An Ecological History

of North America and Its Peoples.

By Tim Flannery.

Illustrated. 404 pp. New York:

Atlantic Monthly Press. $27.50.

As we know, but tend to forget, American history didn't begin at Jamestown, or with Columbus, or with the rise of the Sioux and the Iroquois nations. It didn't begin 13,000 years ago when Asiatic migrants crossed the Bering land bridge into a hemisphere that was blessedly untrammeled by humans, to become known eventually as the Clovis people.

Long before the Clovis, long before anybody, the landscape itself had a history. The shape and the size of our continental slab, its isolation relative to other slabs, the circumstances of climate, the topography, the ebb and flow of plant communities, and the immigration and extinction of various animal species have combined, along with later human doings, to create the big American story, one encompassing Mexico, Canada and a lonely superpower prone to the delusion that it invented itself by sheer will. North America was never a timeless Eden, and the United States is not such a glorious aberration as we might like to believe. Rather, as Tim Flannery reminds us in his new book, North America is a 65-million-year evolutionary work in progress, a series of contingencies, causal forces, drastic upheavals and transitional phases, amid which can be seen a single recurrent theme: the frontier.

Flannery is an Australian mammalogist, a respected authority on tree kangaroos and extinct giant wombats, who has done hard-traveling fieldwork in the rain forests of New Guinea and northeastern Australia. He's also a man of broad interests, long views and considerable intellectual chutzpah, as revealed in ''The Future Eaters,'' his earlier book about human colonization of Australasia. He defines himself as an ''ecological historian'' in the manner of Jared Diamond, whose ''Guns, Germs, and Steel'' he cites as an inspiration and point of departure. Ecological history is a growing field, and its practicioners are increasingly ambitious. But no one before Flannery, so far as I know, has been brave enough to tackle the whole pageant of North America, from the asteroid impact of 65 million years ago (which seems to have knocked off the dinosaurs, thereby opening American niches to mammals) up through such recent developments as the water crisis in the West, the fast-food culture and the northward return of the armadillo. In ''The Eternal Frontier'' Flannery synthesizes a vast range of scientific studies and a decent selection of historical and cultural writings, leavening those with his own forceful ideas and a modest acquaintance with the landscape, in order to explain America, in the largest sense, to Americans -- and to everyone else. It's no task for the fainthearted or cautious. What he has done, reckless soul, amounts to offering himself as the Tocqueville of American biogeography.

Continue reading the main story

Reckless or not, ''The Eternal Frontier'' persuasively illustrates why the frontier image, though tired, is so enduringly apt. Flannery traces that notion far beyond the scope of Frederick Jackson Turner's famous argument in ''The Frontier in American History.'' Not just for five centuries but for at least 57 million years, since the arrival of a rabbit-size Asian mammal known as Arctostylops and the other pioneering species that soon followed it, North America has been a land of fresh opportunities for immigrants, who have reshaped the place as much as it has reshaped them.

Invasion and establishment happened in waves, largely dependent on the transitory arrangement of continents as they drifted around after the breakup of the ancient megacontinent Pangaea, and on fluctuations in global climate. During various ice ages ocean water was sucked into icecaps and glaciers, thereby exposing land bridges between North America and other landmasses (mainly Asia and South America, occasionally even Europe), which beckoned invitingly to spillover fauna and flora from those other regions.

About the same time as Arctostylops came a group of primitive mammals now called the uintatheres, which had their origin as unprepossessing herbivores in Asia. The Asian lineage remained humble but, having crossed into a new world, ''their North American cousins embarked on a frenzy of diversification, sprouting horns and fearsome tusks and reaching titanic proportions.'' For 18 million years they flourished on the American plains, numerous in species and abundant in individuals, until a cooling climate evidently made their lives impossible and they disappeared. The uintatheres don't play a huge role in Flannery's book, or in the full sweep of North American history, but they're significant as examples of certain patterns that repeat, through the epochs, among many faunal groups: they immigrated, they thrived in the new place, they adapted to its special conditions, they diversified into many species and then, when conditions changed a bit too drastically, they went extinct.

Eventually the uintatheres were followed out of Asia by rhinos, mastodons, mammoths and others that enjoyed similar success, and suffered a similar fate. Sloths and iguanas moved up from South America and also did well, at least for a while. ''In essence, for the past 32 million years North America has acted as a sort of Hotel California for the great majority of its inhabitants,'' Flannery writes, with that musical allusion meaning they might check out at any time, but they could never leave. The Bering portal seemed to receive traffic in only one direction, a phenomenon Flannery labels the ''enigma of biased immigration.'' For whatever reasons, North America has gained far more biological enrichment from immigrant lineages than it has sent back to the rest of the world. Notable exceptions would be the dog family, which arose here; the aggressive placental mammals that charged south across the Panama land bridge when it surfaced, evidently displacing some South American marsupials; and the North American muskrat, which made a big splash across Europe.

For humans, too, this has been a land of fresh opportunity and a destination for migrant bands driven away from Asian homelands by competition, crowding, hardship or wanderlust. After the Clovis people, two further waves of humanity trekked east across Beringia, their descendants now known as the Nadene group (including the Athabaskans and the Haida of northwestern Canada) and the Aleut-Inuit group (of the far north, including Alaska's Aleutian Islands). As with the other mammals, there was no major early human immigration back into Asia. Finally, just five centuries ago, came the Europeans. ''A 60-million-year tradition of immigration has brought almost everything -- from elephants to Italians -- to North America,'' Flannery writes. ''The Columbian invasion of 1492 was part of that tradition and was therefore in accordance with the rules of zoogeography.'' Then again, in its scale of impact, it also bears comparison with that cataclysmic asteroid wallop.

Flannery makes the important point that all immigrants pioneering any frontier are affected by three evolutionary forces: the founder effect, ecological release and adaptation. The founder effect is a reminder that immigrant populations tend to be unrepresentative subsets, differing somewhat (longer legs on average, maybe, or stronger wings, or a larger sampling of venturesome peasants than complacent landowners) from their source population. Ecological release means that immigrants benefit from escaping a constellation of competitors, predators, parasites and diseases that bedeviled them in the old place. Adaptation is what they must do when the fool's holiday of ecological release comes to an end. But as the uintatheres and the mastodons demonstrated, adaptation takes time and sometimes there isn't enough. Evolution is slow; extinction can be fast.

Because North America happens to be so richly endowed with resources, according to Flannery, its Europe-derived human immigrants ''have as yet experienced very little adaptation caused by environmental constraint. Such adaptation typically occurs when the frontier terminates.'' For Frederick Jackson Turner the American frontier was gone by 1890. But if you view frontier less as a line of westward advance and consider, say, the Arctic National Wildlife Refuge, the still-roadless portions of our national forests or the fact that grizzly bears survive marginally in a few Western ecosystems, you recognize that there are dimensions of frontier still at issue.

Writing as an ecologist, not just as a student of history, Flannery notes: ''The very essence of the frontier experience lies in the extent of its resources, and when resources are boundless, why conserve them or even utilize them efficiently? The principal goal is to exploit them as quickly as possible, then move on.'' That's the American way. But where do we move, finally, when the seas again rise all around?

Continue reading the main story