The Great Dinosaur Discoveries
University of California Press, 2009
192 pp., $36.95
Dinosaur Odyssey: Fossil Threads in the Web of Life
Scott D. Sampson
University of California Press, 2009
352 pp., $52.95
John H. McWhorter
Editor's note: Science in Focus is on vacation in August, resuming our regular schedule in September. Meanwhile, we're going to the archives for science-related pieces from the pages of Books & Culture. This week we're featuring a piece by John McWhorter from the January/February 2010 issue.
I am one of those people who never got over their childhood dinosaur obsession. Yet in the past twenty years or so, I have regretted an increasing sense of diminishing control over the data set, which I have tended to attribute to the distractions of adulthood.
Two new books on dinosaurs have given me sweet relief. Darren Naish's The Great Dinosaur Discoveries and Scott Sampson's Dinosaur Odyssey approach the vast array of dinosaur varieties now known in novel ways, turning what is too often presented as a list into a way of thinking.
Traditional dinosaur books make a stab at this. They begin with a summary of the first dinosaur fossil discoveries in England. They cover the tasty feud between American paleontologists Charles Othniel Marsh and Edward Drinker Cope in the late 19th century, the two competing to name new species from hauls from out west and delighting in one another's mistakes. Finally comes the announcement of the "Dinosaur Renaissance" of the 1970s.
Traditionally, dinosaurs were depicted as sluggish creatures, dragging their tails, inclined to lounging in water, with a general "racial senescence" possibly causing their extinction. However, analyzing skeletons of a close relative of the Velociraptors famous from Jurassic Park, with their lithe bodies, large eyes, and razor-sharp second-toe claws perfect for eviscerating prey, paleontologist John Ostrom suspected dynamism. One look at the wiry, vicious mount of the skeleton of the creature in question, Deinonychus, at the Museum of Natural History in New York leaves us moderns to wonder how scientists could ever have supposed that dinosaurs were iguana-like sluggards.
Reinforcing Ostrom's analysis was how very similar the skeletons of these creatures are to those of birds—lively creatures with warmth generated from within, as opposed to reptiles' reliance upon the sun to warm their blood. A new generation of paleontologists developed a new conception of dinosaurs as fast-moving, warm-blooded creatures, standing erect on land, brightly colored and ready for action, and with birds as their direct descendants—such that technically, sparrows and penguins are dinosaurs.
This vision permeated popular culture and sparked an explosion in scientific work. Despite the plethora of children's books on dinosaurs that people like me devoured in the 1960s and '70s, since the '30s there had been little new research on the creatures, who were considered torpid evolutionary dead-ends.
Here, however, is where the issue of my own fears of senescence come in. A pleasant thing about those old books was that even in the ones covering all species known from more than a few bones, you dealt with perhaps 125 animals, falling into eight or nine major groupings. It was a nice little collection of "figurines" that a nerdy kid could easily commit to memory.
These days, that's a tougher proposition. A modern dinosaur book, after a quick historical survey, typically gets down to The List. Today, however, that means several hundred varieties—and as Naish mentions, 85 percent of the species of dinosaur known today were discovered in just the past twenty years. What was once a compact set subject to recitation, like The Presidents and Their Wives, has become an encyclopedia.
Naish's and Sampson's books both attempt to wrest a narrative for the layman from this newly daunting body of knowledge. Naish's is the first dinosaur book to take an angle it is surprising no one thought of before: to hang the entire presentation on a timeline format. Rather than restricting chronology to a prefatory appetizer and then bringing on The List, Naish presents dinosaurs in the order of their discovery right up to last year, highlighting what contribution the discoveries made to a developing science rather than simply describing them.
Sampson, meanwhile, situates dinosaurs within an ecological conception. Drawing broad but cautious conclusions from details of anatomy, physiology, preservation, and creative reconstruction, Sampson's academic bricklaying translated for laymen cannot be deemed, as one of his blurbers has it, "the best general-audience dinosaur book since the Dinosaur Renaissance began in the 1970s." It is, for one, too specialized for that honor, which arguably could go to Naish's book. Sampson's tome will communicate most effectively to readers who not only want more than the typical "Triceratops had horns above its eyes and lived in herds" museum tour but are ready for lessons in climatology, botany, and entomology in the context of evolutionary history.
Read together, Naish's and Sampson's new books give us a sense of the vast array of dinosaurs as keys to puzzles in a science proceeding ever forward. For example, back in the day, a dino fan knew a rather static fact: the meat-eating bipedal kinds of dinosaur (theropods) came in two types. Some were the big kind, like Tyrannosaurus Rex, and some were smaller, such as the poison-squirting Dilophosaurus in Jurassic Park. Early on, so the story went, one branch of theropods got big while the others stayed small, and The List was a matter of cataloguing a burgeoning list of Big Ones and Small Ones.
But over the past two decades, scholars concluded that this classification was merely impressionistic. Various strains of giant theropods evolved from smaller ones at different times. There were latter-day relatives of Dilophosaurus, unknown until the 1980s, that got as massive as Tyrannosaurus. Meanwhile, Tyrannosaurus was one offshoot of a branch that included critters of moderate size, such as Velociraptors.
Until the past decade, the point was largely made through arcane skeletal likenesses between certain Small Ones and Big Ones. But two additions to The List of late (Dilong and Guanlong), covered in Naish's book, demonstrate it especially clearly. There were, we now know, compact little proto-tyrannosaurs, not yet massive like T. Rex but well on their way to its defining features.
The point that creatures like this illuminate, beyond bulking up The List, is that giantism was an ever-tempting "strange attractor" for theropods. If it were just that once, one line that happened to opt for enormity, we would be left with a happenstance of little interest beyond that which amazes a kid impressed by "monsters." However, enormity was apparently a trend especially likely of dinosaur biology, which leads to a general question: why, really, did dinosaurs get so big? There has never been any such trend among mammals or even modern reptiles.
Sampson shows that the massiveness in question was connected to, of all things, the Dinosaur Renaissance-era theory that dinosaurs were warmer-blooded than lizards. The idea here was that dinosaurs were warm-blooded like mammals and were possibly even covered with fur. Today, however, that dramatic notion is rather "1975." Evidence suggests that, as so often, the truth was in between: dinosaur metabolism was zestier than lizardness (ectothermy) but rested before the tipping point of catness (endothermy). Sampson terms it mesothermy, under what he calls the Goldilocks hypothesis: not too cold and not too hot but just right.
In itself, this neither-fish-nor-fowl conclusion is incommensurate with the notion of dinosaur science as an "odyssey," as Sampson's title has it. Where is the fun in the mundane truth that dinosaurs weren't cold-blooded like snakes but weren't warm-blooded like Saint Bernards either? Sampson argues, however, that this very fact was exactly why dinosaurs could get so large.
As ectotherms' metabolic rate increases, their energy rate increases as well. Two main results of this increase in energy are the generation of heat internally instead of depending on the sun and, notably, the building of bodily mass. Hence giantism is a possibility. Along for the ride also come active childrearing and vigorous courtship strategies, evidence for which has arisen for dinosaurs over the past thirty years.
However, at a certain tipping point in the metabolic rate, so much energy goes into the generation of bodily heat—making, for example, a warm cat on your lap—that there is less available for building bodily mass: there have never been cats the size of trucks. Only mesothermy, wishy-washy as it seems, can create something as staggeringly massive as Brontosaurus, or its even larger relatives that reached lengths of over one hundred feet.
Sampson thinks mesothermy explains a lot of other things about dinosaurs that otherwise seem just so. For example, one branch of theropods that yielded fecund subbranches (i.e., countless additions to The List) were apparently actually warm-blooded. This has become clear from gorgeously detailed fossils unearthed in China of late, revealing feathers, not for flying but for warmth. However, this does not mean that feathers were a quirk of dinosaurs in China: relatives of the same theropods have long been known from elsewhere but not as exquisitely preserved, meaning that the living creatures had feathers, too.
Sampson notes that these warm-blooded theropods are exactly the ones that did not trend toward the enormous. For example, the Velociraptor/Deinonychus type was among them, and there was no version the size of a building. Presumably it was because warm blood puts a limit on how big you can get. This is also the only branch of theropods that includes some varieties that went vegetarian (Naish's book, in a rare lapse, does not include a picture of these massive, pot-bellied freaks with Edward Scissorhands claws). Sampson traces this vegetarianism to warm-bloodedness as well: it's a challenge for carnivores to find enough food to keep their high metabolism going, and easier to do the trick eating plants, which have the courtesy to sit still while being eaten.
Another seemingly arcane fact gives Sampson footing for a further step past The List. In certain fossil beds, what has traditionally been seen as a plethora of coexisting animals can be shown as the result of several separate eras, each inhabited by certain of the animals and succeeded by eras with new ones. Especially interesting are the implications Sampson draws from this data for dinosaurs' famous extinction.
There are two competing hypotheses here. One is that an asteroid was the culprit. Roughly 65.5 million years ago an asteroid hit what is today Mexico, leaving a crater more than 100 miles in diameter and a layer of iridium, traceable only to meteorites, worldwide in rocks of this age. And recently, Sankar Chatterjee of Texas Tech University has argued that there is evidence for a much larger asteroid impact off the coast of India roughly 300,000 years later. The rival view suggests that the more gradual effects of volcanic eruptions and rising sea levels were also critical to the dinosaurs' extinction.
This time, Sampson argues in favor of the more "fun" hypothesis. One argument for the less dramatic view stressing gradual eclipse has been based on the claim that there were supposedly fewer kinds of dinosaur closer to their extinction than before—that is, they were apparently tapering off already before the asteroid hit. However, Sampson argues that this drop-off is an illusion. It isn't that the earlier localities were teeming with an unusual variety of creatures. Rather, what we find there is evidence of various periods during any one of which only a few species existed: even long before the asteroid hit, there were no more species around than in those fossil beds from just before the End of Dinosaur Days. The extinction, then, was truly abrupt.
These two books show the layman how almost any dinosaur on The List is significant not just as a specimen in a collection pinned like a dead butterfly among many in a box, but as a piece of evidence for a larger point about just how such fascinating creatures could ever have existed, how they lived their lives, and why today they only do so as the feathered, flying creatures we know as birds. Now dinosaurs are not just a list, but players in a fascinating drama. They encourage us to surmount tabulation and open up to cogitation.
Example: Tyrannosaur skulls are full of gaping holes. They are, in essence, conglomerations of struts, filled in the living creatures with air sacs. Conventional wisdom has been that this evolved to make their heads lighter as they became enormous. Then, Tyrannosaurs also have strangely tiny arms, of no apparent use. This, we have been told, was because these monsters were basically land sharks, "jaws on feet," with their massive heads, afforded by the skeletal lightness, rendering the arms useless and encouraging their shrinkage.
I have always been nagged by a sense that this did not qualify, in the strict sense, as an explanation. After all, there are plenty of smaller creatures with light, flexible skulls (snakes, for instance). Why would evolution not wend into a smaller rendition of "jaws on feet"?
That, for me, was merely passing query. As I write this, however, exactly such a creature has been discovered. The wires are abuzz with the discovery—in China, of course—of little Raptorex: a Tyrannosaur with all of the major features of T. Rex, but only about as big as a human.
T. Rex did not evolve its airy head to compensate for its enormous size: there actually were, we now know, junior land sharks. Features like the skull and the arms were not after-the-fact copings with the size but built in before it. This leaves the enormity by itself as a mysterious, isolated quirk—or not, if we refer back to Sampson's hypothesis that mesothermy encouraged bulk. As such, a dinosaur obsessive like me can receive Raptorex not as just one more theropod on The List, but as support for an explanation of why dinosaurs were so large.
What popular paleontology now needs is a book based on a more fine-grained timeline than Naish provides, incorporating even more of The List of dinosaur species while making clear their relevance to scientific hypotheses. In other words, a book seeking to bring these animals back alive, Sampson-style.
Until then, I will delight in two books that give me a sense of purchase upon The List which had eluded me since the 1980s. Sure, dinosaurs are, as the young'uns say today in reference to much besides T. Rex, "fierce." The challenge is to show that they are also interesting.
John H. McWhorter is the author of Our Magnificent Bastard Tongue: The Untold Story of English (Gotham).
Copyright © 2010 by the author or Christianity Today/Books & Culture magazine.
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