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Grand Central Political Magazine
Human Disease Cannot Be Eradicated
By Dr. Mark Drapeau
Identification of the breast cancer genes BRCA-1 and -2 is generally considered a success of modern medicine. Each year, thousands are diagnosed with breast cancer caused in part by mutations - alternate non-normal forms - of one of these genes. This past week, stories out of Great Britain of a genetically-altered baby delibrately missing its BRCA-1 gene stunned people around the world. Because of a strong breast cancer risk via women on the father's side, the controversial option of creating a so-called "designer baby" was chosen.
In this essay, I am not writing to oppose or support this kind of genetic engineering. No doubt that ethicists will speak their views as a counterbalance, but in the long run such methods will be approved of and common. People generally desire to live longer and stronger, and indeed they are - in large part because of excellent medical care. Doctors and medical scientists collaborating with pharmaceutical companies are alleviating the effects of many diseases, allowing ill people to live more comfortably. In some cases there has been success in proactive prevention. This is wonderful, and is a testament to incredible progress in science, technology, and medicine during the last century.
However, the media often goes overboard when reporting on topics such as the "designer baby" mainly because of a lack of understanding of the fields they are writing about. It's not their fault, really - journalists have to be generalists. And often academic scientists are all too happy to get some popular press to advance a research funding agenda, or just boost their ego, hence sacrificing a little truth for a lot of coverage.
Because of this, a commonly heard phrase in the media is that scientists are "curing cancer." And readers eat it up. While people's hearts and dreams are in the right place, this is a misnomer. In the broadest sense, modern medicine will never cure all disease, or even most disease, or even most cancer.
This is why.
One of the profound biological discoveries from the last half century was that genes and their protein products can, and often do, have age-dependent effects. In other words, a gene might be crucial for early embryonic development, be "silent" during childhood, and then play a later role during puberty and adulthood. This is something not unique to humans but rather common to all animals, including worms, flies, bees, cockroaches, frogs, mice, and chickens.
A necessary and obvious consequence of this type of time-dependent gene action is that some genes will have effects in very late life. The term "late-life" is defined as being post-breeding-age. Gerontologists and evolutionary biologists have defined two related ways by which harmful gene action occurs in this late-life period, which is becoming longer and longer in humans.
The first mechanism is called "antagonistic pleiotropy," a fancy term describing a situation where a gene has multiple functions; some of these functions are beneficial in earlier life, and some are deleterious in late-life. In this situation, a gene will tend to stay in a population of individuals, because of its important early beneficial effects. The deleterious effects cannot be detected by natural selection, because they occur only after the gene has already been passed on to offspring. Oops.
As an example of such antagonistic genetic double-dealing, imagine a gene that reveals its damaging effects when a person is 60. By that time the maladaptive gene has already been passed on through sperm or egg to that 60 year old's two children, aged 38 and 32...Indeed, the gene may have already been passed on to some grandchildren, and so forth.
The second mechanism, "mutation accumulation," is similar in principle and involves a mutation in a gene that has no net positive or negative beneficial effects, yet yields harmful effects in late-life. This kind of gene will accumulate in genomes over generations because natural selection cannot weed it out, since, again, harmful effects occur after the gene has already been bred into the next generation of individuals. Natural selection cannot "see" the harmful effects of the gene. Oops again.
Many people ask evolutionary biologists like myself why, if natural selection is so powerful, and if it rids genomes of bad traits, every organism dies. That's a good question. The above explanations are evolutionary reasons for why natural selection cannot select against death, and why all higher organisms senesce. More recently, some of these actual genes have been identified through various sophisticated means.
The above discussion also does not even begin to point out that new genomic methods which look at tens of thousands of genes acting simultaneously have begun to show the somewhat surprising conclusion that there are a number of different genetic causes for what seem physically like the same "breast cancer" to the common doctor. The lumps are the same, but they are not caused by the same genes. Oops once again.
So. The designer baby may be all for naught, if the father's family history of breast cancer actually had little to do with BRCA-1. What are the ethics of mis-designing an embryo? Clearly, the baby when born will have had no say in the matter.
Furthermore, diseases and disorders will always exist, no matter how sophisticated our knowledge of genetic medicine. This is not mere pessimism, due to this thought experiment.
Assume an extreme hypothetical case in which medical scientists cured every genetic disease that acts up to, say, 120 years of age. Because of the airtight evolutionary reasoning above, there will always exist genes that exert harmful effects after age 120. Such a gene effect could not possibly be observed before humans commonly survive past the age at which it has a harmful effect on health.
Every day, medical professionals are uncovering mechanisms for preventing specific diseases from occurring, and discovering methods for dealing with such diseases once they've sprouted. These are obviously wonderful advances, and research leading to these outcomes should be pursued, and highly funded. For the average lifespan of humans to be extended to 100, or 120, or 150, particularly if these are "healthy years," would be incredible for many reasons.
However, in the most general sense, doctors will never eradicate disease, and the media does the public a disservice when they imply that they someday will. Modern medicine and media, along with the general public, would benefit greatly from even a brief consideration of underlying biology when discussing disease.
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Dr. Mark D. Drapeau is the AAAS Science & Technology Policy Fellow at the Center for Technology and National Security Policy in Washington, DC. These views are his own and not the official policy or position of the National Defense University, the Defense Department or the U.S. government. (You can follow Mark's musings at http://twitter.com/cheeky_geeky.)