- We know that the unborn is living because he or she (sex has been genetically determined) is growing through cellular reproduction, metabolizing food into energy, and responding to stimuli. So the unborn meets the biological criteria for life.
- We know that the unborn is human because she has human DNA. She is also the offspring of human parents, and living beings reproduce after their own kind (e.g., humans only beget humans). So the unborn is biologically human.
- We know that the unborn is a whole (albeit immature) organism, not a mere part (like a skin cell or the sperm and egg) of someone else, because she is actively developing via a self-directed process through the different stages of life—embryo, fetus, infant, child, adolescent, adult—as an individual member of the species. She needs only a suitable environment and nutrition to develop herself to maturity.
- Finally, we know that the unborn is a living human organism because the embryology textbooks and other relevant scientific authorities tell us so. "[F]ertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed," explains Human Embryology & Teratology. The authors of The Developing Human: Clinically Oriented Embryology write, "Human development begins at fertilization when a sperm fuses with an oocyte to form a single cell, a zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual."
That's how we know beyond any doubt that the unborn is a human being in the biological sense. She is a living organism of the species Homo sapiens, the same kind of being as each of us, only at an earlier developmental stage.
The important question for our society is an ethical one: How should we treat these young human beings? Do they deserve the same kind of respect and protection as the other members of our species? Do all human beings have a right to life, or do only some?