Dark Banquet - Bill Schutt [79]
We’ve already seen the hypothetical results of such mutations (horses and vampire bats), but let’s look at the second of these examples a bit closer. Let’s say that a protovampire bat had a genetic mutation that resulted in a change in tooth structure. If this mutation happened to produce sharper teeth (giving the protovampire a better chance of biting animals without being detected and thus increasing its chances of surviving and reproducing), then this novel characteristic would be considered an “adaptation.” Subsequent generations of protovampires, which would include the progeny of the bat with the mutation, would exhibit greater incidences of sharper teeth since those protovampires without this trait would be less likely to survive and reproduce in their local environments. In time, protovampire populations might accumulate more and more new characteristics (like salivary anticoagulants and amped-up excretory systems), adaptations similarly “selected” by the existing environmental conditions. Eventually, these bats would become different enough from their ancestors to be considered a new species—in this case, true vampire bats. Alternatively (and this is the part that many people overlook), the mutation that altered tooth sharpness could have just as easily been one that produced duller teeth, and this “maladaptive” character would have lessened the chances of that individual surviving to reproductive age, where it could pass that mutation (and the trait) on to the next generation.
Considering this last possibility makes it easier to understand how evolution is, in some ways, a genetic crapshoot. It also allows us to recognize the problem with such assumptions as “The environment changed and ancient vampire bats needed sharper teeth to make painless bites—so they evolved sharper teeth.” This reasoning, which seems to make sense, betrays a common misconception that people have about the mechanism of evolution.
For Jean-Baptiste Lamarck (1744–1829), the first naturalist to propose a mechanism for evolutionary change, the concept of need-based evolution (and other related ideas) got the Frenchman buried in a rented grave and his life’s work all but forgotten. In reality, Lamarck was a scientific heavyweight, and his résumé included prescient insights into botany, taxonomy, and organic evolution. He may have been, in fact, the first scientist to propose that species actually changed gradually over time and that they did so because of natural processes (as opposed to supernatural ones). In his spare time, Lamarck was the first naturalist to separate crustaceans, arachnids, and annelids from insects (although housecleaners had been coping with that very problem for many years), and he also coined the term invertebrate. All in all, a fairly hefty set of accomplishments—most of which go completely unmentioned, unappreciated, and most important (for high school students, at least), unmemorized. Instead, Lamarck has been hammered in nearly every introductory biology text ever written. Indeed Lamarck’s folly, referred to as “the inheritance of acquired characteristics” has hung around the poor man’s neck like an albatross (or more accurately, a giraffe).
In Lamarck’s giraffe story, used to explain how evolution might proceed, there was once a population of short-necked animals (let’s call them protogiraffes) feeding happily on low-lying leaves. For whatever the reason, the environment changed, these plants died out, and the short-necked animals were left with a dwindling food supply.*123 According to Lamarck, the protogiraffes that had previously fed on the vertically challenged (and now extinct) foliage, needed longer necks in order to feed from the higher branches of trees that hadn’t been wiped out. This need somehow produced elongated necks, resulting in the evolution of the modern giraffe.
Although it took a bit of time to discredit Lamarck (Charles Darwin actually fell back on Lamarckian concepts in his later editions