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A poster child for extinction: the thylacine, a prehistoric doglike marsupial once found across much of Australia and Tasmania, was both actively hunted by humans and a victim of competition from human-introduced wild dogs. The last thylacine died in a zoo in 1936.




A New Age?


Prophets who take themselves too seriously end up preaching to an audience of one.
GEORGE DYSON, Darwin among the Machines

There is an often-articulated notion that if there is any consolation in the prospect or process of mass extinction, it is that at the end of the tunnel a new fauna emerges. According to this line of reasoning, the great sacrifice of species is a cleansing of the planet, making way for a renewal. The hope is that after the mass extinction is over, a new Age of some sort will dawn a better, more diverse Age. It is the parable of the Flood: let us call it Noah and the Recovery Fauna. After all, this seems to have been the pattern after the two greatest of all mass extinctions, when the dinosaurs took over from the mammal-like reptiles at the end of the Permian, and the mammals from the dinosaurs at the end of the Cretaceous. Could it be that after the current mass extinction, the one group of chordates still waiting for its own Age the birds will dominate? Will there now be an Age of Birds, a world of land-based bird herbivores and carnivores, burrowers and climbers, as well as the numerous (or even more numerous) flying forms that characterize this class today? Or might some completely unforeseen


group take over, such as giant insects (biomechanically impossible), or something totally new? Unless some altogether new class of vertebrates suddenly appears (highly unlikely), only the birds have yet to hold the honorific of ruling the planet. Perhaps the best bet is indeed an Age of Birds. In such a world mammals would still be present, even if they are no longer the evolutionary dominants.
In discussions about the impending biodiversity crisis, this new fauna argument is sometimes used as a rationalization, even a justification. The Age of Mammals and the Age (or even existence) of Humanity would never have occurred but for the extinction of the dinosaurs, and in like fashion or so the argument goes the modern extinction will yield some new age of organisms, perhaps with some new form of global intelligence.
What might this new evolutionary biota be like? Why not something entirely new? Can we imagine an entirely new type of animal that could replace the current evolutionary dominants, the large mammals? This new class would have to have evolved from some currently existing creature, but it could have characteristics and a body plan vastly different from those of the preceding dominants. Such a new body type could exploit some entirely new food type or habitat. Let us imagine such a breakthrough the conquest of the lower atmosphere by floating organisms called Zeppelinoids.
After the extinction of most mammals (and humanity), Zeppelinoids evolve (lets say from some species of toad, whose large gullet can swell outward and become a large gasbag). The great breakthrough comes when the toad evolves a biological mechanism inducing electrolysis of hydrogen from water. Gradually the toad evolves a way to store this light gas in its gullet, thus producing a gasbag. Sooner or later small toads are floating off into the sky for short hops (but longer hops than their ancestors were used to). More refinement and a set of wings give a modicum of directionality. Legs become tentacles, trailing down from the now thoroughly flight-adapted creatures, which can no longer be called toads: they have evolved a new body plan establishing them as a new class of vertebrates, the Class Zeppelinoida. Like so many newly evolving creatures, the Zeps rapidly increase in size: when small they are sitting ducks (flying toads?) for faster-flying predatory birds. Because their gasbag is not size-limiting, they soon become large. Eventually they are the largest animals ever to have evolved on Earth, so large that terrestrial and avian predators no longer threaten them, reaching dimensions greater than the blue whale. Their only threat comes from lighting strikes, which result in spectacular, fatal explosions visible for miles. The Zeps can never get


around this inherent flaw, for there is no biological means of producing the inflammable, inert gas helium and thus avoiding instant death from lightning. But then, life is never perfect, and the Zeps still do well, especially in areas with little lightning.
Now the dominant animals of the world, the Zeps float above the ground like great overgrown jellyfish, snagging with their dragging tentacles the few species of deer (and other herbivorous vertebrates) still extant and stuffing them into a Jabba-the-Hutt-sized mouth. Because the Zeps evolved from amphibians and are still cold-blooded, they have a very low metabolic rate, and thus need to feed only sparingly. Their design is so successful that they quickly diverge into many different types. Soon herbivorous forms are common, floating above the forests, eating the tops of trees, while others evolve into zep-eating Zeps. Still others become like whales, sieving insects out of the skies; in so doing they soon drive many bird species to extinction. The world changes as more and more Zeps prowl the air, floating serenely above the treetops, filling the skies with their numbers, their shadows dominating the landscape. It is the Age of Zeppelinoids.
A fairy tale but there is a glimmer of reality in this fable. Evolution in the past has produced vast numbers of new species following some new morphological breakthrough that allows some lucky winner to colonize a previously unexploited habitat. The first flying organisms, the first swimming organisms, the first floating organisms, all followed these breakthroughs with huge numbers of new species quickly radiating from the ancestral body type, all improving some aspects of design or changing styles to allow variations on the original theme.
But is the fundamental assumption underlying this scenario a long period of extinction followed by the emergence of a new class of evolutionary dominants at all likely? No. For just as humanity has changed the rules of evolution that have operated on this planet for hundreds of millions of years, so too has the usual sequence of events following mass extinction been modified.

Potential Winners of the Future

Picking the evolutionary winners of the future those species that will evolve to take the place of the losers (those going extinct) is something like trying to pick winners in the stock market, or forecasting the weather. There are some data available to help us make educated guesses, yet the system is so large, and subject to such a plethora of stochastic and chaotic effects, that prediction of specifics is


Whatever happens to life on Earth, one thing is certain: evolution will not stop. Here is one possible scenario for the evolution of the rat.

impossible. The colors, habits, and shapes of the newly evolved fauna can only be guessed at. There is information available that might shed light on the future winners, however, in the fossil record.
One of the interesting (and rather unexpected) findings of paleontological research is that higher taxa (the taxonomic categories above genus and species, such as families, orders, classes, and phyla) seem to show typical rates of evolution. The rate of evolution for a taxon can be described in two ways: as the rate at which some morphological character changes through time, or as the longevity of an average species in geologic time. Related to the rate of evolution are origination and extinction rates. Some groups of organisms seem to produce many new species, others very few. And of the species produced, those of some groups last for long periods of time, while those of other groups die out more rapidly.
The importance of understanding evolutionary rates was first pointed out by George Gaylord Simpson, a pioneering evolutionist. More recently, Steven Stanley of Johns Hopkins University has taken up many of the themes of research pioneered by Simpson and added fascinating new insights. Stanleys landmark


1979 book Macroevolution explored these themes in detail. Paleontologists know well the groups that show high origination and extinction rates, for these are the most important fossils used in biostratigraphy, the science of subdividing and dating sedimentary rocks using fossils. Good biostratigraphic markers are those fossils that have a short temporal duration and thus occur in only a few strata yet are at the same time widespread, common, and have sufficiently distinct morphological attributes that evolutionary change and new speciation events are immediately apparent. Examples include trilobites, ammonites, and mammals, among others. Other groups sometimes called living fossils show the opposite trends: they speciate slowly, and once originated, rarely go extinct. They are thus useless for biostratigraphy, but fascinating evolutionarily what is it about such organisms that bestows the equivalent of near-immortality?
A useful way of quantifying evolutionary rates is by arriving at an estimate of doubling time, the average amount of time for a particular higher taxon to double the number of species within it. Mammals, for instance, show a doubling time of


3.15 million years. In contrast, bivalve mollusks take 11 million years to double their number of species. Mammals show rapid evolution and bivalves very slow evolution. Within both of these groups there is much variation, including subgroups of rapidly evolving bivalves and slowly evolving mammals. In general, however, it is clear that mammals evolve faster (and produce more taxa in an equal amount of time) than do bivalve mollusks.
There is a third group of taxa that can also be recognized in the evolutionary world. Stanley has proposed the term supertaxa for groups of organisms that show both high origination rates (they produce many species) and low extinction rates (their species last a long time). Such groups have a tendency to diversify rapidly, and in so doing they become prime candidates for refilling the world with new species following any mass extinction including the current one.
The title of champion supertaxon in the world today belongs to the family Colubridae: the snakes. Stanley has suggested that rather than being in an Age of Mammals, we are really in an Age of Snakes! And as the future of evolution unfolds, we may find ourselves in a world filled with many new species of snakes. Another champion evolver is the group containing rats and mice, which, perhaps not coincidentally, are one of the prime food sources of snakes. This is probably not what most of us have in mind when contemplating some future world: a world of snakes and rats in untold varieties of form, color, and habit. Joining them will be other rapidly evolving species, many of which can be classified as weeds in that they are capable of rapid and wide distribution and are widely tolerant of harsh conditions. Many insect species both evolve rapidly and are consummate weeds (look at all of the flies in the world). Birds are also relatively fast evolvers. Each of these groups can be projected to be very common and proliferate a diversity of new species. Other mammals evolve slightly more slowly than these groups; in general, the larger the animal, the slower its evolutionary rate or doubling time.
Let us imagine some of these outcomes. Snakes could move into niches that they are rare in, or do not completely occupy, today. Many new species of marine snakes seem possible, as do snakes replacing the many small to medium-sized mammalian carnivores now dwindling in numbers. As agricultural fields and cities continue to enlarge in size over the millennia, and even tens of millennia, rodents will proliferate in a variety of new species to take advantage of these new feeding opportunities, and this too will provoke further evolution of new snake species.
Birds and insects are also potential winners. The many species of birds doing well now in urban and agricultural environments could become the rootstock of


A possible future cladogram, or evolutionary family tree, for the dandelion (bottom to top): original dandelion, cactuslike, aquatic, arboreal, carnivorous, epyphite.


One future cladogram for the snake (bottom to top): timber rattler, walking, millipede, pygmy giant, flying, three swimming types.


One future cladogram for the crow (bottom to top): crow, vulture, shoe bill, raptor, honeyeating, wading, ratite crow.


many new species. Successful forms such as crows, pigeons, and sparrows might undergo great evolutionary diversification. Of all the birds, crows seem best adapted for coexisting with humanity, and might be among the most successful at diversifying into new species the dominant species of the new recovery fauna.
The groups mentioned above are all familiar. What about totally new types of creatures, like the fanciful Zeps the kind that would make entertaining television or great fantasy books? Can there be a reasonable expectation of totally new types of creatures, with novel body plans?

The Cambrian Explosion and the Expectation of Novelty

The history of life, like any history, has occurred as a vector of time. And as in any history, there is never any going back, at least in any meaningful way. Events and their history create irrevocable changes that make each slice of time unique as it passes through the sequence from future to present to past. In the context of the future of evolution, it appears that there will never again be an Age of Fishes, or Reptiles, or Mammals even approximately similar to those that have occurred in our planets past. This is a point that conservationists refuse to accept: the Age of Megamammals is over. There will never again be an African veldt with the rich assemblage of mammals now confined to Africas game parks, and soon enough there may be no game parks at all in Africa. Even if we could somehow remove all humans from the planet in an instant, it is doubtful if things would return to the state they were in 50,000 years ago, at the onset of the end of the Age of Megamammals.
But leaving aside a return to any past era, if humanity suddenly were removed from the planet, could we expect to see new body plans? The reality is that there has been little true evolutionary novelty since the Cambrian Period, 500 million years ago. Although the conquest of land allowed vertebrates and arthropods the two most successful terrestrial phyla to evolve and explore new themes of shape, these were only modifications of existing body plans, and even that evolutionary adventure seems far nearer its end than its beginning. The birds are the last class of vertebrates to have evolved, and they did so almost 200 million years ago. Yet there seems to be an expectation that something altogether new will arise. Part of this expectation is raised by what did happen long ago in the past, when evolutionary novelty was cheap, during an event called the Cambrian Explosion.


One future cladogram for the pig (bottom to top): pig, genetically engineered, rhino pig, aquatic pig, pygmy, giraffelike, garbage-eating.


For the first 3.5 billion years of its existence, our planet was without animal life, and it was without animals large enough to leave a visible fossil record for another half billion years after that. But when, 550 million years ago, animals finally burst onto the scene in the oceans, they did so with a figurative bang in a relatively sudden event known as the Cambrian Explosion. Over a relatively short time, all of the animal phyla (the large categories of animal life characterized by unique body plans, such as arthropods, mollusks, and chordates) that exist today either evolved or first appeared in the fossil record. Uncontested fossils of animals have never been found in sedimentary strata more than 600 million years old, no matter where on Earth we look. Yet the fossils of animals are both diverse and abundant in 500-million-year-old rocks, and they include representatives of the majority of the animal phyla still found on Earth. It appears that in a time interval lasting perhaps 20 million years or less, our planet went from a place devoid of animals that could be seen with the naked eye to a planet teeming with invertebrate marine life rivaling almost any species on Earth today in size.
The rates of evolutionary innovation and new species formation during the Cambrian Explosion have never been equaled. It produced both huge numbers of new species and body plans of complete novelty. That all of the animal phyla would appear in one single, short burst of diversification is not an obviously predictable outcome of evolution. From this observation comes the second finding concerning the Cambrian Explosion that is equally puzzling, if far less well known: The Cambrian Explosion marked not only the start, but also the end of evolutionary innovation at the phylum level. Since the Cambrian, not a single new phylum has evolved. The extraordinary fact is that the evolution of new animal body plans started and ended during the Cambrian Period.
The lack of new phyla and the paucity of new classes after the end of the Cambrian Explosion may simply be an artifact of the fossil record; perhaps many new higher taxa did evolve, and subsequently went extinct. This seems unlikely. It is far more likely that the great surge of innovation marking the Cambrian came to an end as most ecological niches became occupied by the legions of newly evolved marine invertebrates.
Yet there remains a puzzling mystery: why is it that no new phyla evolved after the two great mass extinctions, the Permo-Triassic and Cretaceous-Tertiary disasters? While the Permian mass extinction may have caused the number of species to plummet to levels as low as those found early in the Cambrian, the subsequent diversification in the Mesozoic involved the formation of many new species, but


The Cambrian Era saw an astonishing explosion of diverse new body plans.


very few higher taxonomic categories. The evolutionary events of the Cambrian and the Early Triassic were dramatically different: although both produced a myriad of new species, the Cambrian event resulted in the formation of many new body plans; the Triassic event resulted only in the formation of new species that followed already well established body plans.
Two hypotheses have been proposed to explain this difference. The first supposes that evolutionary novelty comes only when ecological opportunities are truly large. During the Cambrian, for instance, there were many habitats and resources that were not occupied or exploited by marine invertebrate animals, and the great evolutionary burst of new body plans was a response to these opportunities. This situation was not duplicated after the Permo-Triassic mass extinction. Even though most species were exterminated, enough survived to fill most ecological niches. Under this scenario, there was sufficient survival of animals with various body forms to inhabit most of the various ecological niches (even if at low diversity or abundance) and in the process block evolutionary novelty.
The second possibility is that new phyla did not appear after the Permo-Triassic extinction because the genomes of the survivors had changed sufficiently since the early Cambrian to inhibit wholesale innovation. Under this scenario, evolutionary opportunities were available, but evolution was unable to create radically new designs from the available DNA. This is a sobering hypothesis, and one not easily discredited, for we have no way of comparing the DNA we find in living animals with the DNA from the long-extinct forms now preserved only as rock (movies such as Jurassic Park notwithstanding). It could be that genomes gradually become encumbered with ever more information as they gather more and more genes and in the process became less susceptible to critical mutations that could open the box of innovation.
One of the central and currently controversial aspects of the Cambrian Explosion concerns diversity and disparity. Diversity is usually understood as a measure of the number of species present. Disparity is a measure of the number of body plans, types, or design forms among those species. The controversy centers on the wondrous assemblage of fossils found at the Burgess Shale localities in western Canada, where not only early animals with hard parts, but also early forms without skeletons, are preserved as smears on the rocks.
The Burgess Shale has had an enormous impact on our understanding of the initial diversification of animal life. In large part, it is responsible for showing us that most or all of the various animal phyla (the major body plans) originated rela-


tively quickly during the Cambrian. But the Burgess Shale may also be telling us that not only were the body plans found on Earth today around in the Cambrian, but so too were other body plans that are now extinct. One of the central messages of Stephen Jay Goulds book Wonderful Life is that the Cambrian was not only a time of great origination, but also a time of great extinction. Gould (and others as well) asserts that there were far more phyla present in the Cambrian than there are today. How many? Some paleontologists have speculated that there may have been as many as a hundred different phyla in the Cambrian, compared with the thirty-five still living today. In observing this pattern, says Gould, we may acknowledge a central and surprising fact of lifes history marked decrease in disparity followed by an outstanding increase in diversity within the few surviving designs.
This view so forcefully and beautifully described in Goulds Wonderful Life is vigorously disputed in the 1997 book The Crucible of Creation by British paleontologist Simon Conway Morris, also about the Burgess Shale and the Cambrian Explosion. Conway Morris is, ironically enough, a central and sympathetic figure in Goulds book, which portrays him as one of the architects of our new understanding of the Cambrian Explosion. But he is not so sympathetic to Gould. He disputes Goulds assertion that disparity has been decreasing since the Cambrian, citing several cases suggesting just the opposite. Conway Morris also attacks another of Goulds ideas, the metaphor of re-running the tape. Conway Morris argues that convergent evolution (in which distinct lineages evolve similarly in response to similar environmental conditions) can produce the same types of body plans from quite unrelated evolutionary lineages. He argues that even if the ancestor of the vertebrates had gone extinct during or soon after the Cambrian, it is likely that some other lineage would have then evolved a body plan with a backbone, since this design is optimal for swimming in water.
Simon Conway Morriss point is that convergent evolution will dominate evolutionary processes. He even makes what might be the first academic reference to Dougal Dixons book After Man, a semi-whimsical prediction of how animals might look in the far future at a time when humankind has mysteriously gone extinct. Conway Morris notes that the animals conjectured by Dixon all seem to resemble animals living on Earth today, even though they are portrayed as evolving from quite novel sources:

In the book he [Dixon] supposes that of all the mammals only a handful of types, mostly rats and rabbits, survived to repopulate the globe. After Man is


an exercise rich in imagination in its depiction of the riot of species that quickly radiate to refill the vacant ecological niches left after a time of devastation. All the animals, of course, are hypothetical. Certainly they look strange, sometimes almost alien. When we look more closely at their peculiarities, however, they turn out to be little more than skin deep. In this imaginary bestiary the basic types of mammal, those that trot across the grasslands, burrow in the soil, fly through the air, or swim in the oceans, all re-emerge.

It is thus the physics of environments that decides which shapes are adaptive and which are not, which shapes can allow flight or running ability or the ability to chase down and kill prey. And this assumption points to a central conclusion: no evolutionary novelty. Expectations of exciting and bizarre new life forms the types seen in any science fiction movie are pipe dreams. The animals and plants arising in the future of evolution will in all probability look much like those of the present except for being far less diverse.

Expectations of Body Size

Large animals are much more charismatic than small ones. It is no coincidence that the majority of the animals listed as endangered and in need of help by the World Wildlife Fund are large mammals. Lately it has become fashionable to sneer at their popularity. Yet it is unfair to single out this hard-working group for criticism, for the hard fact remains that the large mammals the last of the megamammals are indeed endangered. Assuming that this group will show some of the highest extinction rates of the modern fauna, we might expect that future evolution will produce many new species of large-bodied animals.
Can we expect any new large animals? Recent scientific studies of the size distributions of mammals and their history of evolution suggest that large species might not appear after all. Mammalogists have long noted an interesting aspect of mammalian size distributions. There are over 4,700 species of mammals on Earth today, and their range in body size is impressive: the smallest (e.g., the tiniest shrews, such as the genus Microsorex) have an adult weight of about 2.5 grams, whereas the largest (Balaenoptera musculus, the blue whale) weighs about 1.6 X 108 grams a difference of twenty orders of magnitude. And there are all size (weight) classes in between. Yet if the size distribution of mammals for each major continent on Earth is graphed, it is immediately apparent that each distribution is skewed to


the right of the graph: there is a greater number of large mammal species than would be expected if the sizes were randomly distributed. However, this trend does not occur on small continents such as Australia, on large islands such as Madagascar, or on smaller islands. On smaller landmasses it turns out that the distribution of mammalian sizes is relatively symmetrical. Moreover, the smaller the landmass, the smaller the size of its largest mammals, and the larger the size of its smallest mammals. On small land areas the two tails of the distribution curve disappear. Finally, when small landmasses are completely isolated from other land areas, an extraordinary thing happens: large species evolve into dwarfs, and small species develop gigantism. But these are relative processes: an elephant evolving down to half size (the size of a horse) is still a large mammal (if a small elephant), whereas a mouse that doubles in size may be large for a mouse, but it is still a very small mammal. Can these observations be used to predict the future body sizes of newly evolving mammals (or any other type of animals, which presumably are affected in similar fashion)?
They can. Earlier we saw that global trade and travel are effectively recreating a supercontinent, bringing about the homogenization of the fauna that typified such large, single continents of the past. However, we have also seen that barbed wire, canals, roads, and freeways are subdividing the continents into smaller habitats. This trend is shaping the fauna according to the rules of island biogeography. Thus, we see the world being transformed, in an evolutionary sense, into an environment favoring low diversity, as well as the dwarfing of large species and the enlarging of small ones, with extinction occurring among the largest and smallest. The Age of Megamammals is well and truly over, with the last few wild mega-mammals now consigned to parks and zoos. As long as humanity survives at large population numbers, it will not return.
What might this new world look like? Let us invoke H. G. Wellss vehicle again for a fanciful, if dyspeptic, flight:

The Time Machine came to a stop. Ten million years had passed in the blink of an eye. The Time Voyager stepped from his machine and surveyed his surroundings. He was on the edge of a giant flat plain. Small fires dotted the broad expanse, sending thin blue columns of smoke into the cloudy and humid sky. The sun was setting, looking no different from the sun of his own time. Not for the first time, he wondered whether the machine had somehow malfunctioned.


Walking away from the Time Machine, he took better stock of his surroundings. He seemed to be in a gigantic garbage dump of some sort. Untold numbers of flies filled the air, their buzzing a constant hum of background Muzak. Roads crisscrossed the plain at regular intervals, but no vehicles could be seen. He looked more carefully at the refuse-strewn plain he was striding across, and was startled to see chaotic movement among the material swirling around him in the hot wind. At first he thought that thousands of huge insects were moving in the litter. But on closer inspection he discovered that while there were indeed numerous cockroach-sized insects afoot, many of the scurrying, tiny forms were mammals, a few as large as cats but most rat-, mouse-, or even shrew-sized.
He sat down on his haunches, motionless, and watched as more and more curious small mammals began to emerge. Clearly, many of the species he could now see were unfamiliar to him. Although their bodies looked like those of the rodents of his time, their heads were distinctly different. It was clear that many distinct species were present, some with long tapered heads, others with thin ribbonlike tongues, others with blunt heads and large knoblike teeth, still others with huge batlike eyes. Some had fur in a variety of camouflage patterns, while others were hairless. Some were heavily armored with armadillo-like scales. Some had front legs exquisitely adapted for digging; others had long needlelike claws extending from their toes. The small forms wormed among the garbage, some using their impossibly long tongues to probe into the piled refuse, while others broke open some of the many scattered bones to root out the marrow. While he watched, one of the small mammals was suddenly lifted into the air by a flicking rope of some sort, and then he saw the body being carried into a large, waiting mouth. A huge snake lay coiled not far away. Its tongue was like that of a frog, capable of flicking outward and grasping its prey. He saw another large snake moving on short legs like those of a centipede, and yet another moving its head in and out of the piled garbage, looking for small prey housed within.
Watching this menagerie of the small, he tried to compile a list of species new to him, losing count after tallying more than forty. It was not that everything was alien, for these creatures were surely descended from the mammals and reptiles of his own time, but they were just as clearly evolved, forming entirely new groups of species. And still more and more animals began to appear in the gathering twilight. The biggest animal that he saw was the size


of a pig, and seemed indeed to be some sort of bizarre swine. But this pig, if that is what it was, seemed well adapted for pushing through the piled garbage in search of food. It had a small trunk instead of a nose, which allowed it to root efficiently through the piles of rotting offal. Numerous small ratlike creatures hung from its sides, like remoras clinging to a shark. He thought at first that they might be babies, but they were clearly parasites of some sort, looking like hairy lampreys with greedy sucking mouths. Or perhaps vampires would be a better description. The rats, it seemed, had evolved.
He shuddered in revulsion at this bestiary. All seemed exquisitely adapted to these piles of garbage; in fact, all seemed adapted exclusively for life in this setting. In the distance he saw a copse of trees, and decided to leave the gigantic dump for a more natural setting, not realizing how natural garbage dumps were in this world. He began striding through the garbage, heading for the distant patch of green. Suddenly, shadows below and a cacophonous, raucous cawing from above announced a flight of birds over his head. They were crows, but bigger than those from his own time, and with brilliant plumage. He ignored them, but was jolted from behind with a sharp, piercing pain. Swearing, he put his hand to the back of his head, and found it covered with blood. He looked up to see another of the large crows diving at his head. He ducked just in time, seeing a large, eagle-like beak and great talons with a long, knifelike barb extending from one of the large feet. He began running back toward the center of the garbage, seeking shelter of some sort, but the crows, more than a dozen strong, attacked viciously. They let him run in terror back toward the trees, and as he got closer, he saw why: more than a hundred sat perched in the first row of trees, watching as their compatriots herded this particularly stupid human toward the waiting, hungry flock. The lions of the world now had wings.






Biological Futures
Niles Eldredge
PREFACE   xiii
INTRODUCTION The Chronic Argonauts 1

The Deep Past: A Tale of Two Extinctions

TWO The Near Past: The Beginning of the End of the Age of Megamammals 37
THREE Into the Present 47

Reuniting Gondwanaland


The Near Future: A New World


The First Ten Million Years: The Recovery Fauna


After the Recovery: A New Age?


The Future Evolution of Humans


Scenarios of Human Extinction: Will There Be an After Man?


Deep Time, Far Future



INDEX   183

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