However, man had one dread weapon effective against even the largest and fiercest animals: fire. In the fall, when the plains were covered with a mat of dried grass and the animals were in prime condition for butchering, a well-placed fire, fanned by a favoring wind, could stampede several animals to their destruction, furnishing enough meat to feed the hunting band throughout the winter.
Over all the plains the hunting fires were set each fall, some of them burning unchecked for days and blackening thousands of acres. With each small hunting band setting even one or two fires a year, and lightning adding a few more, the entire plains area suffered millions of burned acres each year. Such recurring fires were an important factor in keeping the grasslands free from encroaching shrubs and trees, and in pushing back the forests along the eastern edge of the plains. The Shawnees used this method to keep several thousand square miles of Kentucky free from forests in the eighteenth century.
Through all this time the ice sheet was melting, each year exposing large new areas for grasses. These two factors, the hunting fires and the melting of the ice sheet, probably aided by other factors not yet identified, gave central North America the largest pasture lands known. The open lands stretched from the Canadian forests southward to the Gulf of Mexico and from the Rocky Mountains eastward almost to the Mississippi River. Fingers of the prairie country extended eastward across the Mississippi, across Illinois, Indiana, and Ohio to the western ridges of the Alleghenies.
Then came a puzzling development. With conditions seemingly more favorable than ever for the grazing herds, many of the large species disappeared entirely, while similar species flourished and multiplied. The mastodon and the giant sloth suffered a rather swift destruction, while remnants of the horse herds lived on for several thousand years before succumbing.
Since the only identifiable new factor at this critical period was the appearance of man and his fires, some geographers suggest that the extensive burnings might have triggered the catastrophe. Large, slow animals such as the mastodon and the giant sloth would be especially vulnerable to fire, but this explanation does not account for the killing off of the tough, agile wild horses, while the larger, clumsier, more stupid bison not only survived but thrived to an astonishing degree (although all other species of the bison did disappear in the widespread disaster).
Traces of the vanished bison have been found all across the United States from New Jersey to California, with the fossil remains usually estimated as about 40,000 years old. So far none of the bones identified as belonging to these vanished herds have been found in association with early artifacts. But this is negative evidence that does not really prove anything, since hunters of this period stripped away meat at the site of a kill and seldom bothered to carry large bones back to their caves.
About the time the herds were facing destruction, the route from the Yukon Valley to the Great Plains reopened as a result of the continued melting of the ice sheet. More hunting bands came across Siberia into North America, bringing with them a new weapon more effective against large game: the heavy dart projected by an atlatl, or throwing stick. The darts, four to six feet long and stone tipped, could be thrown with some accuracy for a hundred yards or so, and at fifty yards could inflict a serious wound on an animal struck in the intestines. Many thousands of years later other migrants from Siberia brought bows and arrows. Hence any bison remains associated with artifacts left by hunters using atlatls would be much older than remains left by hunters using bows and arrows. So far all the bison remains found with artifacts have been of the period of the atlatl or later. With the refined method of dating remains by carbon 14, it is now possible to place early kills in accurate sequence.
Near Folsom, New Mexico, in about 15,000 B.C. hunters using the atlatl and darts killed twenty-seven bison in one place. The species found here has been named the Taylor bison. It was somewhat larger than the modern bison.
At Big Sandy Creek in southeastern Colorado a large kill of bison was made about 6500 B.C. All of these animals are classed as Bison occidentalis. In northwestern Iowa the skull of another B. occidentalis was found at a village site and dated 6471 B.C. In this case the skull had probably been brought to the village for use in some sort of religious rite.
There is some question whether the B. taylori and the B. occidentalis are not actually the same species. At any rate, they are closely related and are considered to be extinct, although some geographers believe it is possible that the extant wood buffalo in northern Alberta is actually the B. occidentalis.
Wood buffalo have been protected for nearly a century and the herd has increased during that period, but it is probable that they have crossbred with the plains buffalo for the last sixty years. Hence it is considered impossible to secure an animal known to be a specimen of the true wood buffalo that could be compared in detail with the skeletons of the
B. taylori
from the Folsom kill and the
B. occidentalis
from the Big Sandy Creek kill.
During the period when many species of large grass-eaters were destroyed, the modern bison was common in Mexico, as shown by the many fossil remains. It is possible that the conditions that killed off the animals on the plains did not occur in Mexico, or perhaps the Mexican bison had a biological edge that enabled it to survive. When the northern grasslands were left almost empty and the Mexican pasture changed to desert scrub with the changing climate, these bison moved north and filled the vacant spaces.
Over many thousands of years, between about 10,000 B.C. and A.D. 1000, the natural increase of the modern buffalo filled the plains. Eventually the necessity for more pasture forced the animals on the outer edges to move beyond the plains and occupy marginal lands on the east and the west. The eastward-moving herds crossed the Mississippi into northern Illinois, then into Indiana and Ohio. Some of them turned south and crossed the Ohio River into Kentucky and northern Tennessee, finally reaching the tidewater regions of the Carolinas and Virginia. On the west the herds found rather easy passes through the Rockies and across the continental divide in both Montana and Wyoming. On the western slope of the divide they occupied the Bitterroot, upper Snake, Bear, and upper Colorado valleys.
These marginal herds were small and scattered compared to the dense masses that filled the plains. They had not even filled their new pastures before their further growth was stopped rather abruptly by the arrival of white settlers with their guns and horses. The settlers and the Indian tribes attacked the herds in the east with guns, while the Plains Indians secured horses and greatly increased their annual kill on the plains. Horses were also used for buffalo hunting by the Columbia Basin tribes west of the divide.
Imaginative writers, visualizing the movements of these many herds and ignoring the hundreds of years involved, have developed the theory that the thousands of buffalo, moving in orderly columns on regular migrations, trampled out a vast network of broad trails the length and breadth of buffalo land and that these trails were later taken over by the Indians and still later became wagon roads and highways for the early settlers.
The writers support their premise by pointing to the pattern of well-beaten trails leading to salt licks and water holes in buffalo country. Sometimes these trails were worn down as much as six or seven feet below the surface of the surrounding land where they crossed a small swell or dropped down a bank. However, there are some fundamental errors in this concept, stemming from a lack of knowledge of the buffalo as a grazing animal.