Petri Dish Politics

Biotechnology will make it possible for us to live longer and better. So why are some people dead set against it?

Ronald Bailey from the December 1999 issue

(Page 3 of 4)

One day it may be possible to take any adult stem cell back to the embryonic, and hence protean, stage. But the research to figure out how to do that depends on work with embryonic cells and the resulting cells, of course, would themselves be embryonic. People who oppose stem cell research on the ground that any cell that can become a human being already is a human being are essentially arguing that every cell in your body is another person.

"What happens when a skin cell turns into a totipotent stem cell [a cell capable of developing into a complete organism] is that a few of its genetic switches are turned on and others turned off," writes University of Melbourne bioethicist Julian Savulescu in the April 1999 issue of the Journal of Medical Ethics. "To say it doesn't have the potential to be a human being until its nucleus is placed in the egg cytoplasm is like saying my car does not have the potential to get me from Melbourne to Sydney unless the key is turned in the ignition." Since nearly every cell in the human body contains the complete genetic code of an individual, it is logically possible using biotech to turn every one of a person's cells into a complete new human being. If one doesn't turn on the ignition of a car (or one doesn't strip the suppressor proteins from a nucleus and put the cell into a womb), then the car won't go (or the skin cell won't grow into a human being). In other words, simply starting a human egg on a particular path, either through fertilization or cloning, is a necessary condition for developing a human being, but it isn't sufficient. A range of other conditions must also be present.

"I cannot see any intrinsic morally significant difference between a mature skin cell, the totipotent stem cell derived from it, and a fertilised egg," writes Savulescu. "They are all cells which could give rise to a person if certain conditions obtained." Those conditions include the availability of a suitable environment like a woman's womb. A petri dish is not enough.

"If all our cells could be persons, then we cannot appeal to the fact that an embryo could be a person to justify the special treatment we give it," concludes Savulescu. "Cloning forces us to abandon the old arguments supporting special treatment for fertilised eggs."

The DNA content of a skin cell, a stem cell, and a fertilized egg are exactly the same. The difference between what they are and what they could become is the environment in which their DNA is found. Thus, Savulescu argues, the mere existence of human DNA in a cell cannot be the source of a relevant moral difference. The differences among these cells are a result of how the genes in each are expressed, and that expression depends largely on which proteins suppress which genes. Does moral relevance really depend on the presence of the appropriate proteins in a cell? Trying to base moral distinctions on this level of biochemistry seems a bit quixotic.

So, asks Savulescu, is it immoral for you to take one of your skin cells, put it into an enucleated egg, and begin to grow it in a petri dish with the intention of making new brain cells to cure your Parkinson's disease? The cell was your tissue, with your genes. The transformed cell would not exist except for your intention--it would simply have flaked off and gone down the drain. "It's important to remember that essentially every cell in our body has a full complement of genes and in that sense is potentially totipotent," Varmus, the NIH director, reminded the National Bioethics Advisory Commission. That a cell contains a complete set of human chromosomes, yours, surely does not make that cell the moral equivalent of a baby. But as Savulescu and Varmus point out, if one is committed to the sort of genetic essentialism relied on by many opponents of cloning and embryonic stem cell research, then one is also logically committed to maintaining that the only difference between your skin cell and your twin is which proteins decorate their DNA strands.

The next step in stem cell research will occur when biotechnologists learn how to strip off the suppressing proteins from a mature cell's genes and transform it directly into a stem cell without having to use enucleated human eggs. That advance will take human eggs out of the discussion. Once it is possible to make stem cells without eggs, perhaps the moral intuition of many people will shift.

"It may eventually become possible to take a cell from any one of our organs and to expose it to the right set of environmental stimuli and to encourage that cell to return to a more primitive stage in the hierarchy of stem cells," explains Varmus. "Under those conditions, one might in fact generate the cell with as great a potential as a pluripotent cell [capable of becoming many different, but not all, types of tissues] from a very mature cell. One might even in fact imagine generating a cell that is totipotent in that manner." (Again, a totipotent cell is one that could develop into a complete organism if put in the right circumstances.)

Stem cells produced this way would be identical to the human embryonic stem cells that currently must be harvested from embryos. A cell whose suppressor proteins have been stripped off could become a nerve stem cell, a liver stem cell, or a baby--depending on the intentions of the patients and doctors. Researchers are experimenting right now to see if new embryonic stem cells could be formed by introducing the nucleus of an adult cell into an already existing enucleated embryonic stem cell, thus bypassing the need to use human eggs.

One final consideration is that those committed to claims that individual human beings are defined by their DNA must take into account the fact that up until the eight-cell stage any one of an embryo's cells could become a separate embryo and, under the right circumstances, develop into a baby. So until that point are there several persons, or one, in a fertilized human egg? It is now possible after a fertilized egg has first divided into two cells to take one cell and use it to test for genetic diseases. The tested cell could have developed into a baby if placed in a woman's womb. Has the genetic test killed a twin?

Stem cell research opponents might respond that these arguments are just splitting hairs. But there are quite a lot of biochemical hairs to split. And just how you split them determines how you regard the moral status of all types of cells.

Does human uniqueness really reside in our genes? Try this thought experiment. Imagine that transplant surgery has so improved that it is possible to remove your brain and place it safely into another body. So after your brain transplant, is your original body "you"? Or are "you" residing now in a different body? A new body could certainly change "you" in certain ways, since your senses and biochemistry would be different. But humans already affect the operation of their brains by giving themselves different drugs. When people take therapeutic drugs, say Prozac, L-dopamine, or even steroids, we do not believe they become different people.

"The human mind, of course, is a dynamic entity, but genes are static," explains Princeton biologist Lee Silver. A person's genes provide the instructions for building his or her brain, and the mind which comes out of that brain can respond to the environment. Unlike genes, a mind can change. "The human mind is much more than the genes that brought it into existence," concludes Silver.

What makes us distinct and unique is not our genes but our brains and the minds they contain. Persons generally have brains that are capable of supporting enough mental activity to give rise to a mind. As one of my old philosophy professors once put it, "I have never seen a mind that was not located in fairly close proximity to a brain."

The point that brains, not genes, are the source of our uniqueness is further underscored by the fact that no one argues that natural clones, otherwise called identical twins, are the same person, even though they share an identical set of genes. They have two different brains and experience the world from two different points of view. Human brains--malleable, fluid, flexible, changing--not static genes, are the real essence of what defines us as people. We are not mere meat puppets at the mercy of our genes. In fact, with biotech it might better be said that our genes are now at the mercy of our minds.