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Planet of the Reptiles
Marsh's Dinosaurs Edited by John H. Ostrom and John S. McIntosh Yale University Press 416 pp $85.00
A few months ago, on Denver public television, two fire-breathing creationists debated several of us scientists and historians. The gentlemen sneered at modern laboratory genetics, mocked carbon dating, and dismissed all Australopithecus specimens as tall chimps killed by Noah's flood. They even snorted derisively at church fathers who had studied Genesis and become convinced that the six days of Creation were periods of unknowable length. "Saint Augustine was wrong!" one of the men hissed.
But when I popped open a cigar box and drew out a fossil tooth from the huge carvnivorous dinosaur Allosaurus, the pair of stratigraphic debunkers grew silent. They knew that Homo sapiens, especially in the juvenile stages, love dinosaurs. They knew that thousands of parents listen to their fourth-graders correct them on fine points of dino history: "No, Mom. Allosaurus didn't live with T. rex. Rex came millions of years later, in the Cretaceous period. Our human ancestors were little twitchy-nosed fur balls back then." Simply put, know-nothing creationists are scared of dinosaurs.
Jurassic bones have been silencing geo-Luddites since the spring of 1817, when a roofing-slate quarry at Stonesfield, near Oxford University, yielded two lots of fossils. One lot preserved jaws, hips, and a torso from Megalosaurus, a predator that was in life as heavy as an elephant. Megalosaurus was the first anatomically adequate dinosaur specimen known. The Reverend William Buckland, arguably the greatest Jurassic scholar of all time, described it as a gargantuan reptilian surprise. Though the design of its teeth and jaws mixed crocodile and lizard, its legs and backbone brought to mind higher zoological grades. They resembled the legs and spines of hot-blooded mammals (such as rhinos and bears) and giant birds (such as ostriches). Buckland's protégé, Richard Owen, argued that the Dinosauria were the most sophisticated physiological adaptation ever produced within the class Reptilia.
The second lot of Stonesfield fossils were three mouse-sized jaws armed with prickly, high-cusped teeth. Buckland and Owen recognized that the minimolared fossils were members of our own class, the warm-blooded Mammalia. These mammals were at a lowly grade of organization--simpler and stupider than even a Virginia possum.
Buckland and Owen offered two alternative explanations for the humble status of us mammals in Jurassic times. Explanation A: The hot and steamy Jurassic atmosphere was unsuitable for high-class mammals, whose brains are large and delicate. Explanation B: God elected to put the highest form of reptile, the hot-blooded dinosaur, in the Jurassic period, and early mammals could only survive by being small and inconspicuous.
Many Victorian biologists had trouble accepting that Jurassic mammals were uniformly diminutive. That is because they resisted the idea of biological progress--the notion that while some species become extinct, those who survive might progress from lower to higher forms. Anti-progressionists, led by Charles Lyell, argued that Stonesfield was a misleading sample. They insisted that big, smart Mammalia--cows, elephants, maybe even humans--had been cavorting elsewhere in Jurassic days, in spots not recorded by the fossilization process. Those who distrusted the available evidence had their own refrain: "The fossil record is mostly gaps in time and space." Darwin himself was deeply embarrassed by the gappiness of the record. Lyellians envisioned a steady-state earth where high mammals had always coexisted with low. As long as Jurassic bones consisted of fragmentary skeletons dug here and there in England and France, the steady-state view was defensible.
It became indefensible in 1877, with the discovery of bone-rich layers of sediment at Como Bluff--a windy, red-blotched ring of low hills on Wyoming's High Plains--and in nearby Colorado. Railroad cars carried freshly uncovered skeletons back to New Haven, where Professor Othniel Charles Marsh directed a laboratory a hundred times bigger than Buckland's. Yale lab benches strained under the load of a hundred brontosaurs and dozens of giant predators--many species represented by near-complete skeletons--plus dozens of mammal jaws. For the first time, scholars and the public alike could see the full-body profile of long-necked Jurassic brontosaurs, plated stegosaurs, and snaggle-jawed predators.
Marsh was one of the earliest bone diggers to convert whole heartedly to Darwinism. He coined Marsh's law, which states that since bigger brains confer adaptive advantages, brain size increases as a species evolves. The average mammal today is brainier than its ancient ancestors. Jurassic mammals were dumb, Marsh explained, because they had only recently evolved from reptiles.
Marsh's Wyoming fossils offered compelling evidence of evolution at work in mammal history. In molar structure and jaw architecture, the Como mammals from the late Jurassic were distinctly more advanced than the Stonesfield critters, which dated from the middle Jurassic. Nonetheless, all Como mammals were still tiny--implying that the dinosaurian overlords maintained an adaptive superiority. In fact, as further discoveries by Marsh showed, dino domination continued into the next period, the Cretaceous, the era of the three-horned vegetarian Triceratops. Not until the last dino died did mammals begin to evolve larger body sizes.
Marsh's spectacular discoveries had an especially wide impact on popular culture because of the superb quality of the anatomic art that was created to illustrate his fossils. Underwritten by his own personal fortune, plus generous wads of taxpayers' cash transmitted via the U.S. Geological Survey, hundreds of lithographic plates were prepared at New Haven. Woodcuts in smaller format supplemented the folio-sized lithos.
But, strange to relate, the richest lode of Marsh lithos, illustrating the Como dinosaur menagerie, remained largely unpublished at his death in 1899. Perhaps the amount of text demanded by such luxurious illustrations daunted the Yale professor. Whatever the cause, these hundreds of bone images were inaccessible to scholars and dinophilic public alike for more than a half century.
I remember vividly when Yale University Press first issued Marsh's Dinosaurs, the long-delayed publication of most of the Como lithographs, in 1966. I was a Yale undergrad, doing a senior thesis on Como dino legs. I had been converted to Buckland and Owen's belief that dinos were high class in limb architecture, the near equal of rhinos, elephants, and ostriches. But my research was hampered by the sheer size of the petrified objects: It's extremely difficult to lay out a brontosaur shoulder joint and make an accurate diagram free from parallax. The human eye distorts such a monstrous shape, because we're too close to the bone. Unaided, our vision can't make an "ortho-projection," an image on paper of the true bone geometry.
Marsh's Dinosaurs provided the solution. Every lithograph was an ortho-projection. Every drawing had been executed by anatomic illustrators who employed proportional dividers to locate all the landmarks on the bone surface. Bones were shown in three, four, or even six views: top, bottom, front, back, sides. So detailed were the lithos that I could identify the marks left on the bones by their attachments to muscles, joint cartilage, and ligaments. So accurate were the lithos that I could perform mechanical analyses that combined images of hip sockets with those of upper thighs. The first dozen papers I published in technical journals, plus my first book, Dinosaur Heresies, came in large part out of investigations assisted by Marsh's lithos, and many of my colleagues likewise credit the lithographs as key elements in their work.
The 1966 book was more than a dinosaur biomechanical atlas. Ostrom and McIntosh provided the first reliable account of where in the strata each Marsh quarry had been dug; Marsh himself had been deliberately vague. In 1974, when I wrote my very first grant request, I proposed to take these data and go back to Como to study the evidence of habitat preserved in the rocks at each dino quarry. Supported by the Dinamation International Society, I've dug at Como nearly every summer since then, always with photocopies of Marsh's Dinosaurs folded up in my backpack.
Contrary to what the extreme creationists say, evolutionary paleontology is a predictive science. On average, higher beds should contain more advanced species than lower beds. And so it is at Como. We've found a new mammal jaw bed, just a wee bit higher in the strata than where Marsh dug in 1879. Our new mammal layer--now known as the Breakfast Bench Fauna--contains several mammals whose molars are a marked improvement over those of their earlier Como relatives. More evidence for Darwinism comes from the dinosaurs themselves. Marsh's men dug all their best Brontosauri from high in the late Jurassic layers. My crew has exhumed bronto skeletons from lower beds, and in the contours of the shoulder blade, these Eobrontosauri are distinctly more primitive.
Yale's reissue of Marsh's Dinosaurs is greeted by loud huzzahs from us Wyoming bone diggers. Those superb lithographs don't photocopy clearly, and now, at last, professional paleontologists can get the plates printing-press fresh. But I want something more: I want Yale University Press to be deluged with orders from fourth-grade teachers, parents, dinophilic kids, and all folks concerned about science teaching in public schools. The dinosaur lithographs are immensely pleasing to the eye, so the book makes a fine coffee-table accessory. And after just a little study of the bone anatomy contained therein, any literate adult can take Marsh's Dinosaurs, march into the school-board meeting, and face down creationists. The dinosaurs of Como Bluff are so awesome that they win converts even among evolution's skeptics.
Robert T. Bakker is dinosaur curator at the Graves Museum in Fort Lauderdale, Florida, and distinguished research professor at Florida Atlantic University. His most recent book is the novel Raptor Red (Bantam).