When does human life begin?

Let’s start with some basics. Prior to uniting during fertilization, a human sperm and a human egg are both alive and human. That they are both human is undeniable, based on their sourcing. That they are alive can easily be demonstrated by autoclaving them and then testing whether they can still participate in fertilization (they can’t; autoclaving kills gametes). So in a real and meaningful sense, human life precedes fertilization. Indeed, there has been no point in the history of our species when human life began, since it is a continuum. Are you with me so far?

So if by “human life,” you mean human diploid life, then does it begin when the sperm head (containing the paternal haploid complement) fuses with the oocyte (containing the maternal haploid complement)? Well, no, because it takes several hours for the two pro-nuclei to fuse. Then there’s the small matter of when the zygote implants in the uterus. Without implantation, the zygote is lost. Many human conceptuses are lost that way. Don’t blame science; that’s just God’s will.

But each conceptus is a genetically unique individual, since both gametes are products of both meiotic recombination and independent assortment. Well, as the fertilized egg divides and divides again and the cells proliferate, there is a significant period of time during which the zygote can break apart. This is the basis for monozygotic twinning (identical twins). If unique human life began at conception, then is one of these identical (and therefore not genetically unique) twins human life and the other not? Since they are genetically identical, one is just a back-up, right?

Human conception is terribly inefficient. Most conceptuses don’t make it to birth, due to genetic defects. Most of this loss occurs during the first trimester. So God is the greatest abortionist of all time. Maybe God is telling us something—that S/He doesn’t consider human tissue to be a human life worth protecting until after the first trimester?

If a cluster of human cells is a human life that demands legal protection, then what about a wart? What about amputation? What about expired blood donations? And finally, what about the millions of zygotes in freezers of fertility clinics? If a freezer thaws, is that mass murder?

Look, if your religion tells you that legally human life begins at conception, then you are confusing church and state. Don’t have an abortion, but you don’t have a right to have the nanny state enforce your personal religious beliefs. And don’t draft science to support your forced-birth beliefs. Science doesn’t establish the idea that there is any single point at which “human life begins.”

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