A second means of selecting our kids’ genetic constitutions is embryo screening, or preimplantation genetic diagnosis (PGD). In this already common procedure, a single cell is removed from a six- or eight-cell embryo in vitro and a genetic test performed on it. The results then are used to decide whether to implant that embryo or discard it in favor of another.

The ultimate means of changing human reproduction, however, is through direct germline intervention — direct alteration of the genetics of the first cell of the human embryo. This would be the beginning of conscious human design. Technologies like human artificial chromosomes, which would be required for this, are under development and already have been used in tissue culture.

If we could stop biotechnology dead in its tracks, other technologies would still reshape our society. When we contemplate the future, we should remember that our great grandparents would not be comfortable in the world of today, yet few of us would really want to live in their world. So it could be with our future, too. We might not find it appealing, but our descendants will, and they will likely look back at the present era as primitive and uninviting.

Gregory Stock is director of the UCLA School of Public Health’s Program on Medicine, Technology, and Society.

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