THE ETERNAL FRONTIER - TIM FLANNERY

An Ecological History of North America and its Peoples.

# CONTENTS
~ Introduction: Ground Zero
~ Act 1: In Which America is Created and Undone
~ Act 2: In Which America Becomes a Tropical Paradise
~ Act 3: In Which America Becomes a Land of Immigrants
~ Act 4: In Which America is Discovered
~ Act 5: In Which America Conquers the World
~ Beyond The Book

# INTRODUCTION: GROUND ZERO

There are forces in the lives of people, and animals and plants too, that have made them what they are. Some are big forces factors of climate and topography, isolation and landmass size that exert their power for eons and in the process shape species and whole environments. Others are more transient and affect populations, communities and individuals as circumstances change rapidly around them. Ecological historians range far and wide through time and space, rounding up these disparate forces to show the evolution of a particular species or an entire region.

The US now trains and employs more palaeontologists than any other nation and its innovative techniques, explorations and studies are the global engine of the discipline. North America, paradoxically, is also the global centre of Creationism, whose dogmatic followers believe that the Earth was formed just 6000 years ago. Enigmas such as this abound on the continent, and indeed seem typical of it.

What are the quintessential determinants of life in North America?

The roots of causality in North America are profound, and to address these questions we must go far back in time, to when modern North America came into being. That continent-defining moment occured one balmy day 65 million years ago, when a great fiery ball appeared in the sky and came crashing into Earth. Where would the asteroid hit? Ground Zero, as it happened was to be North America. This fact, this utterly random event, would change world history. The scene opens on a continent not conceived in liberty but riven in two, and soon to be visited by fire, flood and famine.

# ACT 1: AMERICA IS CREATED AND UNDONE

Continents are not born like people, for there is no day, century or even millennium that we can hail as a continental 'birthday'. This is because continents are born of inexorable geological forces that move at glacial speed. Most of the existing continents were formed of fragmentation: Australia, Antartica, South America and Africa came into existence as a result of the breakup of the super-continent Gondwana. North America, however, was created differently - it resulted from a victory of the forces of union. It was born in the twilight moments of the age of the dinosaurs. A vast shallow seaway, dubbed the Bearpaw Sea, occupied its southern and central portions, dividing North America into separate eastern and western landmasses.

The great smoking pit left by the asteroid impact must have been an incomprehensible sight. How long, I wonder, did the ocean continue to pour into it? This was an impact so intense it could send portions of the Earth spinning into space.

By sweeping away almost all of the larger organisms, the asteroid had reset the evolutionary clock, allowing a few humble if not meek survivors to inherit the Earth. Despite more than 100 million years of evolutionary change mammals had been unable to evolve into creatures larger than a domestic cat. Now all that would change, for the age of mammals - the Cenozoic era - was at hand.

The Bearpaw Sea that had divided the continent drained away as uplift raised the land's surface until it had shrunk to a brackish expanse known as the Cannonball Sea. Sixty million years ago, when the Cannonball retreated for the last time from Montana and North Dakota, North America, east and west, was finally united across a broad front by this awesome organic process.

North America's only connections to other land after the asteroid impact were polar portals providing limited potential contacts with Europe and Asia. Consequently, for the first few million years after the impact, plant evolution on the continent seems to have continued on a uniquely North American path.

Trees evolve far more slowly than other organisms such as mammals. One need only consider the rat-like creatures living 65 million years ago that were to morph through time and space into elephants and whales, yet many of the trees growing during the last part of the age of the dinosaurs would not look out of place in the modern world.

The spectacular rates of evolutionary change among mammals seem inconceivable today. They bespeak an empty world - the proverbial vacuum abhorred by nature - being progressively filled, each new species filling a small niche until an entire ecosystem was created. In those days of vacuum-driven evolution the ancient hoofed mammals diversified into a variety of unlikely niches. One kind, the mesonychids, evolved into leopard-sized killers.

For all this rapidly evolving diversity, North America was still a post-apocalyptic world, inhabited by inept-looking smallish creatures lacking the breadth of form and size present during the age of the dinosaurs.

# ACT 2: AMERICA BECOMES A TROPICAL PARADISE

Between 57 and 55 million years ago a motley collection of mammal immigrants made the journey from Asia to North America, including the ancestors of rats and their kin and some very odd-looking beasts. Imagine an animal, say a hedgehog or a shrew, that had adapted to eating vegetation and grown to the size of a cow and the shape of a hippo. There you have 'Coryphodon'. The cause of their migration was a gradual warming trend that continued for 14 million years after the asteroid impact, making the Bering land bridge more hospitable for many creatures.

Until 33 million years ago Europe was an island archipelago, its 10 million square kilometres being quite separate from Asia but intermittently connected to North America.

One remarkable effect of the heatwave was that it opened a veritable highway to Europe. Then, the relative positions of the continents were very different. The North Pole lay directly over northern Beringia. North America, however, were joined by overland connections at less northerly latitudes. During the early Eocene Europe was a distinct continent bounded to the south and east by seas. The Thule land bridge connected North America - via Greenland and the Faroes - with the British section of the European archipelago.

What was the result of this first joust between the inhabitants of North America and Europe? The fossil record is clear, it was a hands-down victory for the invading North American forces. As this diverse horde took up the new lands on their eastern frontier the old Europeans died out. By the end of this interchange, at least half of the 61 land mammal genera in Europe had close relatives and common ancestors in North America, principally as a result of Europe acquiring a new fauna. Sich close faunal similarity between these two continents has never been seen before or since.

One of biology's more iron-clad rules seems to be that the inhabitants of larger lands are likely to be more successful immigrants than those of smaller ones.

I do not think that continent size is everything in determining how the inhabitants of continents fare during periods of faunal exchange, but I do concede it is a powerful explainer of success for larger, warm-blooded creatures.

Rapid evolution can of course occur at the margin, such as when a species first reaches an offshore island. Then one sometimes sees truly spectacular rates of evolution as birds become flightless or creatures such as elephants become pygmy versions of their former selves. This evolution is quite different from that occuring on continents, for on islands species adapt quickly to environmental constraint while on great continents competition from other organisms seems to be the driving force of evolutionary change.

# ACT 3: AMERICA BECOMES A LAND OF IMMIGRANTS

Temperature ranges in North America can vary incredibly over a brief period. The town of Spearfish in South Dakota holds the world record, going from -18.9 degrees Celsius to 3.3 degrees above in two minutes.

When Earth is warm (in greenhouse mode), North America is a verdant and productive land. Almost all of its land is covered in luxuriant vegetation. But, as the Earth cools, North America's capacity to amplify change rapidly drives it to a break point, beyond which it falls into the frigid grip of the poles. It can then be said to be in icehouse mode, a mode that characterises the present.

33 million years ago a cooling so dramatic occured that it closed the length Eocene epoch. The Palaeogene extended for 41 million years, from 65 to 24 million years ago, and is divided into three geological epochs: The Palaeocene (ancient), Eocene (dawn) and Oligocene (slight epoch). Palaeogene means 'ancient period' because the mammals that lived then seem to alien to the modern world. It is followed by the Neogene, the time of the new, which is itself divided into the Miocene (less new), the Pliocene (more new) and Pleistocene (most new).

Europe was being transformed by the cooling. The rising oe the European Alps and a fall in sea level opened Europe to Asia. Most of the archaic creatures that had inhabited Europe since the North American migrations of 10 to 15 million years earlier were exterminated as new Asian species invaded, including ancient bears, weasels, bear-dogs, rhinos, beavers, squirrels, mice and rabbits.

A curtain of ice descended on Beringia 32 million years ago, bringing about a cessation of faunal interchange with Asia. North America was to go it alone for a while, an isolated continent in the grip of great climate change.

In the Miocene the planet warmed, but strangely rainfall did not increase as it had in previous warm phases. Large tracts of North American became a wooded savanna. North American fossil desposits of this age regularly yields the remains of 15 or more species of mammals weighing more than 5 kgs, a diversity never seen before or since in North America and in our time existing only in the richest grasslands of east and south Africa.
15 million years ago, America's Serengeti boasted five locally evolved ecological equivalents of Africa's "big five" - the elephant, buffalo, black and white rhino and lion - as well as smaller game. The elephant niche was filled when the mastodons reached North America via Beringia. The living elephants are known in ecological parlance as 'keystone species' because they alter the environment in ways that allow smaller creatures, such as antelope, to thrive. The arrival of elephant-like creatures in North America just before the height of the golden age may well have changed the environment in ways that were favourable to mammal diversity.

John Byers makes the observation that "pronghorns are ridiculously too fast for any modern predator". Their extraordinary speed, up to 100 kms per hour, and their considerable stamina bespeak a creature that evolved in clear and present danger. That danger, Byers thinks, came in the form of the continent's extinct meat-eating megafauna, which included cheetahs, running hyenas and short-faced bears.

Why the American savanna fauna of 15 million years ago should so closely resemble that of present-day Africa is an intriguing question. Some researchers have sought explanations in the idea of co-evolution. They say that each species on Earth is shaped by interactions with the other species in its environment and that on the savanna there are only limited choices available as the various species compete.

For the past 32 million years it has been all too easy for immigrants to come in to North America through the Beringian front door, but has proved almost impossible for most to leave via that exit. Furthermore, the great majority of groups that established themselves in North America have in turn been overwhelmed by the new waves of immigrants continually arriving from Eurasia. This presents a striking parallel to the human history of North America.

By 2.8 million years ago the first dry land connections to exist between North and South America for at least 62 million years had been established. Then the Isthmus of Panama was a flat plain covered in woodland and savanna. For the fauna of North America, it was a veritable highway. The charge south was led by the skunks. Horses quickly followed, then came a mass invsion of dogs and foxes, bears, weasels, cats great and small, squirrels, shrews, rabbits, tapirs, camels, and deer. These creatures were to transform South America, sweeping away many archaic groups and fixing in their place a fauna of predominantly North American origin.

The great faunal exchange initiated by the Panamanian land bridge was described by the famous palaeontologist George Gaylord Simpson as "one of the most extraordinary events in the whole history of life". It was a vast natural experiment; a promiscuous mixing of whole continents full of organisms that had been isolated for tens of millions of years.

The first North American mammals to travel to South America were members of the racoon family. They arrived around 4 million years ago, and once ensconsed in South America evolved into bear-size and bear-like creatures, something they had never done in their old home.

The strangest of all the creatures to travel north at this time was an enourmous, flightless bird, 'Titanus', belonging to a family that had dominated the large carnivore nice in South America for over 50 million years. Three metres high, 400 kgs in weight and with a beak 30 cms long and shaped like a hatchet, these birds known as phorusrhacoids were formidable predators.

Only 20,000 years ago North America was a veritable empire of ice.

What is North America like during a glacial maximum? Ice sheets over 3 kms high at their centre cover most land north of New York. The weight of the ice actually deforms the continent, bowing the rocks until they sit about 370 metres below their present level. The seas drop by around 120 metres, exposing a great coastal plain right round the continental margin. The Atlantic is frigid and berg-choked while the Pacific remains quite warm. Eighteen millennia ago tundra grew on Manhattan, reindeer frolicked in New Jersey, bison roamed Florida and in what is now the arid southwest of the US, forests grew around large freshwater lakes.

What would we have seen if we could have visited the American west of 18,000 years ago? We would have found a fabulous array of large creatures. The most visible animals would have been the mammoths and mastodons. The most common large mammal was a long-legged pig-like creature known as the flat-headed peccary that was about the size of a European wild boar. Much more bizarre would have been the giant sloths, the largest of which were the megatheres. Imagine a creature six metres long from nose to tail-tip, weighing three tonnes and covered with coarse shaggy fur, in whose skin countless of tiny pebble-like bones are embedded.
This odd-looking fauna was tasty fodder for a wde range of carnivores. Among the most common was the dire wolf, larger and more heavily built than the living grey wolf. The dire wolf was probably a pack hunter and scavenger, capable of killing the smaller sloths, llamas, deer and bison. Dwarfing these impressive creatures were the short-faced bears. Unlike grizzlies and black bears, short-faced bears were pursuit predators that ran down their prey in open country. They are a North American production, and, at around 700 kgs in weight, one species of short-faced bear was the largest meat-eating mammal ever to have trod the Earth. Members of the cat family were also numerous. The lion was then common in Alaksa north of the ice, while to the south lived an even larger kind, the American lion, which were the largest  lions ever. Other cats of the ice age include the sabretooths and scimitar cats. The sabretooth was a powerful, lion-sized cat that may have been able to kill adult sloths and half-grown mammoths. The New World cheetah doubtless stalked the magnificient American pronghorn across the plains of ice-age America, while in the cold northern forests jaguars hunted their prey - perhaps deer and purcupines.

The deep past seems to leave a limited legacy in North America. Change in the form of climatic shifts and massive immigration has reshaped the continent's ecology continuously. It is as if the continent knows no rest, no equilibrium, no consistent state to which we can point and say, "Ah, see, that is North America."

# ACT 4: AMERICA IS DISCOVERED

We have watched the evolution of those truly North American creatures, the dogs, camels and horses. We have seen the results of contact between the two halves of the New World, a North American takeover of the south, and the more selective South American march northwards. We have seen an ice age begin and a new fauna take shape - including mammoths, mastodons, great sloths and teratorns. We have sampled only coarse segments in the vast expanse of time. We have dealt in millions of years rather than centuries. Next is a new realm of time, this new realm consists of the 13,200 or so years since the first Indian sighter his (or her) great new discovery - a whole New World.

Beringia was an inhospitable, frigid and boggy corridor largely devoid of life. After threading they way past freezing mires, under louring walls of ice and through dense fogs for a hundred miles or more, those early explorers emerged somewhere near present-day Edmonton. To the south lay an enormous, megafauna-dotted plain. A whole New World, stretching almost from pole to pole, lay before them.

What did these first Americans look like? Christopher Columbus might have been confused when he called the people he met 'Indians', but the name was felicitous. Perhaps he noticed a resemblance to the Asian people of the East Indies in their coarse, straight black hair, light-brown skin, brown eyes and high cheekbones. These traits, coupled with close genetic similarities, indicate that America's Indians are an Asiatic people. Despite the many physical resemblances, there are differences between American Indians and most contemporary Asians. Few Indians, for example, possess the fold of skin over the corner of the eye that is such a striking feature of most modern people from north Asia. These differences indicate that the American Indians left north-east Asia before all the characteristics of the modern Asian population had become established.

"It is impossible to reflect on the state of the American continent without astonishment. Formerly it must have swarmed with great monsters; now we find mere pygmies compared with the antecedent, allied races."
        - Charles Darwin

"We live in a zoologically impoverished world, from which all the hugest, and fiercest and strangest forms have recently disappeared."
        - Alfred Russell Wallace

Until very recently, the precise time that the continent's fiercest and strangest creatures became extinct has been difficult to pinpoint. Studies now under way by Russ Graham, however, indicated that with three vital exceptions, almost all of the more common North American late Pleistocene megafauna perished about 13,200 years ago. The exceptions are the mighty mammoth, the mastodon and the short-faced bears, all of which held on longer, the first two until about 12,800 years ago and the bear for perhaps 1000 years after that. The cause of the extinctions has been exceptionally tricky to resolve in North America becayse the time of extinction overlaps both a critical one for climate change and the time that the Clovis people flourished.

The key to deciphering the riddle of the North American extinctions, I believe, is to examine extinctions in a global context. The Americas, Australia, Madagascar and many oceanic islands suffered dramatic extinctions. North America lost 73% of all genera weighing more than 44 kgs, but Australia lost every terrestrial vertebrate species larger than a human as well as many smaller mammals, reptiles and flightless birds.

One final and very important challenge to the climatic theory of extinction has recently emerged. In 1999 researchers interested in the fossil fauna of the Caribbean published rigorously tested radiocarbon dates that give a 'last time of occurence' for the ground sloths that once inhabited Cuba. These dates indicate that the creatures survived until at least 6250 years ago - around the same time people reached the island. What climatic phenomenon, the advocates of the climate driven model must ask, could drive ground sloths to extinction from Canada to Tierra del Fuego in an instant of time around 13,200 years ago, yet leave the ground sloths of Cuba untouched? Extinctions correlate not with climate change but with the arrival of people.

The lesser, non-asteroid-caused extinctions of North America during the last 65 million years have been liniked with climate change. But the extinctions of 13,200 years ago occured during a period of rapid warming, while all of the earlier ones have been linked with dramatic cooling. Furthermore, the species lost in the earlier extinctions are just those one would expect to be vulnerable tto a cooling climate, such as browsers and arboreal species.

Leo Tolstoy began 'Anna Karenina' with the observation, "All happy families resemble one another, but each unhappy family is unhappy in its way". I think that ecosystems that have been stable for a long period are all stable in the same way. Their stability is the result of being held in shape by the same basic ecological forces, which results in the evolution of primary producers, herbivors and carnivores in predictable numbers relative to one another. Astonishing similarities between elements in isolated ecosystems can be caused by these forces: witness the likeness of the thylacine and the wolf. Extinction events, however, are much more like Tolstoy's unhappy families: each extinction happens in its own way.

Dr Dale Guthrie argues that when the mammoth lived, Alaska and Beringia supported a very different kind of vegetation which, despite the intense cold of the last glacial maximum, was much more productive that today's. Guthrie has called this vanished vegetation the mammoth steppe.

Elephants and other truly large mammals (those weighing over a tonne) are profound modifiers of their environment. In Africa, elephants can convert forest into savanna through their destructive feeding on trees, thereby reating much usable habitat for grazing species.

In respect to both the moose and jaguar, they stay-at-home European populations gave rise to different-looking species (modern moose and leopard) while their immigrant American cousins remained similar to their fossil ancestors. In a related phenomenon, North America has often acted as a last refuge for archaic groups such as mastodons and sabretooths, long after their extinction elsewhere.

There is a clear benefit to storing meat in chilled water - it won't rot as quickly as if it were left exposed to the air. If one is living with a whole megafauna there are other reasons why one might want to do this, for dead bodies attract scavengers, making it a very unpleasant camping location.

A few large mammal survivors of the Pleistocene blitzkrieg quietly expanded their ranges... Bison is just another name for European wisent, elk for red deer, and grizzly for brown bear. All of these creatures are very recent Eurasian immigrants to North America south of Alaska, so recent in fact that they either entered the continent at the same time or just a little after the Clovis people.

The giant short-faced bears would have had no experience or fear of humans, and may have viewed them as very slow-moving prey. As a consequence, many probably ended their days impaled upon Clovis points. The more versatile omnivorous brown bear, with its long experience of human hunters, soon filled the continent in its wake.

North America's new megafauna dramatically changed the continent, and it is in the crucible of change that a distinctive American ecosystem was forged. The America of Geronimo and Buffalo Bill would be assembled in a breathtaking evolutionary whirlwind of change that acted for just thirteen millennia.

With the end of the Clovis culture about 12,900 years ago, America's first frontier closed. The first pan-North American culture had vanished and the varied Indian cultures to which it gave rise would live within the bounds of a diverse yet impoverished continent. Of all the great beats that fed the Clovis people, just one was still present, the American buffalo or bison, but even it had become restricted to the great prairie of the American west.

Life in a herd has many disadvantages. In addition to increased competition for food and a mate the chance of catching any infectious disease is increased. Why did the plains bison adopt the lifestyle so dramatically over such a brief period of time? The answer lies, it seems, in the dangers that plains bison faced. Herd behavious is often a response to the presence of predators that can easily pick off isolated individuals or small groups. Such predators find it much more difficult to kill one of a herd. There were only three predators capable of hunting adult bison: wolves, grizzlies and Folsom point-wielding men. Humans are thus the only force capable of 'making' the plains bison... the bison is a human artefact, for it was shaped by Indians and its distribution determined by them.

Bison have been shrinking in size throughout the last 12,000 years. In both Australia and North America dwarfing of species as a survival response coincides with the arrival of humans and not with climate change. Kangaroos had begun to shrink by 40,000 years ago while in the Americas dwarfing began 12,000 to 13,000 years ago.

Not all native people of North America are descendants of Clovis. At least two other migrant groups established themselves on the continent before 1492, the ancestors of the Nadene and the Aleut-Indian cultural complexes. Nadene people look more like modern north Asians that the Amerindians, suggesting that they branched off from their Asian ancestors more recently. Studies indicate that they entered the entered the continent around 9000 years ago. They must have come across the sea from Asia, as Beringia was submerged by this time. The traditional Nadene strongholds were the boreal forests and western coast of Canada. A few hundred years before the arrival of Columbus, one Nadene group adapted to life on the Great Plains, on the way becoming Navajo and Apache. Either these people or the Inuit brought the bow and arrow with them. The Aleuts and Inuit represent a more recent development, for linguistic, genetic and archaeological evidnece indicate that they arose 5000 years ago. In an important sense the Inuit are neither a North American nor Eurasian people, for like the polar bear they have a true circumpolar distribution. The Inuit differ from all other pre-Columbian people in that they never lost contact, at least for extended periods, with their relatives in Eurasia. The Inuit even received goods from the people of Europe via the Viking settlements of Greenland. Were we to see American history through their eyes, the arrival of Columbus in 1492 may well have been a rather unexpected event.

While Inuit cultural contacts were extensive both east and west, they enjoyed no such relations with the people to their south, for contact between Indian and Eskimo have always been miminal; active avoidance alternating with hostility. The very name 'Eskimo' supposedly derives from a derogatory Indian term connoting 'eater of raw meat'.

One important point to make about the history of immigration from Eurasia is that each successive wave of human invaders found their niche in a more marginal part of North America. No human invasion ever went the other way - from North America to Europe. Here is a pattern of migration that persisted for 33 million years and would persist into the future.

By the time of Columbus the people of North America had created an astonishing cariety of human societies. All had been shaped by the opportunities and the imperious demands of the North American continent as mediated through human ingenuity, and almost all had developed in isolation from the inhabitants of other lands. Taken as a whole, they represent a constellation of human possiblities - a corpus of cultural experiments - that really does represent a New World. In their encounters with such people the European explorers came as close as anyone ever will to meeting the alien societies so vividly brought to life in science fiction fantasies such as 'Star Wars'.

Despite the fact that grizzlies had inhabited North America south of Alaska for just 13,000 years, up to a dozen genetically discrete populations of grizzly had begun to form in North America by 1492. How I wondered, did such large mammals diversify to quickly? The answer lies not only in the richness of the continent but in the ecological release experienced by the bears in their new home. With few competitors and a huge variety of resources they quickly diversified and adapted to local conditions. Indians of course do not represent incipient new subspecies as grizzlies do, but for millennia before 1492 they were adapting through cultural change to local conditions even more rapidly than grizzlies were through natural selection.

The end of pre-Columbian America would commence in the same southern region that was its greatest strength. It would be heralded by the arrival of creatures that the Indians at first mistook for gods. In reality they were the first horses to paw the ground of the New World since their kin died at the point of an Indian spear some 13,000 years earlier. Had the conquistadores been met by mounted Aztec battalions, the result of the war of the worlds might just have been different.

# ACT 5: AMERICAN CONQUERS THE WORLD

From an evolutionary perspective, reading the recent past is a bit like examining, from very close up, a newspaper photograph that has been enlarged a hundred times. We can see the individual dots clearly, but it's an effort to make out the bigger picture, much is lost in the excess of detail.

A 60-million-year-tradition of immigration has brought almost everything, from elephants to Italians, to North America. The Columbian invasion of 1492 was part of that tradition and was therefore in accordance with the rules of zoogeography as played out over the millennia. But it is almost unique in the last 45 million years of Earth history, for virtually every other Eurasian invasion of the Americas had come from east Asia, across the Bering land bridge, or the sea that at times covers it.

Asia is so rich that although it comprises just one seventh of the globe's land surface it is home to over half of humanity. It was Asians who peopled the Americas 13,200 years ago. Beginning 6000 years ago another Asian peple began moving into south-east Asia and Pacific Islands. By 800 years ago they had reached as far as New Zealand, spawning the Maori and Polynesian cultures. By the Middle Ages over 60% of the Earth's habitable land surface was then occupied by people of Asian origin.

So why was Columbus not Japanese or Korean or Chinese?

Europe has long acted as a cul-de-sac and last refuge for various vanishing peoples, such as Neanderthals and Celts.

Europeans had been travelling to the New World since at least the 10th century, when Vikings attempted a short-lived settlement in Newfoundland.

An enormous windfall of resources fell into the hands of the Europeans upon the
discovery of the New World.

The geographer George Seddon once quipped that there is only question you need to ask a continent in order to determine the fate of its people: "Did you have a good ice age?"

It is no accident that Spanish colonisation began in the Caribbean for islands are ideal places for immigrant populations to gain a foothold.

The Spanish recruited members of the Aztec ruling class and relied on Aztec tribute books to determine what regions could yield which resources. The extent to which the Spanish took over the Aztec empire can be seen in their rebuilding of Mexico City. A cathedral was built on the ruins of the main Aztec temple, the symbolism of which would not have gone unnoticed by the Aztec survivors. From the perspective of the subject peoples, and if we set aside the ravages of disease, Cortez's conquest ultimately might have meant little - they were simply changing one overlord for another.

At first the English looked to be inept colonisers, for their mortality rates were fearful and profits were meagre. What would eventually make them great was their character of their frontier - theirs was not to be a frontier of vassals or of fur but of the soil. The implications of the English frontier for the Indians were to be dire, for by and large these settlers viewed Indians not as valued trading partners (as the French did) or a resource to be exploited (as the Spanish did), but as competitors. They were 'varmints', and they were chased from the land like any wolf or coyote.

The new American nation was born out of two remarkable movements - a revolution and an act of union. Over time most colonies have sought independence, so revolutionc omes as little surprise. Successful union, however, is a much rarer event... successful federation may well be so infrequent because if it is to work it requires that politicians relinquish some power - a rare occurrence indeed in the real world.

Thomas Jefferson designed his Monticello mansion and its construction was the workd of a lifetime. It has an amazing modest and compact beauty, revealing the Jeffersonian mind as nothing else does. In Jefferson's time the frontier lay just across the Blue Ridge Mountains, so beautifully beckoning from his high hill. To enter Monticello is to be transported back to the time when the frontier had just begun to open. In the foyer the fossilised bones of a mastadon that had been excavated nearby are displayed. Standing there I could still sense the excitement, the anticipation roused when he finally obtained the funding to send Lewis and Clark over those mountains and on to the distant sea. The mementoes that they returned with - the Indian clothing, the buffalo skin and antlers of elk - still adorn the house, and they still speak to me of that magical time when the west was not yet won.

"The wilderness masters the colonist. Complex society is precipitated by the wilderness into a kind of primitive organisation based on the family... in the crucible of the frontier the immigrants were Americanised, liberated and fused into a mixed race, English in neither nationality nor characteristics."
 - Frederick Jackson Turner, "The Frontier in American History" (1893)

Turner also argued that there was not one but several frontiers that followed one after the other, with each successive frontier exploiting more intensely the resources on offer. The first frontier was that of the hunter and trader, then came the pastoralist, the farmer and finally the city-builder.

The North American experience of 'ecological release' encouraged its inhabitants to develop new ways of harvesting an almost unimaginable natural plenty, while the Australians found themselves facing adversity almost from the moment they entered the continent. Australian cultural evolution tells of a long struggle to exist within the limits that nature placed upon its people. In other words, they adapted to their new home, while North Americans were relased by theirs.

Most contemporary ecologists look on animal and plant introductions with disfavour, citing the very worst cases of damage to argue against such introductions. Yet these cases have usually occured on long-isolated islands such as in the Caribbean and Australia. Extensive ecological damage as a result of the historic introduction of a large mammal has never occured in North America. Given the fact that the continent has never supported a more impoverished mammal fauna in the last 50 million years that it does at present and that the existing fauna is unbalanced, appopriate introductions are more likely to be beneficial than deletrious. The one great exception to this concerns our own species. It alone has caused massive extinctions on immigrating to the New World, not once but twice.

The smallpox epidemic of 1838 would kill 10 out of every 12 Assiniboin in the region of Fort Union, as well as about 6000 Blackfeet. Of the Assiniboin who survived, about half had been vaccinated by fur traders during visits to the Hudson Bay Company's trading posts in Canadian territories. The Company had been trading with Indians for nearly 200 years and well knew the importance of a healthy Indian population to its business. It sent supplies of smallpox vaccine to its traders for the benefit of their Indian trading partners. Perhaps predictably, the Americans failed to provide any such protection to the Indians on their frontier.

The extent to which disease assisted the European conquest of North America can be gauged by comparing experiences of European colonisation with those of Afro-Eurasia. European colonists in Africa and Asia were every bit as brutal as their counterparts in the Americas, but they almost never managed to extirpate the indigenous populations, who were often as poorly armed as the American Indians.

The final phases of the Indian war were shameful and unrelenting. In the 25 years between 1865 and 1890 the United States Army alone killed 6000 Indian men, women and children. It was an expensive business, for by 1870 the campaign was costing approx. one million dollars for every dead Indian. Such a high ratio of effort for return has not been matched in any other North American extermination program, except perhaps the campaign against the last wolves in the US.

As the reach of the United States spread west, much of the native flora and fauna of the continent came to be seen either as a resource to be exploited to the full, or as a pest to be gotten rid of. In the process, men blind to nature would blast marvels from the face of the Earth, destroying forever the best of America's wildlife.

The North American species that fared worst in the late 19th century - the passenger pigeon, the buffalo and Eskimo curlew - were those that congregated in vast flocks or herds in order to overwhelm predators. This appears to be a unique aspect of the North American extinctions. The herding behaviour of the bison, and possibly the passenger pigeon, first arose as an adaptation to avoid the human predator, and this strategy protected these species for at least 13,000 years. Only by 1880-90 did European machinery become sophisticated enough to destroy the great herding and flocking species.

The American Civil War in many ways represents the decisive moment in the country's history, for it definitively resolved the tensions that had been evident in British-settled America since its inception. It was a struggle against forces that had the potential to convert North America into another Europe - a constellation of rival states descending into centuries of self-destructive feuding.

Fire behaves much like mega-herbivores do, consuming dry and coarse vegetation that smaller creatures, being more dainty eaters, turn their nose up at. Competition between large creatures, such as elephants and bison, and fire does exist, with fire being less frequent and intense where such herbivores live in large numbers... I believe that the great question faced by park managers in North America today is whether, where it is suitable, they should reintroduce elephant, camel, llama, panther and lion into their reserves.

We have seen that, upon entering a new homeland, all immigrant species are affected by three evolutionary forces - the founder effect, ecological (and social) release, and adaptation. We can think of these forces as forming a great trajectory, like an upward arrow shot from a bow. The founder effect is the point of origin, ecological release the rapid rise of the arrow until it reaches its zenith, and adaptation the slow fall back to Mother Earth.

Adaptation is the opposite of release. Societal changes resulting from release are not adaptations to one's new homeland, for by definition they result only from escaping the constraints of the old, while adaptation is a response to the constraints of the new. Because North America is such a rich continent, Europeans have as yet experienced very little adaptation caused by environmental constraint.

The 'American society' identified by writers such as Frederick Jackson Tuener was created largely from ecological and social release on the frontier. Release can produce a non-European society, but it cannot produce a society genuinely adapated to North American conditions. That can only exist after the frontier closes.

The majority of immigrants to the United States were transformed into citizens of that distinctive nation who seek not separation but inclusion within American popular culture. Because of the disparate origins of its people this popular culture must be stronger and able to stick more diverse parts together than is normally required from a cultural adhesive. In a sense American popular culture has to be a superglue, and to do that it must appeal to the lowest common denominator. American culture thus has no choice but to be mass culture, from baseball and football to hot dogs, Coco-Cola, McDonald's, baseball caps, pop tunes and Hollywood movies. It will always be superficial, full of self-reference to big-screen cliches, to soaps and their stars, and to a consensus news media. That's why it appeals to everyone, paricularly teenagers, and that's why American popular culture is now a global phenomenon.

# BEYOND THE BOOK

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.
        - David Quammen, from his "New York Times" review of "Eternal Frontier"

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