MZT cases, the splitting occurs 8-13 days after fertilization, resulting in monochorionic-monoamniotic twins (one placenta and one amniotic sac).
Rarely, the splitting occurs after 13 days, resulting in conjoined twins.”
Let me point out that conjoined twins can sometimes be surgically separated, and they will tell you that each is a distinct person.
A religious person (and I am one) might argue that God placed one immortal soul into the embryo at the instant of conception and then placed a second immortal soul in other cells a few days later. Alternatively, two immortal souls were placed at the start in a single embryo destined to split. These possibilities might be true. But as a scientist, I often adhere to Occam’s razor, which invokes the simplest explanation. In religious language, delayed ensoulment, perhaps two weeks after fertilization, is the most straightforward explanation.
The Alabama lawmakers might not have realized that birth control pills block the implantation of a fertilized egg into the uterine wall. So, a poorly written law might make it seem that birth control pills are causing the deaths of children rather than just preventing the very early development of the embryo. Perhaps part of the controversy could be dissipated by carefully rewriting the law so that the personhood of embryos is not deemed to exist until after fourteen days.
James Magner, MD, is an endocrinologist and scientist who has worked in academic medicine and the pharmaceutical industry. The author of five books and scores of scientific articles, he was an Eagle Scout and likes chess and poker. He lives with his wife in Connecticut.
