The Sixth Extinction Themes

Scientific Discovery as a Process

The Sixth Extinction provides an up-close look at the scientific process, painting it as a slow, human-centered method. Beginning with the ideas of extinction and natural selection, author Elizabeth Kolbert explains that these notions were unexplored by scientists until very recent history. The book not only explores the science of extinction and human influence on the world, it also looks at the scientific process as a living entity similar to evolution itself, showing how people’s understanding of science is constantly growing.

By defining American philosopher Thomas Kuhn’s “paradigm shift” as the way humans process disruptive information, Kolbert demonstrates time and again how scientists pushed aside information that conflicted with their beliefs. She offers the example of the scientific community’s reluctance to accept French zoologist Georges Cuvier’s extinction principles—even ridiculing scientists who proposed such theories and backed them with evidence.

Kolbert does not claim that today’s scientific understanding is perfect or even complete. She points out numerous times that scientists don’t yet understand various issues facing the planet today, such as the incongruity of rising ocean temperatures and the decrease of species. Scientists continually encounter new evidence that forces paradigm shifts.

Human Destruction and Potential

The major premise of The Sixth Extinction is that humans are inextricably, and rapidly, changing the face of the planet. Kolbert weaves this theme into the text from the prologue, in which she describes Homo sapiens (modern-day humans) as a strange species—not particularly strong, but cunning and often brutal. As they spread to every corner of the planet, humans leave their indelible mark, forever changing nearly everything with which they come into contact.

Kolbert’s focus on the Anthropocene Epoch—a destructive geological time period in which human activity is driving ecological factors more than anything else—further develops this main idea throughout the text. Another major premise of the book is that humans are the singular cause of the sixth mass extinction in the history of the planet, occurring right now. Kolbert argues that in global history, humans will be known not for their intelligence or adaptability but for their impact on Earth itself.

However, toward the end of the text, Kolbert seemingly retracts the assertion that humans are primarily destructors by noting that they are the only species who dedicate themselves to helping other species. She sees this firsthand in her travels as she visits conservatories and interacts with scientists who have dedicated their professional and sometimes personal lives to the planet’s preservation. Ultimately, Kolbert offers a slightly more hopeful perspective—that “life is extremely resilient but not infinitely so.” While humanity’s impact on the planet can never be erased, it can, perhaps, be mitigated by human efforts to preserve and protect the environment.

Time as a Ticking Clock

Kolbert spends much of the book exploring the concept of time to educate the reader on the different mass extinction events that occurred during Earth’s geological time periods. But Kolbert emphasizes the impact of time in the current world, as Earth teeters on the edge of a sixth catastrophic mass extinction.

While the planet has experienced temperature fluctuations and changes in chemistry in the past, these changes occurred over a long period of time, often in spans of hundreds of millions of years. In Chapter 6, Kolbert compares current changes in the ocean’s acidity to human alcohol consumption. Just as the effects on the body of consuming alcohol differ vastly “whether [they] take a month… or an hour,” the impact of CO₂ on the ocean varies when it’s added “over the course of a million years or a hundred.”

Considering that the Anthropocene began between 50,000 and just 70 years ago, rather than millions or hundreds of millions of years, can help readers to see what Kolbert is emphasizing. The timeline with which humans are altering Earth’s chemistry and temperature is alarming, at the least, and likely catastrophic. As scientists now know, the primary feature that “disparate events have in common is change, and, to be more specific, rate of change.”