The Sixth Extinction

During the Earth's long history of life, there have been five catastrophic extinctions, in which life almost completely disappeared. The most famous of these is the Cretaceous-Tertiary, which did in the dinosaurs and was the result of a meteorite. But there have been four more of these, and species who had been around for millions of years disappeared.

Are we today on the cusp, or even in, the sixth extinction? Do extinctions happen quickly, or over several thousand years? And is mankind the cause of this extinction? These are the questions tackled in Elizabeth Kolbert's Pulitzer Prize-winning The Sixth Extinction, an eminently readable book about science for the layman, that looks at extinction from all angles.

The first thing I noted about Kolbert's research is all the traveling she got to do. She went to such far-flung places as Scotland, an Italian island, the Brazilian rain forest, the mountains of Peru, and the Great Barrier Reef. She also visits the Cincinnati Zoo, where a veterinarian performs an ultrasound on a rhino by shoving her fist up its ass, and in San Diego she watches a researcher milk the semen out of a crow. We learn about the acidification of the oceans and how humans may have been responsible for wiping out the mastodon and the Neanderthal, our thick-skulled cousins (don't fret, though, if you are not African in descent, you are up to four percent Neanderthal).

Kolbert also looks at the history of extinction. Of course, no one knew animals went extinct until people starting finding fossils of animals that weren't around anymore. "Extinction finally emerged as a concept, probably not coincidentally, in revolutionary France. It did so largely thanks to one animal, the creature now called the American mastodon, or Mammut americanum, and one man, the naturalist Jean-Leopold-Nicolas-Frederic Cuvier, known after a dead brother simply as Georges." Kolbert calls Cuvier "an equivocal figure in the history of science," who was far ahead of his contemporaries. His rival was the Englishman, Charles Lyell, who disputed many of Cuvier's findings. Both men were influential on Charles Darwin.

She also goes into a brief history of the discovery that a meteorite did in the dinosaurs. The theory was first posited about thirty-five years ago, and was roundly ridiculed. Today it is accepted fact. This mass extinction is the one most of us know, and Kolbert points out that we know about it early on: "Extinction may be the first scientific idea that kids today have to grapple with. One-year-olds are given toy dinosaurs to play with, an two-year-olds understand, in a vague sort of way at least, that these small plastic creatures represent very large animals. If they're quick learners--or, alternatively, slow toilet trainers--children still in diapers can explain that there were once lots of kinds of dinosaurs and that they all died off long ago."

Kolbert also advances the notion that we are now living in an epoch called the anthropocene, anthro the prefix meaning "man." The possible sixth extinction is the first that would be with Homo sapiens on the planet, and to a great extent the onus is on us. "Since the start of the industrial revolution, humans have burned through enough fossil fuels--coal, oil, and natural gas--to add some 365 billion metric tons of carbon to the atmosphere. Deforestation has contributed another 180 billion tons. Each year, we throw up another nine billion tons or so, an amount that's been increasing by as much as six percent annually. As a result of all this, the concentration of carbon dioxide in the air today--a little over four hundred parts per million--is higher than at any other point in the last eight hundred thousand years."

The blame rests squarely on the shoulders of mankind, and the solution also rests with us. Like Neil deGrasse Tyson in the TV show Cosmos, Kolbert throws down the gauntlet. "Right now, in the amazing moment that to us counts as the present, we are deciding, without quite meaning to, which evolutionary pathways will remain open and which will forever be closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy."