IN THE FIELD OF evolutionary biology, as virtually everywhere else, these are times of ferment. New information pours in daily from all over the globe, data from such diverse sciences as paleontology, genetics, geology and even astronomy and meteorology combining simultaneously to modify and enhance the basic Darwinian understanding of life's unfolding. At the same time we see the Darwinian vision brought under attack, not only by its traditional "creationist" opponents but also by a growing variety of critics disturbed by the role of chance in natural selection.
Such critics suggest that mere chance could not have produced the living system as we see it today, nor could it have played even the limited part envisioned by Darwin and his successors. Some other principle, they say, some purposeful direction must from the beginning have directed the formation of genetic material to propel life along its multifarious paths.
The Great Evolution Mystery is Gordon Rattray Taylor's posthumously published contribution to this point of view. A British science writer and participant in the production of several award-winning science-oriented television series, Taylor prepared this last of his 15 books in hopes of debunking natural selection in favor of what he calls "an inner necessity," some sort of "forces at work in the universe of which we have as yet scarcely an inkling." Hence, you see, the "mystery" in Taylor's title.
Now, invoking such ''forces" permits Taylor easily to resurrect the Lamarckian theory of evolution through inheritance by offspring of characters acquired in response to some need on the part of their parents. Because no one can as yet isolate and identify his "forces," Taylor uses them with impunity, asking us to accept them a priori in following his argument for the demolishing of natural selection as evolution's guiding force.
For example, Taylor examines the ostrich, born with calluses on its rump, breast and hip, calluses located precisely where the bird will rest when sitting on the ground. "It is tempting," he says, "to suppose that ostriches once developed these calluses in the course of life . . . and that somehow the capacity to produce them became incorporated in the genome (heredity)."
That "somehow," of course, is Taylor's "inner necessity"; he goes on to say that "while naturalists cling to the idea of inheriting acquired characteristics, which seems only common sense, geneticists reject it entirely, solely on the grounds that they know of no mechanism which the genome could be appropriately ordered by experience." This "mechanism," he implies, is no doubt there --it is simply one of those "forces . . . of which we have as yet scarcely an inkling."
In my own experience, on the other hand, most contemporary "naturalists" would not "cling to the idea of inheriting acquired characteristics." Indeed, most would presume that the first ancestral form to acquire these calluses did so by chance genetic mutation, and that the advantage (in preventing abrasion of the skin and potential infection) conferred by this animal to its offspring was significant enough to enhance their own chances, etc. This view, however, disregards mysterious "forces" and "inner necessities," relying instead on the simpler Darwinian mechanism of natural selection.
As his title implies, Taylor seeks to re-establish a "great mystery" with which to replace the dynamically successful Darwinian analysis. In so doing, he adopts an odd tone, a sort of raised-eyebrow questioning rather comparable in my mind with the style of proponents of visitations by spacemen in ancient times. These advocates of extraterrestrial contact are fond of asking questions in rapid series, thus: "Why are the edges of the Pyramids so straight? Did the spacemen give the Egyptians laser-directed surveying devices? If not, how else could the ancients have acquired these devices thousands of years before their re-invention in modern times?"
You understand the tone. This sort of logical leap-by-question is rife in Taylor's book, as is a misinterpretation of particulate aspects of the works and words of Darwinians themselves. "Punctuationism," the idea that evolution may proceed in spurts followed by periods of relative stability, is said by him to destroy the Darwinian synthesis; if such apparent quickenings of evolutionary pace take place, he says, "natural selection is ousted from its unique position." He does not, however, explain precisely how this is so, nor does he mention that the fossil record was too scantily understood in Darwin's time to show the changes in evolutionary tempo that are apparent to Darwin's successors.
Too, by citing gaps in the fossil record (there are many such gaps, fossils being formed only under certain rare conditions and at certain times), Taylor attempts to pry more chinks in the Darwinian analysis. Here again he employs the leap-by-question--like a rapier--wondering, for example, about "the change from spineless jellyfish to fish with brains and backbones," a change which no one except Taylor has ever suggested actually occurred! Assuming falsely that Darwinian evolutionists maintain that all organisms are perfectly adapted through relentless competition, Taylor mentions countless organic "imperfections" like the incidence of slipped disc in human beings, somehow concluding that these deny the validity of natural selection as a guiding evolutionary force.
In all, for anyone interested in the questions facing modern evolutionary thought, I would recommend The Great Evolution Mystery. Highly readable and immensely entertaining, it is a superb exercise in the use of logical gaps as polemical weaponry.
Quite another of evolution's many faces appears in Hen's Teeth and Horse's Toes, the latest collection of essays by Stephen Jay Gould. Gould is an evolutionary biologist, and in an age when scientific prose is all too often as dry as a pile of bills, his delight in his work shines through as both a goad and a joy to his readers. Pursuing in some cases the same "mysteries" we find in Taylor's book, Gould entices us to follow him on a multifaceted Darwinian hunt for answers to age-old questions about ourselves and the rest of the living world.
Like evolution itself, Gould explores possibilities-- any that come to hand--and his range of interest is stupendous. In what manner do new living forms arise? How do they maintain their integrity over the rocky road of selective pressure? What causes extinction? More particularly, Gould probes individual aspects of the evolutionary process: are zebras white with black stripes, or black with white stripes?--or is there such a thing as a zebra? Who perpetrated the Piltdown Hoax? What evolutionary rules govern the ratio between the mass of Hershey bars and their prices over time? How were the population biologies of Europe and North America affected by census-takers? How did horse feet evolve? And how may that rarest of rarities, a hen's tooth, be found?
In 30 essays, Gould examines these and many more questions. He spars with creationists, sharing in depth both his amusement at their contentions and his fear of their potential power to manipulate the ignorant. He looks with sympathy and empathy at the lives of eminent men of science and of God, permitting us an intimate understanding of the social and scientific forces shaping their thought. Throughout, he displays with force and elegance the power of evolutionary theory to link the phenomena of the living world as no other theory seems able.
It would be mean of me to elaborate further on the contents of this delectable book. Suffice it to say that if science be regarded as a religious process, as one of delight in one's own perceptual processesand in the workings of the universe, then Stephen Jay Gould deserves a place as its current high priest. Hen's Teeth and Horse's Toes is a happy evolutionary tour de force, its author a true natural philosopher in the grand tradition of the Enlightenment. Read, learn and enjoy.