Pleistocene Diversity as a Biological “Baseline”

Authors


The Eternal Frontier. Flannery, T. 2001 . Atlantic Monthly Press , New York . 404 pp. $27.50 (hardcover) . ISBN 0-87113-789-5 .

The Eternal Frontier by Tim Flannery is a masterfully woven tapestry of paleontological, biological, and human histories of North America. The result is a historical framework on which a reader can pin an understanding of where we are biologically as a continent and where we might go. The book begins with the close of the Age of Dinosaurs, some 65 million years ago. One will understand why, as a biologist, I sped through the bulk of that time span to settle more deliberately into a period 18,000 years ago, when a spectacular array of great mammals was on hand to greet the arrival of humans and to suffer the massive extinction episode that quickly followed.

To explain the sudden loss of North American mammalian megafauna some 13,000 years ago, when creatures were suddenly faced with Clovis hunters, Flannery focuses on the naiveté the animals surely exhibited regarding the bipedal predators. “Ecological release,” he writes with reference to the Clovis people, “… is a profoundly important factor in determining the fate of translocated animals… The release is heightened if there is a ‘naïve’ resource base that the new species can use to grow rapidly in numbers [and] is usually short-lived, lasting only as long as the species' ‘frontier’ remains open” (  p. 293 ). He contrasts the North American situation of the period with that of Africa, in which creatures dwelt alongside humanity over many hundreds of millennia, evolving survival-based behavior patterns that have allowed the kind of great mammalian diversity still seen in Africa.

While acknowledging that contemporary ecologists are not inclined favorably toward animal introductions, Flannery argues that they cite worst-case scenarios of the sort usually taking place on long-isolated islands. He continues to write that “… extensive ecological damage as the consequence of an historic introduction of a large mammal has never occurred in North America” (p. 298 ).  Later he notes that humans are the single exception: “Given the fact that the continent has never supported a more impoverished mammal fauna in the last 50 million years than it does at present, and that the existing fauna is unbalanced, appropriate introductions are more likely to be beneficial than deleterious”             ( pp. 298–299).

Flannery deals head-on with the famous current issue of “introduced” horses and burros, pointing out that half a dozen native equines disappeared during the Pleistocene extinction. The post-Columbian appearance of equines therefore amounts to a reintroduction following a 13,000-year absence. Rather than spelling doom for “native” species such as bighorns and mule deer, equine introductions may be “… an instance of range stabilization somewhat as it was in the Pleistocene, rather than extinction of a native by an introduced species” ( p. 295).

Flannery's thinking parallels that of ecologist Paul Martin, whom he clearly admires, in that he argues for increasing mammalian diversity through introductions of species closely related to those that disappeared en masse only 13 millennia ago. “We could begin with considering the two living species of elephant and their suitability as ecological replacements for the mammoth and the mastodon” (  p. 345). Flannery later adds llama, tapir, jaguar, camel, and Chacoan peccary, “… all of which are close relatives of … America's original megafauna,” as species that a century from now could “… roam North America” ( p. 347 ).

Although Flannery is detached in dealing with the predations of the Clovis culture 13 millennia removed, he becomes unforgiving when confronting recent and ongoing effects of the post-Columbian period. By Chapter 24 ( “America Under the Gun”), in which he describes the process by which “… men blind to nature would blast marvels from the face of the Earth, destroying forever the best of America's wildlife” ( p. 317), his prose becomes laced with withering indictment. Flannery employs such phrases as “binge of spectacular profit-taking,”“sorry story of greed,”“mindless development,” and “the rape of its fresh waters” ( p. 331) to describe this period of American history. His accounts of the astonishingly rapid disappearances of passenger pigeons, bison herds, Eskimo curlews, wolves, and grizzlies, as well as vertebrate and invertebrate aquatic life forms, are jarring for an American reader who must identify with the causative culture. “What right do we have to extirpate creatures that have been 70 million years in the making?” ( p. 334), Flannery asks rhetorically. “To do so is as stupid and unforgivable as tossing the contents of Fort Knox into the sea” ( p. 334).

There is a growing awareness that a proper biological “baseline” by which to understand North America is not what Lewis and Clark beheld two centuries ago, but what greeted humans newly arrived on the continent 14,000 years ago. “Today America is nothing like it was ‘to begin with,’ even if we go back to Indian times” ( p. 340), Flannery writes. In connection with this, before the middle of the nineteenth century, Charles Darwin was aware that America must have “… swarmed with great monsters” ( p. 186 ); Alfred Russel Wallace, thinking in more global terms, generalized that “… we live in a zoologically impoverished world” ( p. 186 ).

The most fundamental argument for a ( re )introduction of mammalian species similar to those that disappeared some 13,000 years ago (closely related “surrogates” that would “restart the engine of evolution,” to use the terminology of Paul Martin) is that continents, left to internal processes, given sufficient time, and without a uniquely creative, expansionist, and rapacious bipedal predator, produce megafaunal diversity such as was on hand in Pleistocene North America and the sort one can still see in parts of Africa.

Noting that America's pre-eminence continues to cost much in terms of the continent's natural wealth, Flannery wonders aloud whether an “unalterable ethic” of frontier over-exploitation is part of our society. He follows his own musing, optimistically answering in the negative because of what he claims is our ability to “reinvent ourselves.” An Australian, Flannery seems sensitive to the fact that he is dealing with the home turf of Americans, such that he is obliged to leave this opening—this positive note—of inventiveness. But given the current sociopolitical and economic direction of American culture and the fact that we are a population of 300 million and growing rapidly, I cannot be so sanguine. It would take a mighty force to alter the current ethic, and any such force as may exist presently in the culture seems puny compared with that which predominates.

This book is a wonderful read. Flannery is a fine writer with an easy style that carries a reader along effortlessly. But with its 37 pages of valuable references and notes central to the issues of conservation biology, it is a book not simply to read once but one to have always ready at hand.

Ancillary