Once Upon a Time

“Come look at what we’ve found,” he said, wriggling his eyebrows significantly. About a dozen fossil collectors were scattered over grassy hills, bent over, carefully exposing bone beds that contained the remains of a new discovered species of dinosaurs, an odd, horned dinosaur skull and dozens of egg shells, the remnants of a dinosaur nesting ground that was once a mile long and more than a quarter mile wide.

My colleagues and I had driven all the way from Texas. It was late summer, 1986. We were participating in an international study of dinosaurs and had been comparing historic sites along the eastern slope of the Rockies. Nearing the Canadian line in northern Montana, we wheeled down a dirt road to a cluster of tepees, a cook tent and the expansive presence of John Horner. The spirit of discovery hung in the air. We were looking at what would prove to be the largest dinosaur rookery in the Western world.

Over a period of 20 years, Horner has probably collected more dinosaur bones than any other living American. He has written many tersely worded papers on his discoveries and published them in the world’s foremost journals. He has fostered the research of many fine graduate students, thereby exploring unknown facets of dinosaur biology. His counsel was sought in guiding the artists who fashioned the cinematography behind “Jurassic Park” and “The Lost World: Jurassic Park.” And Horner, with his able assistant, wordsmith Edwin Dobb, has just crafted a wonderful benchmark of dinosaur studies called “Dinosaur Lives.” Anyone wishing to find out what it’s like to be a superb itinerant bone hound should read it.

It’s a very straightforward book. Though clearly and entertainingly written, it should be savored again in a second reading. Set entirely in Montana, “Dinosaur Lives” is an account of the latest discoveries in North America’s oldest dinosaur field. (The first remains were found here in 1856.)

The badlands of sediments, which were deposited during the Mesozoic Era and are scattered across the state, have become for Horner an evolutionary arena analogous to the Galapagos Islands, but here Darwin’s finches are duckbilled dinosaurs. The more he scrutinizes the contents of these badlands, the more completely he discerns a great polarity and disarming similarity between dinosaurs and ourselves. “Wherever fate leads us . . . we’ll continue to turn around now and again, glancing backward, taking the measure of who we are against everything that ever was. And once upon a time the dinosaur was. It actually was.”

Once upon a time was a long time ago. While focusing on the dinosaurian era about 65 to 150 million years ago, Horner most closely examines a span of time about 74 to 80 million years ago, during which a great wedge of sediment formed in Montana, creating the upper part of a geological formation called the Two Medicine Formation. For 6 million years, these sediments slowly accumulated on a warm coastal plain situated between the ancient Rocky Mountains and the Great Plains, covered by a shallow inland sea to the east.

The quarry sites that Horner and his crew excavated into these sediments bear names that often evoke images of these chosen collectors as they wandered across this promised land lying to the west of Jordan, Mont. Jack’s Birthday Site was discovered on the day that Horner turned 42; Jason’s Giant Site yielded the skeleton of a large duckbill found by his son, Jason; and one wonders if the music of “West Side Story” was wafting through the consciousness of its discoverer when Westside Quarry was unearthed.

The nucleus of the book is presented as a sequence of events during successive field seasons between 1984 and 1996, and the significance of these sites, mostly on the Blackfoot Reservation, grows with each season. The most ancient site is Hillside Quarry, formed 79.6 million years ago when the eastern sea began to retreat before an expanding coastal plain.

The coastal plain was at its broadest 76.7 million years ago, during which time sediments in the West Hadrosaur Bone Bed site were deposited. This was also the time when Egg Mountain formed, far to the south near Choteau, on the Willow Creek Anticline (the southern sites were described by Jack and James Gorman in their spirited book “Digging Dinosaurs,” published in 1988). As the sea advanced toward the west 74 million years ago, the coastal plain narrowed, and the bone beds of Landslide Butte were buried.

Across this ancient topography and through this span of nearly 6 million years, the patterns of dinosaurian evolution were recognized in the course of a “modest epiphany,” as Horner sat atop “Thunder Butte and was . . . granted the supreme privilege of observing creation [dinosaurian evolution] at work.” Upon these half dozen place names rests the framework of “Dinosaur Lives.”

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The introductory chapters smoothly sweep the reader from the 1993 film “Jurassic Park” back almost a century ago as mankind slowly became aware of the presence of these huge, extinct creatures. Eventually Horner lands us in the badlands of Montana. Lest one think “Dinosaur Lives” is a book for readers unfamiliar with dinosaur paleontology, it contains for professionals some provocative insight: “. . . we may one day discover a universal theory of evolution--something resembling the law of gravity . . . “; as well as some important aphorisms: “evolution is nothing more, and nothing less, than change through time”; “Paleontology is not a field for people who want to be right, it is a field for people who want to know what’s real”; “[We must] actively seek evidence that might contradict what we would like most to believe”; and “finding dinosaurs . . . is as much a matter of knowing where evidence is likely to have been erased as where it might still be preserved.”

The chapters on fieldwork aptly describe days that are blisteringly hot and days that are mercilessly cold. Rain falls without end. Emotions range from elation to boredom, pain to shock and even tragic loss. Yet somehow, there is usually a cold beer after an exhausting day and the time to quietly discuss the lessons learned and the possibilities that lay ahead.

What one concludes depends on what one expects to find. For example, in 1916, a pioneer in dinosaurian paleontology mistook the giant dinosaur rookery with its myriad eggshell fragments for a bed of freshwater clams. He had no search image for dinosaur eggshells. This deficiency is shared to a greater or lesser extent by all dinosaur collectors and, as Horner so painfully admits, “I shudder to think how many times I may have stared at a monumental find and failed to see it, or stood on top of something I’d been pursuing for weeks, then walked away without realizing how close I actually was.”

Beautiful semi-complete skulls and skeletons were found: raptors, ostrich dinosaurs and tyrannosaurs; boneheaded dinosaurs; horned dinosaurs and duckbills. Traditionally sought for anatomical information and museum displays, these specimens are lean sources on dinosaur reproduction, growth and behavior. It is the disarticulated and scattered bones that excel in providing data of this kind, and Horner has been a pioneer in extracting information from bone bed sites.

From his discoveries, we have learned how many kinds of dinosaurs lived in herds and how large the herds were, how long infants of various kinds of dinosaurs remained in their nests and what the eating habits of flesh-eaters were. From the bone beds come images of weakened herbivores dying near dwindling water holes and of their corpses being torn apart by tyrannosaurs. From tiny bones and broken shells, Horner helps us visualize a thousand or more crested dinosaurs turning to abandon their unhatched eggs, leaving them behind to cook under a layer of hot ash raining down from volcanoes in the region.

In the end, Horner turns to bigger themes. He tells us that while sitting on the summit of Thunder Butte, he started to wonder whether the methods we use to classify ancient organisms might obscure our understanding of evolution. Regarding the evidence of dinosaur herds interbreeding in this locale, Horner discerns two patterns of evolution.

In one theory, contingent on an expanding flood plain, he portrays the duckbilled dinosaurs diversifying into varieties with long legs and powerfully grinding jaws, which render them more competitive in exploiting different environments. On a dwindling flood plain, he postulates the evolution of dinosaurs with grotesque spines and shields that render them more successful in competing for mates. These are interesting patterns that merit further study.

As for the extinction of dinosaurs, an occurrence that took place about 10 million years after the Montana sites were abandoned, Horner believes that a gradual loss of habitat led to their demise. Geophysicist Walter Alvarez, however, has a different point of view. In “T. Rex and the Crater of Doom,” Alvarez argues for catastrophic loss of habitat resulting from the impact of a comet or asteroid. The title of his book is no doubt inspired by title of the movie “Indiana Jones and the Temple of Doom” and, indeed, something of a Jones mystique clings to Alvarez, who for 20 years has led the chase from the grave of Tyrannosaurus rex to a mighty, extraterrestrial killer responsible for the destruction of dinosaurs and their world.

Guided by his mother into the field of geology; assisted by his Nobel Laureate father, who became his companion in research; and aided by his charming wife, who accompanied him in his travels, Alvarez is a member of the prestigious United States National Academy of Sciences and has written a wonderful volume on the widely reported and still mysterious link between dinosaurs and their killer comet (or asteroid).

The book is very well written and so engrossing that a reader with little or no background in the earth’s geologic history will enjoy an easy and vastly entertaining summary of how we came to our present understanding of the past. In addition to offering his own theory, Alvarez provides an excellent summary of the competing theories regarding dinosaur extinction. Many readers will surely be scholars in various branches of science who will appreciate both the clarity of presentation and the many references to pertinent scholarly works in the notes following the text. (References to the work of those who reject the impact-extinction hypotheses are also amply cited.)

Indeed, the controversy about the extinction of the dinosaurs has been unusually vigorous. The author observes, “It would be misleading to represent the Cretaceous-Tertiary debate as always well-mannered and friendly. Strongly held opinions were being challenged on all sides and new information was forcing most of us to revise our understanding and our published views again and again.” Indeed, rather than take a contentious tone, Alvarez is warmly grateful to all his colleagues for the exciting intellectual adventure he has enjoyed.

The book begins with a vivid description of a comet crossing and recrossing the path of the earth’s orbit, then its impact and the rapid sequence of horrendous stresses accompanying the gargantuan explosion: a flash of light from temperatures four to five times that of the surface of the sun, a double fireball, sheets of rock vapor condensing to incendiary droplets burning forests on continental scales, gigantic tidal waves, worldwide blackout, torrents of acid rain, a return of daylight after a few months and finally sweltering heat for thousands of years. There followed death unto extinction on a scale too staggering to contemplate and, from a seared world, survivors emerged. They grew in numbers and variety to become, after 65 million years, the world we know.

How can we reconstruct a 65-million-year-old catastrophe utterly without precedent in the history of humanity? The steps are slowly retraced from a time two centuries ago, when the antiquity of the earth was discovered, and the effects of eons of incremental change were understood to produce mountain ranges of consequences. Time in spans of hundreds of millions of years was clocked using organismal change, radiometric clocks and reversals of the earth’s magnetic shield. On these time scales, the motions of continents become as apparent as the motions of a runner in ordinary time. But hidden within those hundreds of millions of years was a gigantic catastrophe, unrecognized because it was so brief.

Alvarez’s discovery was really the conclusion of a line of inquiry that began as he was trying to measure a slow rotation of the Italian Apennine mountains through geologic time and discovered that the surfaces between the strata had slipped, thereby frustrating his attempts. When he eventually realized that it was possible to date reversals of the earth’s magnetic shield in these rocks, he learned that another team was already engaged in similar work. When he wished to use a radioactive isotope (beryllium-10) to precisely date a layer of clay that was laid down about the time the dinosaurian age ended, he discovered that the rate at which the isotope decayed had been incorrectly reported and that the dating technique was useless. Then, when he tried to date the clay using a trace element (iridium), he found that it was far too abundant to be used for his purpose. When he sought to demonstrate that the iridium had been left behind by a nearby exploding star, he found no trace of an isotope (plutonium-244), which would have been present if such a star had exploded.

In this series of failures, however, was a thread of success. The clay that showed an abundance of iridium was also found in Denmark and New Zealand and, along the way, the Alvarezes, father and son, and nuclear chemists Frank Asaro and Helen Michel published a historic paper suggesting that the clay was contaminated by iridium during the fallout that occurred after a comet or asteroid struck the earth 65 million years ago.

The discovery of the iridium clay was a conceptual turning point for Alvarez. Many scholars puzzled over how a minute amount of iridium, measured in concentrations of parts per billion and deposited long ago within a thin layer of clay, could have anything to do with the extinction of the dinosaurs. It was generally perceived that events in earth history took place gradually over intervals much longer than human life spans and that it was impossible for a single event to have changed life on the planet. Alvarez found it not so improbable and, after he and his teammates presented their findings, an enormous controversy arose.

Rather than focus on the controversy, which dogged the impact hypothesis in thousands of scientific papers published during the 1980s, Alvarez prefers to tell it in a different way: “I want to focus on the search for the crater, which must have been excavated if the impact hypothesis was right, and to consider why finding that crater was so difficult.”

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The pursuit of another thread of iridium clay eventually led to an impact site, Alvarez’s Crater of Doom. Along the eastern edge of the Rocky Mountains, he discovered clay that contained tiny particles of quartz, typically found only in association with meteorite impacts. This quartz-filled clay was then coincidentally found lying over enormous tidal wave deposits surrounding the Gulf of Mexico.

Situated within the bull’s-eye of tidal wave deposits was the Yucatan Peninsula. Using remote sensing techniques, a giant circular structure was identified, buried in this portion of Mexico. This circular structure was found to be the edge of a crater more than 100 miles in diameter.

Alvarez’s journey south along the Rocky Mountain front, across the tidal wave deposits bordering the Gulf of Mexico and on to the Crater of Doom is a high drama of prediction and discovery, carried out in the heat of inspired but collegial competition. It is a wonderful adventure in science.

The book closes with a description of the collision of Comet Shoemaker-Levy 9 into Jupiter in 1994: “ . . . as we watched the violence being inflicted on another planet, we were seeing a reenactment of the last spectacle ever witnessed by Tyrannosaurus rex--the deadly flash from the Crater of Doom, on the day the [dinosaurian] world ended.”

Long ago, when this reviewer was a young dinosaur paleontologist, it was impossible for him to believe that the key to understanding dinosaur extinction was not on earth but in space. There are exciting intellectual journeys yet to be made following the implications of this hypothesis. These two books, “Dinosaur Lives” and “T. Rex and the Crater of Doom,” will become classics.