The Flight of the Iguana (5 page)

Were the predecessors of birds runners or tree climbers? Were they jumpers or were they gliders?

Did warm-bloodedness evolve two separate times—once in our mammal lineage and once among birds—or did we all inherit that handy attribute from a frisky two-legged dinosaur?

Did the dinosaurs ever really go extinct? Or do they survive among us today, in discreet and more humble forms such as
Turdus migratorius,
the robin? Are feathers merely the means that allowed dinosaurs, while becoming smaller, to stay warm?

If a bird can fly, why can't I?

•   •   •

To each of those questions the
Archaeopteryx
evidence is central. But that evidence is as resonantly ambiguous as a good haiku poem. Read from it what you will. Prove with it what you can. That's what the scientists have been doing with it for a century and a quarter. And it isn't their fault that
Archaeopteryx
lies there, sphinx-like, on its beige limestone slabs, granting many answers but no certainty.

The runners-versus-climbers controversy is a good example. From the time of Darwin right up through the Eichstätt conference in 1984, this has been one of the most fundamental dichotomies within the range of interpretations of
Archaeopteryx.
Some paleontologists have insisted that
Archaeopteryx
evolved from a tree-climbing dinosaur, which jumped from its high perches, then later developed gliding ability, then finally flew. Others have argued that
Archaeopteryx
came from the ground up, a fleet bipedal runner that stretched out its arms, leaping and sailing, until it developed the wing power to get airborne. These two schools of opinion know themselves respectively as the
arborealists
and the
cursorialists.
If you are an arborealist on the subject of
Archaeopteryx,
your professional attitude inclines toward polite but dogmatic scorn for all misguided cursorialists. And vice versa.

The arborealists point out that flight of some kind or another, from modest gliding to powered flapping, has evolved separately no less than sixteen times among the nonavian vertebrate animals—that is, in four distinct groups of flying fishes, in one frog, in two groups of extant reptiles as well as the pterosaurs, in two kinds of flying squirrels, in bats, and in three kinds of marsupials, not to mention a few other weird little kamikaze mammals that neither you nor I have ever heard of. Among those sixteen instances, all but the flying fish and maybe the pterosaurs are known to have gotten their start as tree climbers. The force of statistical probability, as well as the force of gravity, seems to favor the arborealist side.

So what? say the cursorialists. Evolution is not roulette. And
besides, they say, the case of feather-assisted bird flight is obviously a drastic exception to the general pattern—peregrine falcons and hummingbirds are spectacularly proficient, after all, while those poor cloddish “flying” frogs and lizards and squirrels are still careening down half out of control and slamming themselves into tree trunks. Furthermore, say the cursorialists, it is hard to imagine
Archaeopteryx
doing much tree climbing with those long primary feathers sticking way out past its foreleg claws. Try opening your car door while wearing an outfielder's mitt on each hand, and you'll appreciate the problem.

To all of which the arborealists, of course, have ready rebuttals.

The first of the arborealists was none other than Othniel C. Marsh, a preeminent figure in American paleontology during the nineteenth century, and one of the two principals behind the great wild dinosaur wars that were fought out between rival collectors in frontier Montana and Wyoming. (The other paleontological warlord was Edwin Drinker Cope, and it's a bizarre story all to itself.) Concerning the evolution of flight, Marsh argued: “In the early arboreal birds, which jumped from branch to branch, even rudimentary feathers on the forelimbs would be an advantage as they would tend to lengthen a downward leap or break the force of a fall.” Arguing the other view, among the first of the cursorialists, was Franz Baron Nopcsa von Felso-Szilvas, an elusive but unmistakably demented Hungarian who happens to be my own personal favorite in the paleontological pantheon. Baron Nopcsa was a brilliant prodigy who made significant contributions toward the study of
Archaeopteryx
until certain other interests pulled him aside toward Albania, motorcycle touring, and death.

Nopcsa was born in Transylvania, always a good sign. He published his first paleontological monograph as a university freshman, and thereafter turned into an arrogant snot. Somehow he became infatuated with the geography and ethnography of Albania.
He learned the dialects, amassed a huge library of books about the country, made many visits; eventually he offered himself for the position of King of Albania, based on what he considered his surpassing competence for the job, but the Hapsburg overlords picked someone else. During World War I he served the Austro-Hungarian Army as a spy along the Romanian border, letting his hair grow and dressing as a Romanian peasant. He spoke the languages. He passed. Much later, when he was bored and impoverished, his baronial lands having been confiscated in the peace settlement, he took off on a long motorcycle ramble with his male lover, an Albanian named Bajazid. Finally, in April 1933, for reasons we'll never know, Nopcsa came to the end of his tether. He slipped Bajazid a mickey, shot him through the head, then put the pistol to himself. But before he died—in fact, it was way back in 1907—Baron Nopcsa had published a paper titled “Ideas on the Origin of Flight.” The central datum was of course
Archaeopteryx.

Nopcsa wrote: “We may quite well suppose that birds originated from bipedal long-tailed cursorial reptiles which during running oared along in the air by flapping their free anterior extremities. By gradually increasing in size, the enlarged but perhaps horny hypothetical scales [would] . . . ultimately develop to actual feathers; this epidermic cover would also raise the temperature of the body, and thus help to increase the mental and bodily activities of these rapacious forms.”

Nopcsa was just deranged enough (well, maybe more than enough) to be a bold, original thinker. In suggesting an earth-bound
Archaeopteryx
that flapped its feathered arms to help itself gain speed as it ran, he had broken through a basic assumption in the debate over whether feathers evolved first for insulation or for gliding—the assumption that, if those earliest feathers served
any
aerodynamic purpose, the purpose must have been flight. But ground travel too involves aerodynamics. Ask any designer of racing cars; ask anyone who rides touring motorcycles.

For three quarters of a century Nopcsa's view was dismissed as nonsensical. Ground-travel aerodynamics seemed an unlikely precursor to feathered flight since, as soon as the animal made that next little evolutionary leap, becoming airborne, it would have lost all the running leverage from its legs; losing that leverage, it would have achieved a net
decrease
instead of a net increase in speed, and therefore also a net decrease in its prospects of survival. The gap between feather-assisted running and feather-assisted flying seemed evolutionarily unbridgeable. But now again the notion of ground-travel aerodynamics is being given some careful thought.

One of the hot new ideas on the subject, as of the 1984 conference in Eichstätt, is that maybe
Archaeopteryx
used its arm feathers as
rudders,
for changing direction erratically as it ran along. Assisted by aerodynamic rudders, this little beast might have streaked out a wild zigzag path across the floor of Cretaceous forests, escaping from bigger and faster predators.

The cursorialists at Eichstätt were intrigued. The arborealists were not swayed. The disputation goes on.

•   •   •

What is the thing with feathers? It might be a dinosaur dressed for warmth in a chicken suit. It might be the earliest bird, hot-blooded and flapping its way from tree to tree. It might be your nephew or mine or Woody Allen's, in need of a visit to Zurich. It is a mystifying cross between fowl and reptile, a chimera sculpted in fossil stone—an oxymoronic creature that actually lived and died, rather like Baron Nopcsa himself.

It perches on the soul, this thing, singing a tune without words.

We call it
Archaeopteryx.
The name is Latin, standing for:
Thank God there are some riddles we can't solve.

An African Bedbug Buggers the Proof-by-Design

A fellow named Duane T. Gish was in town here last week, playing his practiced role in a debate on the subject of “scientific creationism” versus evolutionary theory. I didn't go. It was dollar night at the movies. But now I regret having missed a precious opportunity, since just the next day, in my random reading, I came upon an account of the startling deportment of the hemipteran insect
Xylocaris maculipennis,
an animal that demands pondering by creationists and evolutionists alike. A question-and-answer period followed the debate, but with me off watching
Peggy Sue Got Married
and pushing popcorn into my face, the important
Xylocaris maculipennis
question never got asked of perhaps the one human being most qualified to attempt an answer. Namely, Duane T. Gish.

Duane T. Gish, as it turns out, is a famous (some would say, notorious) man, vice president and leading spokesman of the Institute for Creation Research, which is a fundamentalist think tank based in Santee, California. He travels across America arguing the creationist viewpoint—that the Earth is only 10,000 years old, that evolution is an atheistic delusion, that the myriad types of plants and animals which some of us think of as evolved species were all in fact created individually by God—and according
to most reports he is a glib and effective debater, a man of some charm, good with crowds and capable of making fools of opponents who underestimate his intelligence. He holds a doctorate in biochemistry and seems possessed, if the photos do justice, of a bad toupee. A
country slicker,
is what you might call him.
Xylocaris maculipennis
is an African bedbug. There had to be more than blind coincidence involved in bringing this man and this insect both into my purview during the same week, but the precious opportunity nevertheless slipped past me. Dr. Gish was packed and gone to the next town before I could solicit his thoughts concerning
X. maculipennis
and the Proof-by-Design.

What I refer to as the Proof-by-Design is a venerable piece of logic, lately refurbished by the creationists. One of its earliest and most influential formulations was by John Ray, an English naturalist of the seventeenth century who did pioneering work in botany and then, in 1691, published a book called
The Wisdom of God Manifested in the Works of the Creation.
Ray's argument in this book was (as the title declaims) that the elaborate design of the natural world—the matching of form to function within living creatures, the harmonious intermeshing of creatures with each other—proved the necessary existence of an omnipotent, benevolent Creator. A century later Linnaeus himself (often thought of as the first hardheaded taxonomic biologist) voiced the same idea. Right up to the time of Darwin, this view of nature was cited by both naturalists and theologians as cogent evidence for the sort of avuncular, dependable God we could all love and admire. According to one version: “This perfect Unity, Order, Wisdom, and Design, by which every Individual is necessarily related to, and made a dependent Part of the Whole, necessarily supposes and implies a universal, designing Mind, an all-powerful Agent, who has contrived, adjusted, and disposed the Whole into such Order, Uniformity, concordant Beauty and Harmony, and who continues to support, govern, and direct the
Whole.” Clearly the cheerful sport who wrote that sentence had never heard of
Xylocaris maculipennis.

Now the same Proof-by-Design is back in fashion among creationists, brought up to date for a new post-Darwinian purpose. These days the argument is used to prove, not merely that God does exist, but also that evolution doesn't.

•   •   •

Consider the cleaner wrasse, for instance. This little fish is the hero of an article titled “Nature's Challenges to Evolutionary Theory,” published by Duane T. Gish's own outfit, the Institute for Creation Research. As any marine biologist knows, a cleaner wrasse makes its living by swimming into the opened mouths of much larger, predaceous fish and picking away parasites that have infested the soft mouth tissues. The bigger fish not only permit this to happen; they come to the stations where these little wrasses have set up shop and literally wait in line to be serviced. When the cleaning is done, the little fish is allowed, gratefully, to swim safely back out of the jaws of death. In the view of the ICR, this symbiotic interaction is too complex and too improbable to have arisen by evolution. “The case for creation will be evident in certain special ecological relationships like cleaning symbiosis,” we are told. “The Christian recognizes that such processes reflect the continuing care by which God faithfully upholds His creation.”