Natural Acts
Page 16
The command bunker and the base camp are long since gone. Oppenheimer and Groves are gone. Hiroshima and Nagasaki are not the same cities they were. But Trinity Site was just a spot out in the desert, and so it remains.
On the first Saturday of October, four decades later, you can still see the frizzled steel stumps left behind when the tower was vaporized. You can still pick up a chirpy reading on a Geiger counter. You can hear speeches by the commander of the missile range and the president of the Chamber of Commerce, and you can join in a prayer with an army chaplain who says: “…and guide us, Lord, that we may then begin beating our plowshares into…uh, beating our swords into plowshares.” The confusion is understandable. You can even chat with Joe McKibben, the man who threw that last switch, now a retirement-age gentleman in casual clothes with a friendly and slight dotty manner, who happens to be back for the tour this year himself. McKibben is genial about answering questions, but there is an unreachable look in his eyes.
He says: “Well, you have to wonder how it would have gone if some things had been different.”
There is one more stop on the Tularosa circuit; one more element in the Tularosa design. This one could easily be overlooked, so watch carefully for a small sign along the two-lane that runs north out of Alamogordo toward Carrizozo. Again you will be about halfway from White Sands to the Malpais, but with no motorcade surrounding you now, no men waving you forward with flashlights, no guard stations or crossbars. You stay alert for an inconspicuous junction, at the corner of which sits the bulky white shape of what once was a merry establishment. The building is boarded up; lettering on the window says 3 RIVERS AND DEVIANTS M/C CLUBHOUSE. PRIVATE. BEWARE OF DOG. An M/C, in case you need telling, is a motorcycle club. The 3 Rivers boys and the Deviants (evidently a syncretic group) are not presently in session. But that’s your landmark to turn right.
You drive east for another five miles on dirt, into the foothills of the Sacramento Range. You park and begin walking, up the crest of a sharp north-south ridge. Another sign shows you the way. Welcome to the Three Rivers Petroglyph Site, famous among archeologists of the Southwest and unknown to almost everyone else.
A community of the Mogollon people, those pacific agriculturalists, lived here at the start of the present millennium for a span of about four hundred years. Their village was down lower in the Three Rivers drainage; this exposed ridge seems to have served as a lookout, from which they could spot game or approaching enemies far out in the Tularosa Basin. The view is indeed good. Gazing westward across the desert, you can see the great white shape of gypsum and the great black shape of lava. You can see the barren upthrust that is Oscura Peak, and if a fireball 10,000 feet high were suddenly to blossom behind it, you would sure as hell see that too. Mogollon scouts may have spent many hours and weeks and years up on this boulder-toothed ridge, watching. After four centuries, though, the whole community disappeared.
Probably they migrated north, out of the Tularosa. They could have been fleeing a drought. Or their exodus may have been linked to that dolorous remnant of collective memory, the one telling about “a year of fire, when this valley was so filled with flames and poisonous gases as to be made uninhabitable.” Maybe they saw something distressful. A sudden thunderous ebullition of cinder and smoke and liquidy black rock, for instance. Or who knows what.
All they left behind were a few potsherds, a few fallen adobe pit-houses, and about five thousand rock carvings, scratched and chipped onto the boulder faces along that ridge.
Some of these carvings are far more artful than others. Some are vividly representational—a bighorn sheep impaled by three arrows—and some aren’t. There are a few human figures, but no romantic and elegant portrayals of prowess in battle or hunting; mainly large ovoid heads, wide-eyed and jug-eared. No warriors on horseback. Aside from those arrows in the bighorn, weaponry is conspicuously absent. Animal portraits abound, especially birds and horned mammals and even a few fish. Also there are carven images of tracks: bear paws, bird prints as though in mud, human foot shapes. The preponderance of the petroglyphs on the ridge, though, are abstract designs.
Among these, the most common motif, appearing in many variations, is a circle or several concentric circles surrounded by a ring of dots. Similar circle-and-dot patterns are known from Mogollon petroglyph sites throughout the Southwest, but they seem to have held a special fascination for the artists at Three Rivers. You can see in them almost anything you might choose: a circle of family members, the solar system, the nucleus and electrons of an atom.
Walking the ridge trail up among these carvings, you find another arresting motif. Having made a lucky detour off the main path, watching for rattlesnakes as you step, you notice it first on the western side of a large dark boulder cropping out high on the ridge’s westernmost knob. This design is more elaborate and sophisticated than others, even beautiful, and something about it stops you short:
It recurs, in its variations, a dozen times on the ridge. In a few instances it is less squarish, more curvilinear; in several it is done with linked or interlocking spirals. Despite transmutations, in each the essence is unmistakable.
Evidently the people at Three Rivers had a concept of yin and yang. They drew rock pictures of dialectical oneness. They cherished some notion—maybe it was only wishful—of a unity within which all worldly flux remains balanced.
What did that mean to them? Obviously, we don’t know. They watched and they drew and then they departed. But the yin-and-yang notion is easily reduced to truism, and these figures, like the dotted circles, can be taken to represent almost anything. John Donne’s idea, for instance: “As West and East…are one, / So death doth touch the Resurrection.” Or another idea, maybe in this case more applicable: “For they have sown the wind, and they shall reap the whirlwind.”
Now suddenly a pair of turkey vultures wheel into view above you, cruising on thermals that rise off the west slope of the Three Rivers ridge. With typical lazy grace, they are scouting for a meal. One of the vultures sweeps closer to scrutinize you.
This bird pauses, holding position not 30 feet over your head, like a kite on a short string. It seems unsure whether to take you for a pile of dead meat. And you are sitting quite still. The confusion is understandable.
AFTER THOUGHTS
Planet of Weeds
HOPE IS A DUTY from which paleontologists are exempt. Their job is to take the long view, the cold and stony view, of triumphs and catastrophes in the history of life. They study the fossil record, that erratic selection of petrified shells, carapaces, bones, teeth, tree trunks, leaves, pollen, and other biological relics, and from it they attempt to discern the lost secrets of time, the big patterns of stasis and change, the trends of innovation and adaptation and refinement and decline that have blown like sea winds among ancient creatures in ancient ecosystems. Although life is their subject, death and burial supply all their data. They’re the coroners of biology. This gives to paleontologists a certain distance, a hyperopic perspective beyond the reach of anxiety over outcomes of the struggles they chronicle. If hope is the thing with feathers, as Emily Dickinson said, then it’s good to remember that feathers don’t generally fossilize well. In lieu of hope and despair, paleontologists have a highly developed sense of cyclicity. That’s why I recently went to Chicago, with a handful of urgently grim questions, and called on a paleontologist named David Jablonski. I wanted answers unvarnished with obligatory hope.
Jablonski is a big-pattern man, a macroevolutionist, who works fastidiously from the particular to the very broad. He’s an expert on the morphology and distribution of marine bivalves and gastropods—or clams and snails, as he calls them when speaking casually. He sifts through the record of these mollusk lineages, preserved in rock and later harvested into museum drawers, to extract ideas about the origin of novelty. His attention roams back through 600 million years of time. His special skill involves framing large, resonant questions that can be answered with small, lithified clamshells.
For instance: By what combinations of causal factor and sheer chance have the great evolutionary innovations arisen? How quickly have those innovations taken hold? How long have they abided? He’s also interested in extinction, the converse of abidance, the yang to evolution’s yin. Why do some species survive for a long time, he wonders, whereas others die out much sooner? And why has the rate of extinction—low throughout most of Earth’s history—spiked upward cataclysmically on just a few occasions? How do those cataclysmic episodes, known in the trade as mass extinctions, differ in kind as well as degree from the gradual process of species extinction during the millions of years between? Can what struck in the past strike again?
The concept of mass extinction implies a biological crisis that spanned large parts of the planet and in a relatively short time eradicated a sizable number of species from a variety of groups. There’s no absolute threshold of magnitude, and dozens of different episodes in geologic history might qualify, but five big ones stand out: Ordovician, Devonian, Permian, Triassic, Cretaceous. The Ordovician extinction, 439 million years ago, entailed the disappearance of roughly 85 percent of marine animal species—and that was before there were any animals on land. The Devonian extinction, 367 million years ago, seems to have been almost as severe. About 245 million years ago came the Permian extinction, the worst ever, claiming 95 percent of all known animal species and therefore almost wiping out the animal kingdom altogether. The Triassic, 208 million years ago, was bad again, though not nearly so bad as the Permian. The most recent was the Cretaceous extinction (sometimes called the K-T event, because it defines the boundary between two geologic periods, with K for Cretaceous, never mind why, and T for Tertiary), familiar even to schoolchildren because it ended the age of dinosaurs. Less familiarly, the K-T event also brought extinction of the marine reptiles and the ammonites, as well as major losses of species among fish, mammals, amphibians, sea urchins, and other groups, totaling 76 percent of all species. In between these five episodes occurred some lesser mass extinctions, and throughout the intervening lulls extinction continued too—but at a much slower pace, known as the background rate, claiming only about one species in any major group every million years. At the background rate, extinction is infrequent enough to be counterbalanced by the evolution of new species. Each of the five major episodes, in contrast, represents a drastic net loss of species diversity, a deep trough of biological impoverishment from which Earth only slowly recovered. How slowly? How long is the time lag between a nadir of impoverishment and a recovery to ecological fullness? That’s another of Jablonski’s research interests. His rough estimates run to 5 or 10 million years. What drew me to this man’s work, and then to his doorstep, was his special competence on mass extinctions and his willingness to discuss the notion that a sixth one is in progress now.
Some people will tell you that we as a species, Homo sapiens, all 6 billion of us in our collective impact, are destroying the world. Me, I won’t tell you that, because “the world” is so vague, whereas what we are or aren’t destroying is quite specific. Some people will tell you that we are rampaging suicidally toward a degree of global wreckage that will result in our own extinction. I won’t tell you that either. Some people say that the environment will be the paramount political and social concern of the twenty-first century, but what they mean by “the environment” is anyone’s guess. Polluted air? Polluted water? Acid rain? Toxic wastes left to burble beneath neighborhood houses and malls? A frayed skein of ozone over Antarctica? Global warming, driven by the greenhouse gases emitted from smokestacks and cars? None of these concerns is of itself the big one, paleontological in scope, though some (notably, climate change) are closely entangled with it. If the world’s air is clean for humans to breathe but supports no birds or butterflies, if the world’s waters are pure for humans to drink but contains no fish or crustaceans or diatoms, have we solved our environmental problems? Well, I suppose so, at least as environmentalism is commonly construed. That clumsy, confused, and presumptuous formulation “the environment” implies viewing air, water, soil, forests, rivers, swamps, deserts, and oceans as merely a milieu within which something important is set: human life, human history. But what’s at issue in fact is not an environment; it’s a living world.
Here instead is what I’d like to tell you: The consensus among conscientious biologists is that we’re headed into another mass extinction, a vale of biological impoverishment commensurate with the big five. Many experts remain hopeful that we can brake that descent, but my own view is that we’re likely to go all the way down. I visited David Jablonski to ask what we might see at the bottom.
On a hot summer morning, Jablonski is busy in his office on the second floor of the Hinds Geophysical Laboratory at the University of Chicago. It’s a large open room furnished in tall bookshelves, tables piled with books, stacks of paper standing knee-high off the floor. The walls are mostly bare, aside from a chart of the geologic time scale, a clipped cartoon of dancing tyrannosaurs in red sneakers, and a poster from a Rodin exhibition, quietly appropriate to the overall theme of eloquent stone. Jablonski is a lean forty-five-year-old man with a dark full beard. Educated at Columbia and Yale, he came to Chicago in 1985 and has helped make its paleontology program perhaps the country’s best. Although in not many hours he’ll be leaving on a trip to Alaska, he has been cordial about agreeing to this chat. Stepping carefully, we move among the piled journals, reprints, and photocopies. Every pile represents a different research question, he tells me. “I juggle a lot of these things all at once because they feed into one another.” That’s exactly why I’ve come: for a little rigorous intellectual synergy.
Let’s talk about mass extinctions, I say. When did someone first realize that the concept might apply to current events, not just to the Permian or the Cretaceous?
He begins sorting back through memory. In the early and middle 1980s, he recalls, there occurred a handful of symposiums and lecture series on the subject of extinction, for which the rosters included both paleontologists and what he whimsically calls “neontologists,” meaning biologists who study creatures that are still alive. An event was held at the Field Museum here in Chicago, with support from the National Science Foundation, that attracted four hundred scientists. Another, at which Jablonski himself spoke, took place at the New England Aquarium, in Boston. “The chronology is a little hazy for me,” he says. “But one that I found most impressive was the Elliott meeting, the one in Flagstaff.” David K. Elliott, of the geology department at Northern Arizona University, had pulled that gathering together in August of 1983 and later edited the invited papers into a volume titled Dynamics of Extinction. The headliner among the neontologists was Paul Ehrlich, eminent as an ecologist, widely famed for his best-selling jeremiad The Population Bomb, and coauthor of a 1981 book on human-caused extinctions. Ehrlich spoke mainly about birds, mammals, and butterflies, sketching the severity of the larger problem and offering suggestions about what could be done. For the paleontological perspective, it was Jablonski again and a few others, including John Sepkoski and David Raup, later to be his colleagues at the University of Chicago. Sepkoski and Raup, while sorting through a huge body of data on the life spans of fossil groups, had lately noticed a startlingly regular pattern of recurrence—at about 26-million-year intervals—in the timing of large and medium-sized mass extinctions. The Sepkoski-Raup paper at Flagstaff, building on their own earlier work as well as the hot new idea that an asteroid impact had killed off the dinosaurs, suggested a dramatic hypothesis for explaining those recurrent mass extinctions: that maybe an invisible twin star (an “undetected companion,” they called it) orbits mutually around our sun, returning every 26 million years and bringing with it each time, by gravitational pull, a murderous rain of interplanetary debris that devastates ecosystems and wipes out many species. Sepkoski’s brief presentation of the idea was provocative enough to draw attention not just in Science and Science News but also in the Los Angeles Times. Some people labeled that invis
ible companion “Nemesis,” after the Greek goddess of vengeance, and others casually called it “the Death Star.” Meanwhile, another of the presentations at Flagstaff was attracting no such fuss, but that’s the one Jablonski remembers now.
It was a talk by Daniel Simberloff, an ecologist then at Florida State University, highly respected for his incisive mind but notoriously reluctant to draw sweeping conclusions from limited data. Simberloff’s remarks carried the title “Are We on the Verge of a Mass Extinction in Tropical Rain Forests?” His answer, painstakingly reached, was yes.
“That’s a really important paper, and a scary one,” Jablonski says.
He vividly recalls the Flagstaff situation. “It wasn’t a media event. It was scientists talking to scientists, being very up-front about what the uncertainties were and what the problems were.” The problems were forest destruction, forest fragmentation, the loss of species that follows from those factors, and the cascading additional extinctions that come when ecosystems unravel. The uncertainties were considerable too, since there is no positive evidence left behind, no corpus delicti, when a species of rare bird or unknown beetle disappears as a consequence of the incineration of its habitat. Proving a negative fact is always difficult, and extinction is inherently a negative fact: Such-and-such no longer exists. Some biologists had begun warning of an extinction crisis that would be epochal in scale, their concern based on inference from the destruction of habitats that harbor vast numbers of highly localized species—in particular, tropical forests—and a few of those biologists had vivified their warnings with numerical estimates. Simberloff set himself to a skeptic’s question: Is the situation really so dire? From his own cautious inferences and extrapolations, he reported that “even with an increase in the rate of destruction, there is not likely to be a mass extinction by the end of the century comparable to those of the geological past.” He meant the twentieth century, of course. But was he saying that the alarms were illusory? Simberloff’s reputation was such that no one could doubt he would make any unfashionable, spoilsport pronouncement to which the data, or lack of them, led him. Instead he added that in the next century, “if there are no major changes in the way forests are treated, things may get much worse.” His calculation suggested that if tropical forests in the Americas were reduced to what’s presently set aside as parks and reserves, 66 percent of all the native plant species would disappear by the end of the twenty-first century, and 69 percent of all Amazon birds. Yes, it would be a catastrophe on the same scale as every mass extinction except the Permian, Simberloff concluded.