The Evolution Explosion: How Humans Cause Rapid Evolutionary Change
- Stephen R. Palumbi
Many students open The Origin of Species expecting intellectual fireworks, but are disappointed to find a soporific discussion of sheep and pigeons. Yet Darwin's tedious opening chapter on artificial selection was a stroke of rhetorical genius: by recounting the familiar triumphs of animal and plant breeders, he paved the way for his infinitely more heretical evolutionary ideas. (This strategy nearly misfired: one of the publisher's readers, noting that “everybody is interested in pigeons”, recommended that Darwin drop the messy stuff about evolution and concentrate instead on birds.)
Although darwinism is now firmly established in scientific and intellectual life, it is far from entrenched in the public consciousness. This is due partly to the prevalence of creationism, but also to the notion — familiar to anyone who teaches premedical students — that evolution has nothing to do with everyday life. In The Evolution Explosion, Stephen Palumbi, a biologist at Harvard University, tries to dispel this view, using Darwin's own strategy of appealing to the reader's experience and hoping that familiarity breeds consent.
Palumbi concentrates on cases in which humans have produced rapid evolution in other species by changing their environments: his examples include the evolution of antibiotic resistance in bacteria, herbicide resistance in plants, pesticide resistance in insects, and changes in the growth rate of fish caused by overfishing. Remarkably, many people familiar with these phenomena have failed to see that they demonstrate evolution driven by selection. There is, for example, a public misconception that 'drug resistance' involves not evolutionary change in pathogenic bacteria, but some process whereby a person becomes acclimated to antibiotics.
Palumbi writes enthusiastically and clearly, and his stories are based on extensive research documented in an appendix. His chapter on AIDS is particularly useful, describing in detail how HIV evolves to avoid the double depredations of our immune system and new generations of antiviral drugs. Elsewhere, we learn that antibiotic resistance in pathogenic bacteria has been caused both by the overprescription of drugs (leading, for example, to the resurgence of drug-resistant tuberculosis) and by the use of antibiotics that increase growth rates in farm animals (producing chickens harbouring dangerous, drug-resistant salmonellae and explaining the absence of carpaccio di pollo in Italian restaurants).
Sadly, our understanding of these evolutionary responses seems to have contributed little to solving the attendant medical and economic problems. Combating drug or pesticide resistance usually involves applying more drugs or poisons — solutions that hardly require a sophisticated understanding of evolution. Moreover, new treatments are eventually stymied by further evolution, so that human ingenuity seems nearly impotent in the face of recurring mutation and selection.
By compiling and explaining these diverse cases of anthropogenic evolution, Palumbi has made a useful contribution to the public understanding of science. However, The Evolution Explosion suffers from a few problems. Palumbi's narrative runs out of steam in a final chapter about memes, the 'units of culture' (slogans, ideas and inventions, for example) that serve as analogues to genes in theories of social evolution. Despite much attention, 'memetics' has ultimately proved a sterile metaphor, of little value in understanding history or society. It is not clear why Palumbi chose to drag a perfectly straightforward book about science into this pseudo-philosophical quagmire.
The book's style poses an equally serious problem. Straining mightily to achieve what the dust-jacket calls “popular imagery”, Palumbi produces an incessant stream of exuberant metaphors and similes that can distract rather than enlighten. In places the prose causes near-physical pain, as in the discussion of memes: “Bad ideas, rejected like anchovy daiquiris, live on only in a few people with fishy breath. Good ideas duplicate quickly and spread far and wide, generating clutches of mental ducklings, with some subsequently turning into brilliant swans and others fated to remain only brain geese.”
Finally, although the science is generally accurate, Palumbi's discussion is occasionally confusing or incorrect. For example, he repeats as truth the common belief that artificial selection has made domestic turkeys so dim-witted that during storms they look up at the rain, forget to look down, and drown. This is, in fact, an agro-urban myth that has been branded an “unfounded turkey rumor” by Turkey Call, the official organ of the National Wild Turkey Federation. (Turkeys have, however, suffered greatly from domestication. Responding to human fondness for breast meat, farmers have bred birds too buxom to bonk, and new turkeys must be produced by artificial insemination.)
Nevertheless, The Evolution Explosion should help quash the eternal student complaint that evolution is irrelevant. Alas, it is unlikely to change the minds of creationists and advocates of 'intelligent design'. Many who reject darwinism on religious grounds already accept anthropogenic evolution as 'adaptation within a species', but argue that such small changes cannot explain the evolution of new groups of plants and animals. This argument defies common sense. When, after a Christmas visit, we watch grandma leave on the train to Miami, we assume that the rest of her journey will be an extrapolation of that first quarter-mile. A creationist unwilling to extrapolate from micro- to macroevolution is as irrational as an observer who assumes that, after grandma's train disappears around the bend, it is seized by divine forces and instantly transported to Florida. Those not besotted by the anchovy daiquiris of creationism, however, will be convinced by Palumbi's book that evolution is alive and well, if not always welcome.
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Microbial Pathogenesis (2017)