Читать книгу Bioethics - Группа авторов - Страница 27

It will be useful to begin by considering some of the facts of sexual reproduction. The standard embryology texts indicate that in the case of ordinary sexual reproduction the life of an individual human being begins with complete fertilization, which yields a genetically and functionally distinct organism, possessing the resources and active disposition for internally directed development toward human maturity.¹ In normal conception, a sex cell of the father, a sperm, unites with a sex cell of the mother, an ovum. Within the chromosomes of these sex cells are the DNA molecules which constitute the information that guides the development of the new individual brought into being when the sperm and ovum fuse. When fertilization occurs, the 23 chromosomes of the sperm unite with the 23 chromosomes of the ovum. At the end of this process there is produced an entirely new and distinct organism, originally a single cell. This organism, the human embryo, begins to grow by the normal process of cell division – it divides into 2 cells, then 4, 8, 16, and so on (the divisions are not simultaneous, so there is a 3‐cell stage, and so on). This embryo gradually develops all of the organs and organ systems necessary for the full functioning of a mature human being. His or her development (sex is determined from the beginning) is very rapid in the first few weeks. For example, as early as eight or ten weeks of gestation, the fetus has a fully formed, beating heart, a complete brain (although not all of its synaptic connections are complete – nor will they be until sometime after the child is born), a recognizably human form, and the fetus feels pain, cries, and even sucks his or her thumb.

There are three important points we wish to make about this human embryo. First, it is from the start distinct from any cell of the mother or of the father. This is clear because it is growing in its own distinct direction. Its growth is internally directed to its own survival and maturation. Second, the embryo is human: it has the genetic makeup characteristic of human beings. Third, and most importantly, the embryo is a complete or whole organism, though immature. The human embryo, from conception onward, is fully programmed actively to develop himself or herself to the mature stage of a human being, and, unless prevented by disease or violence, will actually do so, despite possibly significant variation in environment (in the mother’s womb). None of the changes that occur to the embryo after fertilization, for as long as he or she survives, generates a new direction of growth. Rather, all of the changes (for example, those involving nutrition and environment) either facilitate or retard the internally directed growth of this persisting individual.

Sometimes it is objected that if we say human embryos are human beings, on the grounds that they have the potential to become mature humans, the same will have to be said of sperm and ova. This objection is untenable. The human embryo is radically unlike the sperm and ova, the sex cells. The sex cells are manifestly not whole or complete organisms. They are not only genetically but also functionally identifiable as parts of the male or female potential parents. They clearly are destined either to combine with an ovum or sperm or die. Even when they succeed in causing fertilization, they do not survive; rather, their genetic material enters into the composition of a distinct, new organism.

Nor are human embryos comparable to somatic cells (such as skin cells or muscle cells), though some have tried to argue that they are. Like sex cells, a somatic cell is functionally only a part of a larger organism. The human embryo, by contrast, possesses from the beginning the internal resources and active disposition to develop himself or herself to full maturity; all he or she needs is a suitable environment and nutrition. The direction of his or her growth is not extrinsically determined, but the embryo is internally directing his or her growth toward full maturity.

So, a human embryo (or fetus) is not something distinct from a human being; he or she is not an individual of any non‐human or intermediate species. Rather, an embryo (and fetus) is a human being at a certain (early) stage of development – the embryonic (or fetal) stage. In abortion, what is killed is a human being, a whole living member of the species homo sapiens, the same kind of entity as you or I, only at an earlier stage of development.