Hen’s Teeth and Horse’s Toes (28 page)

THE SOLACE OF MY YOUTH
was a miserable concoction of something sweet and gooey, liberally studded with peanuts and surrounded by chocolate—real chocolate, at least. It was called “Whizz” and it cost a nickel. Emblazoned on the wrapper stood its proud motto in rhyme—“the best nickel candy there izz.” Sometime after the war, candy bars went up to six cents for a time, and the motto changed without fanfare—“the best candy bar there izz.” Little did I suspect that an evolutionary process, persistent in direction and constantly accelerating, had commenced.

I am a paleontologist—one of those oddballs who parlayed his childhood fascination for dinosaurs into a career. We search the history of life for repeated patterns, mostly without success. One generality that works more often than it fails is called “Cope’s rule of phyletic size increase.” For reasons yet poorly specified, body size tends to increase fairly steadily within evolutionary lineages. Some have cited general advantages of larger bodies—greater foraging range, higher reproductive output, greater intelligence associated with larger brains. Others claim that founders of long lineages tend to be small, and that increasing size is more a drift away from diminutive stature than a positive achievement of greater bulk.

The opposite phenomenon of gradual size decrease is surpassingly rare. There is a famous foram (a single-celled marine creature) that got smaller and smaller before disappearing entirely. An extinct, but once major group, the graptolites (floating, colonial marine organisms, perhaps related to vertebrates) began life with a large number of stipes (branches bearing a row of individuals). The number of stipes then declined progressively in several lineages, to eight, four, and two, until finally all surviving graptolites possessed but a single stipe. Then they disappeared. Did they, like the
Incredible Shrinking Man
simply decline to invisibility—for he, having decreased enough to make his final exit through the mesh of a screen in his movie début, must now be down to the size of a muon, but still, I suspect, hanging in there. Or did they snuff it entirely, like the legendary Foo-Bird who coursed in ever smaller circles until he flew up his own you-know-what and disappeared. What would a zero-stiped graptolite look like? In any case, they are no longer part of our world.

The rarities of nature are often commonplaces of culture; and phyletic size decrease surrounds us in products of human manufacture. Remember the come-on, once emblazoned on the covers of comic books—“52 pages, all comics.” And they only cost a dime. And remember when large meant large, rather than the smallest size in a sequence of detergent or cereal boxes going from large to gigantic to enormous.

Consider the Hershey Bar—a most worthy standard bearer for the general phenomenon of phyletic size decrease in manufactured goods. It is the unadvertised symbol of American quality. It shares with Band-Aids, Kleenex, Jell-o and the Fridge that rare distinction of attaching its brand name to the generic product. It has also been shrinking fast.

I have been monitoring informally, and with distress, this process for more than a decade. Obviously, others have followed it as well. The subject has become sufficiently sensitive that an official memo emanated in December 1978 from corporate headquarters at 19 East Chocolate Avenue—in Hershey, Pa. of course. Hershey chose the unmodified hang-out and spilled all the beans, to coin an appropriate metaphor. This three page document is titled “Remember the nickel bar?” (I do indeed, and ever so fondly, for I started to chomp them avidly in an age of youthful innocence, ever so long before I first heard of the nickel bag.) Hershey defends its shrinking bars and rising prices as a strictly average (or even slightly better than average) response to general inflation. I do not challenge this assertion since I use the bar as a synecdoche for general malaise—as an average, not an egregious, example.

Hershey Bars bite the dust, a quantitative assessment.
GRAPH BY L. MESZOLY
.

I have constructed the accompanying graph from tabular data in the Hershey memo, including all information from mid-1965 to now. As a paleontologist used to interpreting evolutionary sequences, I spy two general phenomena: gradual phyletic size decrease within each price lineage, and occasional sudden mutation to larger size (and price) following previous decline to dangerous levels. I am utterly innocent of economics, the dismal science. For me, bulls and bears have four legs and are called
Bos taurus
and
Ursus arctos
. But I think I finally understand what an evolutionist would call the “adaptive significance” of inflation. Inflation is a necessary spin-off, or by-product, of a lineage’s successful struggle for existence. For this radical explanation of inflation, you need grant me only one premise—that the manufactured products of culture, as fundamentally unnatural, tend to follow life’s course in reverse. If organic lineages obey Cope’s rule and increase in size, then manufactured lineages have an equally strong propensity for decreasing in size. Therefore, they either follow the fate of the Foo-Bird and we know them no longer, or they periodically restore themselves by sudden mutation to larger size—and, incidentally, fancier prices.

We may defend this thesis by extrapolating the tendencies of each price lineage on the graph. The nickel bar weighed an ounce in 1949. And it still weighed an ounce (following some temporary dips to
⁷
/
₈
oz.) when our story began in September 1965. But it could delay its natural tendency no longer and decline began, to
⁷
/
₈
oz. in September 1966 and finally to ¾ oz. in May 1968 until its discontinuation on November 24, 1969, a day that will live in infamy. But just as well, for if you extrapolate its average rate of decline (¼ ounce in thirty-two months), it would have become extinct naturally in May 1976. The dime bar followed a similar course, but beginning larger, it held on longer. It went steadily down from 2 oz. in August 1965 to 1.26 oz. in January 1973. It was officially discontinued on January 1, 1974, though I calculate that it would have become extinct on August 17, 1986. The fifteen-cent bar started hopefully at 1.4 oz. in January 1974, but then declined at an alarming rate far in excess of any predecessor. Unexpectedly, it then rallied, displaying the only (though minor) reverse toward larger size within a price lineage since 1965. Nonetheless, it died on December 31, 1976—and why not, for it could only have lasted until December 31, 1988, and who would have paid fifteen cents for a crumb during its dotage? The twenty-cent bar (I do hope I’m not boring you) arose at 1.35 oz. in December 1976 and immediately experienced the most rapid and unreversed decline of any price lineage. It will die on July 15, 1979. The twenty-five-cent bar, now but a few months old, began at 1.2 oz. in December 1978.
Ave atque vale
.

The graph shows another alarming trend. Each time the Hershey Bar mutates to a new price lineage, it gets larger, but never as large as the founding member of the previous price lineage. The law of phyletic size decrease for manufactured goods must operate across related lineages as well as within them—thus ultimately frustrating the strategy of restoration by mutational jump. The ten-cent bar began at 2 oz. and was still holding firm when our story began in late 1965. The fifteen-cent bar arose at 1.4 oz., the twenty-cent bar at 1.35 oz., and the quarter bar at 1.2 oz. We can also extrapolate this rate of decrease across lineages to its final solution. We have seen a decrease of 0.8 oz. in three steps over thirteen years and four months. At this rate, the remaining four and a half steps will take another twenty years. And that ultimate wonder of wonders, the weightless bar, will be introduced in December 1998. It will cost forty-seven and a half cents.

The publicity people at Hershey’s mentioned something about a ten-pound free sample. But I guess I’ve blown it. Still, I would remind everyone of Mark Twain’s comment that there are “lies, damned lies and statistics.” And I will say this for the good folks in Hershey, Pa. It’s still the same damned good chocolate, what’s left of it. A replacement of whole by broken almonds is the only compromise with quality I’ve noticed, while I shudder to think what the “creme” inside a Devil Dog is made of these days.

Still, I guess I’ve blown it. Too bad. A ten-pound bar titillates my wildest fancy. It would be as good as the 1949 Joe DiMaggio card that I never got (I don’t think there was one in the series). And did I ever end up with a stack of pink bubble gum sheets for the effort. But that’s another tale, to be told through false teeth at another time.

Postscript

I wrote this article (as anyone can tell from internal evidence) early in 1979. Since then, two interesting events have occurred. The first matched my predictions with uncanny accuracy. For the second, that specter of all science, the Great Exception (capital G, capital E), intervened and I have been temporarily foiled. And—as an avid Hershey bar chomper—am I ever glad for it.

The twenty-five cent bar did just about what I said it would. It started at 1.2 oz. in December 1978, where I left it, and then plummeted to 1.05 oz. in March 1980 before becoming extinct in March 1982. But Hershey then added a twist to necessity when it replaced its lamented two-bit bar with the inevitable thirty-cent concoction. Previously, all new introductions had begun (despite their fancier prices) at lower weights than the proud first item of the previous price lineage. (I based my extrapolation to the weightless bar on this pattern.) But, wonder of wonders and salaam to the Great Exception, the thirty-cent bar began at a whopping 1.45 oz., larger than anything we’ve seen since the ten-cent bar of my long-lost boyhood.

As cynical readers might expect, a tale lies behind this peculiar move. In the
Washington Post
for July 11, 1982 (and with thanks to Ellis Yochelson for sending the article), Randolph E. Bucklin explains all under the title: “Candy Wars: Price Tactic Fails Hershey.”

It seems that the good folks at (not on) Mars, manufacturers of Three Musketeers, Snickers, and M & M’s, and Hershey’s chief competitor, had made the unprecedented move of increasing the size of their quarter bars without raising prices. After a while, they snuck the price up to thirty cents but kept the new size. Hershey tried to hold the line with its shrinking quarter bars. But thousands of mom and pop stores couldn’t be bothered charging a quarter for some bars and thirty cents for others (and couldn’t remember which were Hershey’s and which Mars’s anyway)—and therefore charged thirty cents for both Mars’s large bars and Hershey’s minuscule offerings. Hershey’s sales plummeted; finally, they capitulated to Mars’s tactics, raising prices to thirty cents and beefing up sizes to Mars’s level and above predictions of the natural trend.

As a scientist trained in special pleading, I have a ready explanation for the Great Exception. General trends have an intrinsic character; they continue when external conditions retain their constancy. An unanticipated and unpredictable catastrophe, like the late Cretaceous asteroid of the next essay, or the sneaky sales tactic of Mars and Co., resets the system, and all bets are off. Still, the greater inevitability prevails. The thirty-cent bar will diminish and restitutions at higher prices will shrink as well. The weightless bar may come a few years later than I predicted (even a bit past the millennium)—but I still bet ya it’ll cost about four bits.

THE TEN PLAGUES
of Moses are the archetypal disasters of western thought. I am therefore not surprised that popular explanations for major catastrophes in the history of life have tended to follow their scenarios in spirit. The most famous (although not the most profound) mass extinction occurred some sixty-five million years ago at the close of the Cretaceous period. All surviving dinosaurs died, as did their giant cousins of the air (pterosaurs) and seas (ichthyosaurs, plesiosaurs, mosasaurs). The oceanic plankton virtually disappeared with dramatic suddenness at a boundary that geologists call the plankton line. Several major groups of marine invertebrates perished, including all ammonites and the curious rudistid clams, which looked like corals and formed reefs.

Evidence for the cause of this great dying is so sparse that speculation receives free rein (and reign). The primal scenarios of Moses force themselves upon us. Theories of pandemics run wild recall the murrain that killed Pharaoh’s cattle and the boils “breaking forth upon man, and upon beast.” Poisoning of the oceans by copper washed in from the land or by a lens of fresh water spreading out from a fractured arctic lake reminds us of the Nile turned to blood—“and the fish that were in the river died; and the river stank….” Dramatic change of climate conjures up the great hailstorm that fell “upon man, and upon beast, and upon every herb of the field….” Voracious predators and parasitic pestilences have their counterpart in the successive deluges of frogs, lice, flies, and locusts that Pharaoh endured. Even the slaying of the children recalls the common (if rather silly) speculation about primitive mammals happily munching on dinosaur eggs. The only Mosaic plague that has not been well represented among the catalog of late Cretaceous disasters is the great darkness that blanketed Egypt for three days—“even darkness which might be felt.”

I am happy to report that this serious omission has now been rectified. I am even more delighted to report that this latest entry has a basis in evidence of an entirely new sort. It has made legitimate, for the first time, a large class of explanations heretofore characterized by perfect plausibility in theory combined with utter lack of confirming evidence—extraterrestrial events. Would you believe an asteroid so big that it hit the earth and threw up a dust cloud thick enough to block photosynthesis entirely for a decade? Pharaoh almost tossed in the towel after a mere three days. But let me bypass the asteroid for a few paragraphs to discuss some ground rules and principles about mass extinction.

The major theories of mass extinction can be divided into two groups according to their stance on each of two issues:
source
(within or outside the earth) and
rate
(truly sudden or only relatively rapid). The earth itself is a source for some proposed causes, either by such physical mechanisms as changing climates engendered by shifting continents, or such biological factors as disease, competition, and collapse of food chains. Extraterrestrial hypotheses have ranged from variation in solar output, to cosmic radiation from nearby supernovae, to impacts of various bodies. Speaking of rate, some theories posit not merely a relatively rapid blip in the vastness of time but true cataclysms, disasters on the short scale of a human life—impacts of extraterrestrial bodies, for example. Other theories invoke processes that would be too slow to note during a human lifetime, but do their work in thousands or even millions of years, against a backdrop of billions. Most of these noncatastrophic theories implicate changes of climate, including drops in sea level and the growth of glaciers.

Geologists, like all folks, have their prejudices. They prefer causes emanating from their own domain, the earth. Since Lyell’s day they have been trained to view major change as the accumulation of small inputs based on processes that can be observed in the relatively calm geologic present. These preferences have combined to give cataclysmic extraterrestrial theories a poor shake. Yet I think that few geologists would deem it inherently impossible, or even unlikely, that the earth might have suffered grievous cosmic insults at infrequent intervals during its vast history.

But another reason, better than traditional prejudice, governs the low esteem of extraterrestrial catastrophes. Geologists have not known, even in principle, any way to obtain direct evidence for them. What direct sign would a supernova or pronounced variation in solar intensity impose upon the earth? Indeed, the traditional argument for zapping by cosmic rays from supernovae relies upon total lack of evidence—the fact of mass extinction accompanied by no recognized geologic agent that might have caused it! Thus, many geologists, including myself, have long found themselves in the uncomfortable position of viewing extraterrestrial catastrophes as inherently plausible but rooting strongly against them. For what good is a theory, even a correct theory, that can generate no confirming evidence? The asteroidal theory has changed all that.

The facts of the Cretaceous extinction exert constraints upon the types of theories we may propose to explain them. We know, for example, that the extinctions occurred throughout the world and in all major environments—land, air, and sea. This fact alone virtually invalidates the entire panoply of popular theories that would attribute the extinction of dinosaurs to a cause related only to their supposed lumbering inefficiency—mammals eating their eggs, flowering plants pumping too much oxygen into the atmosphere, hyperpituitarism arising from large size and leading to sterility. Any harebrained idea can win notoriety in a context of such public fascination. Someone once proposed in all seriousness that male dinosaurs simply became too heavy to mount their partners for sexual intercourse, although I could never figure why little
Velociraptor
became extinct along with its giant cousins (not to mention what the giant brontosaurs were doing during the 100 million years or so of their success). The primary fact of dinosaur extinction is its timing as part of a global mass dying. We need a general theory, not a set of facile speculations for single groups.

We also know that the Cretaceous extinction included some aspects of geologically sudden death and others of more lingering demise. For some groups, the final phase of the Cretaceous seems to have acted more as a
coup de grâce
than an exterminating angel. Dinosaurs and ammonites had been in decline for millions of years. The dinosaur fauna of the latest Cretaceous did not include one of everything around a waterhole (as the multicolor chart on my kid’s wall suggests), but a sharply reduced assemblage consisting largely of
Tyrannosaurus, Triceratops
, and a few smaller creatures. We can also correlate these slower declines with some geological events often implicated in extinctions (but please remember that correlation need not imply cause). Sea level declined steadily throughout the late Cretaceous; the continuous seaway that had split North America in two, running from Alaska to the Gulf of Mexico, withdrew gradually in both directions. As sea level dropped and continents grew in height and extent, temperatures began a general decline that continued throughout the next seventy million years, culminating in our recent (and still uncompleted) cycle of glacial ages.

Falling sea level has accompanied nearly every mass extinction that the earth has suffered; this correlation is about the only aspect of mass extinction that evokes general agreement among geologists. Its negative effect upon biological diversity also makes sense—for falling seas drained the extensive but shallow continental shelves, thereby removing a large chunk of living space from the domain of shallow-water invertebrates, the dominant fauna of our fossil record. Harsher conditions then spread across the land as the increasingly erratic and generally colder weather of a more “continental” earth prevailed. I doubt that any dinosaur ever ate an ammonite (although the giant mosasaurs, overgrown varanid lizards, did), but the coordinated decline of both groups may be causally related to dropping sea levels.

Yet we cannot attribute the entire Cretaceous extinction to a gradually deteriorating climate. Something more dramatic must have happened, as the plankton line testifies. Perhaps this dramatic cause gained greatly in effect because more groups than usual were in decline and therefore susceptible to a
coup de grâce
. In this sense, any complete account of the Cretaceous extinction will probably include a complex combination of dramatic end superimposed upon general deterioration.

In any case, geologic evidence constrains us to look for a contributing cause that is worldwide in effect, able to exterminate groups in all major habitats, and geologically sudden for at least some of its results. Which brings me back to asteroids.

The asteroidal theory, like so many interesting hypotheses in science, had its root in a study with markedly different aims (you cannot actively look for the utterly unexpected). A team headed by Luis and Walter Alvarez at Berkeley, California, thought that they might use the amount of iridium in sediments as an indicator of their depositional rate. Iridium, a rare metallic element of the platinum group, is one to ten thousand times more abundant in asteroids and meteorites than in the earth’s crust and upper mantle. (Since both the earth and meteorites congealed from the same source, we must assume that the earth as a whole contains as high a percentage of iridium as the meteorites. But the earth melted and differentiated, and such heavy, unreactive elements as iridium sank into the inaccessible central core. The smaller bodies that form meteorites and asteroids never differentiated and therefore maintain iridium in its primeval abundance.) Hence, most iridium in the earth’s sediments comes from extraterrestrial sources. Working with the common assumption that meteorites and cosmic dust fall upon the earth in a fairly constant rain, the Alvarezes reasoned that sediments high in iridium must have formed slowly since relatively less earth-based debris had accumulated to dilute the cosmic influx.

But the Alvarezes were not prepared for the anomalously high concentrations of iridium that they found in two places: in the Umbrian Apennines of Italy and near Copenhagen. Iridium levels were 30 times higher than average in Italy and 160 times higher in Denmark. Moreover, an analysis of twenty-seven other elements in the Italian sample showed that none departed by more than a factor of 2 from “average behavior” in ordinary sediments. The anomaly involves iridium alone.

The Alvarezes wondered if they could apply the style of explanation they had originally favored: could sedimentation have been slow enough in these two places to yield such a high concentration of iridium from the normal cosmic rain alone? But they could find no evidence or even think of any reason for believing that these sediments had formed during a virtual shut-off of normal, depositional processes in the ocean. Instead, they were forced to reverse their perspective: sedimentation had been more or less normal; the iridium represented a genuine cosmic influx of unusual amount, not an undiluted gentle rain. The Alvarezes had another outstandingly good reason to favor such a reversal. Both samples came from thin clays deposited at the very top of the Cretaceous—coincident with the great extinction.

But what extraterrestrial source might have both produced the iridium and acted as a cause of the great extinction? The Alvarezes looked first to that venerable old standby of cosmic theories—the supernova that exploded near the earth and zapped our planet with so much cosmic radiation that many creatures mutated themselves out of existence. Yet, after flirting with the idea (partly in public) for a while, they dropped it—to my great delight, for it has never made any biological sense to me, despite its almost knee-jerk popularity in the “disaster literature.”

Radiation increases the mutation rate and yields a population with more variation. But more variation per se leads neither to extinction by prevalence of monstrosities nor to unusually rapid rates of evolution, because evolutionary tempos seem to be controlled by a different force—natural selection. Ordinary populations possess enough variation (without external goosing) to permit evolutionary rates so rapid that they appear instantaneous in geologic perspective. Mutation rates so high that they kill animals directly (not through the passage of defective genes to offspring) require supernovae too close to our sun to be plausible, given the spacing of stars in our part of the galaxy.

The Alvarezes now cite three reasons for rejecting a supernova:

1. A supernova would also have produced a high concentration of an ion of plutonium (
   ²⁴⁴
   Pu), yet the Italian and Danish clays contain levels of this ion ten times below the predicted value for a supernova.
   
2. Iridium occurs as two common isotopes (
   ¹⁹¹
   Ir and
   ¹⁹³
   Ir). Since all the objects of our solar system had a common origin, the ratio of these two isotopes should be the same in meteorites and in the small amount of iridium indigenous to the earth’s crust. Iridium formed in other stars might exhibit a different ratio. The ratio in the anomalous Italian and Danish samples matches that of the earth’s indigenous iridium and probably came from our solar system.
   
3. In order to zap the earth with as much iridium as the Italian and Danish samples contain, the exploding star would have to be so close to our sun that the probability of such an event becomes too small to be believed.
   

Since the ratio of iridium ions led the Alvarezes to seek a source within our own solar system, they turned to objects that might hit the earth with reasonable probability and do sufficient damage. Most asteroids orbit the sun in the large space between Mars and Jupiter, but a few follow more erratic paths, and some, called Apollo objects, cross the earth’s orbit in their wanderings. Since the asteroid Apollo was discovered in 1933, twenty-seven others that cross the earth’s orbit have been sighted. Astronomers discover an average of four more each year, while two independent estimates yield about 700 for the probable number of Apollo asteroids more than one kilometer in diameter. The Alvarezes conclude that occasional collisions between Apollo asteroids and the earth are inevitable.