In an Evolutionary Crucible

Isolated oceanic islands are the great natural laboratories of evolution. They enjoy this status for two rather different reasons. For the first, practicality, they provide nature’s closest approach to the controlled and manageable conditions that every scientist tries to create in laboratory experiments. They are usually small, isolated, and tenanted by a unique and poorly or imperfectly developed fauna; the hurly-burly of a rich continental community of plant and animal life, or “biota,” yields to tractable complexity—nature is never simple.

For the second reason, peculiarity, island biotas are replete with uniquenesses that both fascinate for their own sake and test general principles by probing the limits of their applicability. They are often populated not by a well-balanced set of species sifted in the fine meshes of continental competition, but by a peculiar association of forms that happened, by chance, to cross vast oceanic spaces. Major ecological roles are often without occupants—many islands lack large predators, for example. Or, in the absence of usual tenants, animals may evolve so that they occupy roles that would never be open to them on continents.

Many features conspire to turn islands into crucibles for profound and rapid evolutionary change among their inhabitants: absence of competitors, ecological availability of unconventional niches, the small size of founding populations. Islands therefore become homes for bizarre versions of animals that may be stereotyped in continental situations throughout the world. Sicily, for example, once was host to an elephant that stood less than one meter tall, yet bore all the defining features of its group. The extinct dodo of Mauritius was a giant flightless pigeon.

Since our minds prefer not to deal in abstractions, we tend to create prototypes for categories: Brontosaurus (or is it Tyrannosaurus?) becomes the dinosaur, and Einstein becomes a synecdoche for human intelligence. Among islands, the Galapagos enjoy an unquestioned status as the Mecca of biologists. They are, to be sure, archetypical oceanic islands, replete with all the beauty and fascination of their class. But, like Mecca, they owe their status not to their intrinsic character, but rather to the visit of a primary saint, in this case Charles Darwin, who spent in month in the Galapagos on the first stop of the Beagle’s long voyage home. Conventional mythology proclaims that Darwin finally saw the truth of evolution amid the finches and tortoises of these islands, hence their status as a site for secular pilgrimage. As usual, conventional mythology is largely wrong (see below), but it hardly matters. For if the Galapagos are not transcendent among islands for their own merits, they are certainly among the most fascinating.

The Galapagos Islands lie just below the equator, in the Pacific Ocean 500 to 600 miles west of Ecuador. They have formed over a “hot spot,” an area where magma generated deep within the earth’s mantle intersects the surface and builds volcanoes reaching from the floor of the ocean to its top. The hot spot has not changed its position recently, but the earth’s surface is moving above it as the Nazca Plate drifts toward South America. A sequence of islands forms as the conveyor belt of drifting plates brings new sea floor over the hot spot and older volcanoes move away. (The Hawaiian Islands have emerged sequentially in the same manner.) Therefore, the Galapagos Islands are relatively young (three million years or so for the oldest), and they have neither been nearer to South America than they are now, nor ever been connected to it by a land bridge.

The Galapagos share the stark beauty of all active volcanic regions, with large expanses of unvegetated black rock, some covered with the sinuous and ropey pattern of pahoehoe flow (a Hawaiian word), others with finer ash or blocky fragments. Their biota, a curious mixture of fortuitous migrants, mostly from South America, displays all the characteristics cited above. Some groups that would dominate in any continental fauna never arrived at all. Among terrestrial mammals, only bats and a few rodents successfully crossed the ocean. No large mammalian (or other) predator lives here, and visitors still marvel (as Darwin did) at the fearlessness that nearly all native creatures display toward humans.

Reptiles did better, and live in the Galapagos in fair abundance and stunning peculiarity (the sea-going iguanas that eat algae from the rocks, and the famous giant tortoise, of which Darwin wrote: “I frequently got on their backs, and then giving a few raps on the hinder part of their shells, they would rise up and walk away;—but I found it very difficult to keep my balance”). Darwin reported that this reptilian abundance in the face of a mammalian dearth, and the stark character of the landscape, conjured up images of an ancient world: “These huge reptiles, surrounded by the black lava, the leafless shrubs, and large cacti, seemed to my fancy like some antediluvian animals.”

The subtitle of Moore’s book trades upon this impression of antiquarian stasis, but it is a false one. The Galapagos, like so many other islands, are an evolutionary crucible. The tortoises had evolved into separate races on each island, and Darwin’s finches, beginning from a single South American source, have differentiated into thirteen species occupying a range of ecological roles that would be filled by several families of birds on any tropical continent (one of them uses cactus thorns to pry insects from plants).

But did Darwin read the truth of natural selection in the form and diversity of the Galapagos fauna? Was he able to break through ancient prejudice because pristine nature spoke so relentlessly on the relatively unambiguous terrain of desolate oceanic islands? This impression, too often conveyed by accounts in the heroic mode, rests on the false notion that biological geniuses succeed because they can free their minds of cultural baggage and see nature objectively. The Galapagos biota did increase Darwin’s growing doubts about divine creation, and he did become a tentative evolutionist before the Beagle docked in England many months later. But Darwin devised the theory of natural selection only after a year of intense intellectual struggle in England, and as a result of deep cultural immersion in a wide range of contributing influences, including Comte’s philosophy and Adam Smith’s economics. In fact, on the Galapagos, he failed to make (with later regret and self-recrimination) the most important evolutionary observation of all.

Two aspects of the Galapagos fauna pointed strongly to evolution. First, the fauna was clearly South American in affinity, but consisted largely of different species. If God had peopled the Galapagos directly, why should he have made its creatures so similar to others on the mainland (especially since the Galapagos terrain, ecology, and climate are so different from Ecuador’s)? Did not the similarity suggest accidental transport with subsequent modification? Darwin appreciated this point:

The natural history of these islands is eminently curious…. Most of the organic productions are aboriginal creations, found nowhere else…yet all show a marked relationship with those of America. We seem to be brought somewhat near to that great fact—that mystery of mysteries—the first appearance of new beings on this earth.

Second, several groups of organisms have evolved within the Galapagos Islands themselves, so that different races or species inhabit the various islands. Mr. Lawson, the vice-governor, told Darwin that “the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought,” yet, as Darwin admitted, he “did not for some time pay sufficient attention to this statement.”

As for the famous finches, he missed the tale entirely; the differences among them were so great that Darwin did not recognize their common taxonomic source. (He understood the significance of what he had seen only later when a British Museum taxonomist identified all the birds as finches.) While on the Galapagos, he mixed collections from different islands because he “never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted.” By the time he recognized this cardinal evolutionary fact, it was too late, and he lamented: “It is the fate of most voyagers, no sooner to discover what is most interesting in any locality, than they are hurried from it.”

Fortunately, Tui De Roy Moore had no FitzRoy to whisk her away. Although born in Belgium, she moved to the Galapagos as a young child and has lived most of her life there. Her beautiful and sensitive photographs, nearly three hundred of which grace this book, portray the life and landscape of these islands in tones so alluring that I can only rejoice in my own coming pilgrimage, now only ten months away. I am not a photographer, and I consider myself a poor judge of visual material, but several aspects of Moore’s style struck me. She achieves a remarkable depth of field, and manages to keep in focus both a hawk on the near edge of a caldera (a collapsed volcanic cone) and the entire span of the caldera itself—a stunning juxtaposition of organic and geological activity. Her tones tend to be dark; against this general background, the brilliant red of a frigate bird’s throat pouch or the stark white of a booby’s neck stand out even more dramatically.

Would that her introductory text matched the photographs in beauty; but then, polymaths are rare these days. Traditional, descriptive nature writing is a tricky business (at least, I can’t do it). One feels the awe, power, and beauty easily enough, but only a poet can convey it without lugubrious clichés or hackneyed phrases. For most of us who are not poets, the danger lies in trying to translate the powerful emotions within us by ever more frantic adjectival superlatives. Why, oh why, must everything on the Galapagos be mysterious, magnificent, or miraculous? Can’t something be merely admirable, or even pretty, rather than “fantastic” (her favorite adjective)? In fewer than twenty lines, we learn that an “effervescent” Darwin observed “incredible” animals in “exquisitely delicate equilibrium” with their environment.

Moore also falls into the other leading trap of anthropocentric interpretation. Thus we learn that the long courting ritual of frigate birds “builds mutual trust,” and that a sea lion male will occasionally yield his harem to a competitor because he is “tired from the exertion.” Moore correctly argues that our tendency to see struggle and harshness in nature records “the projection of a human whose knowledge is hampered by too little perspective.” But does she believe that her vision of “a fundamental harmony” is any less tempered by personal hopes and feelings?

Unfortunately, Moore propagates a major misunderstanding with dangerous consequences in this frustrating age of resurgent Yahoos who call themselves, in perfect newspeak, “scientific creationists.” Moore writes: “Evolution is still only a theory, because our human life span is not long enough to enable us to witness its process in a natural environment.” But theories are not imperfect facts; they are structures of ideas that interpret facts. We can argue endlessly about why apples fall; the apple, quite oblivious to all of this, continues to fall. Evolution is a fact; we also have theories (including natural selection) that attempt to explain how and why evolution occurs. Our current healthy and vigorous debates about evolutionary mechanisms have been consciously distorted by creationists into claims that biologists now doubt the fact of evolution itself. But the debate can only occur because all participants accept the basic fact of evolution, and thus have a common ground for arguing about mechanisms.

As for the claim that evolution isn’t a fact because we don’t see it directly, one might as well deny gravitation and electrons. Most abstract phenomena in science are not perceived as we view a dog wagging its tail. There are many ways of “seeing” beyond direct visual observation. In any case, the claim isn’t even true, for many evolutionary changes, including the origin of new species, have frequently been observed in nature. If I sound defensive, it is only because my own work, critical of certain aspects of Darwinism, has been a primary target for creationist distortion. Besides, I’m angry; and I hate to see my own colleagues unconsciously falling into semantical traps.

But I would forgive Ms. Moore volumes of conscious and more outrageous statements just to have her magnificent photographs—yes, the adjective is unavoidable here. I will even put aside the paradox that the larger purpose of her work—advocating a vision of “oneness” with nature through her photographs—is probably doomed by the advanced technology that permits her, in the form of lenses and filters, to record the beauty behind her hopes.