Leonardo’s Mountain of Clams and the Diet of Worms (25 page)

The hump also serves as a focal point for other markings of uncertain meaning—probably either lines of color, folds of skin, or separations between regions of differing colors, lengths, or conformations
of coat hair. All four drawings with interior features show a prominent line extending from the hump in a grand diagonal across the entire flank to the back legs. In three of four animals, another line runs from the forward edge of the hump on an opposite diagonal to the chest just above the forelegs. Finally, one animal from Chauvet bears a large diagonal black band across the entire neck,
while a male from Cougnac carries a line of color in the same position.

The hump does form on the region of the back that overlies the dorsal spines. This “preexisting condition” of long spines to anchor a ligament for support of the heavily antlered head surely provides a substrate for the evolution of a discrete hump. But, equally surely, the hump of the giant deer has become more than a passive
expression of the skeleton beneath—for passive expression only requires the broad and indistinct raised area developed by many other species over their enlarged dorsal spines. The hump, with its discrete and exaggerated form, and its bold accent by color (and by diagonal lines radiating out in both directions), must represent a distinctive product of evolution. But why?

We cannot answer this
question with any confidence, but comparison with living relatives suggests a primary function in the signaling and display that accompany the central Darwinian activity of reproductive competition. In my earlier work, I suggested that giant deer might not have used their antlers in actual combat, but rather to announce status and to permit competition by symbolic posturing rather than by overt and
harmful fighting. In short, and a bit crudely, bigger antlers win the bluff and secure more copulations for their bearers.

I now believe that I was wrong in making this suggestion. Later work by Tim Clutton-Brock and Andrew Kitchener has convinced me that giant deer almost surely used their antlers in actual combat. But fights for reproductive success among male deer (and other large mammals)
also involve substantial ritual, posturing, and display—undoubtedly employing the antlers as a major element of the routine. Deer posture, bellow, and strut before an actual engagement. They often perform a “parallel walk” to observe the full length and conformation of a rival—and any feature that might accentuate an impression of power, fierceness, or bulk should help to establish a position of
dominance. I agree with both Kitchener and Lister that the large and boldly colored hump would work especially well as an intimidating device and a mark of potential power. Kitchener writes that “the Irish elk [giant deer] probably assessed its opponents in a parallel walk which would have emphasized the massive shoulder hump and, hence, indicated body size and potential fighting ability.” Lister
adds that “the prominent, dark-colored dorsal hump would have formed part of the display
gestalt.
”

I doubt that display for fighting can explicate the full function of the giant deer’s hump—if only because females seem to grow an equally prominent hump, but presumably did not fight. Incidentally, the female hump also indicates a distinct functionality for this feature beyond the mere expression
of underlying dorsal spines—for the dorsal spines of non-antlered females are much shorter than those of males, but the female hump seems no smaller than the male version! Similar form and strength in both sexes may suggest further function as a general signal for recognizing other members of the species, or for other purposes yet unknown and unsuspected.

In any case, the uniquely shaped and
distinctively functioning hump of the giant deer provides a superb illustration for a fundamental principle in evolutionary theory. The hump, we must presume, did not initially arise “for” eventual functions of display and recognition. The original structure probably developed, at first, as a simple and passive consequence of the underlying dorsal spines, themselves evolved for the very different,
and obviously crucial, function of holding up a head with maximally heavy antlers—for all large mammals with dorsal spines must (and do) develop a broadly raised, if indistinct, bulge on the back over the spines. But most mammals never alter this indistinct structure in any substantial way; the bulging back remains a passive consequence of the underlying spines and may serve no function by itself
at all. However, for some unknown reason, giant deer actively evolved this preexisting passive consequence into a discrete and prominent hump with complex adaptive functions in its own right.

Therefore, structures that initially arise as nonadaptive side effects of a primary adaptation (the raised area on the back as a necessary expression of underlying dorsal spines) may later be “coopted” for
a special role vital to the animal’s evolutionary success. Much of the fascination, the quirkiness, and the unpredictability of evolution lie in this principle of cooptation of structures initially evolved for other purposes, or for no purpose at all. Feathers that evolve as thermoregulatory devices in small running dinosaurs get coopted for flight in birds. Brains that evolve for whatever our
australopithecine ancestors needed on the African savannahs get coopted by later Cro-Magnons for artistic expression and utility—and so (and only for this reason) do we learn about another coopted structure: the hump of the giant deer!

The hump of
Megaloceros
may intrigue us as an illustration of this important general principle. Nonetheless, I do not wish to advance such an argument as our major
reason for fascination with this bump on a back—however dear the principle of cooptation may be to me (as a prominent theme in my own technical writings), or however much the movement from little fact to large generality forms the trademark of these essays. After all, the principle of cooptation has been both well established and well illustrated for many years. To be sure, another good example
never hurts—especially for such a striking structure in such a fascinating species. But we break no theoretical ground with this illustration.

May I suggest instead that we should value the hump of the giant deer primarily for a very different reason—as an item of natural history, precious beyond words simply because it once existed, and because we would never have known either its factuality
or its fascination if our ancestors had not been moved to leave such beautiful visual records.

For simple items regulated by natural laws, we can often infer existence (and conformation) without actual observation. We know the record of solar eclipses for the last several thousand years, even though many went unrecorded in all human chronicles. But for complex items of natural history, unrepeatable
in their unique and detailed glory, and crucially dependent upon a contingent and unpredictable sequence of prior historical states, we cannot know their existence unless the paltry and grossly imperfect records of history leave direct evidence. Every item of natural history is both a joy to behold and an instrument for our potential enlightenment. But the vast majority of items have been permanently
lost in the bottomless pit of history’s failure to record. And a loss at any moment is a loss forever.

You may say, “So what, we are surrounded by such a plethora of items, and we can’t know everything.” But I am insatiably greedy and infinitely curious. Each and every loss becomes an instance of ultimate tragedy—something that once was, but shall never be known to us. The hump of the giant deer—as
a nonfossilizable item of soft anatomy—should have fallen into the maw of erased history. But our ancestors provided a wondrous rescue, and we should rejoice mightily. Every new item can instruct us; every unexpected object possesses beauty for its own sake; every rescue from history’s great shredding machine is—and I don’t know how else to say this—a holy act of salvation for a bit of totality.

We will never know the Paleolithic painter who rescued this precious fact—the hump of the giant deer—and vouchsafed it to us, his grateful descendants. To this anonymous person, I can only say: “You’re a better man than I am . . .” For I can only report and interpret, but you salvaged a real and true item of earthly beauty.

OUR UNUSUAL UNITY

A
TRULY STUPID MISTAKE OFTEN INITIATES A PATH TO ENLIGHTENMENT.
Fortunately, my latest experience of this common phenomenon occurred (and got corrected) in total privacy—so I can avoid embarrassment because no one need know!
The Herald
, Zimbabwe’s major newspaper, printed a government notice in its issue for January 14, 1997:
Licensing of dogs and cycles.
The annual fee,
they reported, would be twenty Zimbabwean dollars (about $2.00 U.S.) for a bicycle, and thirty for a tricycle. I laughed to myself at the blatant absurdity of charging more for a kid’s toy than an adult’s necessity—an amusement no doubt tinged (I must admit) by residual and unconscious racism so pervasive in our culture that even white folks of decent will cannot entirely extinguish the blight: those
primitive Africans got it backward again. But the joke was entirely on me—for I soon remembered that local tricycles are the three-wheeled, human-powered vehicles that serve as short-haul taxis, or for transporting heavy goods, in so much of the non-Western world. These sturdy adult tricycles are larger and generate more income than a bicycle—and may therefore be fairly taxed at a higher rate.

This example of one of the most common fallacies in human reasoning—the elevation to universal status of a local, limited, and potentially false belief held by an individual or a culture—did no harm and lasted only a few minutes. But other more potent and pervasive cases often serve as the greatest impediments to improved scientific and scholarly understanding. The larger theme behind my little
blunder about two- and three-wheeled vehicles—the assumption that human history should progress in a linear sequence of improvement (with Africans behind Europeans)—may be the most harmful and widespread of all culturally embedded errors falsely promoted to universal truth.

I recently encountered a striking example during some heavy travel between two monthly essays. I saw, for the first time,
the magnificent remains of the great Mayan cities of Chichen Itza and Uxmal. Among the many anomalies presented by this ancient and complex Mesoamerican civilization, the problem of deciphering Mayan writing stands out. Mayan culture peaked in the second half of our first millennium and then mysteriously collapsed from the ninth to the tenth century A.D. (Several resuscitations occurred thereafter,
partly in amalgamation with other Mesoamerican groups—and Mayan people, speaking Mayan languages, still inhabit Guatemala, the Yucatán, and surrounding areas. But knowledge of the classical writing system, and much of their elaborate astronomical and calculational learning, did not survive the European invasions.)

Spanish conquerors destroyed most of the Mayan books (written on paper made from
bark, and folded accordion-style)—and only four codices survive. But Mayan writing appears on hundreds of large stone stelae, originally erected as ceremonial proclamations in front of major buildings, and as numerous inscriptions on walls, statues, and pots. The recent deciphering of this script—a mixture of symbols for syllables and for entire words (and therefore similar in concept to Egyptian
hieroglyphs, though independently invented)—ranks as one of the greatest scholarly achievements of the twentieth century.

We may rejoice in this success, and in the striking reinterpretation of Mayan history thus provided, but we must also wonder what delayed the decipherment for so long—for as Michael D. Coe points out in his recent and justly acclaimed book,
Breaking the Maya Code
, the tools
for successful resolution, and adequate data for the task, had been potentially available from the beginning of serious Mayan scholarship in the mid-nineteenth century.

The reasons are complex and many, including the cruel and systematic destruction of Mayan documents by early Spanish colonialists, but Coe shows that the old error of construing human history as linear progress also played a major
role. Since the Mayans peaked so long ago (while Europe remained a backwater), and belonged to an ethnic group judged inferior by many scholars of European extraction, several leading experts on Mayan culture simply refused to believe that these inscriptions could represent a complete written language. Mayan writing must, they argued, represent the crude pictorial scribbles of limited people
who, despite surprising and considerable achievements in architecture and astronomy, could never master the full complexity of recorded language.

For example, Coe quotes one Mayan scholar who, in 1935, denounced the good start made by Benjamin Lee Whorf, a great linguist of the last generation. Whorf had correctly ascribed phonetic value to the Mayan glyphs, but his critic replied that Mayan
symbols could only represent “embryo” writing—crude pictures with limited informational content, and not full sentences with grammar. Invoking this progressivist, linear (and racist) assumption, Whorf’s critic wrote:

Coe also shows how the “hyper-evolutionism” of Sylvanus Morley, the dominant Mayan scholar in the first half of our century, also became an impediment to deciphering this largely phonetic script with complete grammar. Coe writes:

Since Morley viewed the Mayans as more primitive than the Chinese—and therefore largely in the pictographic stage—he could never have deciphered their predominantly phonetic writing!