Once upon a time I didn’t know much about the case for abortion rights or the case for the right to life of unborn children. My reason for not reading much about it is that I thought that it was kind of a subjective issue. But, I started a project to read 1-2 books on every conceivable topic, including one on abortion. Lo and behold, it turned out that one side did have the backing of science.

This article from The Public Discourse explains: (links removed)

The following are typical examples—only three of the many, many we could cite. These are from standard texts by embryologists, developmental biologists, and microbiologists:

“Human life begins at fertilization, the process during which a male gamete or sperm unites with a female gamete or oocyte (ovum) to form a single cell called a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual.” “A zygote is the beginning of a new human being (i.e., an embryo).” Keith L. Moore, The Developing Human: Clinically Oriented Embryology, 7th edition.

“Fertilization is the process by which male and female haploid gametes (sperm and egg) unite to produce a genetically distinct individual.” Signorelli et al., Kinases, phosphatases and proteases during sperm capacitation, Cell Tissue Research.

“Although life is a continuous process, fertilization (which, incidentally, is not a ‘moment’) is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte” (emphasis added; Ronan O’Rahilly and Fabiola Mueller, Human Embryology and Teratology, 3rd edition.

The genetically distinct part is key – this unborn child is has a different DNA signature (a human signature) than either the mother or the father. Nothing will be added or taken away from this new signature as the unborn child grows. It never changes.

More:

These authorities all agree because the underlying science is clear. At fertilization—or, more precisely, when the sperm (a male sex cell) fuses with the oocyte (a female sex cell, more commonly referred to as an egg)—each of them ceases to be, and a new entity, one that is both genetically and functionally distinct from either parent, is generated. This new entity, initially a single totipotent cell, then divides into two cells, then (asynchronously) three, then four, eight, and so on, enclosed all the while by a membrane inherited from the oocyte (the zona pellucida), which then dissolves during implantation, allowing for continued growth in the direction of maturity as a member of the species. Even prior to implantation, however, these cells and membrane function as parts of a whole that regularly and predictably develops into the more mature stages of a complex human body.

How do we know that the result of sperm-oocyte fusion is a new entity, rather than a continuation of the oocyte? We know that a new entity exists because, once the sperm penetrates the oocyte, a completely new trajectory of biological development commences. The biological activity of an oocyte is directed toward successful fertilization; the biological activity of sperm is directed toward penetration of an oocyte. The biological activity of the new entity that results when sperm and oocyte fuse, however, is directed toward nothing less than the development of a mature human organism, distinct from either parent. Further, this new entity’s activities are directed not by instructions from the mother’s body, as some people wrongly suppose, but by its own unique set of instructions, especially the blueprint for development contained in its unique genetic material. The mother’s body recognizes the zygote and then the embryo as an entity distinct from itself. In fact, the embryo must send out chemical signals to prevent the mother’s immune system from attacking it. The embryo also emits chemical signals that induce changes in the lining of the mother’s uterus to enable successful implantation.

If this embryo is provided a suitable environment, nutrition, and protection from deliberate attack, serious injury, or disease, it will develop to the mature stage of a human organism. Thus, from the zygote stage onward this distinct, new organism has all of the internal resources—in its genetic and epigenetic structure—needed to develop itself (or, rather, himself or herself, since in the human sex is determined from the very beginning) to the mature stage of a human organism. At no point after fertilization—implantation, gastrulation, birth, puberty, etc.—does a fundamental change in biological trajectory occur. These subsequent stages of development are simply the unfolding of the zygote’s inherent dynamism toward human organismal maturity. This shows that the zygote already is a human organism—a member of the species Homo sapiens—albeit at an early stage of his or her development.

So, since I like to win arguments with science, I just took the side of the debate that was backed by science. I really hate to lose debates, you know. I really like to cite scientific evidence when I’m debating.

The crime of abortion, it seems to me, is that you are depriving a human being of his or her future, because of your convenience right now. Human beings don’t have the right to take away the futures of other human beings because they want to be unburdened by the results of their own actions. We shouldn’t resort to violence in order to escape responsibility for our own actions. In almost every case, (except to save the life of the mother), killing the unborn child isn’t justified. It’s actually very scary to me that anyone would think that hurting other people was a reasonable response to one’s own diminished happiness. How did we ever get to a place in society when people don’t think that taking responsibility to care for the unborn child is morally better than killing the unborn child? It’s a baby for goodness sake. We ought to be serious about setting up our lives and controlling ourselves so that we never hurt an unborn child.