Leonardo’s Mountain of Clams and the Diet of Worms (24 page)

Here is the most famous of all fossil ruminants, the one that naturalists regard, with greatest unanimity, as lost from the earth . . . It is certain that the Irish antlers
could not belong either to the moose or the reindeer . . . This [fossil] species could not possibly be confused with any large [modern] deer on any continent.

2. D
ID HUMANS EVER INTERACT WITH GIANT DEER?
Once the fact of extinction had been settled, scientists turned their attention to the timing and manner of dying. Proponents of human interaction with giant deer suffered a major setback in
the key Irish localities, for humans did not reach the Emerald Isle (or at least did not leave any known bones or artifacts to indicate their presence) until well, after the demise of
Megaloceros.
What, then, of the giant deer’s large European range? Our Neanderthal cousins and, later, our Cro-Magnon ancestors certainly overlapped the giant deer in time, but did humans ever interact with
Megaloceros
, or did we share territory in mutual ignorance, like Longfellow’s ships passing in the night?

Giant deer are never common in continental European fossil beds. From this and other evidence, paleontologists infer that the species always lived at low population density, and would probably have been noted by humans only as a minor element in any local fauna. Some giant deer bones had been found in
apparent conjunction with human artifacts, but evidence remained inconclusive because the most undeniable criterion—representation of the species in Paleolithic art—had long yielded nothing positive. In a key article published in 1949, G. F. Mitchell and H. M. Parkes wrote: “It may perhaps be pointed out again that there are no representations of the Giant Deer in Paleolithic cave art.”

Science
tends to be difficult, subtle, ambiguous, and biased by all manner of social and psychic prejudice—though surely directed in a general way toward increasingly better understanding of a real world “out there.” But every once in a while, we do achieve the reward of a simple, pristine, and undeniable fact—and then we can simply rejoice. In 1952, the first clear
Megaloceros
appeared on a newly discovered
cave wall—a gift from our ancestors, and a positive solution to the question of whether humans ever interacted with giant deer. The cave of Cougnac, in south-central France, yielded three paintings of
Megaloceros
, two males and a female. Deer can be difficult to distinguish in cave art, for the paintings are partly symbolic and not entirely representational, and some species of deer differ only
subtly. But the antlers of
Megaloceros
are so distinctive, and the second male of Cougnac so clearly painted, that the attribution could scarcely be doubted. Few deer have palmated, or platelike, antlers. The fallow deer,
Dama dama
, presents the only real possibility of confusion with
Megaloceros
—but the tines (points) of fallow deer spring from the posterior border of the palm, while giant deer
tines project from the front edge. The Cougnac painting clearly depicts a large palmated antler, with tines springing from the anterior border.

One is a great discovery, but generalities require at least two. Forty-five years after the opening of Cougnac, giant deer remain rare in cave art—thus supporting my earlier inference that
Megaloceros
remained an uncommon animal in ice-age Europe. Only
four sites have been identified, and only one other locality satisfactorily affirms the Cougnac discovery. The cave of Peche Merle, known before Cougnac, contains a schematic figure of a probable giant deer—really little more than a rough finger sketch in clay. The antler does emit a strong whiff of
Megaloceros
, but I wouldn’t put much money on this figure—and no one did before Cougnac confirmed
the presence of giant deer in cave art. The recently discovered cave of Cosquer also contains two probable giant deer, but the identification requires comparison with Cougnac—and the Cosquer images alone could not have made a convincing case for
Megaloceros
in Paleolithic painting.

Thus, only one other find truly ranks as an independent affirmation of Cougnac, and as proof that our ancestors
interacted with giant deer. The recently discovered cave of Chauvet (see the previous essay) contains two beautifully rendered giant deer. Neither painting includes the distinctive antlers, but all other defining features, as known from fossil bones and the Cougnac paintings, have been faithfully depicted, and the identification seems firm. (Both deer have been interpreted as females, and probably
correctly so, but I wonder if one or both might not be males with shed antlers, for a small projection next to the ears could represent pedicels—the projecting bases of shed antlers, found only in males. In any case, the depiction of one sex alone makes sense in natural history, though such a decision may, of course, only reflect the symbolic purposes of the artists. In two excellent articles in
the 1980s, paleontologist Anthony Barnosky proved from Irish localities that males and females lived in separate herds for part of the year—as many species of deer do today.)

For paleontologists, cave art provides precious evidence far beyond a mere proof of interaction with ancient humans. Consider the chief frustration of the conventional fossil record: that we must rely upon the evidence of
bones and other preservable hard parts. So much that is so vital for any understanding—shapes of soft parts, colors, sounds, behaviors—simply do not fossilize. Our science depends crucially on modes of inference (often dubious or even fanciful) from a paltry preserved record to the richness of nature’s totality. Sometimes we can draw a reasonable conclusion: When we find a shark’s tooth embedded
in an ammonite’s shell, we know something about the diet of ancient fishes. But often we just can’t tell: I cannot, for example, even imagine how we might learn crucial details about the emergence of human language, since so many millennia passed between original invention and the codification of any written system that might be preserved in the geological record. (In this context, I confess to wry
amusement, bordering on annoyance, at the success of “dinomation” exhibits in museums—robotic dinosaurs that gyrate and howl. Public fascination for these models centers upon the very features—colors, sounds, and soft body flaps and frills—that must remain entirely conjectural.)

Paleontologists therefore treasure the rare geological circumstances that permit an occasional preservation of soft
parts. Much of our most crucial knowledge about life’s history requires these precious “windows” upon the complete anatomy of ancient creatures. We would never have known the full range of the Cambrian explosion if the Burgess Shale had not preserved soft parts as well as shells—for many of these earliest animals grew no hard parts at all. We would never have identified
Archaeopteryx
as the first
bird if the lithographic limestone of Solnhofen did not preserve feathers as well as bones.

All these “windows” exist as a result of rare geological conditions, usually involving rapid burial in fine-grained sediments lacking both oxygen and a bacterial biota poised to decompose anything soft and organic. (Entombment in amber produces the same effect.) Only one new mode has been added by life’s
own complexity—unfortunately rather late in time, and quite limited in range. Human artists rendered the soft parts (and sometimes even the colors) of the fauna of ice-age Europe—and we, their descendants, are forever in their debt for this unique style of window into the past.

Even without a boost from cave art, we can learn more about ice-age mammals than about most other creatures of a more
distant past—for complete and well-preserved skeletons can often be found, and the animals tend to be familiar as a consequence of their close affinity with living species. But many important features must still remain obscure when bones provide our only evidence. For example, we can infer the existence of an elephant’s or tapir’s trunk from the distinctive form of nasal bones, but we cannot learn
much about size, color, or function. Similarly, fossil camels are almost always drawn without humps—not because we have any reason to assert their absence, but because we cannot infer their probable presence from bones alone.

Consider the most pressing question that bones alone cannot resolve about the form of giant deer. Our interest in this species has always focused—quite understandably, given
their outlandish size—upon the antlers. How could an animal with a five-pound skull grow up to one hundred pounds of antlers year after year? Any structure of such size and exaggeration must require a substantial set of compensatory adaptations in other bodily parts—and much of the scientific discussion about giant deer has centered upon the redesign of the rest of the body to support the gigantic
antlers. Adrian Lister argues, for example, that the remarkably thickened lower jaw bones may act as a source of recruitable storage—as they do to a lesser extent in some modern species of deer—for calcium that can be transferred to the antlers. Valerius Geist has shown that such enormous antlers impose severe constraints upon forage, for only a few plant species can supply enough minerals in
the time required. Geist inferred that only willows could suffice, and he then discovered willow remains stuck in the teeth of giant deer fossils!

But most compensatory adaptations perform the more basic function of supporting the antlers in a biomechanical sense. For example, the top of the skull is unusually thick, and the first few vertebrae of the neck remarkably powerful and especially wide
(as needed for the insertion of large muscles and ligaments that support the head). Most remarkably, as shown in the figure drawn by the great British anatomist Richard Owen (see page 191), the spines of the first few dorsal vertebrae (in the shoulder region) project far up from the backbone. In his
History of British Fossil Mammals and Birds
, published in 1846, Owen first noted the existence
and significance of these projections as compensatory adaptations for the enormous antlers:

Modern studies have affirmed Owen’s insight
about the crucial status of spines on the dorsal vertebrae. A key structure, appropriately named the
ligamentum nuchae
(or neck ligament), supports the neck in modern deer (and other mammals) by attaching both to the occiput (back) of the skull and the first few cervical (neck) vertebrae in the head region, and then extending back to an insertion on the spines of the dorsal vertebrae in the shoulder
region. The stronger the neck vertebrae, and the longer the spines of the dorsal vertebrae, the more powerful the ligament—all the better to hold up the massive head. All these structures, unsurprisingly, grow especially large in giant deer! (On the form and function of the
ligamentum nuchae
, see the 1985 article, listed in the bibliography, by N. J. Dimery, R. McN. Alexander, and K. A. Deyst.)

The long dorsal spines of giant deer imply some expression in the shape of the body—but of what form, and to what significance for the animal’s function and behavior? Other large deer and related animals also possess elongated dorsal spines, and a broadly raised area around the shoulder region as a consequence—as in modern moose or bison.

But how could the even longer dorsal spines of giant deer
influence the body’s external form? Classic reconstructions of giant deer have either ignored this issue entirely and drawn a straight back (clearly an error), or they have depicted a long and low bulge on the back, as in modern moose. For example, the “standard” painting of Charles R. Knight, the finest and most influential artist of prehistoric life, uses the “moose model” and draws an extensive
but quite indistinct bulge.

At this point we are completely stuck; bones alone can take us no farther. And we would have been stuck forever—if not for a crucial gift from our artistic ancestors. The giant deer of Cougnac and Chauvet—two males and a female at Cougnac, and two probable females at Chauvet—teach us many things that we could not have known from standard paleontological evidence. Faces
are slender and pointed as in most deer, not wide and fleshy as in moose. The males have broad and powerful necks. As in most deer,
Megaloceros
held its head low and in line with the backbone behind, not elevated above, the back (with the neck virtually at right angles to the body) as in many reconstructions, including Owen’s of 1846, as reproduced here.

But one feature of all these paintings
stands out as a wonderful surprise and an unexpected result—and all commentators in the literature have emphasized this discovery. Paleolithic artists drew every giant deer, both male and female, with a large, discrete, localized, and prominent hump—not just a diffuse and indistinct raised area as minimally implied by the dorsal spines. (This unique and distinctive hump, first revealed at Cougnac,
has since become the criterion for identifying giant deer in cave art. The poorly preserved figures at Cosquer can only be recognized by the hump. The two excellent paintings of Chauvet could be identified by other features but, in the absence of antlers for these probable females, the hump clearly marks the species.)

Moreover, the hump featured distinctive colors and markings that define the
animal’s appearance (and could also never be known from the conventional data of fossils). In all paintings that depict interior markings, the hump has been darkly colored—as a striking black blob, discretely outlined and covering the entire hump, in two animals from Cougnac; and as a more diffuse, but equally extensive, black patch on the first Chauvet female, and a thickened and accentuated border
on the second animal. (Paleolithic artists drew the large male of Cougnac only in outline, with no interior markings—presumably as a stylistic decision, not a representation. I do, of course, recognize that common features of these paintings may represent artistic convention or at least accentuation or exaggeration, rather than nature’s measurable reality. But why draw such a discrete hump if
none existed—especially since Paleolithic artists did accurately represent bison, elk, and reindeer with the broad and indistinct raised areas that usually cover the dorsal spines in large herbivores?)