Are We Headed for Extinction? An Epoch Question

"With their four-dimensional minds, and their interdisciplinary ultra verbal way, geologists can wriggle out of almost anything.”

John McPhee, American writer

“It is the microbes who will have the last word.”

Louis Pasteur

When Earth entered a warming trend 11,750 years ago, the Holocene Epoch began. (Holocene comes from two Ancient Greek words: “holos” meaning whole and “cene” meaning new.) It has been a relatively stable time period that enabled human civilization to flourish. But, beginning around 1950, the geographical record changed dramatically.

About 14 years ago, the Anthropocene Working Group (AWG), an expert panel of 33 scientists, proposed that because of human activity, the warming of Earth had gone too far, and we had entered a new time period—the Anthropocene Epoch. (Anthropocene is from the Greek words “anthropo” meaning human and “cene” meaning new.) Recently, geologists rejected the AWG’s proposal. (See March 23, 2024 New York Times article “Geologists Make It Official: We’re Not in an ‘Anthropocene’ Epoch.”) 

I was stunned by this rejection. Like my editor, you might ask why an infectious diseases specialist would care about such a seemingly arcane subject, and why would it be the subject of a Germ Gems’ post? It’s because the origin of life on our planet emerged from microbes (bacteria and archaea) about 3.8 billion years ago and, more importantly, because climate change, caused by our newcomer species Homo sapiens (emerging only 300,000 years ago), poses the single biggest threat to human health and could ultimately lead to another mass extinction. In this week’s Germ Gem post, I support the case for a reassessment of this “epoch” question.

Five Mass Extinctions. Extinction is defined as the complete loss of a species from our planet. Geoscientists agree that since the inception of life on Planet Earth there have been five mass extinctions—defined as a loss of at least 75% of the world’s species. (For a complete analysis of the topic, see The Sixth Extinction: An Unnatural History by Elizabeth Kolbert.)

The most notorious of the so-called “Big Five Mass Extinctions” occurred about 252 million years ago when massive volcanic eruptions caused catastrophic climate change. This “Permian-Triassic Extinction,” dubbed the “Great Dying,” wiped out 96% of all marine species and 75% of species living on land. Some experts suggest that Methanosarcina— a methane-producing bacterium, that flourished in these hellish conditions— played a pivotal role in the extinction by producing massive amounts of the greenhouse gas (GHG) methane. Now, it is global warming caused by GHGs (mainly carbon dioxide and methane) produced by human activity that threatens the Earth with a sixth mass extinction.

Modern day geology (geoscience). According to the American Geosciences Institute, geoscience is the study of the Earth—its oceans, atmosphere, rivers and lakes, ice sheets and glaciers, soils, its complex surface, rocky interior, and metallic core. It includes many aspects of how living things, including humans, interact with the Earth. And while geoscience has many tools and practices of its own, it is intimately linked with the biological, chemical, and physical sciences.

Many geoscientists are involved in dating how old something is or how long ago something happened. They divide the geological time scale into three “Eras” (Cenozoic, Mesozoic, and Paleozoic), a number of “Periods,” and eleven different “Epochs” or “Ages.” According to these scientists, we are living in the Cenozoic Era, the Tertiary Period, and the Holocene Epoch.

It's official: we’re still living in the Holocene epoch. The AWG’s main goal was to provide robust scientific evidence for the Anthropocene to be formally ratified by the International Union of Geological Sciences (IUGS) as a new epoch. In 2023, twelve teams of scientists reporting from around the globe presented evidence to help determine a single site where the shift from the Holocene to the Anthropocene could be exemplified. Crawford Lake in Canada was chosen by the AWG as the “golden spike” of the Anthropocene.

But the Subcommission of Quaternary Stratigraphy (SQS), part of IUGS, was the final arbiter in the controversy over whether we’re living in a new epoch, the Anthropocene. On March 20, 2024, 12 SQS members voted “no.” In doing so, they killed the AWG’s proposal.

A raft of publications expressed outrage at the SQS’s decision. The most compelling that  I read was Anthony Barnosky’s and Mary Ellen Hannibal’s article “Despite Official Vote, the Evidence of the Anthropocene Is Clear,” (See Yale School of Environment, April 2, 2024.)

In their article, Barnosky and Hannibal note that there was not only “savage academic infighting” but also irregularities in the proceeding; for example, 11 of the 12 SQS members who voted “no” were ineligible to do so because they had exceeded their term limits. Barnosky and Hannibal surmise, however, “Some cultural commentators have opined that whether geologists officially define the Anthropocene, they will continue to recognize it. Artists, writers, historians, sociologists, epidemiologists, and others don’t depend on a formal designation to confirm we are living in an environment that’s becoming more unstable. ... The window for taking effective actions to change our dangerous trajectory is closing fast.”

Why the concept of the “Anthropocene epoch” is here to stay. The theory behind adopting the designation Anthropocene epoch is based on the view that due to major impacts on the global environment, humanity should be considered a major geological and geobiological factor on Earth. This view was championed by the atmospheric chemist and Nobel Prize laureate, Paul J. Crutzen, who coined the term Anthropocene in 2000 and popularized the concept. (Crutzen died in 2021.)

In her April 20, 2024 New Yorker article, “The Epic Row Over a New Epoch,” Elizabeth Kolbert suggests that if Crutzen were still alive, he would respond to the SQS’s recent ruling claiming that is wasn’t important to him whether “Anthropocene” was included in geology texts, but rather “whether it prompted people to think more carefully about the consequences of their collective actions. What he hoped was the term ‘Anthropocene’ will be a warning to the world.”  

Just two days ago, on April 22, “Earth Day” was observed throughout the world. Since its inception in 1970, hundreds of millions of people who care deeply about the environment (clean water, air, and land) have assembled to draw attention to crucial priorities for protecting the Earth. My guess is that many of these advocates realize that the term “Anthropocene” is indeed a warning to the world and that despite the lack of an official SQS designation we’re living in the Anthropocene Epoch.