The Flight of the Iguana Read Online Free PDF

comparable in value to the Rosetta stone.” Maybe so, but the hieroglyphics in question here still haven’t been conclusively deciphered.
    Three more specimens have been found in this century, none nearly so graphic as the Berlin fossil, but all nonetheless precious. The second of those had actually been dug up back in 1855 (near Eichstätt, once again) and incorrectly identified for 113 years as a pterodactyl. The last showed only the faintest feather impressions, which were overlooked, and it spent two decades mistakenly labeled as Compsognathus, which is a small dinosaur.
    To say that Archaeopteryx is known from “just six fossil specimens” might be somewhat misleading. For such a delicate creature, a species with small bones and fragile feathers that disappeared160 million years ago, six decent specimens amounts to a lot. Thanks to a convergence of accidents—six individual deaths, occurring at just the right place and time to be preserved within fine-grain sediments, and later discovered largely because mankind had a commercial reason for excavating those same sediments— Archaeopteryx is exceptionally well represented within the fossil record. Between it and the next-oldest bird or bird-like fossil there stretches a gap of ten million years, and not nearly so much is known about that next-oldest relative. Disproportionally well documented, Archaeopteryx nevertheless (or maybe therefore) raises a disproportionate number of questions.
    To paleontologists this creature is by now a familiar riddle. But, familiar or not, it’s still very much a riddle.
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    How did flight begin among birds?
    Why did it begin?
    Were the dinosaurs warm-blooded or cold-blooded?
    Is a chicken more closely related to a crocodile or to Tyrannosaurus rex?
    Did feathers come into existence for aerodynamic reasons or as insulation to keep body heat in—or maybe to serve as adjustable reflectors that kept heat out?
    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?
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    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