In a previous life, I spent a lot of time in classes with titles like Genetics, Human Evolution, and Vertebrate Embryology. The struggles of philosophers, ethicists, and biologists to decide when ‘human life starts” are legendary and different people have come to different conclusions about this. This background seems relevant today because we now have 40 million women in the US population living in places where they have just lost access to reproductive health care. And, many more American women will if the GOP-Evangelical-Catholic cult of death and the Supreme Court they now control have anything to say about it.
However, there is a fundamental flaw in the question, “when does human life start?” – because life does not start and stop, it’s continuous. None of us came from gametes that were not living. The idea that a fertilized egg is human is widespread, and I have heard right-wing political candidates echoing it. So, if human life starts at conception, a fish, an amphibian, a reptile, a bird, or a non-human mammal must also have their life begin at conception.
Unfortunately, it’s not that simple – look inside a fertilized egg cell from any vertebrate, and there is no little animal (or human). What is in a fertilized egg? The genetic code, half the chromosomes (23) from the mother and half the chromosomes (23) from the father. This pattern holds true for vertebrates (but the number of chromosomes changes with the species). The genetic code is stored in the chromosomes, packets of DNA wrapped in proteins. The code is a set of instructions on how to make an animal. Think of it as a blueprint to make the animal. If you have a blueprint for your house – you don’t call the blueprint a house, It’s not a house, it’s directions to make a house.
Pro-life proponents will be quick to tell you that each fertilized egg is unique. They are correct but are misleading you into believing that the differences make each person special. For example, a female American Bullfrog lays clutches of 20,000 eggs several times each summer. And, each one of the fertilized eggs is unique in having its own genetic code – so if all of those eggs develop from one clutch, you have 20,000 genetically unique Bullfrogs.
Thomas Aquinas (1225 –1274) was an Italian Dominican friar, priest, and influential philosopher, theologian, and jurist. He was a prominent proponent of natural theology and the father of a school of thought known as Thomism. He argued that God is the source of both the light of natural reason and the light of faith. He has been described as “the most influential thinker of the medieval period” and “the greatest of the medieval philosopher-theologians.” His influence on Western thought is considerable, and much of modern philosophy is derived from his ideas, particularly in the areas of ethics, natural law, metaphysics, and political theory.
In the 13th century, Aquinas argued that an embryo or fetus is not a human person until a rational soul informs its body. Contemporary biologists have generally rejected Aquinas’s explicit account of human embryology because it was based on medieval biological data, which has been far surpassed by modern scientific research.
In placental mammals, gestation is a gradual process, and the embryo and fetus are best thought of as parasitic on the mother’s body. The embryo needs oxygen and nutrients (sugars, fats, amino acids, vitamins, and minerals). The embryo/fetus also needs to remove nitrogenous waste and carbon dioxide. The only way the developing embryo/fetus obtains these molecules and services is via the maternal blood stream and placenta. Once the embryo reaches viability – the point in development where it can survive outside the uterus seems to be the most obvious point at which it can be considered human.
Banning abortions post 22-23 weeks seems reasonable. Anything before that is draconian. The GOP-Evangelical-Catholic cult of death is untrustworthy–in how they portray embryos and how they have manipulated their extremist followers to terrorize and kill abortion providers.
The cult will go out of its way to protect those parasitic, incompletely formed embryos, but obviously has no problem selling AR-15s to massacre school children.