From asteroid invasion to human destruction

Tim Flannery is director of the South Australian Museum in Adelaide and was recently visiting professor of Australian studies at Harvard University. Like many academics who have visited the US, he became fascinated by the big stories that seem to swirl around the North American continent and by the rich literature and record of scientific inquiry that stretches back over the best part of 500 years.

What we have here is the ecological history of North America as seen by an Australian palaeontologist/archaeologist/botanist. The story is divided into five acts. Enter: an asteroid hurtling to earth about 65 million years ago, landing somewhere in the vicinity of Chixulub, off the northern tip of the Yucatan Peninsula, and spreading devastation from the Gulf of Mexico at least as far as Alberta, obliterating most faunal life and rubbing the slate clean for new climates, vegetation, animals and eventually new peoples. The latest arrival, the European Americans, have been superseded by genetically more adaptable pre-contact peoples, particularly those from Mesoamerica. The book deals "in millions of years rather than centuries, and this has affected the way the story of the continent has opened to us". So sit back and enjoy a read of this American drama that takes you on a journey to the past as well as the future. If that sounds a little whimsical and far-fetched, all one can say is that such is the structure of this book.

Act one, "In which America is created and undone" (66 million to 59 million years ago), begins with the pre-asteroid continent of Pangaea that was shattered beyond recognition by the asteroid impact. Act two, "In which America becomes a tropical paradise" (57 million to 33 million years ago), recounts the warming of the continent, a period about which little is known. Act three, "In which America becomes a land of immigrants" (32 million to 13,000 years ago), traces the influx of big mammals across the Asian/American land bridge of Beringia, so that the continent was roamed by elephants, buffalo, black and white rhino, lions and musk ox. Act four, "In which America is discovered" (11,000 years ago - AD1491), deals with the influx of the first humans, the Clovis people about 13,200 years ago and their material culture, in particular their finely crafted spear points.

This brings us to the controversy about the cause of the remarkable extinction of the continent's megafauna. Some think it was climatic change, but most agree that it was the result of slaughter by humans on an unprecedented scale.

Finally, act five, "In which America conquers the world" (1492-2000), has all the familiar stories of human degradation of the environment, from the destruction of forests, the overgrazing of pastures and the extinction of the passenger pigeon. Then, from the late 19th century on, comes the rise of consciousness about the need to halt this exploitation and conserve the environment. It ends with Flannery taking a peek at what he considers to be possible scenarios for America's future.

Flannery's ability to weave a story from the bewildering faunal and floral fossil fragments has inspired comparisons with the late Stephen Jay Gould.

He is good at linking past and present, alerting us to the fact that similar species, now separated across continents, are perhaps related. We discover that the Tasmanian Huon pine has distant relatives in the fossils of Seymour Island off Alaska. And Flannery describes how a handful of metasequoia, strikingly similar to the dawn redwoods that became extinct 40 million years ago, were discovered in the mountains of Hubei Province by the retreating Chinese army during the Sino-Japanese war of 1940-41.

Another positive attribute is the way the personalities and characters of the geologists, zoologists et al of the past are brought to life, with an eye for human detail - for example, the legendary palaeontologist Morris Skinner and his unlikely patron, the steel millionaire Childs Frick, and George McJunkin, the black cowboy who found the first Clovis slaughter pit at Folsom in 1908.

Flannery's swag of references is impeccable, up-to-date and well within the canon of this particular natural science. But it is a bit of a rollercoaster ride - through past and present, through science and social gossip - and this reader had difficulty following the "story line", which seems to fragment like the fossils Flannery writes about. A chart of the stratigraphy and fossil finds would have helped.

Act five so oversimplifies that at times it misrepresents the complexities of the arguments about America's post-contact past and the impact of pre-contact peoples on the environment. I also found the continual harping on the Turnerian "frontier" as a unifying metaphor a little false. The "frontier thesis" was, as Carl Sauer once said: "A nice story but it is not our history." But I am grateful for the accessible account of the pre-Clovis years, and many who would never have ventured into this territory of fossil remains and geological ages will have their appetites whetted.

Michael Williams is professor of geography, University of Oxford.