Embryonic stem cell research necessarily ends a human. Richard M. Doerflinger observes:
Let us begin with a simple fact of science. The human embryo, even in the first week of development before
implantation, is a human being — a living, developing individual of the human species, not just a part of
another member of the species. Albeit at a very early and immature stage of development, the embryo is
part of the continuum of human development that stretches from that first formation of a unique organism to the natural end of life. One major embryology textbook says simply: “A zygote is the beginning of a new human being.”2 Another states: “The time of fertilization represents the starting point in the life history,
or ontogeny, of the individual.”3 It makes no sense to say “I was once a sperm cell” or “I was once an egg cell,” but makes perfect sense to say “I was once an embryo” — exactly the same sense it makes to say “I was once a fetus” or “I was once an infant,” though I remember neither of these stages. Recent biological findings