Throughout most of Earth's history, the rate of species extinction has been very slow. For mammals, it has been calculated as one species disappears once every 700 years. This is such a slow process that no human could notice. In extraordinary times, many species die off rapidly. Our planet's fossil records suggest that this has happened five times in the distant past, most recently when an asteroid slammed into the Yucatan Peninsula sixty-six million years ago, killing off the dinosaurs. According to science journalist Elizabeth Kolbert, we are again in an extraordinary time, as many species are disappearing. She explains in The Sixth Extinction: An Unnatural History.
The idea of extinction is historically new, first proposed by French naturalist Georges Cuvier two hundred years ago to explain fossils that resembled no living animals. Up to that point, scientists and people in general had assumed that all life was current, abundant, and inexhaustible. (Some people still believe this despite the many cases of specific extinctions that have been proven.) Once the extinction idea was accepted, scientist identified five mass extinctions, but the explanations for these were not clear. Some appeared to have resulted from quick and catastrophic environmental events, such as monstrous volcanoes or asteroids. Our current extinction seems to be caused by environmental changes brought on by the actions of humans.
In each chapter of The Sixth Extinction, Kolbert recounts the disappearance of a species or genus or even a family of animals or plants. She describes her visits all over the planet with scientists in the field who are documenting the disappearance of frogs, mastodons, ammonites, giant auks and other flightless birds, Neanderthals, and coral reefs. Some of the missing were hunted to extinction. Non-native species or diseases introduced by humans did in others. Fossil-fuel-created global warming is the newest threat.
Comments about The Sixth Extinction from our church book club were mostly positive. Many agreed that the subject is ultimately depressing but the book is fair and very readable. It will surely be on many of the best books lists that should proliferate soon.
Kolbert, Elizabeth. The Sixth Extinction: An Unnatural History. Henry Holt and Company, 2014. 319p. ISBN 9780805092998.