Not Just a Reproductive Choice
Ten months ago, events in Scotland sent a shock through the scientific community and the moral fiber of the world. Ian Wilmut and colleagues cloned a sheep from the cell of an adult, and the possibility of cloning a living (or dead) human suddenly became a reality. A rush of presidential commissions, ethicists and scientific societies quickly condemned human cloning. But scientists and the public are beginning to view human cloning as inevitable and not so bad after all.
How practical is cloning? Wilmut’s success was accompanied by 276 failures. The success rate is nowhere near clinically acceptable, and cloning remains in an entirely different class from techniques such as in vitro fertilization. Moreover, humans may be considerably more difficult to clone than sheep. In sheep, the embryonic genome is silent for the first three cell divisions. In humans, it is active after the second division; in mice, after the very first. The need for immediate expression of genes in mice and humans may render the technique of nuclear transplantation far more difficult, as the speed with which “reprogramming” of the genetic material is required is much greater than for sheep.
The long-term prospect of cloned organisms remains in question. We don’t know how healthy Dolly, the cloned sheep, will be, how long she will live and whether she will be fertile. Attempts to clone frogs led to a surprising discovery: Only males could be produced. Could mammalian cloning hold in store a similar surprise? Could Dolly find herself unable to bear offspring? Could Dolly be a walking time bomb of tumors waiting to form? One of the keys to being able to reprogram a cell’s genome is for the cell to lose some of its differentiated characteristics in a manner similar to the changes that occur when cells become cancerous. The udder cell that donated its DNA to Dolly might have been a slightly dedifferentiated, cancer-prone cell.
One of the often-mentioned potential uses of human cloning is in allowing individuals who have lost a child to replace it. The concept is flawed. A clone would not be exactly like the “original” person except in DNA sequence. Environment is critical in translating the genetic information or genotype into the actual manifestation of the individual, the phenotype. Many of the traits we value most are influenced by nurture rather than nature. Identical twins usually can be distinguished by physical as well as mental traits. Personality appears to be particularly plastic as a result of the different environments of even identical twins reared in the same home. For the identical twin produced by cloning, the environment would be different from the moment of conception: a different egg, a different in utero environment, a different nursery. Further, the child would be raised later, at a time when society is different, literature is different, even the television shows are different.
Another potential use for human cloning would be to provide bone marrow donors for cancer patients. An individual diagnosed with cancer need only authorize a clone who could then become the source for perfectly matched bone marrow or organs. Robin Cook’s novel “Chromosome Six” pointed out the moral outrage accompanying one biotechnology company’s efforts to create chimpanzees with tissue-matched human organs. Would we allow the use of human babies to culture such organs?
Many people now seem to consider human cloning to be just another reproductive technology which, like in vitro fertilization, we will soon accept. But humans are the product of a long evolution optimizing reproductive potential and screening out catastrophic mutations. If there is a genetic basis for the infertility, then the cloned “offspring” would likely be infertile as well. In a few generations, we’d be seeing great- grand-clones.
There is a fundamental difference between cloning and other reproductive technologies. Cloning subverts the reshuffling and editing of the genetic material that accompanies sexual reproduction, stripping evolution of the main source of the variation that drives it. A few individuals might see benefits now. The costs and consequences will reverberate for eternity.
