This worried me. I started to think that maybe I hadn’t found a buffalo skull, and that I was getting all excited about some wayward domestic cow that had wandered into the mountains and died. Maybe it was a weird breed of cow with a weird-shaped head that I was unfamiliar with. I anxiously got in my van and drove down a long forest service road to its intersection with highway 287. I turned to the west. The road curved through the mountains for a while and then dropped down to the northern bank of Earthquake Lake. The lake began to form at 11:37 p.m. on August 17, 1959, when an earthquake along the face of the Madison Range dumped a mountainside into the Madison River. The debris completely blocked the river’s flow and buried nineteen people, mostly campers. The chimney on Old Faithful Inn, miles away in Yellowstone National Park, fell through the roof.
I drove through the earthquake’s debris field and entered the broad, grassy valley of the lower Madison River. When I got to the town of Ennis, the Madison River split away from the road to flow through Bear Trap Canyon. I continued along northward until I hit I-90, and then I headed west, crossing the Continental Divide and dropping down into the town of Butte, where I bought a bean burrito. From there I paralleled the headwaters of the Clark Fork River, which flows all the way to the Columbia River and into the Pacific Ocean. I drove through long expanses of ranchland punctuated by short spurts of town, looked at passing cattle, particularly the horned varieties, and was visited again and again by my pestering suspicion that I was driving around with a cattle skull on my front seat. Where the Clark Fork River receives the Blackfoot and Bitterroot rivers in the town of Missoula, I exited I-90, crossed over Rattlesnake Creek, and pulled in to my local public library. I grabbed Skulls and Bones, by Glenn Searfoss, from the stacks, checked the index, and turned to page 32. There it was, the same thing that I’d dug out of the ground. I’d found a buffalo skull.
I hung the skull from my living room ceiling by a length of nylon cord. At night, with the floor lamp next to it, the skull would cast a huge shadow against the opposite wall, as big as a buffalo. When one of my housemates slammed the door, the shadow would sway in eerie patterns. In the evenings, before I’d go out and hit the town, I liked to sit beneath the skull and read. As it happens, I was around this time reading Francis Parkman’s Oregon Trail, which chronicles the author’s journey to the Great Plains in the summer of 1846. My friend Sandy had given me the book because Parkman does a lot of hunting in it; but because I happened to be thinking about buffalo skulls, I noticed something else entirely: when Parkman, a historian, isn’t complaining about his travel mates, or discoursing on tobacco, or eating a puppy, or complaining about his physical ailments, he is usually describing a Great Plains covered so thick with the skulls of buffalo that it must have been hard to get from place to place. In a meadow full of wildflowers, he sits down on one of the many available buffalo skulls and lazily contemplates the skulls surrounding it. Near the Arkansas River, he sees a white wolf skulking through camp at night and fires a shot at it. When he runs over to what he believes is the wolf’s carcass, it turns out to be nothing more than a large sun-bleached buffalo skull. At another point in his trip, up near the Black Hills of South Dakota, Parkman gets lost. There’s a big thunderstorm headed his way, and he’s terribly afraid of being caught and killed by Pawnee Indians. He writes, “I felt the most dreary forebodings of ill-success … the passage was encumbered by the ghastly skulls of buffalo.”
Reading Parkman inspired me to read more about buffalo skulls. I became especially interested in stories about the things that people can learn by digging them up. For instance, a guy named William Fisher in 1932 unearthed a large buffalo skull while digging water lines in downtown Toronto. The skull had settled into sediments predating the Great Lakes, and it was estimated to be somewhere around ten thousand years old. The find was interesting, because the skull did not look like a modern buffalo and it was found in a locality that was not known to have ever had any of the animals.
About twenty years later, on the other end of Canada, a warden named Ulysses La Casse found a buffalo skull along the upper Bow River in Banff National Park. La Casse noticed a steel arrowhead stuck into the skull, with “I. & H. Sorby” stamped into the metal. As it happens, John Sorby (back then, people used Is in place of Js when registering trademarks) was a toolmaker from Sheffield, England. He and two of his sons, Edwin and John, had long produced “edge tools,” shears, spades, saws, blades, and so forth, under the trademark I.S. In 1827, his third son, Henry, joined the business and they changed the trademark to I. & H. Sorby. Through unknown but no doubt interesting circumstances, one of their tools ended up buried in a buffalo’s head about four thousand miles away.* Before La Casse came along, it was not known that buffalo had lived so far up the Bow River valley. And not only was this proof of their existence there, but it showed that they were present until at least 1827.
Another interesting story came out of Alaska. In 1979, a husband and wife named Walter and Ruth Roman were mining for gold near Fairbanks when they happened to unearth the skull of a type of Ice Age buffalo known as Bison priscus. The flesh and skin were still attached to the skull, and so was the animal’s body; it had been frozen in the permafrost and almost perfectly preserved. The animal had been killed in the fall or early winter by an American lion, an extinct cat that was quite similar in appearance to, though larger than, the African lion of today. The lion opened up the buffalo’s hide along the spine and ribs and upper limbs. On the buffalo’s body, pockets of coagulated blood were still visible beneath its wounds. It had died thirty-six thousand years ago. Dale Guthrie, a professor emeritus at the University of Alaska, cooked and ate part of the animal’s neck. He reported it to be “well aged but still a little tough.”
While reading about old buffalo skulls, I encountered a lot of arguments and speculations about the various species and subspecies of buffalo that lived in North America at one time or another. This was initially very confusing to me, and since then I’ve found that it’s confusing to other people as well. First off, it’s important to be clear that there is no difference between the American buffalo and the American bison. The word “buffalo” likely originated in a roundabout way involving the English. In Shakespeare’s time, military men often wore a type of protective jacket known as a buff coat; these coats were thick and soft and made of undyed leather. When Englishmen arrived in the New World, they would often describe any animal that yielded such leather as a “buff,” be it a moose or a manatee. Eventually all of the other North American animals acquired their own particular names, and the largest of them, the American buffalo, walked away with exclusive rights to the title. The name bounced around a bit—buffs, bufle, buffle, buffelo, buffaloe—but it had begun to settle into its modern form by the time of the American Revolution.
The problem with the word “buffalo” is that it had already been given away a couple of times earlier, once to the water buffalo of Asia and once to the Cape buffalo of Africa. Taxonomists, the people in the business of naming and classifying organisms, saw this as a problem, particularly because the American buffalo is not closely related to either of those creatures. As a solution, they began promoting the word “bison,” which had already been used in the Latin name of a closely related European animal, the wisent (Bison bonasus). It seems as though these efforts to clarify the situation were in vain: we’ve now got an animal with two perfectly serviceable names, and many discussions about the animal inevitably begin with the question, “What’s the difference between buffalo and bison?”
The scientific system for classifying organisms, whereby an animal gets two names, such as Bison bison, is known as binomial nomenclature. Under this system, the first word is the generic name, or genus. The second word is the specific name, or species. Carl Linnaeus, who invented binomial nomenclature, was born in 1707 and believed that all of the world’s species were distinct creatures independently created by the hand of God; more simply put, he didn’t know about evolution. This excusable bit of
oversight, considering his time period, makes his system less than ideal for naming fossils.
Bison latifrons skull recovered in North Dakota.
Here’s why: Over the years, archaeologists and paleontologists (and guys like me) have unearthed many buffalo skulls that look a lot different from the skulls of modern buffalo. For instance, a full-grown modern buffalo has a horn span, from tip to tip, of about three feet. Some ancient buffalo skulls, however, have a horn span of seven feet. And while the modern buffalo’s horns sweep upward and backward, these seven-footers were mostly straight with slight forward-facing curves toward the tips. Other skulls fall in between the two extremes, and each has its own idiosyncratic shape and horn configuration. Logically, taxonomists gave these skulls different names. The really big ones became Bison latifrons; other, smaller types of skulls picked up their own names, including Bison priscus, Bison athabascae, Bison alleni, Bison antiquus, and Bison occidentalis. For much of the twentieth century, the relationships between these different buffalo were not very well understood. Scientists believed that at least some of them coexisted in the present-day United States, where they interbred to produce the modern buffalo. We now know that this is not the case; in fact, the different “species” of “extinct” buffalo were just discrete points along the continuous path of a single species’ trajectory of change.
The bulk of buffalo history is set in the geologic epoch known as the Pleistocene, which spanned from about two million years ago to ten thousand years ago. Of the geologic epochs, the Pleistocene is by far my favorite. Its relationship to the modern world reminds me of my own relationship to my grandparents: their lives were distant and obscure enough that it’s difficult for me to really know and understand them, but what I do know about them helps explain a lot about how I turned into the kind of person I am.
However, whether or not bison history actually began in the Pleistocene depends on how you define “began.” If we think in terms of life beginning at conception rather than at birth, we might say that the bison “began” during the epoch that preceded the Pleistocene, called the Pliocene. During the Pliocene, it must have felt as if the gods had turned on an air conditioner and a dehumidifier—imagine a hot and swampy earth cooled off and dried out. Savannas and grasslands had spread across most continents, giving rise to a great diversification of long-legged grazing mammals. One of these mammals was a now-extinct critter known as the Proleptobos, which appears in the fossil record of Asia at about four million years ago. By the end of the Pliocene, the Proleptobos had split into two different groups, cattle and bison. The bison at that time were small and slightly built, and they were soon to enjoy a great expansion of their range; during the early Pleistocene, they spread across most of Eurasia.
The earth more or less continued to cool off during the Pleistocene, which is known somewhat generally as the Ice Age. Really, it’s more accurate to say that the Pleistocene epoch contained many ice ages. There were at least seventeen glacial episodes during the epoch’s two-million-year span. The episodes varied in terms of severity, but each one followed a cycle that lasted about a hundred thousand years. Each cycle was marked by a glacial period, when ice sheets expanded and climaxed, and an interglacial period, when ice sheets receded. Sometimes the changes were extremely rapid, occurring in just a matter of decades. During the interglacial periods, global temperature averages were as warm as or warmer than today.
Some geologists refer to the most recent glacial episode as the Wisconsinan. It peaked about twenty thousand years ago, and it was a doozy. Glacial ice covered much of the Northern Hemisphere; the Great Lakes region of the United States was under one and a half miles of ice.* With so much of the earth’s water tied up in glaciers, ocean levels were much lower. This caused a phenomenon of tremendous ecological significance: dryland corridors formed between landmasses usually separated by immense bodies of water.
There were many such corridors that opened between various landmasses during the Pleistocene, but for our topic here—the advent of the American buffalo—one of them is particularly important: the Bering Land Bridge. When I was a kid, the Bering Land Bridge always baffled me. I pictured it as a long, narrow hallway running between two continents, with walls of ice and water mounded up on the sides. When I heard about animals and man crossing it, I imagined them making a mad dash, like Moses crossing the parted Red Sea. Actually, though, that is not a good way of looking at it. Instead of picturing a “bridge” connecting Siberia and Alaska during times of lower ocean levels, one should imagine them as being connected by a landmass. That landmass has a name—Beringia—and it was huge. Basically, the entire western border of present-day Alaska stretched out to join the entire eastern border of present-day Siberia. That’s one thousand miles from north to south, or about the distance between Miami and New York City. Beringia was dominated by rolling hills, grasslands, and broad valleys. It did not get much snow and was free from glaciers. The dire wolf fed on horses where king crabs now feed on clams.
Several times during the Pleistocene, the dryland corridor of Beringia was open long enough to allow a nearly complete homogenization of wildlife between Siberia and Alaska. That is, animals were able to move freely back and forth between the continents. Of course, these migrating animals would probably have had no idea that they were “going” anywhere. They were just moving along, heading where there was food and a more suitable climate. Individual animals would have been born and would have died on land that is now underwater, and it may have taken several generations for a population of animals to actually “cross” the land bridge.
While there was some interchange going from North America to Siberia, such as the horse, the predominance of faunal exchanges went in the other direction, from Siberia to North America. It seems that the first of several bison migrations happened during the second-to-last glacial episode, about 140,000 years ago. Scientists often refer to these early arrivals as Eurasian steppe bison (Bison priscus). In the cave art of Paleolithic European hunters, the steppe bison is often portrayed with curvaceous horns, a large shoulder hump, and a mane so thick that it almost appears to be a second hump. The steppe bison shared the North American landscape with a host of bizarre and fascinating animals that I wish were still around: flat-headed peccaries and beavers that were the size of modern pigs; an armadillo the size of a black bear; the ox-sized Jefferson’s ground sloth, which had lips capable of gripping things; the twenty-foot-long, elephant-sized Rusconi’s ground sloth, which dragged itself along on its knuckles and used its tail as a support when it stood up to feed on leaves; the one-ton giant short-faced bear, which had catlike teeth and a skull that was almost as wide as it was long; as many as six different camels, including one that was seven feet tall at the shoulder; two horses, including one that may have been striped like a zebra; several elephants, including the five-ton Columbian mammoth, the ten-ton woolly mammoth, and the forest-dwelling American mastodon; and also an impressive array of large cats, including the 275-pound dirk-toothed cat, the 400-pound Ice Age jaguar, the 600-pound scimitar cat, the 700-pound saber-toothed cat, the 850-pound American lion, and two American cheetahs of indeterminate size.
The steppe bison thrived alongside many of these mammals on the semi-arid grasslands of eastern Beringia, where it was confined by the same factors that had allowed for its arrival. That is, the glaciers that caused the ocean levels to drop also served to block the animal’s southward migration into what is now the Lower 48 of the United States, or the mid-continent.
Eventually, during the interglacial period that separated the last two glacial periods, a north-south corridor opened through western Canada. Bison passed through the corridor maybe a hundred thousand years ago, emerging on the Great Plains near the location of Edmonton, Alberta. During the next and final glacial period, the Wisconsinan, that corridor was closed again by advancing glaciers. The bison in the south would never again interbreed with those in the north, and they would each follow their own evolutionary paths: the no
rthern path led to extinction, the southern to the American buffalo.
Populations of animals that are colonizing new territory sometimes undergo sudden and dramatic evolutionary changes. There are a couple of reasons for this. First, the colonizing population is likely to be numerically small and may contain only a fraction of the original population’s genetic diversity. Thus, the new founder population can turn out to be slightly different from the parent population, and there’s less genetic anchoring, or genetic stability, to “pull” the founder population back into line. When it comes to colonizing postglacial territory, the new population is also likely to have abundant access to food and a low population density. The Russian-born zoologist Valerius Geist has linked these conditions to the phenomenon of “giantism” in ungulates such as buffalo. The animals develop what Geist describes as “altered body proportions” and “huge and often bizarre horns.”
That’s what happened to Bison priscus; the animal experienced an evolutionary growth spurt and turned into the monster-horned Bison latifrons. It was one and a half times as big as the modern form of the animal, with horns as long as an NBA player. That relatively quick move toward giantism, however, was followed by a much longer movement in the opposite direction. For whatever reason, the large horns and body size of B. latifrons became disadvantageous to the animal. Perhaps B. latifrons’s predators learned to exploit the animal’s ungainly size, and quicker, more agile animals were more likely to survive. Or perhaps a reduction in the available food supply, or greater competition for that food, gave an advantage to animals with smaller body sizes. The evolutionary trend toward smallness, or diminution, continued for thousands of years. By around twenty thousand years ago, the long, straight horns of B. latifrons had given way to the shorter, curved horns of B. antiquus. The animal continued to get smaller, and by about five thousand years ago it had assumed the basic shape and size and behavioral characteristics of the buffalo that we know today, Bison bison.
American Buffalo Page 4