By Elizabeth Kolbert, Bloomsbury, January 15, 2015, 978-1408851241

The Sixth Extinction is the period in which we live. Humans are killing off species in geologic time, just like the other five mass exinctions. Elizabeth Kolbert documents that this is happening and has been happening for millenia and why. This isn’t an industrial age problem: we are the problem. (Machines don’t cause extinction, people do.)

We’ve only recently begun to understand the meaning on extinction. It’s a relatively new concept, and our understanding of what happened when evolved rather rapidly with the discovery of the iridium layer in 1980. We have only just begun to confirm the anthropocene extinction, which is the primary subject of Kolbert’s book.

This is an excellent summary of the science. I plowed through it in five days, which is unusual for me. It was recommended by Dylan who was assigned it for a geology class at Colorado College. I highly recommend it.

[k252] Such wholesale losses have led paleontologists to surmise that during mass extinction events–in addition to the so-called Big Five, there have been many lesser such events–the usual rules of survival are suspended. Conditions change so drastically or so suddenly (or so drastically and so suddenly) that evolutionary history counts for little. Indeed, the very traits that have been most useful for dealing with ordinary threats may turn out, under such extraordinary circumstances, to be fatal.

[k975] But human-caused extinction is of course troubling for many reasons, some of which have to do with Darwin’s own theory, and it’s puzzling that a writer as shrewd and self-critical as Darwin shouldn’t have noticed this.

[k1207] The bolide arrived from the southeast, traveling at a low angle relative to the earth, so that it came in not so much from above as from the side, like a plane losing altitude. When it slammed into the Yucatan Peninsula, it was moving at something like forty-five thousand miles per hour, and, due to its trajectory, North America was particularly hard-hit. A vast cloud of searing vapor and debris raced over the continent, expanding as it moved and incinerating anything in its path. “Basically, if you were a triceratops in Alberta, you had about two minutes before you got vaporized” is how one geologist put it to me.

In the process of excavating the enormous crater, the asteroid blasted into the air more than fifty times its own mass in pulverized rock. As the ejecta fell back through the atmosphere, the particles incandesced, lighting the sky everywhere at once from directly overhead and generating enough heat to, in effect, broil the surface of the planet. Owing to the composition of the Yucatan Peninsula, the dust thrown up was rich in sulfur. Sulfate aerosols are particularly effective at blocking sunlight, which is the reason a single volcanic eruption, like Krakatoa, can depress global temperatures for years.

[k1268] In times of extreme stress, the whole concept of fitness, at least in a Darwinian sense, loses its meaning: how could a creature be adapted, either well or ill, for conditions it has never before encountered in its entire evolutionary history? At such moments, what Paul Taylor, a paleontologist at London’s Natural History Museum, calls “the rules of the survival game” abruptly change.

[k1297] “In science, as in the playing card experiment, novelty emerges only with difficulty,” Kuhn wrote.

[k1298] Crisis led to insight, and the old framework gave way to a new one. This is how great scientific discoveries or, to use the term Kuhn made so popular, “paradigm shifts” took place.

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.

[k1306] “Though the world does not change with a change of paradigm, the scientist afterward works in a different world” is how Kuhn put it.

[k1308] Within a few decades, so many extinct creatures had been identified that Cuvier’s framework began to crack. To keep pace with the growing fossil record, the number of disasters had to keep multiplying. “God knows how many catastrophes” would be needed, Lyell scoffed, poking fun at the whole endeavor. Lyell’s solution was to reject catastrophe altogether.

[k1312] The uniformitarian account of extinction held up for more than a century. Then, with the discovery of the iridium layer, science faced another crisis. (According to one historian, the Alvarezes’ work was “as explosive for science as an impact would have been for earth.”)

[k1478] (A recent study of pollen and animal remains on Easter Island concluded that it wasn’t humans who deforested the landscape; rather, it was the rats that came along for the ride and then bred unchecked. The native palms couldn’t produce seeds fast enough to keep up with their appetites.)

[k1510] Crutzen wrote up his idea in a short essay, “Geology of Mankind,” that ran in Nature. “It seems appropriate to assign the term ‘Anthropocene’ to the present, in many ways human-dominated, geological epoch,” he observed.

[k1521] Crutzen published “Geology of Mankind” in 2002. Soon, the “Anthropocene” began migrating out into other scientific journals.

[k1938] Some of the scientists, who had dived all over–in the Philippines, in Indonesia, in the Caribbean, and in the South Pacific–told me that the snorkeling at One Tree was about as good as it gets. I found this easy to believe. The first time I jumped off the boat and looked down at the swirl of life beneath me, it felt unreal, as if I’d swum into the undersea world of Jacques Cousteau. Schools of small fish were followed by schools of larger fish, which were followed by sharks. Huge rays glided by, trailed by turtles the size of bathtubs. I tried to keep a mental list of what I’d seen, but it was like trying to catalog a dream.

[k2127] As a general rule, the variety of life is most impoverished at the poles and richest at low latitudes. This pattern is referred to in the scientific literature as the “latitudinal diversity gradient,” or LDG, and it was noted already by the German naturalist Alexander von Humboldt, who was amazed by the biological splendors of the tropics, which offer “a spectacle as varied as the azure vault of the heavens.”

“The verdant carpet which a luxuriant Flora spreads over the surface of the earth is not woven equally in all parts,” Humboldt wrote after returning from South America in 1804. “Organic development and abundance of vitality gradually increase from the poles towards the equator.” More than two centuries later, why this should be the case is still not known, though more than thirty theories have been advanced to explain the phenomenon.

[k2178] Coca, Silman told me, made a heavy pack feel lighter. It also staved off hunger, alleviated aches and pains, and helped counter altitude sickness. I had been given little to carry besides my own gear; still, anything that would lighten my pack seemed worth trying. I took a handful of leaves and a pinch of baking soda. (Baking soda, or some other alkaline substance, is necessary for coca to have its pharmaceutical effect.) The leaves were leathery and tasted like old books. Soon my lips grew numb, and my aches and pains began to fade. An hour or two later, I was back for more. (Many times since have I wished for that shopping bag.)

[k2407] For most of the Pleistocene temperatures were significantly lower than they are now–such is the rhythm of the orbital cycle that glacial periods tend to last much longer than interglacials–and so an evolutionary premium was placed on being able to deal with wintry conditions.

[k2456] The project has now been running continuously for more than thirty years. So many graduate students have been trained at the reserves that a new word was coined to describe them: “fragmentologist.” For its part, the BDFFP has been called “the most important ecological experiment ever done.”

[k2632] Yet another possible explanation for why observations don’t match predictions is that humans aren’t very observant. Since the majority of species in the tropics are insects and other invertebrates, so, too, are the majority of anticipated extinctions. But as we don’t know, even to the nearest million, how many tropical insect species there are, we’re not likely to notice if one or two or even ten thousand of them have vanished.

[k2704] The body temperature of a hibernating bat drops by fifty or sixty degrees, often to right around freezing. Its heartbeat slows, its immune system shuts down, and the bat, dangling by its feet, falls into a state close to suspended animation.

[k2974] Before humans arrived on the scene, many whole categories of organisms were missing from Hawaii; these included not only rodents but also amphibians, terrestrial reptiles, and ungulates. The islands had no ants, aphids, or mosquitoes.

[k3293] The Anthropocene is usually said to have begun with the industrial revolution, or perhaps even later, with the explosive growth in population that followed World War II. By this account, it’s with the introduction of modern technologies–turbines, railroads, chainsaws–that humans became a world-altering force. But the megafauna extinction suggests otherwise. Before humans emerged on the scene, being large and slow to reproduce was a highly successful strategy, and outsized creatures dominated the planet. Then, in what amounts to a geologic instant, this strategy became a loser’s game. And so it remains today, which is why elephants and bears and big cats are in so much trouble and why Suci is one of the world’s last remaining Sumatran rhinos. Meanwhile, eliminating the megafauna didn’t just eliminate the megafauna; in Australia at least it set off an ecological cascade that transformed the landscape. Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did.