Germline Intervention

Germline genetic engineering alters the genes in sperm or egg cells (or their immediate precursors), the zygote, or the early embryo. The usually stated goal of such genetic modifications is the same as somatic genetic engineering, i.e., to correct (or prevent) a disease state caused by a defective gene.

The phrase “genetic engineering” can be used to refer to two very different things. Somatic genetic engineering targets somatic (body) cells, and can also be called genomic medicine, since it is in effect traditional medicine at the level of the genes. It affects only the individual who is treated. Germline genetic engineering, however, makes possible changes that will spread to every subsequent generation. It can also be called inheritable genetic modification, and has the potential to change the human species along eugenic lines. Princeton biology professor and biotech enthusiast Lee Silver has written of a future in which the “GenRich,” who are the descendants of those with “improved” germlines, may be so distinct that they will not even be able to have children with standard human beings. It is this prospect that has led some writers to look ahead using the terms “transhumanist” and “posthumanist,” and others to speak of the “abolition of man.” And it has led the nations of Europe, in the first international bioethics convention (the European Convention on Human Rights and Biomedicine), to outlaw germline changes altogether.

The somatic/germline distinction is vitally important, and focuses attention on the dramatic implications of the “genetic engineering” of embryos, sperm or egg cells or their immediate precursors, i.e., the germ cells. Germline genetic engineering alters the genes in sperm or egg cells (or their immediate precursors), the zygote, or the early embryo. The usually stated goal of such genetic modifications is the same as somatic genetic engineering, i.e., to correct (or prevent) a disease state caused by a defective gene.

However, germline genetic modifications affect prospective individuals, including not only the ones who are engineered, but also all their descendents. Both techniques could be abused—either could be used for enhancements of genetically-determined abilities, as opposed to therapeutic treatments for disease. Germline genetic engineering also can allow for the selection of genetic characteristics in a prospective child, producing a “designer baby” with desired traits. More broadly, it could lead to the “re-designing” of the human species.