The Sixth Extinction

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Note: all page and citation info for the quotes below refers to the Picador edition of The Sixth Extinction published in 2015.
Prologue Quotes

The process continues, in fits and starts, for thousands of years, until the species, no longer so new, has spread to practically every corner of the globe. At this point, several things happen more or less at once that allow Homo sapiens, as it has come to call itself, to reproduce at an unprecedented rate. In a single century the population doubles; then it doubles again, and then again. Vast forests are razed.

Page Number: 2
Explanation and Analysis:

In the prologue to her book, Kolbert paints an eerie picture of the human race. Instead of writing in terms of “we humans,” Kolbert distances readers from their own species, portraying humans as a strange, even barbaric race: humans have colonized the entire planet, massacring other species, and permanently altering the surface of the planet, leading to a global environmental crisis.

The passage is important because it uses a literary technique called “defamiliarization,” in other words, portraying a familiar subject (here, the human race) in a strange or confusing way. Kolbert is writing about the human race and its connection to the Sixth Extinction, and she wants her readers to look at humanity with fresh eyes. Many of the human practices that Kolbert writes about, such as driving cars, using electricity, flying or sailing to other countries, etc., are utterly uncontroversial. And yet, by defamiliarizing humans, Kolbert allows readers to see how objectively bizarre their own species is. In this way, Kolbert allows us to understand how greatly we human beings have damaged our own planet.

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Chapter 1 Quotes

The history of life thus consists of "long periods of boredom interrupted occasionally by panic."

Page Number: 16
Explanation and Analysis:

In the long history of the planet, species tend to go extinct. Here, Kolbert succinctly describes one theory for the process of extinction, which combines two previously-dueling scientific ideas. These ideas, as Kolbert will go on to outline, are “uniformitarianism” and “catastrophism”—the former is the belief (following Darwin) that extinction occurs slowly as a result of natural selection, and the latter holds that there can be sudden and widespread extinctions due to catastrophic events.

This quotation is notable for two reasons. One is that it is the product of the scientific method at work. The two previous theories of extinction individually failed to explain the historical evidence, which was compelling when cherry picked to apply to each theory, but could never account for the evidence supporting the other theory. The combination of these two theories is a good example of the ways in which scientific thought advances. It often dialectically combines competing ideas in order to arrive at a theory that most compellingly explains the entire array of available evidence. This process emphasizes the “unfinished” nature of science—it is always evolving as new ideas and evidence arise. Second, this quote is important because it introduces a moral tone. By using the word “panic” to describe catastrophic phases of mass extinction, Kolbert is implicitly labeling the present day as a period of panic. It’s a strong and startling word to apply, and one that points towards the need for action.

Chapter 2 Quotes

By the middle of the nineteenth century, many of [Georges Cuvier’s] ideas had been discredited. But the most recent discoveries have tended to support those very theories of his that were most thoroughly vilified, with the result that Cuvier's essentially tragic vision of earth history has come to seem prophetic.

Related Characters: Georges Cuvier
Page Number: 25
Explanation and Analysis:

In Chapter Two, Kolbert discusses the life and ideas of a great French naturalist, Georges Cuvier. Cuvier is important in the history of naturalism because he was one of the first notable thinkers to propose that some animals go extinct over time. Cuvier examined the fossils of extinct creatures, and theorized that animals die out over time, leaving their skeletons to be discovered millions of years later. As Kolbert points out here, Cuvier had many incorrect ideas about biology and naturalism (notably, he rejected the theory of evolution). However, Cuvier’s theories about extinction have been proven correct by the evidence, making him an important figure in scientific history.

The passage is a great example of how new scientific theories—or, to use the terminology of Thomas Kuhn, “paradigms”—appear over time. Often, a scientific figure, such as Cuvier, will propose a new paradigm to explain the existing evidence. Cuvier’s paradigm—that some animals go extinct over time—was unpopular at first, but eventually, it became an accepted part of scientific discourse.

Another important thing to note about this passage is Kolbert’s use of the word “tragic.” Cuvier was, first and foremost, a scientist—his duty was to describe natural phenomena, not to pass moral judgments about them. But even if Cuvier took a more dispassionate view of extinction, Kolbert, in her book, views the Sixth Extinction, and extinction in general, through a moral lens. She argues that the mass-extinction of life on the planet is a tragedy, and she implies that human beings should try to prevent such a tragedy from continuing.

… if there were four extinct species, Cuvier declared there must be others. The proposal was a daring one to make given the available evidence. On the basis of a few scattered bones, Cuvier had conceived of a whole new way of looking at life. Species died out. This was not an isolated but a widespread phenomenon.

Related Characters: Georges Cuvier
Page Number: 30
Explanation and Analysis:

In this passage, Kolbert writes about Georges Cuvier’s most influential scientific insight. Like many naturalists of his era, Cuvier had studied the fossils of extinct animals and decided that these animals were no longer in existence. However, Cuvier went one step further with his analysis—he argued that there must be many, many animals that had once walked the Earth, but were now extinct. In such a way, Cuvier became the first major scientist to believe in a theory of extinction—the notion that, over time, species die out altogether.

It’s important to note that Cuvier’s theory, while a big step forward for Western science, wasn’t perfect. Cuvier recognized that animals went extinct, but he didn’t have a convincing explanation for why (Charles Darwin, writing more than half a century later, would provide one). All in all, Cuvier’s contributions to naturalism exemplify the importance of paradigms in scientific discourse. As Thomas Kuhn argued, a paradigm (like Cuvier’s idea of extinction) is never a dead-end—instead, a new paradigm raises new questions, and it challenges other scientists to develop new theories of their own (just as Cuvier’s extinction paradigm brought up a natural question for his colleagues to answer—why do some animals go extinct while others don't?). Science is a constant process of approximating the truth, with each successive paradigm doing a slightly better job of explaining the world than the paradigm before it.

Cuvier's essay was pointedly secular. He cited the Bible as one of many old (and not entirely reliable) works, alongside the Hindu Vedas and the Shujing. This sort of ecumenicalism was unacceptable to the Anglican clergy who made up the faculty at institutions like Oxford, and when the essay was translated into English, it was construed … as offering proof of Noah's flood.

Related Characters: Georges Cuvier
Page Number: 45
Explanation and Analysis:

In this interesting passage, Kolbert talks about how the European community in general interpreted Georges Cuvier’s theory of extinction. Cuvier, later in his life, tried to answer the question that his own theory of extinction posed: why do some animals go extinct? Cuvier’s answer to his own question was that some animals die in natural disasters and global catastrophes, such as floods and earthquakes. Cuvier’s discussion of floods prompted certain people, especially Anglican professors at Oxford University, to interpret his extinction theory as proof of the account of world history in the Biblical Book of Genesis—in other words, people thought that extinct species like mammoths and mastodons had died in Noah’s flood.

The passage is a good example of how the general public can misinterpret and decontextualize science to reconfirm their beliefs about the world. Implicitly, Kolbert suggests that it’s important for people to interpret scientific theories fairly and accurately, instead of distorting them to confirm what they already think they know. Authors like Kolbert herself play an important part in the scientific process: they “translate” scientists’ complex ideas for the lay-reader, ensuring that ordinary people understand what the scientific community has discovered.

Chapter 3 Quotes

Darwin's familiarity with human-caused extinction is also clear from On the Origin of Species. In one of the many passages in which he heaps scorn on the catastrophists, he observes that animals inevitably become rare before they become extinct, "we know this has been the progress of events with those animals which have been exterminated, either locally or wholly, through man's agency." It's a brief allusion and in its brevity, suggestive. Darwin assumes that his readers are familiar with such "events" and already habituated to them. He himself seems to find nothing remarkable or troubling about this.

Related Characters: Charles Darwin
Page Number: 69
Explanation and Analysis:

In this chapter, Kolbert discusses the life and ideas of Charles Darwin. Darwin played an important role in the history of extinction theory by arguing that species go extinct because they fail, for whatever reason, to reproduce (a process that Darwin famously summed up as “survival of the fittest”). However, as Kolbert argues in the passage, Darwin’s understanding of extinction wasn’t perfect. He recognized that species go extinct slowly and gradually, and he even recognized that human beings could contribute to extinction, but he didn’t realize that sometimes many species go extinct in rapid succession, and he certainly didn’t realize the magnitude of the implications of his acknowledgement of human involvement in extinction. Instead, Darwin treated human-caused extinctions as isolated, unimportant examples, an attitude that was reflected in the scientific understanding of extinction for many years afterwards.

While Kolbert has a lot of respect for Darwin, she makes it clear that Darwin’s ideas about natural selection were highly limited. For the century after Darwin’s death scientists continued to doubt that humans had the capacity to permanently their environments. It has only been in the last few decades, in fact, that the paradigm has changed—the scientific community now believes that humans have the power to cause mass-extinctions.

But how, then, to make sense of cases like the great auk or the Charles Island tortoise or, to continue the list, the dodo or the Steller's sea cow? These animals had obviously not been done in by a rival species gradually evolving some competitive advantage. They had all been killed off by the same species, and all quite suddenly—in the case of the great auk and the Charles Island tortoise over the course of Darwin's own lifetime. Either there had to be a separate category for human-caused extinction, in which case people really did deserve their "special status" as a creature outside of nature, or space in the natural order had to be made for cataclysm, in which case, Cuvier— distressingly—was right.

Related Characters: Georges Cuvier, Charles Darwin
Page Number: 69
Explanation and Analysis:

In this passage, Kolbert further explores the differences between Darwin’s theory of extinction and the modern scientific understanding of extinction. Darwin, who believed that animals go extinct simply because of the inevitable process of natural selection, was committed to the belief that human beings are “just animals” who obey the same rules of natural selection as other species. This belief—while held under the auspices of good, dispassionate science—blinded Darwin to the special role human beings play in species extinction.

While Kolbert accepts Darwin’s premise that humans, no less than other species, obey the laws of natural selection, she disagrees that humans are no different than other species. Instead, she argues that humans are unique in the history of the Earth, since they’re the only species that has ever altered its own environment so dramatically.

The modern theory of extinction is, in a way, a hybrid of Darwin’s belief that extinctions take place slowly and gradually and Cuvier’s theory that animals go extinct because of sudden catastrophes. Kolbert shows, then, that, Darwin and Cuvier were both right: sometimes, animals go extinct because of ordinary natural selection, and sometimes, they don’t. However, just because each had lasting ideas does not mean that all their ideas were equally valid.

Chapter 4 Quotes

Darwin's successors inherited the "much slow extermination” problem. The uniformitarian view precluded sudden or sweeping change of any kind. But the more that was learned about the fossil record, the more difficult it was to maintain that an entire age spanning tens of millions of years, had somehow or other gone missing. This growing tension led to a series of increasingly tortured explanations. Perhaps there had been some sort of “crisis,” at the close of the Cretaceous but it had to have been a very slow crisis. Maybe the losses at the end of the period did constitute a "mass extinction."

Related Characters: Charles Darwin
Page Number: 79
Explanation and Analysis:

In this passage, Kolbert describes the lead-up to a major paradigm shift in evolutionary science. In the decades following the death of Charles Darwin, scientists interpreted the theory of evolution to mean that animals went extinct because of the gradual process of natural selection. However, over time, it became clear that such an interpretation didn’t support the existing evidence. There were major gaps in the “fossil record”—in other words, it appeared that there were long stretches of planetary history in which there were almost no life forms. This evidence suggested that, at various points in the past, global catastrophes wiped out the Earth’s life—the opposite of the slow, gradualistic view of life that Darwin and his disciples favored.

The passage is a good example of the way that paradigms change over time. In the mid-20th century, naturalists tried to use the old, gradualist paradigm to explain the fossil evidence, but to no avail. Eventually, the evidence made it clear that science needed a new paradigm—a hybrid theory, according to which animals occasionally experienced mass-extinctions. It’s notable that Kolbert describes the gradualist attempts to fit an outdated paradigm onto new evidence as “tortured explanations” of the fossil record—this shows a major peril of scientific thought, which is the inability to let go of a bad explanation that has been heretofore accepted as truth. It’s important, then, for scientists to be more loyal to the scientific method than to the theories that have been previously posited.

Ammonites produced very tiny egg, only a few hundredths of an inch across. The resulting hatchling, or ammonitellae had no means of locomotion; they just floated near the surface of the water, drifting along with the current. Nautiluses, for their part lay very large eggs among the largest of all invertebrates, nearly an inch in diameter.

Page Number: 90
Explanation and Analysis:

In this passage, Kolbert discusses the extinction of a prehistoric animal, the ammonite. Ammonites resembled the modern-day nautilus in many ways—they had, for example, the same spiral-shaped shells. However, there is evidence to suggest that nautiluses survived the mass-extinction that took place at the end of the Cretaceous period of the Earth’s history, while ammonites went extinct around the same time. Here, Kolbert outlines the crucial difference, which is a seemingly small discrepancy between the egg sizes of each animal. That such a specific detail could doom one species and save another shows just how non-linear natural selection can be; certain biological qualities are evolutionary advantages at times, and disadvantages at other times. For millions of years, the ammonite’s small eggs helped the species survive (small eggs were more likely to drift far through the ocean, scattering ammonites across the globe). But after the extinction of the dinosaurs, small eggs became a huge evolutionary liability. As Kolbert says later in the book, past success is no guarantee of future results.

Chapter 5 Quotes

The history of the science of extinction can be told as a series of paradigm shifts. Until the end of the eighteenth century, the very category of extinction didn't exist. The more strange bones were unearthed—mammoths, Megatherium, mosasaurs—the harder naturalists had to squint to fit them into a familiar framework. And squint they did. The giant bones belonged to elephants that had been washed north, or hippos that had wandered west, or whales with malevolent grins. When Cuvier arrived in Paris, he saw that the mastodon's molars could not be fit into the established framework, a "My God" moment that led him to propose a whole new way of seeing them.

Related Characters: Georges Cuvier
Page Number: 93
Explanation and Analysis:

In this passage, Kolbert introduces the concept of paradigm shifts. Citing the ideas of Thomas Kuhn, she suggests that the scientific community has interpreted extinction using a succession of different theories, or paradigms. The first important paradigm for understanding extinction was Georges Cuvier’s: specifically, Cuvier’s theory that animals die out over time. Later paradigms included the Darwinian paradigm (that species die out because of the competition for finite resources), and the modern, hybrid paradigm that the Earth occasionally goes through phases of mass-extinction.

Kuhn argued that the scientific community makes progress over time by forming paradigms that explain available evidence and then testing them rigorously as new evidence appears. When a paradigm no longer does a good job of explaining all the available evidence, a new paradigm will arise that describes the known world better. Kolbert uses Kuhn’s ideas to suggest that, in the last 150 years or so, scientists have become steadily better at understanding the complex phenomenon of extinction; furthermore, scientists will continue to get better at understanding extinction in the future.

On the one hand, the paradigm is a generally accepted idea in the history of science. On the other hand, however, Kolbert’s book is a bit allergic to the idea of natural “progress”—it’s steeped in Darwin’s idea that natural selection propels change that is more about random circumstance than concerted improvement, and Kolbert is unwilling to entertain that humans are making progress, morally or logistically, in confronting their environmental challenges. Thus, it’s notable that Kolbert is able to concede the possibility of linear progress to the field of science alone. It’s unclear whether this is an assumption that is as rigorously examined as her others.

"Because of these anthropogenic emissions" Crutzen wrote, the global climate is likely to "depart significantly from natural behavior for many millennia to come."

Crutzen published "Geology of Mankind" in 2002. Soon, the 'Anthropocene" began migrating out into other scientific journals.

Related Characters: Paul Crutzen
Page Number: 108
Explanation and Analysis:

At the end of Chapter Five, Kolbert introduces the word, “Anthropocene,” which describes the “age of man.” The scientist Paul Crutzen argued that the modern era is defined by the behavior of the human race. Human beings, he pointed out, are the only animals in the history of the planet who have altered the face of the Earth so extensively. Humans block off rivers, cut down trees, expel billions of tons of carbon dioxide into the atmosphere, etc. As a result, the most accurate way to describe the modern era is to call it the age of man—in other words, the Anthropocene.

It is a mark of the newness of environmental science that Crutzen coined the word “Anthropocene” less than twenty years ago. The notion that humans have the power to irreversibly alter the planet is still fairly new. While virtually everyone in the scientific community believes in such an idea, it has yet to catch on with the general public. By writing The Sixth Extinction, Kolbert could play an important role in popularizing the new theory of the Anthropocene.

Chapter 6 Quotes

Ocean acidification increases the cost of calcification by reducing the number of carbonate ions available to begin with. To extend the construction metaphor, imagine trying to build a house while someone keeps stealing your bricks.

Page Number: 121
Explanation and Analysis:

In Chapter Six, Kolbert explores one specific aspect of the environment in which humans have played a major role: the acidity of the oceans. By emitting billions of tons of carbon dioxide into the atmosphere, humans have caused the oceans to absorb larges quantities of carbon dioxide; as a result, the oceans have become considerably more acidic since the dawn of the industrial Revolution, when humans began burning large amounts of fossil fuels, such as coal and gasoline. Because the oceans are becoming more acidic, certain creatures, known as calcifiers—i.e., marine creatures such as barnacles, clams, or oysters, who have a calcium-heavy shell or exoskeleton—are having a lot of trouble surviving.

As Kolbert notes later in the chapter, scientists only recently discovered that carbon dioxide emissions have a major impact on the acidity of the oceans. Now that the scientific community recognizes the impact of human technology on the oceans, it’s clear that humans are indirectly causing the mass-extinction of calcifiers, among many other marine species. Kolbert drives this point home with a literary analogy meant to provoke human sympathy for calcifiers (who are, themselves, without the characteristics that generally endear nature to humans, such as intelligence, cuteness, or essential utility for human life). It’s significant that Kolbert uses the verb “stealing” in the phrase “someone keeps stealing your bricks”; this strongly points a finger at humans (whose activities are corroding the calcifiers’ shells), implying that human activity is, in this case, violent and unethical.

Chapter 7 Quotes

Thousands—perhaps millions—of species have evolved to rely on coral reefs, either directly for protection or food, or indirectly, to prey on those species that come seeking protection or food. This coevolutionary venture has been under way for many geologic epochs. Researchers now believe it won't last out the Anthropocene.

Related Symbols: Great Barrier Reef
Page Number: 130
Explanation and Analysis:

In Chapter Seven, Kolbert explores another kind of ecosystem that’s being threatened by the advent of human industry: the coral reef. Near Australia’s Great Barrier Reef, Kolbert interviews scientists and researchers, who tell her that, if humans continue to pollute the atmosphere at their current rate, then the average ocean temperature will continue to rise to the point where the Great Barrier Reef—and almost any other coral reef—will begin to disintegrate.

The passage is a good example of the strong emotional tone that Kolbert adopts throughout her book. Kolbert is writing a serious science book: in this chapter, for example, she uses chemistry, biology, and ecology to study the erosion of coral reefs. However, Kolbert sometimes adopts a more overtly poignant tone. Here, for example, she conveys the unspeakable tragedy of the Sixth Extinction by stressing that, after countless years and epochs, human beings are going to destroy the Great Barrier Reef, one of the most beautiful things on the face of the planet. She also stresses the vast (and, perhaps, unknowable) ripple effects of destroying such a complex organism, which points to the foolishness of this human-fuelled destruction.

Chapter 8 Quotes

There are various ways to calculate migration rates: for instance, by the number of trees or, alternatively, by their mass. Feeley grouped the trees by genus. Very roughly speaking, he found that global warming was driving the average genus up the mountain at a rate of eight feet per year. But he also found the average masked a surprising range of response. Like cliques of kids at recess, different trees were behaving in wildly different ways.

Related Characters: Kenneth Feeley
Page Number: 159
Explanation and Analysis:

A team of scientists, including Miles Silman, and his student, Kenneth Feeley, are measuring the rate of natural selection in the rainforests of South America. One way of quantifying this is by measuring the rate at which temperature change pushes tree species to higher altitudes, which is an adaptive mechanism by which the tree species seeks out a temperature to which it is accustomed.

In short, Kolbert is describing a sped-up version of the natural selection process that Charles Darwin described in On the Origin of Species more than 150 years ago. As Darwin pointed out, species are in a constant struggle to adapt to their changing surroundings. However, Darwin believed that the environment changes at an incredibly slow, gradual rate. The rainforests of South America, on the other hand, are getting warmer year after year. In this sped-up scenario, the “stakes” of adaptation are extremely high: if species can’t find a way to migrate up the hill, it will die out. This is particularly frightening considering that, on average, a tree species must migrate eight feet per year—a stunning change for a species that we don’t generally consider to be mobile.

Kolbert’s “cliques of kids at recess” metaphor is also notable. For one, she uses it to humanize tree species, painting them as being similar to human children in their individuality. She also uses it to dramatize the significance of their migration—trees seem much more dynamic when their movements are compared to the choices and reactions of children at recess.

How many species overall will be capable of moving fast enough remains an open question, though, as Silman pointed out to me, in the coming decades we are probably going to learn the answer, whether we want to or not.

Related Characters: Miles Silman
Page Number: 162
Explanation and Analysis:

In this passage, Kolbert continues with her analysis of the mass-extinction taking place in the rainforests. Due to the escalating temperature of the ecosystem, species have had to migrate to new areas of the rainforest. While some species have been successful in seeking the cooler temperatures of their old environments, other species have failed to do so; as a result, they’ve begun going extinct. As Silman says in this passage, the future of the rainforests looks pretty bleak: species will be forced to adapt or die—and, in all probability, many rainforest species are going to die out altogether.

The passage is important because it conveys some of the inevitability of mass-extinction. Kolbert suggests that, after hundreds of years of burning coal and cutting down trees, the “damage is done.” In other words, no matter what the human race chooses to do from now on, species will continue going extinct. However, there are other passages of The Sixth Extinction in which Kolbert takes a more optimistic view of the future of mass-extinction. While it’s probably true that plants and animals will continue going extinct for decades to come, perhaps it’s possible that, by changing their behavior now, humans will be able to stave off the extinction of some species.

You could be studying a chain of islands or a rainforest or a nearby state park, and you'd find that the number of species varies according to the same insistent equation: S = cA squared.

Page Number: 166
Explanation and Analysis:

At the end of Chapter Eight, Kolbert introduces an important mathematical law. According to the law, there is a directly proportional relationship between the number of species on the planet (S) and the square of the amount of available space in which those species can live. Put another way, the more natural land human being develop and clear, the fewer total species there will be on the face of the Earth.

The species-area law is depressing for a number of reasons. Most obviously, the amount of untouched land on Earth is constantly decreasing—humans cut down trees, clear forests, burn fields, etc. As a result, the number of different species on Earth is always going down.

While Kolbert will discuss the precise reasons for the direct relationship between diversity and land area in the following chapter, the basic reason for relationship is clear: species need untouched land in which they can live safely. When humans destroy rainforests and burn fields, they’re indirectly causing thousands of animals to go extinct. The clarity of a mathematic formula, though, implies a solution: perhaps by “de-colonizing” developed land (by re-planting trees, introducing wild species, or other actions) humans could undo some of the damage that they’ve done to the environment, and increase the number of living species once again.

Chapter 9 Quotes

Smaller areas harbor smaller populations, and smaller populations are more vulnerable to chance. To use an extreme example, an island might be home to a single breeding pair of birds of species X. One year, the pair's nest is blown out of a tree in a hurricane. The following year, all the chicks turn out to be males, and the year after that, the nest is raided by a snake. Species X is now headed toward local extinction. If the island is home to two breeding pairs, the odds that both will suffer such a string of fatal bad luck is lower, and if it's home to twenty pairs, it's a great deal lower. But low odds in the long run can still be deadly.

Page Number: 180
Explanation and Analysis:

In this passage, Kolbert gives a partial explanation for the mathematical law she described in the previous chapter. As she’d discussed, there is a direct relationship between the number of living species on the Earth and the amount of available land. One reason that this is the case is that, in smaller land areas, the chances of catastrophic mass-extinctions are greater. This drives home the point that, first of all, the vagaries of nature (as Darwin knew) can have profound evolutionary effects. This might suggest that humans have less responsibility for extinction than Kolbert has previously argued, but Kolbert’s specificity about the connection between land area and survival odds makes it clear that there is a human role to play in both endangerment and protection of species. If human beings continue to reduce the amount of natural land then the odds of extinction for species that rely on such lands will continue to increase. Kolbert, though, is also implicitly positing a relatively straightforward way to go about protecting species; by increasing the amount of available land (through reclamation of developed lands and by halting development activities), humans can easily increase the odds that more species will survive.

I thought about this as we trudged back to camp. If Cohn-Haft was right, then in its crazy, circus-like complexity the ant-bird-butterfly parade was actually a figure for the Amazon's stability. Only in a place where the rules of the game remain fixed is there time for butterflies to evolve to feed on the shit of birds that evolved to follow ants.

Related Characters: Mario Cohn-Haft
Page Number: 192
Explanation and Analysis:

At the end of Chapter Nine, Kolbert describes an important experience she had in the Amazon. Late one night, she and her friend, the scientist Mario Cohn-Haft, woke up in the hopes of witnessing army ants marching through the forest. However, Kolbert was disappointed to find that the army ants were nowhere to be found.

As Kolbert points out in this passage, the disappearance of the army ants from the Amazon is a symbol for the plummeting biodiversity of the Earth itself. Over the course of the last few thousand years, species have been going extinct at a phenomenal rate. Furthermore, the disappearance of a few species is causing a “chain reaction.” The extinction of army ants, for example, would threaten the survival of hundreds of other species that depend on army ants for food and nutrition. The birds that eat army ants, and the butterflies that do the same, will have to find new food sources, or face extinction. And because species are already going extinct at an alarming rate, it’s doubtful that birds and butterflies would have enough time to adapt to their changing circumstances—in all likelihood, they would go extinct, too, furthering the chain reaction. In general, Kolbert shows that different species are connected to one another in close, significant ways, meaning that the extinction of one species may lead to the extinction of many other species, too.

Chapter 10 Quotes

Long-term relationships between pathogens and their hosts are often characterized in military terms; the two are locked in an "evolutionary arms race," in which, to survive, each must prevent the other from getting too far ahead. When an entirely new pathogen shows up it's like bringing a gun to a knife fight. Never having encountered the fungus (or virus or bacterium) before, the new host has no defenses against it.

Page Number: 204
Explanation and Analysis:

In Chapter Ten, Kolbert discusses another impact of human development on biodiversity. Because humans travel around the world, they transport plants,, animals, and pathogens with them (sometimes knowingly, sometimes unknowingly). The result is that humans have introduced many life forms, particularly microscopic life forms, to new environments. Often, this causes major problems. Every ecosystem on the planet has its own delicate equilibrium: pathogens, plants, and animals balance one another out by consuming each other. The introduction of a new pathogen often poses a grave threat to an ecosystem, because there are no predators or rivals to keep the pathogen’s population low.

It’s significant that Kolbert continues to use metaphors about social activity to humanize nonhuman entities. “Bringing a gun to a knife fight,” for instance, is a phrase that evokes a certain kind of unfairness. If a human were to do this, he or she would be accused of manipulation or not playing by the rules. By applying this logic to the struggle between a pathogen and a host, Kolbert is adding a moral tone to a situation that might otherwise seem purely natural. Introducing a pathogen to an unfamiliar environment is unfair to that environment because the environment has no adequate protection against the pathogen, which is metaphorically figured here to be violent. Kolbert often uses metaphor to impose a moralistic tone on a natural situation without overtly expressing her opinion.

If we look even farther ahead than Elton did—millions of years farther—the biological world will, in all likelihood, become more complex again. Assuming that eventually travel and global commerce cease, the New Pangaea will, figuratively speaking, begin to break up. The continents will again separate, and islands will be re-isolated. And as this happens, new species will evolve and radiate from the invasives that have been dispersed around the world. Hawaii perhaps will get giant rats and Australia giant bunnies.

Related Characters: Charles Elton
Page Number: 213
Explanation and Analysis:

In this passage, Kolbert suggests that, at some point in the future, the world will develop a new “biological equilibrium.” This is based on the scientist Charles Elton’s argument that the world’s ecosystems are perfectly balanced: plants, animals, and microbes consume one another, preventing any single species’ population from growing out of control. However, in the modern era, thanks to human travel, life forms have migrated to new ecosystems, growing out of control and rupturing the fragile biological equilibrium.

The implication of the passage is that, at some point in the future, human beings will go extinct, likely due to the chaos that their own actions have set in motion on the planet. The post-human future that Kolbert suggests is notably dystopian and even rings as science fiction (giant rats ruling Hawaii, for example). This is a passage meant to shock and dismay through its sheer uncaring about the future of the human animal. The “new equilibrium” sounds like exactly what a forward-thinking human being would want, but here the new equilibrium is predicated on the extinction of the creature that ruined the pre-existing equilibrium in the first place.

Chapter 11 Quotes

If, on the other hand, people were to blame—and it seems increasingly likely that they were—then the import is almost more disturbing. It would mean that the current extinction event began all the way back in the middle of the last ice age. It would mean that man was a killer—to use the term of art an "overkiller"—pretty much right from the start.

Page Number: 239-240
Explanation and Analysis:

In Chapter Eleven, Kolbert addresses the hypothesis—which is becoming increasingly common in the scientific community—that prehistoric human beings were responsible for the extinction of many large mammals, including the mammoth, the mastodon, and the giant sloth. There is considerable evidence that large prehistoric mammals had survived ice ages, heat waves, and other sudden environmental changes leading up to the dawn of man—this suggests that humans (and not some mysterious temperature change, as certain scientists continue to believe) caused the large mammals to die out.

As Kolbert acknowledges in this passage, the idea that humans wiped out prehistoric species is disturbing, because it suggests that humans have been mass-killers for as long as they’ve been in existence. One could even argue that the ability to cause mass-extinction is the essence of human nature. Humans seem to have a strong, innate desire to destroy their environments, killing off life forms without, until recently, thinking of the consequences.

Chapter 12 Quotes

It’s only fully modern humans who start this thing of venturing out on the ocean where you don't see land. Part of that is technology, of course; you have to have ships to do it. But there is also, I like to think or say, some madness there. You know? How many people must have sailed out and vanished on the Pacific before you found Easter Island? I mean, it's ridiculous. And why do you do that? Is it for the glory? For immortality? For curiosity? And now we go to Mars. We never stop.

Related Characters: Svante Pääbo (speaker)
Page Number: 251
Explanation and Analysis:

In Chapter Twelve, Kolbert sheds some new light onto the concept of human nature by contrasting human beings with their close cousins, Neanderthals. While most people think of Neanderthals as primitive, crude, apelike creatures, it’s possible that Neanderthals were intelligent (their brains are larger than those of modern human beings), compassionate (they took care of their sick and wounded), and spiritual (they planted flowers on the graves of their dead).

The paleogeneticist (scientist who specializes in the DNA of prehistoric creatures) Svante Paäbo has developed an interesting theory about why Neanderthals went extinct while human beings didn’t. In this passage, Kolbert uses his ideas to argue that human beings have an innate desire to explore, conquer, and colonize—in short, a “madness gene.” Humans escaped the extinction that faced the Neanderthals because they had a strong desire to explore the rest of the world—as a result, they migrated around the world, found new resources, and eventually prospered. Neanderthals, on the other hand, may have been more passive and docile (in spite of their intelligence)—as a result, they may have died out because they weren’t aggressive enough. Pääbo’s theory supports the idea that curiosity and “wanderlust” are two of the defining traits of human beings. It also, perhaps, points to a central contradiction of human history (one that Darwin wouldn’t find contradictory at all): that a trait that once helped humans prosper could, in turn, lead them to extinction.

The Neanderthals lived in Europe for more than a hundred thousand years and during that period they had no more impact on their surroundings than any other large vertebrate. There is every reason to believe that if humans had not arrived on the scene, the Neanderthals would be there still, along with the wild horses and the woolly rhinos. With the capacity to represent the world in signs and symbols comes the capacity to change it, which, as it happens is also the capacity to destroy it.

Page Number: 258
Explanation and Analysis:

Kolbert ends Chapter Twelve on an ambiguous note. She points out that Neanderthals may have been compassionate, gentle creatures—and yet there’s very little evidence to suggest that they had art or language of any kind. On the other hand, it’s well-known that human beings have made art—cave paintings, carvings, sculptures, etc.—for tens of thousands of years. Furthermore, linguists argue that humans have had complex language skills for as long as there have been humans.

Kolbert interprets the absence of art and language in Neanderthal society in an interesting way. Perhaps humans’ longstanding love for art and words are symptomatic of the “madness gene” that Paääbo has discussed. Humans have always wanted to explore and even conquer the world—perhaps, in a related sense, they went to use art, language, and symbols to understand and interpret the world. In other words, the human desire to make art and language, and the human desire to conquer the world, are two sides of the same coin—or, put another way, the two sides of human nature.

Chapter 13 Quotes

Certainly humans can be destructive and shortsighted; they can also be forward-thinking and altruistic. Time and time again, people have demonstrated that … they’re willing to make sacrifices on those creatures’ behalf.

Page Number: 261
Explanation and Analysis:

Throughout her book, Kolbert has painted a pessimistic picture of human nature. Humans are destructive and, even worse, oblivious to their own destruction. They burn fossil fuels, indirectly wiping out entire species from the oceans, and don’t even realize what they’re doing. At the same time, Kolbert’s view of human nature isn’t entirely negative. As she points out here, humans are capable of incredible acts of altruism and kindness. Indeed, humans are perhaps the only life forms on the planet who devote their time and energy to preserving other species.

In the end, Kolbert offers a nuanced, ambiguous view of human nature. Humans are destructive, but also creative. They’re cruel, but they’re also compassionate. They’re oblivious, but they’re also capable of deep understanding. Perhaps, once they’re fully aware of their own role in the world’s Sixth Extinction, human beings will choose to change their behavior, protect the world’s endangered species, and rebuild the disintegrating ecosystems of the Earth. Kolbert doesn’t guarantee that this will be the outcome, but she offers the possibility.

Among the many lessons that emerge from the geologic record, perhaps the most sobering is that in life, as in mutual funds, past performance is no guarantee of future results.

Page Number: 267-268
Explanation and Analysis:

At the end of her book, Kolbert reiterates one of her most important ideas, that natural selection is a constant process of adaptation. Different life forms are always facing a new version of the same challenge: in the face of a changing environment, they must adapt in order to continue gaining resources and reproducing. But, as Kolbert (following Darwin) reminds her readers, even if a species has successfully survived for millions of years, the advent of a sudden environmental change could still cause that species to go extinct. There’s no such thing as natural selection that makes a species better and better prepared for the future, because the nature of future change is so unpredictable that advantage can turn to disadvantage on a dime.

The most disturbing thing about this passage is that Kolbert isn’t talking about ammonites, dinosaurs, or army ants: she’s talking about people. While most people would disagree with the idea that human beings could ever go extinct, it seems inevitable that, at some point in the future, Homo sapiens will die out. Throughout The Sixth Extinction, Kolbert has implied that human beings need to become more aware of their own role in mass-extinction. Here, she suggests that, if the human race doesn’t face the facts, it could wipe itself out, along with the rest of the life forms on the planet.

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