@Peter phil,
I do know a fair amount about fetal development, both because I'm a pediatrician and because my wife and I are expecting a baby in about 3 months and we've been learning a lot about it.
But I think that in this debate, it is simply impossible for there to be complete synonymity between 1) ethical views of humanity and human rights, 2) law, and 3) biology.
Are we prepared to make our ideas of humanity hinge upon technology (like amniocentesis and fetal ultrasound), and have interpretation of this technology depend upon scientifically standardized criteria and expert operators? If not, then we CANNOT talk about pain perception, heartbeat, consciousness, etc as criteria for
humanity because in any individual case no one knows when they occur unless you look using technology.
Clearly biological human life begins at conception. But that does NOT mean that a conceptus is morally a human being. Why? Because some fertilized eggs develop into hydatidiform moles, some develop into invasive choriocarcinomas, some implant ectopically, etc. And these are things that will NEVER under ANY circumstances develop into a live human -- and in many cases will also kill the mother. So if treating choriocarcinoma with chemotherapy is considered
murder simply because
this cancer arises from a fertilized egg, then we've got some serious problems in how we define a human.
But it's seldom clear early on that one of these errors has taken place, so even identifying these 'exceptions' requires medical technology. Furthermore, there are more subtle sorts of genetic and developmental error than this, and so the moral distinctions are unclear. I mean, I have ZERO moral problem with aborting an anencephalic baby -- this is a fetus that has no brain due to a neural tube defect, but there are enough brainstem functions for the infant to survive for a few months on a ventilator. I have ZERO moral problem with aborting a baby with Tay Sachs disease, which is fatal in 100% of cases by age 4 or 5. And I'd have no problem aborting a baby with Duchenne's muscular dystrophy, spinal muscular atrophy, or even cystic fibrosis, knowing what I do about these diseases (and also knowing that
some people with CF have long and productive lives).
So we get to the point where our ability to identify a
healthy fetus also forces us to make decisions about an
unhealthy fetus -- and unless you're going to throw up your hands and call it God's will that some children suffer horribly for a 4 year long miserable life, then you're also going to have to weigh the moral implications of abortion versus the moral implications of
not aborting in some cases.
Thus, this decision in the end is almost always utilitarian -- not moral (and certainly not some weird marriage between morality and biology). Furthermore, we
never know when conception occurs except in retrospect after pregnancy has been identified (this is excepting
in vitro fertilization), the use of conception as a morally significant moment has no practical utility at all.
Thus, abortion laws
must be compromises, and moral humanity
must be different than
biological humanity.