The Flight of the Iguana (23 page)

•   •   •

The Gaia hypothesis is a very complicated idea. It would have to be: It merely seeks to encompass all of ecology, biochemistry,
chemical oceanography, tectonic geology, and atmospheric physics. Applying bits of information from each of these disciplines, Lovelock goes on to explain how soil and water acidity, ocean salinity, trace-element distribution, and a number of other crucial conditions are maintained within life-fostering ranges through the active intervention of Gaia. He even suggests that the spawning migrations of eels and salmon, from salt water to fresh, might be Gaia's way of recycling washed-away phosphorus.

Most evolutionary biologists would roll their eyes at that one. And it makes me wonder what other points in Lovelock's grand hypothesis might set the biochemists, the geologists, and the physicists to rolling
their
eyes. Lovelock himself admits that his presentation of the idea—if not the idea itself—is inescapably contaminated with anthropomorphism and teleology. Personally, I can forgive anthropomorphism and, after checking a dictionary, I can even forgive teleology. But I have a different reservation about Gaia.

Lovelock's central tenet is that the Earth possesses a potent, cybernetic, and vastly underrated capacity to keep itself healthy. To heal itself, when its environment has been injured. To clean and restore itself, just as a human's kidneys and liver clean and restore the blood. He is emphatically reassuring on this point. The worry over ozone reduction by aerosols is ridiculous, says Lovelock. The concern over greenhouse-effect warming is unwarranted, he says. All right, possibly that much is true. Possibly. The worst industrial pollution belched forth from smokestacks, puked forth into rivers, spilled forth onto seas is no more than a minor discomfort to Gaia, Lovelock tells us. The most egregiously toxic dumping amounts to nothing, he claims. This, I think, is rather more dubious. Lovelock even goes so far as to state that “a nuclear war of major proportions, although no less horrific for the participants and their allies, would not be the global devastation so often portrayed. Certainly it would not much disturb Gaia.”

Fine for
her.

Evidently this Gaia of Lovelock's is as cold and as Olympian a bitch as any goddess that any man ever dreamed into being. She will endure as she has endured, she will provide as she has provided, she will cure herself of whatever damage humanity may inflict. Which is good, I suppose. It's grounds for a certain stoic and hyperopic sort of satisfaction. Okay, well, whoopee. Life on Earth will continue, according to J. E. Lovelock's hypothesis, whether humankind cooperates, or the contrary.

But the question that nags me is this. When humanity's earthly misbehavior has progressed to the point where even our farts can't redeem us, won't Gaia simply cure herself of
Homo sapiens?

Evolution and Extinction in the Galápagos and Beyond

Imagine a moment in the history of ideas: A young man stands on the coast of a tropical island, many miles and many years from his home, throwing an oversized lizard into the sea.

The lizard swims back to shore. The young man follows this animal, corners it, catches it by its long muscular tail, and throws it again into the sea. Again the lizard swims back to shore. Still another repetition. Always the lizard swims straight back to that same stretch of rocky shoreline where the young man waits to catch it again, throw it again. The lizard is a strong swimmer but seems stubbornly disinclined to try to escape through the water. The young man takes careful note of that fact and, despite his homesickness, wonders why.

“Perhaps this singular piece of apparent stupidity may be accounted for by the circumstance,” the young man eventually writes, “that this reptile has no enemy whatever on shore, whereas at sea it must often fall a prey to the numerous sharks. Hence, probably, urged by a fixed and hereditary instinct that the shore is its place of safety, whatever the emergency may be, it there takes refuge.” The young man of course is Charles Darwin, and the lizard is
Amblyrhynchus cristatus,
better known as the Galápagos marine iguana.

The incident of the tossed iguana occurred in autumn of 1835, during Darwin's brief stopover in the Galápagos Islands toward the end of his five-year trip on board the surveying ship
Beagle.
It was recounted in his popular book
The Voyage of the
Beagle, published a decade later—which was still fourteen years before
The Origin of Species
suddenly made Darwin the most famous and controversial biologist in the world. Today we all know about
The Origin;
we all know about Darwin's great idea, that evolution has been produced by a process he called natural selection; we all know about how this idea was made vivid to him by the Galápagos finches, their different species having evolved to fit different niches on the various individual islands of the group. So we all know, or at least think we know, the biological significance of the Galápagos archipelago. These islands, volcanic nubs pushed up above the ocean surface five hundred miles west of Ecuador, constitute one of the shrines of modern science. We can tune in public television any night of the month, it seems, and find them gorgeously photographed, reverently explained. Giant tortoises, blue-footed boobies, finches with a spectrum of different beak shapes, exotic fauna and flora showing all manner of unique adaptations, Darwin's visit, presto, theory of evolution—the syllogism has been polished by repetition. The incident of the tossed iguana, though, generally passes unmentioned.

This is too bad, because that incident happens to be rather eloquent. It not only tells us about Charles Darwin the person, as he was in 1835—boundlessly curious, unsentimental about nature, doggedly systematic, groping, and yet in some measure still just a wealthy young remittance-man off on a round-the-world lark, riding horseback with the
gauchos
and throwing helpless lizards out to sea on a dull afternoon. It also hints toward a fuller understanding of the Galápagos Islands themselves.

A century and a half after Darwin, in the course of my own modest pilgrimage, I find myself seated on a rocky Galápagos shoreline. This particular island is Santa Cruz, one of the largest
and ecologically most rich. The stretch of coast where I sit, in a jumble of sun-heated lava boulders and salt-tolerant vegetation, is not far from the Charles Darwin Research Station. Across the bay, prickly pear cactuses transmogrified into tree form, tall and thick as oaks, stand in weird silhouette above black lava cliffs. At close range, I am surrounded by a dozen marine iguanas.

One of these animals is a dominant male, looking resplendent with his crest of dorsal spines, his strong stubby face, his black skin mottled with orange and olive; there are also three or four adult females, and the rest juveniles. When I walked up and sat down among them, an hour ago, they paid me little attention. Four feet of distance seems to be all they require. Like most other animals on the Galápagos, the marine iguanas show an indifference toward human proximity that gets them labeled, perhaps misleadingly, with the word
tame.
Now we are all of us sunning. And I am wondering what might happen if I picked up the big male by his tail, swung him around carefully, and tossed him as far as I could into the surf.

I have just reread Chapter XVII of
The Voyage of the
Beagle, and the question intrigues me. The most probable answer is this: I would be arrested.

•   •   •

Today the Galápagos Islands are an Ecuadorean national park, with strict regulations protecting the native wildlife and vegetation from being tampered with by the likes of you or me. Even Darwin himself would now need a research permit, before he heaved his first marine iguana into the brine or (another of his lighthearted experiments during that visit) climbed up to ride on the back of a giant tortoise. Some tourists are prone to the self-indulgent delusion that those regulations can reasonably be bent—surely there's no harm in petting a “tame” sea lion or feeding bread crusts to a finch?—but it isn't so. The Galápagos require extraordinary, uncompromised protection from human impact. They need that extraordinary protection for four reasons: 1) because
they have already, in the past three hundred years, been pillaged almost beyond rescue; 2) because they hold precious significance in both our natural and our intellectual heritage; 3) because they now endure heavy traffic as a tourist destination; and 4) simply because they are
islands.

The first three of those reasons are, admittedly, tendentious and self-evident. The fourth is an intricate, fascinating matter of science.

Islands are different. Evolutionary biology as manifested on islands is an exaggerated and specialized subcategory. The same general principles apply—there's a competitive struggle for reproductive success, in the course of which those organisms best adapted to their environment are “selected” to perpetuate their genes—but, on an island, the application is so stark and unbuffered as to seem almost qualitatively distinct. For one thing, islands are generally poorer in species diversity than any equal area of similar habitat on a mainland. They have more than their share of unusual species, but fewer than their share of species overall. A corollary to that low diversity is that they are more fragile than the mainlands. Complexity translates to stability, for almost any ecosystem, and islands because of their isolation show biologically simplified communities.

Being islands, therefore, the Galápagos are especially vulnerable. Being islands, they are also especially instructive. Being what they are, the Galápagos are both drastically unique and at the same time quite similar to most of the planet's other islands.

That paradox is part of the insular condition: All islands tend to harbor ecosystems that are full of bizarre features (a shared pattern), but each island or group of islands is bizarre in its own eccentric way.

In the case of the Galápagos, so celebrated, so familiar, that paradox is commonly overlooked. Even a fairly eminent biographer of Darwin has declared: “The fame of the [Galápagos] islands was founded upon one thing; they were infinitely strange,
unlike any other islands in the world.” The statement is true, almost tautological, and it's also very misleading. The fuller truth is that
most
islands are infinitely strange, and unlike any others in the world.

The Galápagos are broadly representative for the very fact of being so strange, so unique—and that representativeness is what made them useful to Darwin. He might just as well have based his great insight upon a stop in Hawaii, or the Seychelles, or the Malay Archipelago, or Madagascar. And we might now talk about “Darwin's lemurs” or “Darwin's honeycreepers” instead of Darwin's finches. He might even have recognized natural selection from a study of South American rodents—though an island experience made his task easier, because those simplified island ecosystems display the evolutionary process in a boldface, cartoonish version. He might, he might have, he might—but as it happened, he didn't. Darwin
didn't
go to Hawaii, he didn't go to Madagascar, and he was not forced to derive his idea from the confusing patterns of faunal variation on the South American mainland. Fate and the
Beagle's
survey itinerary brought him instead to the Galápagos.

Where he found an iguana that swam like an eel and lived on a diet of seaweed.

•   •   •

“It is a hideous-looking creature, of a dirty black color, stupid, and sluggish in its movements,” Darwin wrote. Here I think he was a little unfair. In the morning of my second day on Santa Cruz, I am out on the black lava rocks of the shoreline again, with the marine iguanas, watching them as they gape stolidly out at the returning tide, and wondering what—if anything—is going on behind those inscrutable hooded eyes. Are these animals truly stupid and sluggish? Or are they just dignified and calm?

Amblyrhynchus cristatus
is the world's only oceangoing lizard, an interesting distinction for several reasons. Like most other iguanas, it is a vegetarian, which means that it needs to feed
longer and more voluminously for the same amount of nourishment as a carnivore gets from one protein-rich meal. Also like other iguanas, it is ectothermic (dependent on external sources of body heat) and lacking in stamina. Since there is no better way to sap a body of heat and stamina than by dunking it in seawater, the marine iguana seems to have chosen a strange path. It feeds on algae exposed at low tide or, more athletically, swims out into the sea and dives down to graze underwater. Herpetologists who have studied its physiology (which seems scarcely different from the standard iguana physiology, suggesting that its marine adaptation is purely behavioral) continue to sound puzzled that
Amblyrhynchus
can live its life as it does.