Department of Computer Science
University of Waterloo
Waterloo, Ontario, Canada, N2L 3G1.
In 17th century England, life expectancy was 18 years, and only one person in a hundred lived to 75. Today, life expectancy is 70 years or more in most Western countries. What accounts for the difference?
Certainly better nutrition, brought about by improvements in agriculture and transportation, played an important role. But another factor was the rise of modern medicine. James Le Fanu, a British physician and science writer, ably documents medicine's amazing successes from 1940 to 1980 in the first half of his book, The Rise and Fall of Modern Medicine.
Le Fanu identifies ten "definitive moments" in modern medicine: the development of the drugs penicillin, cortisone, streptomycin, and chlorpromazine; surgical techniques such as open-heart surgery, kidney transplants, and in vitro fertilization; the detection of smoking as a cause of lung cancer; the cure of acute lymphoblastic leukemia; and the discovery of the infectious agent helicobacter as a cause of peptic ulcers. Le Fanu narrates the story behind these achievements with flair and style, although the successes of British scientists are overemphasized to the detriment of work done in North America. The first half of the the book can be profitably read by anyone interested in medicine or science.
The second half - "The Fall" - is the controversial one. Here Le Fanu describes why he believes the golden age of discovery of new drugs is coming to a close, and constructs a polemic against two trends in modern medicine: the "New Genetics" and the "Social Theory".
Le Fanu is deeply puzzled by the fact that biological organisms produce secondary metabolites of complex molecular structure, and that some of these prove useful in fighting human diseases. He finds the effectiveness of antibiotics an unfathomable mystery, and rejects the evolutionary explanation that antibiotics are a form of chemical warfare developed by organisms over a period of millions of years. Citing Selman Waksman, the discoverer of streptomycin, Le Fanu argues this explanation cannot be correct because (a) only a handful of organisms produce antibiotics (b) the presence of antibiotics in soil at a level high enough to destroy other organisms has not been demonstrated. But neither of these reasons is compelling.
First, through the process of evolution, organisms adopt a wide variety of strategies to gain a reproductive advantage. There is no more reason to expect that every organism should produce antibiotics than there is to expect that every organism should have sharp teeth, wings for flight, a large brain, insulating fur, excellent eyesight, or any one of a million different adaptations that evolution has provided. The explanation for any particular adaptation is necessarily contingent: depending on, in the words of French biologist Jacques Monod, both chance and necessity. So much for argument (a).
Second, Le Fanu apparently doesn't know about the work of Washington State scientists David Weller and Robert Bonsall, who showed conclusively how the naturally-produced antibiotic 2,4-Diacetylphloroglucinol in soil controls "take-all", a root disease of wheat caused by the fungus Gaeumannomyces graminis, thus undermining argument (b).
Why is Le Fanu so opposed to an explanation of the effectiveness of antibiotics based on evolution? Although he doesn't say so outright, a quote from Ecclesiasticus 38:4 at the beginning of the book -- "The Lord hath created medicines out of the earth; and he that is wise will not abhor them" -- strongly suggests a sympathy with a supernatural explanation. Further evidence for this conclusion is Le Fanu's use of a very lengthy excerpt (p. 204) from Michael Denton's creationist tract, Evolution: A Theory in Crisis. (Denton's unreliable book is marred by very severe misunderstandings that are easily recognized by any professional biologist .)
It is then a little surprising to learn that Le Fanu erects the theoretical foundation of his attack on the "New Genetics" and the "Social Theory" on an evolutionary basis.
By the "New Genetics", Le Fanu means harnessing our understanding of the genetic basis of life to help cure disease, through genetic engineering of new drugs, prenatal screening, and gene therapy. By the "Social Theory", he means the belief that many diseases are caused by dietary and environmental factors, and hence these diseases can be cured or ameliorated by changes in lifestyle.
Le Fanu is probably correct when he says that the initial promise of the New Genetics has not yet been realized, and he is probably correct when he says that the benefits of a low-fat diet have been greatly exaggerated. But he goes beyond far beyond these reasonable claims. Le Fanu contends that medicine will never reap substantial benefits from the New Genetics, and further that there are good theoretical reasons to believe that the Social Theory cannot be correct, even in principle.
For example, Le Fanu states that "....genetics is not a particularly significant factor in human disease. This is scarcely surprising, as man would not be as successful a species as he is (many would argue too successful), were it not that natural selection had over millions of years weeded out the unfit."
Le Fanu's incorrect evolutionary reasoning is a splendid example of how poorly understood Darwin's important theory still is, 150 years after the Origin of Species -- even among medical professionals who could be expected to have mastered it.
Le Fanu is wrong. Genes do indeed play a significant factor in disease. Type 2 diabetes, heart disease, and colon cancer are just a few of the maladies with a strong genetic component, even if we cannot point to specific single genes that cause them. It may be true, as Le Fanu points out, that these diseases are multifactorial, but that just means the fight against them will be challenging, not impossible.
Second, although Le Fanu recognizes that genes are pleiotropic -- a single gene may have multiple effects when it is expressed -- he does not seem to appreciate the devastating consequences this fact has for part of his argument. As explained in the evolutionary theory of senescence, evolution may select for genes that have beneficial effects on reproductive fitness early in life, but deleterious effects later in life. Illnesses such as heart disease, which largely afflict people well after their reproductive years, will not -- contrary to Le Fanu's claims -- necessarily be "weeded out" through natural selection. (Readers interested in this line of reasoning will want to read Randolph Nesse's and George Williams' splendid book Why We Get Sick: The New Science of Darwinian Medicine.)
Examining gene interaction, Le Fanu concludes that its complexity makes our genetic mastery of disease impossible. Quoting geneticist Philip Gell, he says, "The heart of the problem lies in the fact that we are dealing not with a chain of causation but with a network that is a system like a spider's web... The gap in our knowledge is not merely unbridged, but in principle unbridgable and our ignorance will remain ineluctable."
I find this conclusion extraordinarily pessimistic. Our understanding of genetics and development is still in its infancy. We have only this year completed an initial classification of the human genome, and an enormous amount of work remains to be done. Both Gell and Le Fanu need to review Clarke's first law: "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." 
Le Fanu's attack on the Social Theory of disease is also based, in part, on a faulty understanding of evolution. He writes, "Thus the Social Theory might seem plausible enough, but Man as the culmination of millions of years of evolution is capable of surviving in the most diverse of circumstances. It would thus seem highly improbable that suddenly, in the middle of the twentieth century, he should have become vulnerable to lethal diseases caused by his `lifestyle'."
There are many problems with this kind of reasoning. First of all, although people do survive and prosper in a wide variety of different habitats, they do not do so uniformly. For example, life expectancy continues to be substantially lower in countries where malaria is endemic.
Second, an adaptation that is beneficial in one environment, such as sickle-cell gene in the case of malaria, can become deleterious in another environment. Today's human population is much more diverse, with many people living in environments radically different from their ancestors. The lifestyle may change, but the genes haven't had a chance to catch up.
Third, man's life expectancy has probably been 15-20 years for all but a tiny fraction of man's two-million-year existence. It follows that the typical causes of death for people in Western countries today are radically different from what they were for 99.98% of man's evolutionary history. It is not in the least implausible that these modern causes of death, occurring later in life, could be due in part to diet or environmental factors.
Fourth, the typical diet in Western countries, high in sugar and saturated fats, is likely quite different from what most people have eaten over the last two million years. The desire for these foods may have been evolutionarily beneficial in the Pleistocene, but is considerably less so today. For example, diet seems to play a significant role in the development of Type 2 diabetes among the Pima Indians, who eat very different foods today than just 75 years ago.
Le Fanu says, "The environmentalist theory is invalidated by the biological necessity that the human organism be resilient and not readily injured by minuscule levels of pollutants in air and water." This argument may be true when applied to naturally-occurring toxins, such as tannins. But today's humans are exposed to a whole soup of artificial toxins (e.g., dioxins, PCB's, DDT, strontium-90, nickel, carbon monoxide, organic mercury compounds) that people were rarely or never exposed to before in their evolutionary history. There is no reason to believe our biology should be so resilient that it can even handle radically new toxins never before encountered!
It follows that the theoretical basis behind Le Fanu's attack on both the New Genetics and Social Theory is quite flawed.
Despite these flaws, the second half of Rise and Fall is not completely without value. Le Fanu argues that poorly-understood diseases, such as multiple sclerosis and acute childhood leukemia, may be caused by some type of infectious agent, an interesting hypothesis that deserves further study.
One final problem is that the book is marred by carelessness. For example, the last name of open-heart surgery pioneer Walter Lillehei is consistently misspelled as "Lillehai", and the University of Chicago is inexplicably called "Chicago University".
My advice to readers of The Rise and Fall of Modern Medicine is to savor the high adventure of the first half and take the flawed second half with a grain of salt. But not too much salt -- it might adversely affect your blood pressure.
 Arthur C. Clarke, from a chapter entitled "Hazards of Prophecy: The Failure of Imagination", in his book Profiles of the Future, 1962.