I have been privileged to witness thousands of births,several deaths, and I don’t even know how many conceptions. The election-year rhetoric about when life begins annoys me because much of the “science” is being touted by people who have seen at most 2.7 births (and conceptions) and few if any deaths. The argument by the religious right is that all life is sacred (I agree) and the this sacred life begins at conception. Or sometimes, at the presence of the first heartbeat. Well if religious leaders can use science to make theological arguments, I, a scientist, am going to tackle a bit of theology.
When does life end? The term for the end of life is “expire”. This word also means to breathe out. And that is pretty accurate. Whether life ends with the last breath, or with the last heartbeat, in general these occur within seconds of each other so it is usually a moot point. The sister word to this, “inspire” means to stimulation creation, and to breath in. Inspire, expire, breathe in, breathe out, enter life, leave life, create, die. These are ancient concepts, and easily grasped. An exception to this notion is the concept of brain death. Once it became possible to maintain a human body on life support even after all brain function has ceased, this third criterion was necessary. When do you turn off the machine? We needed an answer to this and with the ability to measure brain function, we were able to to devise one. The concept of brain death also allowed us to make tremendous advances in organ transplantation, when a body with its liver, lungs, and heart can be maintained on life support after the brain has died, until that moment when the organs can be harvested for life-saving surgery in others who are unarguably alive.
If we apply these same criteria to when life begins, we come up with a definition close to the traditional Jewish definition of the beginning of life, which is that life begins at first breath. This is actually in the Bible. “the Lord God formed man out of the clay of the ground and blew into his nostrils the breath of life, and so man became a living being,” Genesis 2:7. One must also be able to live without support for one day. The brain-dead cadaver maintained on life support is not alive by these criteria. The 18 week fetus who cannot live outside the mother’s body is also not an independent person by these criteria. The problem is that it takes about 22 weeks from the fertilization of the egg until a baby can possibly live outside the mother’s body and breathe air. The difference between existence of a fertilized egg until a heartbeat appears is 4 weeks. From heartbeat to breathing is at the earliest, 18 weeks. And even then, most infants delivered this early (24 weeks from the last menstrual period) do not survive, not even for one day. The beginning of life, unlike the moment of death, is a gradual process, as first an egg fertilizes, then divides, then separates into embryo and amnion and then over many weeks forms a yolk sac, a heart tube, a body, a head, a gut, limbs, and at last a brain. Once all these are formed, it finally begins to be possible to discern a human embryo from a chick, or a frog, or a goat. Up to that point, they are almost identical except on the molecular level.
The other problem is that if you belong to a misogynist culture, then stating that the life begins as soon as the sperm enters the egg gives you a wonderful way to control a woman’s behavior, at least for 40 weeks (the typical length of a pregnancy). If you also declare that most contraceptives cause abortions because they prevent implantation of fertilized eggs (they don’t), well then she can be pregnant all the time! By the time she is no longer able to bear children, with any luck she will be so indoctrinated that she will just do as she is told.