American Buffalo by Steven Rinella Read Free Book Online Page A

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.