Can you hunt the prey for the lion, or satisfy the appetite of the young lions, when they crouch in their dens, or lie in wait in their covert?
—Job 38:39–40 (NRSV)
“Dying Lioness”. Detail of an alabaster mural relief from the North Palace of Ashurbanipal, Nineveh, Assyrian period, c. 650 BCE. Source: Photograph by Matt Neale, taken in room 10 of the British Museum.
The lion in the Book of Job would have been the Asiatic lion (Panthera leo persica).1 This lion subspecies was formerly found in the coastal forests of northern Africa and from northern Greece across southwestern Asia to eastern India.2 The epitome of fierceness and power, it was used then and now as an emblem of these attributes, such as the Sphinx of ancient Egypt or the incorporation of lion motifs into the regalia of pharaohs. Lion hunts appear on ancient monuments from the origins of Western civilization. One striking example, “The Dying Lioness,” from a 650 BCE alabaster panel from Nineveh, is shown at this chapter’s start. Over two thousand years have not diminished the power of the carving or the beauty and fierceness of the animal represented, even at the point of her death.
Today, the awe-inspiring Asiatic lion’s presence on Earth is represented by about 350 individuals that are found primarily in a biological reserve in India’s Gir Forest and National Wildlife Park.3 Some of the animals in this population, perhaps one hundred, are located outside the reserve.4 Even though poaching is an issue, the population seems stable at this time.5 The Asiatic lion is considered an endangered species because of its small population found in one location. The answer to the whirlwind question, “Can you feed the lion and take care of its young?” would likely be, “no,” or, at best, “maybe” for the Asiatic lion.
“Can you take care of the lion?” is the first of a series of animal questions presented in the whirlwind questions. We have already treated three other creatures in this bestiary, the aurochs in chapter 3 and the onager and the horse in chapter 4, along with birds in chapter 6. Taken as a whole, the animal-based whirlwind questions treat different facets of animal survival: procreation, domestication, life cycles, behavior, and so on. The lion whirlwind question focuses on the feeding and care of wild creatures. Matitiahu Tsevat discussed the passage and noted, “Man is not wont to give much thought to the food supply of wild animals, but it is a problem all the same. Would Job assume the responsibility of providing food for one of their kind who normally has no difficulty in getting what he needs?”6
The lion question that challenged Job continues as a current question in conservation science. Modern society has so altered the planet that knowing how to “feed” the lion takes on additional importance. Let’s rephrase the whirlwind question as, “Can you assure the survival of a dramatic, large predator, such as a lion, which occupies the top tier of the food chain?” This is a central issue in conservation ecology.
In a changing world, the preservation of creatures such as the lion is one of the hardest cases to solve. Such top-tier predators require vast landscapes. Strategies to preserve such animals are sensitive to all sorts of changes, including climatic change. The lion is such a striking creature that its survival commands the public’s interest—these are symbolic and charismatic animals. For a modern conservation scientist, feeding the lion (or the tiger, or the jaguar, or any large, fierce predator) is the ultimate challenge. This chapter will discuss why this is the case and why this already difficult whirlwind question is becoming increasingly more so in a changing planet.
Caring for large predators in the wild is challenging for several rather obvious reasons. First, although it may not seem that way to us when we step on a scale after the festivities of a holiday season, warm-blooded animals are relatively inefficient at converting food into animal tissue. This is particularly the case for herbivores converting plant tissues. Carnivores, animals that eat animals, are more efficient, but it requires a remarkable amount of plant production to feed the prey species that in turn are eaten by a predator and thus provide food energy for the production of predators.7
PATTERNS OF FOOD CHAINS AND FOOD WEBS: WHY IT’S LONELY AT THE TOP
A classic study of the ecology of an abandoned farm field in southern Michigan calculated the energy transferred by feeding from plants to rodents to weasels.8 The result is called a food-chain analysis. To produce a unit of weasel increase (least weasel, Mustela nivalis) requires the production of 45 units of rodents (meadow voles, Microtus pennsylvanicus), which in turn requires 377,000 units of production of plant material.9 So the efficiency of producing weasels from rodents is 1 unit of weasel produced per 45 units of rodents eaten, a production efficiency of 1/45 or about 2 percent. Considering a range of mammalian and avian carnivores in a variety of places, this number varies from around 1 to 3 percent.10 In so-called cold-blooded animals (poikilotherms), the efficiency is higher: around 10 percent on average for fish, 10 percent for social insects (bees, wasps, etc.), 25 percent for nonsocial insects, and 36 percent for other invertebrates.11 These results imply that food chains with some or all of the links featuring cold-blooded animals potentially could have more links than food chains composed of vigorous warm-blooded animals, such as lions and their prey.
It requires a remarkable amount of plant productivity to support a population of warm-blooded, small carnivores such as weasels. A carnivore that feeds exclusively on weasels would be rare simply because it would take a very large area to support the plants that produce the food that feeds the mice that feeds the weasels that feeds the “weaselvore.” Without launching into a chorus of “There was an old lady who swallowed a fly…,” a body of very interesting theoretical work in ecology illustrates just this point: the number of steps in a food chain toward some ultimate predator has limits.12 As a rule of thumb, it takes the productivity of ten thousand kilograms of prey to sustain ninety kilograms of carnivore, regardless of the size of the carnivore species.13
The details of just how many steps a food chain might have in a particular location and the underlying causes for the different lengths and other features of food chains remain a topic of active discussion among ecologists.14 One of the earliest concepts was that since the amount of food available for each link in the food chain was less at each step, as is the case in the Michigan old-field example, there necessarily would be fewer weasels than rodents. One would also expect that the size of the individual predators generally would be larger than that of their prey, with the exception of pack-hunting predators. Thus, the biological limitation on the body size of the top predators could also limit the length of food chains.15 Food webs, a more complex rendering of the way food energy moves through natural systems, would appear to have the same features—both reduced energy inputs and larger animals higher in the food web.16 Food webs provide greater detail on the transfers of food energy in cases in which predators feed on more than one prey or in which omnivores feeding on both plants and animals are important.
Who Runs the Ecosystem?
The patterns of food chains and the dominant factors controlling these patterns have significant implications in the responses of ecosystems to change.17 One line of logic suggests that the predators at the top of a food chain control the numbers of herbivores so that they cannot become dense enough to overgraze the plants.18 This has two significant implications: First, removing the top predator could permit overgrazing by the herbivores. When they have eaten all the vegetation, there is a collapse from starvation. Second, if herbivore grazing is controlled by the predation of the top carnivores in this way, then a “healthy” ecosystem features predators that keep the herbivore density relatively low. Consequently, the factors that control the vegetation would be mostly environmental factors such as climate or nutrient availability (and not grazing). This interpretation, referred to as “top-down” control, has been demonstrated in several ecosystem-level experiments.19
The alternative “bottom-up” control amplifies the observation that the plants control their being eaten by being relatively inedible, thorny, or poisonous to varying degrees. The world may appear to be green with plants, but it is not a gigantic tossed salad. Plants control the number of herbivores, and hence they control the food chains.20 This would imply that the pattern of vegetation would be largely influenced by environmental conditions. There is a repertoire of theories that either elaborate or mix the concept of top-down versus bottom-up control.21 It is not hard to imagine that one of these theories might be in action in one ecosystem but not in another or in the same ecosystem at one time and not another time.
In general, food-web theories point to the situation in which the abundance and productivity of plants respond mostly to environmental controlling factors. Does this imply that the techniques used to map the patterns of vegetation change in different climates (discussed in chapter 7) should work without consideration of the changes in the animal populations? The bottom-up theorists would say, “Yes,” and the top-down theorists, “No.” The understanding how food webs work becomes a question of importance in global change—how much of the vegetation is controlled by climate and how much by other local factors? This issue implies potential uncertainty in our capacity to predict the consequences of global environmental change on the vegetation.
Ecosystems with Lions
For protected ecosystems (parks) that have the African lion as a significant top carnivore, such as those located in Tanzania, Zimbabwe, and the Republic of South Africa,22 there is evidence for top-down control of the carnivores on the herbivores in some locations but not others.23 For these examples, in savanna ecosystems that support lions, the small- to medium-sized herbivores appear to be limited by predation, which would be the top-down control case. Large herbivores, the elephants and rhinoceroses, are not controlled by predation to any great degree or only in exceptional circumstances.24 Presumably their maximum densities are controlled by the amount of suitable vegetation available, the bottom-up control case. These megaherbivores are so large that they have minimal predation from even the top carnivores.25
For lions, sitting at the top of the food chain in the ecosystems in which they occur, rarity is a consequence of the amount of land required to convert energy through food chains to lions. To the degree that they control of the ecosystems in which they occur with top-down control, they are truly the “king of beasts”—a keystone species with great leverage on the overall integrity of the ecosystems in which they are found.
Potentially, a large decline of very large herbivores or large predators could have drastic effects on the African savanna ecosystem. Basically, the vegetation-controlled-by-climate case flips to being a predators-in-control case. Such a flip-flop effect has been postulated in past ecosystems in North America, causing what appears to have been a mass extinction of the “megafauna,” a diverse assemblage of very large herbivores and carnivores extant over ten thousand years ago.26
LIVING ON THE EDGE: ON THE CHALLENGES OF BEING A REALLY LARGE CARNIVORE
For lions, there is another aspect of food webs that must be considered in their management. In general, the animals at the higher levels of a food web need to be larger than their prey, but how much larger? If one considers mammal carnivores, two different groups that differ by size also differ strongly in the manner in which they feed. These differences in foraging behavior also influence the way they function in the ecosystems in which they occur:
1. Small carnivores, which weigh less than twenty kilograms per animal and feed on small prey (invertebrates and small vertebrate animals). Because they feed upon animals that are quite a bit smaller than they are, the relative energy costs for finding and capturing prey for small carnivores is relatively low. The animals cruise at a relatively slow pace through their feeding area. When they find small insects or mice, they capture and eat them with dispatch. Small carnivores that feed primarily on prey similar to their size are rare.27
2. Large carnivores, which weigh over twenty kilograms per animal and eat large vertebrate herbivores.28 They prey on animals that are much closer to their own size. Some of their prey are quite dangerous—armed with horns or antlers and disposed to kicking and fighting when captured. Many of them can outrun large carnivorous predators once they get up to speed. Large carnivores expend considerable energy running down prey animals. Subduing and killing the prey and, in some cases, dragging it back to their lairs costs even more energy.
Large and small carnivores use two essentially different strategies to obtain food. Obtaining a dependable, even if small, payoff using a small energy output is the strategy of the small carnivores. High-rolling large carnivores wager large energy expenditures in capturing their prey in hopes of getting substantial payoffs when they bring down large prey animals.
There is little choice in these matters. Basically, it would be difficult or impossible for lions to make a living by solely hunting mice and insects given the typical densities of these small prey creatures. On theoretical grounds, the payoff going after larger prey versus capturing small prey switches when the carnivore species weighs around fifteen kilograms.29 This prediction is close to what appears to be the body-size boundary (at around twenty kilograms), which separates large-and small-carnivore feeding strategies.
One possible limitation to the number of lengths in a food web is the maximum possible size of the top-of-the-food-chain supercarnivore, such as the lion. Lions are animals weighing 142 kilograms on average.30 Their daily energy expenditures are such that they have to kill an animal(s) of relatively similar mass as theirs on average once a day.31 Lions have a relatively narrow margin between the food they must consume and the energy they must burn to obtain their sustenance.32
The attractiveness of domesticated animal herds with relatively more docile prey to large predators is obvious. However, lion predation on pastoral herds carries substantial risks. It has been estimated that in Kenya ranchers alongside the Tsavo National Park each lose US$290 each year to livestock eaten by lions.33 The comparable number for Waza National Park in Cameroon is US$370.34 These numbers are about 35 percent of the average per capita income in each country.35 From these simple economics, it is small wonder that one of the principal sources of lion mortality is persecution by humans.
Lions partly maintain their energy budgets with behaviors that conserve their energy. They spend over 90 percent of their time inactively: sleeping and looking regal.36
CAN WE FEED THE LIONS?
The Joban whirlwind question could have hardly focused on a more challenging creature for humans to feed, protect, and preserve than the lion. One must pump a remarkable amount of energy through a food web to maintain a lion at the top. If the area of a wildlife preserve is too small, the plant production at the base of the food web is only large enough to support a few lions. Small populations of any animals have several problems. If the populations are too small, there is a chance that “luck of the draw” will produce fewer females than males. This in turn reduces the number of reproductive females, reduces the potential rate that lion cubs are produced over the entire population, and thus reduce the numbers in the population.37 Small, inbreeding populations also tend to lose their genetic diversity over time. This produces a number of effects, such as the increased chance of recessive deleterious genes decreasing the overall hardiness of individuals in the populations. Lion prides on average have four to six adult animals. Lions need populations of fifty to one hundred lion prides to maintain the population’s genetic diversity. Inbreeding becomes a significant issue in populations of fewer than ten prides.38 These conditions are now met in only seventeen large reserves found across Africa, the “lion strongholds.”39
As to our current state of tending of the lions in natural settings, the population seems to be decreasing over Africa. The numbers of lions are thought to have decreased by about 30 percent over the past two decades, and the species is listed as “vulnerable” on the International Union of Conservation Networks “Red List.”40 This is despite the efforts of some remarkably capable and dedicated wildlife ecologists and range managers working to maintain lions, which are major tourist attractions for visitors to African national parks. The source of the decrease appears to be the killing of lions to avoid loss of human life and livestock as well as decreases in the prey species that feed the lions.
Extinction of species is a part of the Earth’s biological history. What appear to be more-or-less periodic catastrophes have been associated with mass extinctions of higher forms of life. These cycles are associated with exceptional occurrences (volcanic eruptions and other tectonic events, changes in sea level, reversals in the magnetic poles, and large prehistoric meteor impacts). These cataclysmic events’ periodicity may derive from the movements of our solar system with respect to the Milky Way’s galactic plane.41
The largest extinction “event” occurred 245 million years ago (in the Permian period) when known genera of marine animals dropped by around 80, and perhaps as much as 96, percent.42 At the end of the Cretaceous period, sixty-five million years ago, the “End of the Age of Dinosaurs” involved the extinction of approximately half of the living genera at the time, including microscopic aquatic plants and animals of a variety of kinds, marine and flying reptiles, and dinosaurs.43 However, other land plants, crocodiles, snakes, mammals, and many kinds of invertebrates managed to survive.44 There will likely continue to be differences of opinion as to the cause. An asteroid impact or violent volcanic eruptions have been suggested.45
The diversity of the species of plants and animals on our planet is the heritage of thousands of millions of years of evolution. We would be wise to preserve this heritage. We have precedents for the potential of humans to eliminate remarkable number of species both in prehistoric and historical times—so much so, that the actions of our species have been termed the “Sixth Asteroid,” likening human action on planetary biodiversity to the great extinction events in geological history. Often in conjunction with a change in climate, humans colonizing and expanding across landscapes have generated substantial drops in the biotic diversity of the Earth. The impacts of humans on lions and the difficulty guaranteeing their survival as a species exemplify a microcosm of the difficulties in preserving biotic diversity in a world with shrinking habitats and other human actions on natural systems. Climate changes working in concert with human pressures on Earth’s systems only exacerbates this problem. The role of humans and the complexity of understanding the causes of decreases in biotic diversity can be seen in examples from the recent past and from the recent geological epoch, the Pleistocene.
The Pleistocene epoch started about 2.5 million years ago and lasted until about 12,000 years ago. Continental movement was likely less than one hundred kilometers over the entire epoch, and the continents were more or less in the same position then as now for the entire Pleistocene. Nonetheless, this was a very dynamic time in the Earth’s history in terms of climate. Glaciations (“ice ages”) that covered as much as 30 percent of the planet’s surface with ice alternated with interglacial periods when the extensive ice retreated. There were also minor fluctuations in the glaciers, called stadials for advances and interstadials for retreats. During the most recent of these glaciations, extensive continental glaciers up to three kilometers thick covered much of the Northern Hemisphere. Mountain glaciers in the Southern Hemisphere were much more extensive than today. So much water was tied up in this ice that the seas stood one hundred meters lower than they do at present.
The end of the last glaciation produced a substantial extinction of large animals in Eurasia, the Americas, Australia, and elsewhere.46 Because of their size, these creatures are called the “megafauna.” For example, in North America about ten thousand years ago, almost forty genera of large North American mammals became extinct during what appears to be a relatively short interval of time.47 Accounts of the megafaunal species stir the imagination.48 Carnivores including huge bulldog-faced bears, saber-toothed tigers, cave lions, dire wolves, dog- and hyena-like animals of various sorts were distributed through Europe, Asia, and North America. An equally diverse array of herbivores, such as long-necked camels, beavers the size of modern bears, horned giraffes, giant armored armadillos, and ground sloths as large as elephants, all grazed on vegetation in the Americas and Eurasia that today supports nothing even resembling such creatures.
A zoo full of the species of large Pleistocene mammals would need to be over twice the size of today’s zoos. Near the end of the Pleistocene, over half of the species of large mammal herbivores in North America, South America, and Australia became extinct. Thirty-seven percent of the large herbivores were lost from Eurasia. However, Africa, where humans evolved in the presence of these large animals, saw only about a 10 percent loss of species.49 Climate change, actions of prehistoric people, and the coincidence of the evolutionary turnovers of species are all candidate causes for this extinction,50 but these could very well work in concert with one another.51
Modern megafauna, notably the elephant, strongly alter the habitats in which they occur. From direct observations in Africa and Asia, the effect of elephant herds and other large herbivores on vegetation structure and composition is significant.52 Elephants in Africa are a major factor in altering dominant tree species and the very nature of the vegetation. Grasslands are converted to closed canopy woodlands where elephants are excluded. It is likely that the effect of the extinct megafauna on the past vegetation in other regions was equivalently substantial. The recent disappearance of so many large mammals would have altered the Earth’s vegetation and the kinds of plants that one would expect to be successful.
The large mammal extinction is called the Late Quaternary Extinction.53 It occurred worldwide. However, the extinction occurred at different times depending on the location. Overall, half of the 167 genera of large animals (animals heavier than forty-four kilograms) found on the Earth’s continents became extinct.54 The loss of the megafauna was quite abrupt in North and South America as compared to Europe. The temporal variation in the location of megafaunal extinction supports a premise that the migration of humans out of Africa had an important role in the extinction of these creatures. The extinction occurred at different times on different continents and islands and correlate with the successful migration of humans to a particular place. In what has been termed a “dreadful syncopation,”55 Homo sapiens arrives in a location, and large mammals and other animals become extinct there.
Examples of this syncopation give an impression of the magnitudes of these changes and endorse the power of Stone Age people to modify species diversity over very large areas. There has been what a long prehistory of human expansion across the world and a disappearance of large animals correlated with this expansion. The details of how this might work are topics of new discovery and debate and a marvelous example of the scientific process.
EXTINCTION OF THE NORTH AMERICAN MEGAFAUNA
In a scientific debate over the interpretation of complex data and with new data constantly being acquired, it is sometimes useful to step back and take inventory of what is known. Globally, and clearly in North America, for the past two million years climate variations have driven ice ages with continental-scale glaciers a couple of kilometers thick moving south to as far as 40°N latitude. These glaciations were periodically terminated with significant glacial retreats called interglacials. We are living in such an interglacial now. We have no expectation from geological considerations that this long-term periodic cycle of change will end in the next million years or so.
The last retreat of the glaciers about 12,500 years ago was attended by a colossal extinction of very large land animals, an event that did not happen during any of the previous glacial retreats. There were large-animal-hunting people in North America before the apparent time of this extinction and at the end of this glaciation. This was a unique aspect of the last glaciation/deglaciation cycle. Thus, humans are a logical suspect as being the cause of the unique megafaunal extinction.
The Classic Explanation of the North American Megafaunal Extinction
Before discussing the complications and excitement caused by recent archaeological findings, it is useful to consider the “classical” explanation of the role of humans in the decimation of the Pleistocene fauna.56 The Clovis culture, named after Clovis, New Mexico, where their artifacts were first found, hunted the megafauna, including the elephantine megaherbivores. Bones, often lots of them, of mammoths, extinct species of bison, mastodons, giant sloths, tapirs, paleo-llamas, and other large herbivores have been found in Clovis sites. Several factors are thought to have aided the spread of these hunters, notably, that the animals they hunted were naïve to the hunting practices that the Clovis people or their ancestors in Siberia had perfected in becoming mammoth hunters. Crossing through a newly formed corridor through the ice sheets that covered Canada about 13,500 years ago, they brought with them a willingness to hunt very large animals and the Clovis stone technology, which included large, doubly fluted spearheads. Clovis culture spread over North America, where most of their artifacts are found. There have been a few Clovis artifacts discovered in Central and South America, as well.57 Recent recalibration of carbon-14 dates for North American Clovis sites indicate that the material culture was in place starting between 13,200 and 13,100 years ago and lasted until 12,900 or 12,800 years ago.58 This has two significant implications. First, if these data are correct,59 the remarkable spread of the Clovis people across North America could have occurred in as little as two centuries and at the most four centuries. Second, the dates are close enough in time that it is difficult to interpret the pattern or direction of the spread of the Clovis.60
The Clovis hunters were seen as originating as a killing force in the far north of North America and then spreading southward in a wave toward increasingly better hunting grounds.61 They would prey on the local megafauna while increasing their own population density.62 The creativity of paleoecologists in unraveling past change is quite remarkable. Sporormiella fungi of different species grows on the dung of large terrestrial herbivores. The spores of these fungi spread through the air and are deposited in lake sediments, where they can be interpreted as indicators of large herbivore densities. In upstate New York, the spores are common in lake sediments until about 12,000 years ago, at which time they virtually disappear. They reappear with the advent of cattle with European settlement.63 This indicates a sudden demise of large herbivores—or at least of their droppings, although it is hard to imagine one without the other.
Computer models were constructed using data from Africa for large-animal densities and reproductive rates to approximate the recovery of the North American megafauna to hunting. From these, a small population of one hundred Clovis people originating in what is now in Edmonton, Canada, could theoretically roll south for a distance of 3,200 kilometers in under 350 years while eliminating megafaunal populations as they went.64 This is termed the “Overkill” or “Blitzkrieg” theory.65 According to the model, they could be at the tip of South America in as little as one thousand years, leaving a megafaunal extinction in their wake.66 This is the now “classic” conception of the role of human hunters in dispatching the North American megafauna.
As we have noted, the human role in the extinction of the North American megafauna is being debated scientifically in ongoing complex arguments. These are exciting times for understanding this event. There are also complications that have developed as we have learned more about the nature of the megafaunal extinction and particularly about the arrival of people to the Americas.
Coming to America
Human arrival to the Americas appears to be more complex than originally was thought.67 The seas were well over one hundred meters lower, and a large land area called Beringia connected Asia and North America. Rising seas from the meltwater of the continental glaciers flooded Beringia and formed the Bering Strait that now separates Asia from North America.
In the Pleistocene, two ice sheets, the Cordilleran and Laurentide ice sheets, joined and covered much of Canada.68 These ice sheets would have blocked entry to much of North America for any people who had crossed into Beringia from Asia. As it became warmer, the ice sheets retreated and separated. This created ice-free corridors: one corridor in the plains east of the Canadian Rockies, the other along the Pacific coast. The corridor between the Rockies and the plains opened about 13,500 years ago and allowed people to move south. Classically, this was thought to be the opening that allowed a land passage and the point of origination of the Clovis megafaunal-hunting culture.
Halfway down the coast of Chile about 13,000 years ago, a Paleoindian people produced fluted projectile points but not Clovis points. They hunted large animals at a lakeside site on the Andean Pacific.69 Even earlier, 14,000 years ago, at the Monte Verde site far into southern Chile in northern Patagonia, people built a complex of twelve rectangular rooms made of planed logs with a roof of mastodon hides.70 An adjoining egg-shaped structure may have had a religious function. From their refuse, the people ate wild potatoes, perhaps with salty seaweed, brought from the coast thirty kilometers away. They used (and discarded) medicinal plants chewed as quids between the cheek and gum. Wooden mortars and grinding stones were used to process plants. Bones of six mastodon-like gomphotheres found at the site imply that the people obtained meat by either hunting or scavenging large animals. There are several other sites in South America that date before the time of the Clovis culture and before the mid-Canadian corridor was open.71 The same case holds for early North American sites.
In North America, there are also sites that date prior to the Clovis culture. Recently, excavations at an archaeological site in central Texas, the Debra L. Friedkin Site on the Edwards Plateau, was shown to be an extensive pre-Clovis site with 15,528 human stone artifacts overlain by younger strata with Clovis tools.72 The importance of the find is that the Clovis and pre-Clovis material were found together. This pre-Clovis “Buttermilk Creek Complex” dates between 12.8 and 15.5 thousand years ago. Artifacts with similar Clovis/pre-Clovis stratification and dates have also been found at the Gault site, which is also on the Edwards Plateau.73
These findings lend credence to the antiquity of archaeological material from other sites with pre-Clovis strata found scattered over North America: stone tools and debris dating to 14.2 and 14.8 thousand years ago occurring in Kenosha County, Wisconsin, found along with the remains of two mammoths;74 tools dated between 13.4 and 15.2 thousand years ago from the Meadowcroft Rockshelter in Pennsylvania;75 human coprolites found at Paisley Caves, Oregon, dated from 14.1 thousand years ago;76 and a small number of flakes appearing at Page-Ladson, Florida, in strata with associated organic matter dating to 14.4 thousand years ago.77 Other sites in Cactus Hill, Virginia, and Miles Point, Maryland, provide additional dates and put human presence on the continent a few more millennia earlier.78
From such data, people seem to have occupied the area that is now the continental United States for at least 15,500 years. The earliest cultures known to date produced bifaces (two-sided stone tools), stone blades, and bladelets. Their early occupation of North America provided them with ample time to settle into the environments of North America and to have colonized South America by at least 14.1 to 14.6 thousand years ago.79 This pre-Clovis, earlier human presence also opens the possibility of other arrival pathways. These early humans in the Americas could not have come to America through the corridor between the Cordilleran and Laurentide ice sheets. It opened too late, 13,500 years ago.
As was mentioned earlier in this section, there is another route, which would have been open as early as 15,000 years ago. It lay along the northern Pacific coast, but traveling this route would have required the use of boats.80 We know that people in North America used boats as early as 13,000 years ago because of the human remains from that time found at the Arlington Springs site on Santa Rosa Island off the coast of California.81
If the pre-Clovis people used boats to travel the northern Pacific route, this would solve the problem of finding evidence of people in the Americas too early. However, it also opens up other possibilities of ocean-based colonization routes. The technology of the production of Clovis fluted points is similar to that of the European Solutrean culture, the culture associated with the cave paintings of aurochs and other large mammals in the French Lascaux caves (discussed in chapter 2). The Solutrean inhabitants of northern Spain made stone tools that have a strong resemblance to Clovis tools. Significantly, they used the same technology in their production.82 The Solutrean culture is more than six thousand years older than the dates of Clovis material, and they were living on a different continent.
In era of the Solutreans, who lived during the harsh Late Glacial Maxima that occurred between 22,000 and 16,000 years ago, there was an ice bridge that connected Europe and North America. If some Solutreans were skin-boat, ice-edge hunters with a lifestyle similar to that of modern Inuits, Aleuts, and Eskimos, then they conceivably could have crossed the distance from Europe to America.83 The distance to North America from Europe across this ice front is comparable to the distances (c. 2,500 kilometers) that the Thule Inuit people now travel in skin boats between Greenland and Alaska.84
Such travel across the North Atlantic would put people in North America very early. It would conform to the still controversial reports for the oldest dates of several eastern North American sites (such as Cactus Hill and Meadowcroft Rockshelter).85 These people would then have had ample time to perfect the Clovis technology and rapidly emerge, perhaps by a cultural transfer of the Clovis technology, as a widespread culture. As will be discussed below, the genetic evidence for such colonization is, at least, not yet found in the genes of Amerindians.
One aspect of very early humans in the Americas is that their appearance seems not to have been particularly like that of modern Amerindians. An example is found in the analysis of human skulls found in caves and rock shelters at a site in central Brazil.86 These skulls are dated older than 11,000 years ago. When their measurements are compared to the measurements on a reference collection of skulls from all over the world,87 the most similar modern skulls are from Easter Island in the Pacific. The skulls of “paleo-Americans” in general are often different from those of more recent Native Americans88 However, the genetics of modern Native American people indicate that they share a common genetic origin.89
From the current genetic analysis of a large sample of Native American people from North and South America, it is believed that they spring from a single population originating in Siberia. This group then moved toward the Americas across Beringia, likely less than 22,000 years ago.90 The subsequent dispersal of these people south from Beringia into the Americas seems have involved a founding population of fewer than five thousand individuals.91 There is no genetic evidence found in Native American people for a European ancestry. However, the genetic record does detect dispersal of Eskimo-Aleut people from northeastern Asia at a later time.
People appear to have been living in western Beringia 32,000 years ago. There were no glacial sheets to block their movement through western Canada during this relatively warmer time. However, there is no current evidence that they moved south at this time.92 Current patterns indicate that people came to America via the Pacific sea route around 15,000 years ago. The Clovis culture could have been a second entry of people of the same genetic stock through the interior passage about 13,500 years ago.
The Clovis also may have represented the perfection of a hunting technology among the people already living in North America. The Clovis technology could have spread as an innovation transferred to established human populations. Or it could be the result of the population growth of the successful Clovis culture resulting from their success as megafaunal hunters. The Clovis culture very likely was involved in the extinction of the North American megafauna. The details of the way that all of this developed remain a topic of very active research and discussion. Before concluding this section, it is useful to outline some of the other theories that have been posited as to the cause.
Other Theories on the Pleistocene Extinction
There are alternative theories as to what might have happened to cause the megafaunal extinctions as well as new refinements to the classic blitzkrieg concept. The use of fire as a hunting and management tool, which was described in chapter 2 as “fire-stick farming” in its use by Australian Aboriginal people, could have had a role in the disappearance of the megafauna.93 Fire appears to have had that role in the earliest colonization of Australia about 45,000 years ago, which will be discussed below. Another theoretical consideration would involve the changes in the nitrogen cycle at the end of the Pleistocene, putting the megafauna under nutrient stress.94
One of the early alternatives to the overkill theory is that there was a “hyperdisease” that arrived with the humans or dogs in North America. This conjectural disease wipes out the megafauna or enough of them that their extinction becomes highly likely. One can reason that the megafauna would be struck more strongly than other animals is because their relatively lower birth rates would slow their recovery from the disease.95 The disease would have a high infection rate and a high lethality. It would also need to be able to infect animals of several different and not closely related species. Within a species it would infect both sexes and all age classes. It would also need a reservoir species (humans?) that could harbor the disease after it had infected and thinned the local host populations.96 The disease organism that might have caused this extinction is not known. If it existed, it is unlike any extant disease. Rabies might be a possible example of such a disease, but it has a low infection rate.97
In addition, the effects of human hunting could have been amplified by food chain effects. Worldwide, human pressures have caused the extinction of elephants and their kin.98 The extinction of the largest of the megaherbivores could have changed the grazing patterns and provided an initiator for further extinctions.99 Human hunting also could have caused other predators to switch to other prey as the larger animals became reduced in number, with an associated collapse in the herbivore community followed by a collapse of the predator population. The loss of the elephantine keynote species, in conjunction with climate change and modest levels of human hunting, could have then produced a diversity collapse.100 Currently, there appears to be a worldwide “shortening” of food webs (loss of the predators at the top of the food web) and an increase in herbivores and associated increased grazing pressure.101
A highly interdisciplinary and controversial theory postulates that an extraterrestrial event, a collision with an asteroid cratering into the melting continental glacier somewhere north of the current U.S./Canadian Great Lakes caused the megafaunal extinction.102 This asteroid impact is postulated to have occurred 12,900 years ago, wiping out the megafauna and disrupting the Clovis people that hunted them. This latter theory provides a large number of testable consequences that involve rather precise timing, feeding the scientific controversy over dating of various finds from the past.103
Complications from Climate Change
One obvious consideration that occurred at the time of the megafaunal extinction was the significant change in the climate as the world transitioned from a glacial to an interglacial condition. Several scientists have proposed this change as the underlying cause of the megafaunal extinction event.104 The end-of-Pleistocene climate change would produce changes in vegetation and in the ecological systems and would stress the megafaunal populations. The wild horses and onagers in Alaska (Equus ferus and E. hemionus) showed a decrease in body size, indicating an environmental stress effect on the population while headed for extinction in North America.105 Beringean steppe bison (Bison bison occidentalis) in Alaska had a similar decline in size.106 Would these species and others have recovered and survived without human pressures? This is really hard to know. There are events that look like natural experiments that perhaps provide insight but still do not answer the question. For example, dwarfed versions of the North American giant ground sloths living on islands survived well past the extinctions of the continental species,107 only to perish with the arrival of humans to the islands. This certainly demonstrates the power of people as agents of extinction, but it does not prove that the extinctions on the continent would have happened without climatic change.108
Of course, it is possible that the influx of human hunters along with a major climate change was the “double whammy” that wiped out the megafauna, which had been exposed to global climate change at the ends of previous ice ages without the massive extinctions.109
The classic interpretation of a wave of Clovis hunters arriving across the Beringian land bridge from Asia and “overharvesting” the megafauna in a wave of colonization is subject to some conditions. There were people in North America before the appearance of the Clovis hunters, and they were hunting (or perhaps scavenging) large mammals. This complicates the idea that the Clovis people were hunting a naïve fauna that allowed them to close the distance on their prey. From observations of the reintroductions of wolves in the western United States, there is evidence suggesting that prey populations alter their feeding habits and habitats fairly quickly when a predator population is introduced.110 Significant ecosystem perturbations from people and/or from the climate changes that were occurring could have produced feedbacks that amplified the negative effects of human hunting. Other aspects of human presence on the landscape, such as increased wildfires, could have made a bad situation for the megafauna worse. At some point, domesticated dogs that would have also come over from Asia with people (see chapter 2) could have had a role in the megafaunal extinction. Generally, hunters with dogs are remarkably more effective than hunters without them.111
Taken in its entirety, the evidence indicting humans as agents of the megafaunal extinction are strong, all the more so if the human effects are accompanied by other factors.112 There may not be enough evidence to convict humans of causing the megafaunal extinctions, but there is certainly enough evidence to hold them without bail while rounding up the other suspects.
THE EXTINCTION OF THE AUSTRALIAN MEGAFAUNA
Forty-six thousand years ago in Australia, another continental-scale extinction event involving large mammals along with large birds, giant carnivorous lizards, and big snakes seems to have occurred.113 A large and genuinely amazing collection of creatures are not found after this date. Some of these extinct mammals were monotremes, egg-laying mammals that are today represented solely by the platypus and the echidna (spiny anteater). The rest were marsupials—mammals that carry their babies through the latter stages of their development in pouches. The largest of these was Diprotodon opatum, a large rhinoceros-like marsupial. Males were three meters long, two meters tall at the shoulder, and weighed up to 2,800 kilograms. Females were quite a bit smaller, about half the size of the males. It is a bit difficult to imagine these giants carrying their babies in pouches, but female skeletons have been found with babies located where the mother’s pouch would have been. Related to huge extinct Diprotodon, there were a smaller (but still large) now-extinct species. Zygomaturus trilobus measured two meters long and one meter tall at the shoulder and may have had a short trunk. Its habitat was thought to be wetland ecosystems, where they foraged by shoveling up reeds and sedges using two forklike incisor teeth. Another diprotodontoid was Palorchestes azael (sometimes called the marsupial tapir). It was similar in size to the Zygomaturus and had long claws and a long trunk. The nearest living relatives to all these creatures are the koala (Phascolarctos cinereus) and the three living wombat species (Vombatus ursinus, Lasiorhinus krefftii, L. latifrons).
Along with these large (over a thousand kilograms) marsupials were many species of large and strange kangaroos. Procoptodon goliah (the giant short-faced kangaroo) was the largest of these, standing at two to three meters tall and weighing up to 230 kilograms. P. goliath had a shortened flat face with forward-looking eyes, which provided it with stereoscopic vision. Its jaw and teeth were adapted for chewing tough semiarid vegetation. P. goliath was one of the seventeen species of kangaroos in the Sthenurine kangaroo subfamily (all now are extinct). Sthenurines were open-woodland creatures. All the toes on the leg (or hindlimb) were vestigial except for an extremely well-developed, hooflike fourth toe. Their forelimbs were long and had two extra-long fingers and claws (unlike the small, stiff arms of modern kangaroos). These may have been used for pulling branches nearer for eating and for moving on all four limbs for short distances. Along with a brace of other extinct kangaroos, one of the stranger, now extinct marsupials was Propleopus oscillans (the “carnivorous kangaroo”), a large (seventy kilogram) rat-kangaroo with large shearing and stout grinding teeth. It may have been an opportunistic carnivore that could eat insects, vertebrates (possibly carrion), fruits, and soft leaves. There was an assortment of large wallabies, leaf-eating kangaroos, large versions of modern kangaroos, and oversized koalas.
There were also marsupial carnivores. Notable among these was a leopard-sized marsupial “lion” (Thylacoleo carnifex) with bladelike slicing teeth.114 It had the ability to use its tail and hind legs to stand as a “tripod,” leaving free its powerful forelimbs, which were equipped with opposable thumbs and retractable, sharp thumb-claws. The marsupial lion was almost certainly carnivorous and likely a tree-dwelling predator. From the geometry of its jaws, it had an extremely powerful bite, one comparable to that of a modern lion.115 Other marsupial carnivores included Thylacine cynocephalus, or the Tasmanian tiger, and a large version of the Tasmanian devil (Sarcophilus harrisii laniarius).
There were other very nasty carnivores as well, notably a large predatory lizard, Varanus priscus. It may have been over six meters long. Predictions of this lizard’s size, based on its fossil vertebra, have produced different estimates of just how big this animal was, depending on which living varanid lizard is used as a model to interpret its morphology.116 If V. priscus was built like the largest of its living relatives (the Komodo dragon lizard, V. komodoensis), then a large one would have weighed 1,940 kilograms.117 It is likely that this monster also was poisonous; the Komodo dragon is, and so are other related large varanid lizards.118 Other strange and dangerous reptiles included a terrestrial crocodile, Quinkana fortirostrum, with long legs, a length of five meters, perhaps more, and serrated teeth for slashing flesh.119 There were three species of omnivorous, flightless birds related to ducks. The largest, Dromornis stirtoni, was three meters tall and weighed five hundred kilograms. The other two, Bullockornis planei and Genyornis newtoni, were ostrich sized. If one throws in giant pythons six meters long (Wonambi naracoortensis) and a genus of huge terrestrial turtles (Meiolania) up to 2.5 meters long with a horned heads and spiked tails, then one has an Australian menagerie that would excite the most jaded zoo visitor.
These creatures are not found in the fossil evidence after 46,000 years ago, the time of the migration of people to Australia.120 There is a relative shortage of good sites for fossil preservation in Australia, and many of these species last were found at times that are quite a bit earlier than 46000 bp. This raises the possibility that they were already extinct when humans arrived. However, several species are found in fossil deposits dated from around 46000 bp but not later. Thus, the estimated age and the rapidity of the extinction of Australia’s megafauna should be considered a reasoned theory but not an established fact.121
Enter Humans, Stage Right
If it seems that getting people to the Americas might have involved the use of boats, the getting of people to the Australian continent certainly involved sea crossings by humans over long enough distances to require boats. Perhaps because of stereotypes in movies and television, there is a tendency to imagine that prehistoric “cave people” would have spent a lot of time banging rocks together, speaking in monosyllables, and generally slapping one another around. These people may not have had the Internet, but they were our species (Homo sapiens). They were fully equipped with the same cognitive capacities that we possess.
For people to get to Australia from southeastern Asia on the coastal route out of Africa, they would have had to make multiple ocean crossings. The longest of these is over ninety kilometers of ocean, even taking into account the lower sea level from glaciation. For Homo sapiens, these crossings are generally thought to have happened about fifty thousand years ago.122 At that time the oceans were one hundred meters or more shallower than today. Borneo, Sumatra, Java, and Bali were joined to the Malay Peninsula to form a continental land mass called Sunda. Similarly, Australia and New Guinea were joined by the lowered seas to form the Sahul landmass. Between these two mainlands was an archipelago of islands (Lombok, Timor, Buru, Sulawesi, Halmahera, Ceram, plus many more small islands). To get to Australia, H. sapiens must “island hop” across this archipelago. Indeed, H. sapiens was not the first human species to make some of these maritime crossings. Hundreds of thousands of years ago, Homo erectus manage to cross the ocean over the same archipelago at least as far out as the Flores Islands.123 H. erectus does not appear to have gotten to Australia.
The human arrival to Australia (or, more properly, Sahul) likely occurred between 42,000 and 45,000 years ago.124 This is a difficult time in the past to gauge, because carbon-14 dating methods produce variable results this deep in the past. These prehistoric sites are often dated by a suite of alternative methods. Reconstruction of past events from bits of fossil evidence is rarely a clear-cut enterprise. There is latitude for debate in specific cases of humans’ role in the demise of any megafaunal species for several reasons. Implication of humans in the megafaunal extinctions involves relatively precise timing of events in the deep past. Is the date for human presence in an area the earliest, or are there other remains of earlier humans not yet found? Similarly, the last fossil is unlikely to be the very last individual of the species.
So how long did a particular species “hang on” after its last fossil was produced? The processes that cause a fossil to form are not random. How does this affect the interpretation of the numbers of fossils and the timing of their deposition? Also, what are the details of how these extinctions occur? Were they a product of human hunting of the animals? Not just in the Australian case but in general, were the extinctions attributable to the animals brought by humans (dogs, rats, etc.)? Were the extinctions caused by the human technologies (ignition of wildfires, bows and arrows, etc.) that made humans a novel and effective predator? Perhaps virulent disease vectored to a native fauna by humans (or their animals) serving as a disease reservoir wiped out the megafauna. Potentially, could complex combinations of any these work in conjunction with climate change and other events?
The time of the disappearance of the Pleistocene megafauna was thought to have occurred with the arrival of humans. One hypothesis that fuses a variety of opinions about the causes of change in Australia, postulates an initial blitzkrieg-type extinction followed by a reduction of grazing and a buildup of plants that then provided fuel for wildfires, causing larger, hotter fires and significant long-term change in the vegetation.125 Supporting this hypothesis was the understanding that the major Australian megafaunal extinction occurred around 46,000 years ago,126 and there are indications of a change in the pattern of wildfires and a reorganization of the vegetation at about this time.127 Several scientists have argued against this model while at the same time endorsing a long-term deterioration of the Australian climate as the cause of the decline in Australian megafaunal diversity.128
In some senses, these issues turn upon timing of events quite a long time ago. There is evidence that in some regions in Australia humans and various megafaunal species seem to have lived on the same landscapes for quite long periods of time, perhaps thousands of years.129 There is and likely will continue to be argument on the causes of the loss of the Australian megafauna.
NO MOA, NO MOA IN OLD AOTEAROA: THE NEW ZEALAND EXTINCTIONS
People in hunting-and-gathering societies can produce manifest changes to their environment, probably to a greater degree than many people might imagine.130 Species extinctions that have occurred on remote islands in fairly recent times provide insight into the ways extinctions may have occurred in the past. Consider this account from Taylor, reporting on his observations in New Zealand:
Resting on the shore near the Waingongoro Stream I notice the fragment of a bone which reminded me of the one I found at Waiapu. I took it up and asked my natives what it was. They replied “A Moa’s bone, what else? Look around and you will see plenty of them.” I jumped up, and to my amazement, I found the sandy plain covered with a number of little mounds, entirely composed of Moa bones; it appeared to me to be a regular necropolis of the race.131
Taylor was reporting on finding the bones of moas, ancient flightless birds of the genus Dinornis and native to New Zealand. The tallest moas were three meters in height and weighed up to 250 kilograms. By comparison, the ostrich (Struthio camelus) is the tallest living bird at 2.5 meters. The smallest moa species were about the size of a large domestic turkey, about a meter tall and weighing twenty kilograms. Moas are known from a diverse array of remains including eggshells, eggs, a few mummified carcasses, great numbers of bones, and some older fossilized bone.132 The eleven moa species currently recognized occupied ecological niches usually filled by large mammalian browsing herbivores elsewhere.133 There is some evidence that they may have had relatively low reproductive rates. They usually laid only one egg at a time.134
Uniquely, they had neither wings nor even any residual wing bones. Moas were herbivores and had muscular gizzards for grinding plant material. They swallowed small stones into their gizzards to aid in this food grinding before digestion. These polished stones, which were up to five centimeters (two inches) in diameter, are called “gastroliths” and often occur in groups along with moa bones. Bones of the larger moas were confused with ox bones by nonscientist observers, at least on initial inspection.
The moas evolved after New Zealand broke away from a giant Southern Hemisphere continent called Gondwanaland between eighty and eighty-five million years ago. As the Tasman Sea formed as a growing separation between New Zealand and Australia, New Zealand’s fauna and flora were launched on an evolutionary trajectory independent from the rest of the world’s. Creatures that could not cross considerable distances over ocean waters could not spread to New Zealand. Snakes and mammals, which evolved after the separation, are not indigenous to New Zealand. Bats, which could fly there, and seals, which could swim there, were the only mammals on New Zealand before the arrival of Polynesian settlers.
The Maori, New Zealand’s Polynesians, arrived around one thousand years ago. They intensively exploited moas for food, feathers, bone, and skin from about nine hundred to six hundred years ago. Moa hunting subsequently declined, but opportunistic hunting of the animals continued until about 500 bp on the east coast of the South Island and on the western interior of the South Island until as recently as 300 to 200 bp.135 It seems possible that when Captain James Cook first visited New Zealand in 1769, moas (or at least one of the moa species—the upland moa, Megalapteryx didinus) may have still survived in the remote areas in the western part of New Zealand’s South Island.136 If so, these individuals would have been the last relics of their kind.
Because they were so unique and because they became extinct so quickly, moas and their sad recent history have piqued the interest of ecologists, paleoecologists, and paleontologists. Climatic conditions in New Zealand appear to have been relatively stable over the period that moas became extinct. Different causes could have worked to some degree in concert with one another to account for the abrupt disappearance of moas:
1. Forest Burning: Vegetation changed with the Polynesian occupation of New Zealand. This change is not easily explained by climate variations but appears to be a product of burning. Forest and shrubland burning appears to have reduced the prime habitat of many of the moa species. The main forest burning started around seven hundred years ago, so that it followed what current archeological evidence indicates as the most intensive stage of moa hunting.137 The east side of the South Island of New Zealand was burned most extensively. This habitat destruction seems to have occurred after the moa populations already were depleted. Large forest tracts remained in the most southern part of the island. Presumably, the presence of some suitable habitat could have sheltered small populations of moas.
2. Human Hunting: On the South Island of New Zealand, hunting appears to have been a significant factor in depleting the moa populations. In one location alone, six railway carloads of moa bones were sent to the bone mills at Dunedin.138 Polynesian settlements and artifacts increased at the time of the most intensive moa hunting (950 to 650 years ago). This was followed by an apparent decline in the Maori population and a societal transition to smaller, less numerous settlements.139 This pattern fits that expected for overexploitation of moas as food resource.
3. Introduced Animals: The Maori introduced the dog (Canis familiaris) and the kiore or Polynesian rat (Rattus exulans) to New Zealand. Either of these could have reduced moa populations by eating eggs from moa nests. The Maori may have brought pests and disease organisms from their chickens, which could have crossed over to eradicate moa populations. The possibility of using ancient DNA to identify past diseases of extinct animals is being explored.140 However, evidence of such diseases is difficult to determine directly from paleoecolgical or archeological remains.
The moas and the rate of their demise raise ecological issues on the vulnerability of species to human-caused changes—including altered vegetative cover of the landscape, change in the physical environment, and modification of the biota from eliminating some species (such as the moa) and introducing others (such as the dog and rat).
The number of moas killed by Polynesians and the numerous bones stored in known archeological sites are sufficient to indicate that hunting alone could have accounted for the disappearance of the moa.141 Modest rates of hunting can significantly reduce the population of an animal with a low rate of reproduction, as technological human societies have demonstrated by virtually eliminating the great whales of the oceans in about half the time interval postulated for the moa extinctions. Computer models of hunting human populations and moas indicate that the moa extinction could have occurred in as little as one hundred to 160 years.142
The demise of the moas on New Zealand is mirrored on other islands and is associated with initial human colonization. The prehistorical human colonization of the islands in Oceania is accompanied by compelling evidence for the extinction of vertebrates.143 The extinction of 20 percent of the world’s bird species were thought to be lost in the human colonization of the Pacific Islands.144 Around 350 BCE, Iron Age people migrated to Madagascar. Their arrival was followed by a decline in the megafauna, which included seventeen giant lemurs, some the size of gorillas; three species of pigmy hippopotami; large grazing tortoises; and “elephant birds” (Aepyornis spp. and Mullerornis spp.), the largest birds ever to have lived.145 The fungal spores indicating herbivore dung on the landscape dropped in lake sediments between 230 and 410 CE. This drop was followed by a substantial increase in charcoal in lake sediments, indicating a change in fire regime, a pattern found worldwide following human colonization.146 Some of the megafauna, including pygmy hippos, elephant birds, giant tortoises, and large lemurs, coexisted for one thousand years or more with human colonizers. As late as 1661, Etienne de Flacourt, the French colonial governor, reported eyewitness accounts of animals that could have been giant lemurs, elephant birds, and hippopotami. Indeed, hippopotami were reported in other accounts as recently as the early twentieth century.147 There is little argument that the advent of humans on islands can have a profound effect on the species found on islands.
What is to be learned from this? First, there is a refreshingly brisk discussion of the role of humans in the extinctions of a diverse array of animals in relatively recent geological time and at varied locations. From the point of view of the workings of science, this represents an excellent parable of the process of scientific discovery and debate.
Second, in the later Pleistocene epoch and in the epoch in which we now live, the Holocene, the record has featured a substantial increase in the extinction of animal species. Species are disappearing much, much faster than new ones are evolving to take their places. We have lost some species, such as the moas, that have been evolving for tens of millions of years. Human alteration of landscapes, hunting, and the variations in the world’s climate, along with other possible factors, are at the root of these extinctions.
The Joban whirlwind question, “Can you hunt the prey for the lion?” would have to be answered thus: we have eliminated the prey for the lion and with that elimination, we have put lions and lionlike creatures in grave jeopardy.148 This past in which human action and climate change act in concert and produce species extinctions does not convey pleasant omens for a future—with human activities altering the climate and human population growth increasing the pressures on the land’s resources.
Francis Galton produced an essay in 1865 (see chapter 2) that listed the attributes necessary to allow different animals to be domesticated: “I will briefly restate what appear to be the conditions under which wild animals may become domesticated; 1. They should be hardy…” In a chilling paragraph that immediately followed, he opined,149
It would appear that every wild animal has had its chance of being domesticated, that those few which fulfilled the above conditions were domesticated long ago, but that the large remainder, who fail sometimes in only one particular, are destined to perpetual wildness so long as their race continues. As civilisation extends they are doomed to be gradually destroyed off the face of the earth as useless consumers of cultivated produce.
If Galton were alive today, he might well be surprised that his prediction has moved so rapidly toward realization. The pieces of this sad future world are the wheat fields, corn farms, rice paddies, cattle feedlots, and so on that can be seen across much of the modern landscape. It does not require a powerful imagination to assemble these pieces to see into the monotonous but productive “Galton World.” The biotic diversity in Galton World would be the weeds, pests, and assorted vermin that are able to adapt and prosper in a land totally dedicated to cultivated production. It would require quite an innovative piece of salesmanship to create a travel brochure able to entice tourists to visit Galton World. Humanity needs to ask itself if we really want to go there; we are certainly on the way.
Somewhere in the trip through time toward Galton World, species begin to be lost.150 The past patterns in diversity loss are understandable in the context of human exploitation of the environment, and we have considerable evidence that climate change, particularly climate change on an already altered human landscape, can have catastrophic consequences for the biota.
HOW MANY SPECIES MIGHT WE LOSE?
We are far from a complete inventory of all the species on Earth, and the species that we have not named are often rare, inconspicuous, or found in very isolated locations. One estimate based on the projected changes in climate that are expected to occur by 2050,151 given our current and expected releases of carbon dioxide into the atmosphere, is that the number of species going extinct will be greater than 10 percent.152 It is important to note that these changes are not expected to occur by 2050 but are an estimate of the long-term consequences that might develop if the expected 2050 climate were to persist over a long period of time.153 The risk of extinction was calculated in several different ways, each representing theories on the expected distribution of abundances of species. For terrestrial species, the risk of extinction was estimated between 18 to 34 percent of the estimated five million terrestrial species based on the statistical models of the abundance of terrestrial species. This estimate amounts to a projected loss of 900,000 to 1.7 million species. This estimate has inspired a book compiling the scientific aspects of this projection under the title Saving a Million Species,154 in which a number of different scientific experts analyze the potential of such a monstrous loss of diversity. Needless to say, these extinction estimates are the subject of hot scientific debate,155 but other scientists have come up with relatively similar results using different methods.156
WHAT IS BEING DONE?
At present, our efforts to conserve biotic diversity have taken a couple of essential directions. One strategy is to conserve species by identifying and protecting critical areas or hot spots for biotic diversity. There are locations that thanks to a combination of biogeography, history, and lack of human utilization contain a remarkable proportion of the planet’s biotic diversity. These locations are “living arks” that could carry the planet’s biotic diversity forward into the future. Such locations are potentially vulnerable to climate change, particularly the drying and warming that is being predicted to be the response of the atmosphere to the increased loading of greenhouse gases as a consequence of human activities. According to the International Panel on Climate Change 2007 report, the last time the greenhouse gases in the atmosphere were as high as we expect to have by 2050 was three million years ago, during the Mid-Pliocene epoch.157 At that time global temperatures were 2° to 3°C warmer than today. Such temperatures occurring today could be expected to shift vegetation up mountains and necessarily shrink the area available for higher-elevation plants and animals. High-alpine ecosystems could be lost if the mountain tops became too warm to support them.158 The disruption to our systems of biological reserves under a 2° to 3°C climate warming could be considerable.159 These numbers are on the low range for the climate changes expected to come from human emissions of greenhouse gases in the coming century.
A second strategy for preserving biotic diversity is to focus on charismatic animals that appear to be keystones to different ecosystems and hope that the conservation of these will bring along the other associated species. The Joban whirlwind question regarding the lion implies this strategy. Perhaps our efforts with the conservation of lions are a microcosm of the challenges of this approach. It is difficult to guarantee the continued survival of lions as it is for many other large, beautiful, and dangerous species. These more species-oriented plans share the vulnerability to climate change.
There is also a mixed strategy in which one preserves species-rich locations hopefully to save the species found there and manages other areas to assure the survival of the species that we do know how to manage. One of the problems with rare species is that we often do not know enough about them to make ecological decisions on how to increase the likelihood of their continued existence. From the megafaunal extinctions of our immediate past we can easily infer what a laissez-faire approach to maintaining the biodiversity that surrounds us will bring—it will bring extinctions and lots of them.
By any reckoning, the Joban question about lions is as pertinent today as it ever was. Considering the story in its entirety, the Book of Job begins with Job as the owner of tremendous herds of domesticated livestock and as an inhabitant of an agricultural world, all of which he controls. Job is a denizen, a very important one, of an ancient version of Galton World, a landscape of human creation under human management. By the end of the account in the whirlwind speech, Job is chastised by God for his lack of understanding of the workings of nature and shown without a doubt that he is but a small piece of nature and not its centerpiece. As was discussed in the introduction, this “man-in-nature” motif is in sharp contrast with the “man-in-charge-of-nature” theme in other creation accounts in the Bible.
In this context, “Can you hunt the prey for the lion, or satisfy the appetite of the young lions, when they crouch in their dens, or lie in wait in their covert?” becomes a seminal question. If the answer is “No,” then we must recognize ourselves as being in nature, one more group of passengers on a planetary bubble whirling through an uninhabitable void, a bubble that must be maintained to survive. We necessarily must lower our planetary footprint, consume more efficiently, and err toward caution when we put our hand to change the planet and alter its parts. If the answer is “Yes,” then we must make certain that our care of the lions and of the nature as a whole that they symbolize is done in a way that can sustain future generations. We cannot tolerate errors in judgment over this hopefully long future. We must manage well and wisely. The past human history is not prologue for this enlightened management. The planet has lost and is losing species at a remarkable rate. The changes that we have made to our planet speak to how difficult it has been for us to shepherd the planet in past times.
Realistically, we probably do not have a good answer in either direction, a point that God hammered home to Job in the whirlwind speech. At our population density, saying “No” and hoping the planet will take care of us seems risky at best. Saying “Yes” implies a wisdom that we do not have and a will not manifested in our actions. We must find better answers than we have. Our future depends upon it.
