In 1956 the 28,000-year-old Paleolithic site Sungir was discovered on the outskirts of Vladimir, east of Moscow. It is one of the oldest sites in which ornaments have been found on human skeletons. At least three of the site’s inhabitants were buried there, including a sixty-year-old man, a girl of about eight, and a boy of thirteen. Interred in shallow graves dug into the permafrost, they were laid on their backs, hands folded at the hips; the children rested head to head.
Workers who unearthed the three were stunned to find that they were buried with thousands of intricately crafted ivory beads, crisscrossed in strands that might have been sewn to long since disintegrated clothing. The bones of the man’s arms were hooped with twenty-five polished mammoth-ivory bracelets. At the boy’s throat was an ivory pin that may have once held a cloak; under his shoulder was an ivory sculpture of a mammoth.
A massive eight-foot-long ivory lance made from a straightened mammoth tusk lay at his and the girl’s side.
The sight of these skeletons showered in tiny bits of ivory must have been startling enough, but the amount of labor necessary to produce the adornment is simply staggering to contemplate, and clear evidence of the deceased’s high status. According to paleoanthropologist Randall White, the beads were produced in a methodical, step-by-step fashion; they were, in effect, standardized. There was more.
They were scored across each face so that when strung they would fall into an interlocking, criss-cross pattern. Careful analysis shows that the scoring was done on each blank bead before the hole was drilled, indicating that the creator had the desired aesthetic effect in mind at even the earliest stages of production.
White’s experiments later showed that it would have taken more than an hour to make each bead. The old man’s beadwork, then, would have taken more than three thousand hours of labor, and each child’s more than five thousand hours.
All the themes that run through the history of human fascination with ivory are present, in embryonic form, in this prehistoric site: the lure of the material; its artistic employment, symbolic power, and value; its use as a means of conferring status; the desire and trade required to obtain it; efforts at mass production; consciousness of its source; its embrace in adornment even to the grave—they are all destined to be replayed through millennia to come.
It’s impossible to know the circumstances in which ivory’s properties were first revealed. We can imagine a firelit corner of a cave, the bank of a thawing river at midday, or a hundred other scenes, crowded or solitary. We can picture the thin creamy streaks left by scraping a flint very hard across a flake of mammoth tusk, or the shallow holes that could be made by twisting the sharp point of a stone tool into the surface. But we can only speculate about the first attempts to work ivory, how early humans unlocked the allure of this unique organic substance and stirred the urge to use, keep, and treasure it.
We know that humans began carving skillfully in ivory in prehistoric times. Ivory figures dating back roughly 25,000 years have been known for some time, but in 2007 archaeologists from the University of Tübingen, Germany, announced the oldest ivory find yet. It is a tiny exquisite rendering of the very animal from which the carving material itself came: a woolly mammoth. Less than an inch and a half long, the softly rounded form is complete with massive trunk, stumplike legs, pointed tail, and strange details—a half dozen incisions on the head, cross-hatching on the soles of its feet. Radiocarbon analyses push its origins back some 35,000 years. It’s one of more than a dozen figurines made from mammoth ivory unearthed at the Vogelherd cave in southwest Germany, a dazzling discovery that joins a clutch of similar small carved ivories discovered four years previously at another Swabian cave, the Hohle Fels, and thought to date to perhaps 33,000 years ago. These groups of powerful and puzzling ivory carvings may constitute the oldest body of figurative art in the world, an array that includes a horse’s head raked with lines, a lovely wing-tucked diving duck, and an enigmatic high-shouldered half human—half cat torso. Their mottled surfaces, burnished smooth and sometimes pierced for suspension, suggest they were amulets, kept close; their precise meanings and purposes are not entirely clear but their animal and human themes are familiar from all subsequent prehistoric art. Indeed, these were created at roughly the same time the first great cave paintings began appearing in Europe.
The profusion of ivory carvings that followed emerged in a period that saw an explosion of plastic expression. Those early uses are not merely the first instances; they are the formative ones, and tell us what to look for as we trace ivory’s luster through history.
It’s now commonly accepted that modern man—Homo sapiens—arose roughly 150,000 years ago in Africa and eventually set out to colonize the world; 100,000 years later they were supplanting earlier hominids (such as H. erectus and H. neanderthalensis) who began to migrate out of Africa over a million years before. After H. sapiens moved into Europe, Neanderthals, who certainly looked the part of cavemen—their powerful, heavy build was well adapted to the harsh waxing and waning ice age conditions that prevailed throughout this period—disappeared, perhaps in as little as a thousand years in southern France, although they may have overlapped for much longer in northern Europe. Neanderthals had stone tools and possibly a concept of decoration (pierced fox teeth have been found in the Neanderthal site of Grotte du Renne in France), but though that’s a sign of more intellectual capability than they are often given credit for, it pales next to the arresting evidence of human consciousness on display on the walls of more than two hundred caves in southwest France and northeast Spain decorated in Paleolithic times.
The art of these anatomically modern humans, still referred to as Cro-Magnons, says more than anything else that those who created it were not so different from us. We sense, intuitively, that it taps into shared imagery. Although the art refers to a world of experience far removed from ours, full of long-gone megafauna—cave bears, huge bison, saber-toothed cats—and shows the pentimenti of various forgotten symbolisms (spots, dots, tridents, handprints), it has a freshness and power that speak directly. Even looking at photographs of the powerfully rendered aurochs painted on the white calcite walls of the Hall of the Bulls in Lascaux, France’s most famous prehistoric cave, we feel that our reaction cannot be completely different from that of those who first created them. We see that those painters saw what we would have seen. They traced the bow of a horse’s neck, the scooping curve of a tusk, or the spear of a horn the very way we would, using outlines that cut out the animal from its background along the boundary between what it was and what it wasn’t: they used drawing, as we do, as an act of definition.
Those little figurines from Germany and all the later ice age carvings that have come down to us are, admittedly, just as shorn of context as cave paintings when seen in reproduction. But by their nature they were designed to carry their meanings with them. Studied directly—even if one has to view them behind protective glass, propped on little pedestals in museum displays, far from where they were created—they still evoke a sense of what it must have been like to hold and carry them, which in turn gives us a glimpse into what it must have been like to make them. As stand-alone, portable, hand-sized pieces worked from chunks and slabs of rock, lumps of clay, and pieces of bone and ivory, they were meant to be handled, caressed, stroked, and pondered by flickering fires, clutched under furs and skins, worn around the neck. The touch of these pieces was surely as important as their appearance, for what can be detected under the ball of the thumb or probing fingertips is apparent even in the dark. What was felt in them surely had to be part of their nimbus of meaning. So many of them were made of ivory.
WHAT WAS IT about ivory that made it a desirable material to early man? There were others at his disposal, from antler and amber to shells and stone. And ivory in substantial quantities—from mammoths or, possibly, in some regions, mastodons—may not have been widely available, although some 15,000 years ago entire shelters on the east European plain were made of mammoth skeletons either scavenged from dead animals or gathered from humans’ own kill sites of these creatures. Bones from the huge, impressively furred creatures were used like lumber. Over a foundation of skulls, nearly a hundred mandibles might be arranged around a yurtlike hide tent that used femurs and tusks as tent ribs. As building posts, tusks had certain disadvantages: they could crack, warp, and be chewed by rodents.
Yet surely chunks and flakes from broken mammoth tusks first fell to hand after the hunt, and it would require no elaborate testing to discover what the material had to offer. Ivory’s density was obvious from its weight, but its surface was not implacably granitic. Ivory wasn’t easy to work, but it didn’t split like bone or wood, which made it useful for spear points, needles, and other small tools.
Its primary creative use in Paleolithic times, however, appears to modern eyes to have been artistic. Any flake of ivory was potentially a plaque on which an exquisitely detailed drawing might be laboriously scratched—often images of mammoths, as evocative examples that have been unearthed demonstrate. A chunk of ivory slowly yields to determined gouging, scoring, and chipping with a sharp tool and can be rounded and smoothed by rubbing with fine abrasive substances known to early man, such as red ocher (hematite), which, as White points out, is no different from the jeweler’s rouge in use today. It is the last stage of polishing, of course, that unlocks ivory’s tactile appeal; something is brought out in the silken surface that makes those who touch it want to touch it again. That was all it would take. The magic of ivory had wormed its way into the human psyche.
NOT ONLY IS ivory a perfect vehicle for plastic expression, but in the right conditions it can last indefinitely. That is why we still have small ice age carvings whose iconography covers not only the range of then extant fauna—ibex and aurochs, hook-jawed salmon and migratory birds in flight, horses and cave lions, mammoths, reindeer and woolly rhinoceroses, all the bountiful and terrifying life that surrounded early man—but also forms used to mirror humans back to themselves. Unlike animal carvings, which are often carefully observed and delicately crafted, many (though not all) of these latter figures are highly abstract. Some are little more than simple forks or wishbone shapes, elongated trunks and pairs of splayed legs with vulva-like notches that seem to mark them female.
Other woman forms are contrastingly bulbous. These so-called Venus figures often feature faceless checkered knobs for heads, tiny feet and swelling torsos, all breasts, belly, buttocks, hips, and thighs, now and then showing carefully detailed navels and genitals. Their adipose, steatopygous shapes were first thought a racial characteristic and, later, evidence of their use as fertility figures, although their precise symbolism is now an open question. Among various possibilities, they may have been created as objects of veneration, as obstetrical models, or simply to stimulate arousal. While the most famous, the Venus (or Woman) of Willendorf, is limestone, many others—including the Venus of Brassempouy or La Poire (“the Pear”), a headless, bulging female torso from the Grotte du Pape in Périgord; and the highly abstracted, wonderfully geometric, almost ballooning Venus of Lespugne, found in the Haut-Garonne—are both carved from mammoth tusks.
That many of these little statuettes were made from ivory suggests something about the meanings that began to accrue to the material. If they were objects of reverence or simple teaching tools, ivory, with its perfect workability, would have been an obvious choice for careful sculptural expression; if they were Paleolithic sex toys, as some have suggested, then too there would be no better material than ivory, with its slip and warmth, to fondle in recalling the pawing and stroking of sex.
Whatever their intended purpose, the considerable effort required to carve an ivory figurine with flint tools would have imbued the resulting object with importance and value. In fact, it’s something of a puzzle as to how early man, lacking anything like a saw, managed to reduce mammoth tusks (which could be up to sixteen feet long) into portable pieces. Tusks don’t fracture easily, and splitting and wedging techniques—the kind used to split logs—won’t work with ivory that isn’t already thoroughly desiccated. Whacking a fresh tusk with a stone tool accomplishes little. But segments of mammoth tusk evidently intended for later carving have been unearthed and show that more careful methods, albeit enormously time-consuming, were devised. A flaked hammer stone was used to stipple a guideline around a section of tusk, which was then laboriously widened into a channel. A stone knife would be drawn around and around to deepen the groove, and finally the section was broken free by blows of one hammer stone on another held against the remaining core.
Ivory is dentin, an essential component of teeth.
Teeth are not bones; the two substances are different in their biology, though both are composed of collagen and minerals. Teeth, which lack the blood vessel system of bones, are denser and although connected to the skeleton are exposed, poking through the skin in some fashion. A tooth consists of a root (or roots) and a crown. The roots, which are covered by cementum, an acellular material, are fixed in the bony sockets of the jaws. All teeth feature a pulp cavity in the root, a chamber filled (in the living tooth) with soft, pulpy tissue well supplied with blood vessels. The crown, which is distinguished by its covering of hard enamel, is what’s on display in the mouth of most animals.
There are further details but we needn’t linger over them; we’re after the main mass inside the tooth, underneath the crown’s surface: dentin. This “very tough and resilient tissue,” as one scientist puts it, is “familiar as the precious material ivory.” In nature there is no shortage of teeth, but there are only a few significant sources of this “precious material.”
A mere half dozen animals have teeth big enough to yield a significant mass of carvable ivory: the hippopotamus, the walrus, the narwhal, various pigs, a few whales, and, most important of all, the elephant and its ancestors, notably the mammoth.
An elephant or mammoth tusk is an enlarged upper incisor. It’s all dentin except for a thin layer of cementum on the surface (called “bark”) and a tiny crown of enamel at the tip or distal end; as a result, virtually the entirety of its bulk can be utilized. A large tusk can be more than six inches in diameter and nearly three yards in length. The “lesser ivories” not only are far smaller in comparison but have various drawbacks, including heavy enamel cladding, different layers of dentin density, and uneven coloring. Each of these examples has had an historic role—hippo teeth were carved in ancient Egypt, pig teeth have been used since ancient Greece, walrus and narwhal ivory were important in medieval Europe and still are in Inuit culture, and whale teeth remain Oceania’s sole native source of ivory—yet all pale in significance next to “true ivory,” which comes from ancient or modern elephants and needs no qualifier.
The exceedingly compact, uniform structure of ivory derives from the network of minute tubules, each about one-fifteen-thousandth of an inch in diameter, that radiate in clusters outward from the pulp cavity. These tiny dentinal structures are surrounded by a meshwork of collagen, whose gelatinous quality contributes to its carvability and polish. It may be difficult to imagine tusks, as solid and weighty asthey are, growing, but that’s exactly what they do, from the root out. Throughout a creature’s life span, specialized mineralizing cells called odontoblasts line up on the growing surface of the dentin that outlines the funnel-shaped pulp cavity, forming tubules that inexorably deposit layer upon layer of calcified tissue, like adding to a stack of cones from the bottom. An elephant’s immense incisors grow some seven inches a year.
“Here, hold this. Be careful, it’s heavier than it looks,” Christopher Norris said as he handed me a two-foot-long tip of a stained and mottled mammoth tusk, one of a trove of similar specimens from excavations at Fairbanks Creek in Alaska in the 1950s.
It was surprisingly heavy and hard, a deep mahogany color, and streaked with fissures toward the broken end. It wasn’t at all like a mammoth tusk that a cave artist would have used. That would have been fresh, or nearly so. This one was tens of thousands of years old, rough and rocklike.
Norris and I were standing in the Childs Frick building at the American Museum of Natural History in New York, whose seven floors house the largest mammal fossil collection in the world, some 400,000 specimens. On this, the fourth (or “bison”) floor, Norris, who is the director of collections and archives in the museum’s Division of Paleontology, had laid out some ancient tusks on a table flanked by aisles of metal shelving. They were filled with boxes and crates of specimens, notably eight hundred skulls of the extinct steppe bison.
“I wanted to bring you down here. It’s kind of like a little shrine in this corner to the mass extinction of Pleistocene megafauna.” Norris is short, with thinning close-cropped black hair, and was dressed in jeans. As he sorted through the specimen boxes and trays, he spoke in rapid-fire paragraphs, weaving an overview of fossil collection issues, but let me steer the conversation toward the subject of ivory.
“Most of what you have on this floor are fossils. It may have once been bone but it’s gone through a process of petrification, so that what was once organic material in the bone has been replaced chemically by inorganic components. What you have looks like a bone, may even have the texture of a bone, and you might even be able to slice into it and see the bone structure, but what it is, essentially, is rock.”
Was it the same process for fossil ivory?
“It might take longer, because ivory’s denser than bone, but over the kind of time scales we are talking about”he shrugged—“it wouldn’t be significant.”
The mammoth tusk in my hands was actually a subfossil, in which the organic material hadn’t been totally transformed; it was mostly weathered. The ivory had lost some fats and oils but most of the dentin was intact.
Norris poked in a tray of small tusk ends. “The problem with these guys is that they’ve been soaked in water, frozen, buried. The major problem with a subfossil is that when it’s dug up it gets dried out far too quickly. Any salts dissolved in the water crystallize,” he explained. Ivory will crack and delaminate if dried out too rapidly. Previously, when tusks would begin to crack, “people used to slather on shellac to try and cope with the fact that most of the crucial damage had been done in the first few days after digging them up.”
True fossils don’t change much, however. Norris offered me another specimen.
“This is a piece of tusk from Gomphotherium from the Snake River in Nebraska, ten to twelve million years old.” It felt like stone. Gomphotherium, which had both upper and lower tusks, was one of roughly three hundred species in the order Proboscidea (named after their obvious proboscis, or trunk), which consists of elephants and their relatives. Most of the earlier evolutionary experiments, like the fearsome-looking Deinotherium (“terrible beast”), which had tusks that hung out of the lower jaw like a giant two-pronged hoe, fell by the wayside. But a million years ago there were still eleven or so species of giant proboscideans roaming the earth’s continents on their pillarlike legs, including stegadons and mastadons. The latter went extinct only about 10,000 years ago, as did their widespread relatives the mammoths, of which the best-known species, the woolly mammoth (Mammuthus primigenius), lasted somewhat longer. All have disappeared, leaving only three species of Elephantidae: the Asian elephant (Elephas maximus) and two African elephants (current thinking recognizes two distinct species on the continent, the savanna or bush elephant, Loxodonta africana, and the forest elephant, Loxodonta cyclotis).
I put the Gomphotherium tusk fragment back in the tray. “Most fossils we never see,” Norris said as he repacked the box, “they just get eroded away.”
“Most of the mammoths found have a tusk or bone or two removed, and the rest stays in the ground and gets eroded and washed down a river and added back into the environment. The natural life cycle of these objects does not include being arrested in time so they can sit on shelves and be studied. Despite the fact that we call this a natural history museum, what we basically do to this stuff is actually very unnatural. We try to stop this process, arrest it by treating it with various things, padding it to prevent mechanical damage, et cetera, so that at the end of the day we can stretch out the process for our purposes.
“The material,” he sighed, “always wants badly to degrade.”
After my meeting I stopped in the fossil halls to look for the mounted skeleton of Mammuthus jeffersonii, a non-woolly type dug up on an Indiana farm. Its huge dark tusks looked almost circular from below and crossed over each other at the tips. Norris had told me to take a careful look and, sure enough, they had been wrapped in loops of thin wire in a vain effort to keep them from cracking.
My eyes were also drawn to the mural on the wall behind the skeleton, an ice age scene by Charles R. Knight, the early-twentieth-century illustrator. Knight’s evocative re-creations of prehistory have been reproduced so frequently that his iconic images have seeped into our collective consciousness. This panorama features a line of mammoths, their long tusks held out like curled pikes, roaming over the frozen wastes of the open tundra and ice-age bogs. Reindeer resting behind trees give way to the approaching herd.
Mammoths must have been primarily walking mountains of meat to early humans, only secondarily sources of ivory. We know they hunted them successfully; we have the evidence of spear points embedded in their bones. It’s difficult enough to bring down far smaller prey consistently, as the practices of any number of hunting cultures demonstrate. It can’t have been easy to knock off such towering creatures with clubs and wooden spears or even the advanced bow-and-arrow weaponry later used that made possible slaying from a safer distance.
I couldn’t help picturing what Knight implies lies just outside the edges of his mural: hunters hidden in the forest, squinting through face-stinging sleet at shaggy beasts plowing closer and closer through the scattered white drifts. I imagined them watching as the herd crosses below them, narrowing into a single, shuffling file between the slopes and the half-frozen river below, trunks unfurling and testing the wind, the young struggling to stay close to their mothers. They see the animals’ steaming breath, the snow clinging to the fringes of their fur. Hearts pounding, gripping their stone-tipped spears and their fur cloaks tighter, the hunters remain motionless in the forest above save for their silent shaking in the deep cold. They tense as the marching line pulls away from a floundering young cow, her small eyes glittering with fear beneath a snow-matted topknot. The silence is rent by screams as the spear-shaking hunters burst out from behind firs and boulders and hurtle down the slope like the crumbling edge of an avalanche . . .
In reality, we don’t know if our human ancestors were daring, spear-chucking predators, clever herders who harried their prey over cliffs and finished them off below, or opportunistic carrion feeders, hacking off what chunks of flesh they could before the arrival of saber-toothed cats, dire wolves, short-faced bears, and other assorted rivals forced them to beat a hasty retreat from a tasty carcass. It’s likely all these strategies, and others, were put to use in the struggle to survive.
Still, they were successful enough. In fact, many researchers believe that early hunters were so skillful they can be blamed, at least in part, for the extinction of the mammoth and other megafauna across Eurasia, the Americas, and Australia. Others say that’s preposterous, for a number of reasons. To pick one: the shift in climate after the last ice age is thought to have had a negative impact on vegetation, the herbivores that fed on it, and the carnivores that fed on them. A creature like the mammoth, so well adapted to cold, might have followed the retreating glaciers northward, then become trapped on the alternately thawing and snow-covered, ever-shrinking tundra left between growing forests and the thick ice sheets. But what appears to be a connection between the rapid disappearance of a number of species from the fossil record and the appearance of the first modern humans makes many theorists think that the drying up of their food supply alone can’t account for such a sudden collapse of species.
Early man, it is hypothesized, had the means (lethal, pointy weapons and a brain large enough to plot deadly teamwork) and the motive (hunger) to be considered the prime suspect. It’s a major point of contention among scientists, quite a few of whom line up on the side of the “overkill” or “blitzkrieg” hypothesis, while others join the doubters who find overkill too problematic to be plausible.
Did early humans expand in population so rapidly that they permeated every pocket of entire continents? Were they remorseless enough to run every last beast to ground? Even if mammoths and other megafauna were primary sources of nutrition in the harsh conditions of the ice age, it’s hard to imagine that there would have been any point to killing more than what was needed. It would have been a waste of time and energy and unnecessarily risky. Whole herds, it seems safe to assume, weren’t being slaughtered for their livers—or, for that matter, their tusks. A valuable byproduct of the hunt, like bone, skin, and hair, mammoth teeth would be something to carve and use and even trade. For early humans, it seems unlikely that ivory could ever have been the sole motivation behind a hunt. That would happen later, although soon enough in history.
Ross MacPhee, a curator in the American Museum of Natural History’s Division of Vertebrate Zoology, has his office far from the fossil halls, at the other end of the two-block-long building. But the fossil record is much on his mind. MacPhee studies the causes and consequences of the massive late Pleistocene extinctions in the Americas and northern Asia. We talked in his high-ceilinged, comfortably cluttered office, with its dark wooden cabinets stuffed with books and papers, a huge old globe, and a yellow MAMMOTH CROSSING traffic sign, complete with a silhouette of the long-gone ice-age giant.
Born in Scotland and raised in Canada, MacPhee taught at Duke before joining the museum. His curly gray hair and beard are a lot trimmer than they appear in the AMNH Web site photographs of him on location in Siberia, peering out of a fur-trimmed parka.
I asked MacPhee if he thought early humans had a role in wiping out the mammoth. “I’m comfortable with the idea of early peoples hunting them. I just don’t see how they could have concentrated themselves in such as way that it could have had such an impact on populations.”
Mammoths, he pointed out, were distributed all across northern landmasses in the Pleistocene. “It’s just inconceivable to me that people with their kind of tool kit could have made any kind of difference whatsoever.” He paused. “With respect to extinction, we still don’t understand even the most rudimentary facts about how losses of this kind occur.”
I thought about one sizable denizen of the ice age that’s still with us: the musk ox. How did it manage to survive climate change and possible hunting pressure?
“The salient facts are that musk oxen originated in Asia, crossed the Bering Strait, and were quite successful.” But they “have reduced genetic variability—obviously went through a bottleneck. Something bad happened, at least that’s what appears. Musk oxen pulled through; mammoths didn’t.”
“The usual: bad luck or bad genes. Sometimes species go down for what look like random reasons. Others persist. Rhinos survive in subtropical regions, but the woolly rhino goes down. We had bison surviving in North America and Asia but mammoths went down.”
The twilight of the mammoths apparently took place on the bleak, windswept tundra of Wrangel Island north of the Arctic Circle between the Chukchi and East Siberian seas. In the 1990s, scientific expeditions there found mammoth tusks and molars in remarkable states of preservation resting in small rivers running to the Arctic Sea. On a 1998 expedition MacPhee himself stumbled across the only mammoth ulna (forelimb bone) ever recovered on Wrangel. The bone oozed grease, as if it had come from a freshly killed animal. The remnant population of these shaggy survivors managed to defy time, clinging to existence until just 3,700 years ago; the arrival of humans on the island a few centuries before may have sealed their fate. Their tusks would be unearthed in many regions, by accident and design, for millennia after their demise.
After talking with MacPhee, I got to thinking that there was something else about the overkill hypothesis that made it hard for many to resist, despite its explanatory shortcomings. Killer cavemen on an unstoppable “blitzkrieg” is an image that taps into contemporary feelings of collective guilt that we’ve been mucking up the environment since we dropped from trees. One doesn’t have to subscribe to the notion of “man the destroyer” to be dismayed by how humans have begun polluting their earthly nest, for themselves as well as for other creatures that share the globe. But MacPhee is surely right that, from a planetary point of view, species extinction is a natural process, not just something that’s exclusively caused by what people do or set in motion. Humans haven’t been around for most of the earth’s biological history. Before we came on the scene, all manner of large and small creatures that once roamed the land and swam in the seas had already become fossilized echoes of former life.
Still, that doesn’t get us off the hook now, not when we are conscious of our various effects on other species—not just our own predation but the introduction of species alien to specific environments, habitat destruction, and even climate change. The mere possibility that Pleistocene overkill might have happened as some say it did lingers in the conscience as a cautionary tale warning of our capacity for snuffing out entire species, as many in the 1980s had said could happen with the African elephant.
Studied closely, a polished cross section of a mammoth or elephant tusk reveals a complex and unique pattern. In the center of the disc there’s always a hole, a large one if the tusk has been sectioned across the pulp cavity, a tiny one if sawn across the central or tip portion where only the nerve channel remains. Surrounding the hole are concentric circles, like tree rings. Less than half an inch apart, these rings are layers of dentin formation, each representing six to eight years of tusk growth. (If the tusk had been cut lengthwise, these rings would have appeared as faint waves, like the moiré patterns on the endpapers of fine old books.) Look again at the surface of the ivory, this time closer to the outer edge of the disc, and you can see a more complex pattern, a characteristic weave of intersecting lines reminiscent of fussy banknote engraving. To scientists of a century ago, these alternating arcs were reminiscent of the delicate scalloped, engine-turned whorls on the cases of pocket watches of the period.
This delicate cross-hatching is known as the Schreger pattern, named after the odontologist Bernhard Schreger, who first described it in 1800. The nineteenth-century biologist Sir Richard Owen regarded it as a defining characteristic: “The name ivory is now restricted . . . to that modification of dentine or tooth substance which in transverse sections or fractures shews lines of different colours or straie proceeding in the arc of a circle, and forming by their decussations minute curvilinear lozenge-shaped spaces.”
The Schreger pattern is a visual reflection of ivory’s structure of microscopic dentinal tubules—microcanals that radiate in rows from the center of the tusk. The tusks of pigs, hippopotami, walruses, and narwhals show no such pattern, which means its presence can be used to distinguish proboscidean (mammoth and elephant) ivory from other ivories, and, in fact, it can even be used to distinguish between mammoth and elephant ivory. If you look at the easily seen lines closest to the outside of a mammoth tusk, they create crosshatched sprays of tiny diamond shapes, like stacked chevrons or a sharp herringbone pattern. In elephant ivory, the lines toward the outer edge of the tusk section appear loosely woven, more open, like stretched netting or soft circumflexes.
At first I saw the crisscrossed matrix of this organic material’s internal structure as an intriguing oddity, nothing more. Much later I came to think of the tightly interlocked design as curiously emblematic of ivory’s story, with its far larger, endlessly repeating historical pattern binding together art and passion, commerce and greed, humans and elephants, down through the ages.