Roughly 11,500 years ago, neolithic villagers in Israel's Dead Sea Basin began practices of farming, deforestation, and sheep and goat domestication, increasing local erosion rates three to fourfold.
Some believe that this discovery, published by researchers at the Tel Aviv University Dead Sea Drilling Project, suggests that the Anthropocene—an unofficial epoch in which humans are defined as the primary drivers for change on earth—began as early as 11,500 years ago.
However, geologists aren't buying it.
The International Commission on Stratigraphy—the governing body of geology—hasn't yet defined the Anthropocene as a formal epoch (a chapter of Earth's history that distinguishes one set of ancient rocks and fossils from another). But since 2009, the Anthropocene Working Group within the ICS has been working to determine whether it should do so.
Shmulik Marco, the geologist who led the Dead Sea Basin team, believes in the Anthropocene as a concept, but said that more research is needed before it's formally designated as an epoch.
"Our research is limited to the Dead Sea Basin," he said to me in an email. "Other places might exhibit different timing and pattern of impact. So again, not yet—it's not right to determine a global geological period based on a single or even a few sites."
The ICS also disagrees with the idea of an 11,500 year-old Anthropocene.
According to Jan Zalasiewicz, a paleontologist and the convenor of the ICS Anthropocene Working Group, it's important to distinguish the words "anthropogenic,"—which encompasses any influence that people have had on the earth—and "Anthropocene," which refers to a recognizable geological boundary.
"The Anthropocene is often interpreted as meaning 'significantly anthropogenic,'" Zalasiewicz told me. "In, let's say, archaeological contexts and others like it, that is fine and inherently valid. But the Anthropocene in a geological, stratigraphic understanding is something else."
According to Zalasiewicz, the the current consensus of Anthropocene Working Group is that the epoch began around 1950. At that time, not only were we producing radiocarbon and plutonium, but we created plastic, carbon dioxide, electronic waste at an unprecedented scale. The result was a marked difference in earth's geological record.
When geologists are defining epochs, they look for factors that affect the composition of rocks and sediment. These factors are typically the warming or cooling of the earth and the growing or shrinking of glaciers. In the case of the Anthropocene, many of the factors affecting the rocks are manmade.
In other words, our waste has become not just an archaeological issue, but a geological issue.
While there's enough agreement within the working group to develop a proposal to officially designate the Anthropocene as an official epoch, not all of its members are on the same page.
Erle Ellis, an ecologist and member of the ICS Anthropocene Working Group, believes that the Anthropocene began before 1950, but he's unsure as to whether the Anthropocene has the same clear physical boundaries that separate other epochs—such as the Triassic period from the Jurassic period.
"What is the definition of human transformation on the earth?" he asked me via Skype. "There's so many different processes at play here. Do we know, in 10,000 years, what are gonna be the most important ones? At this point, I think it's too hard to say. I think we're too close to it in time, and the presence of the signatures is not well enough established."
Ellis also said that while he believes that a majority of the members of the Anthropocene Working Group support a formal definition of the Anthropocene, he doubts that the entire geological community finds the geological evidence in favor of this formal definition to be convincing.
Zalasiewicz told me that the Anthropocene Working Group will be submitting a proposal to designate the Anthropocene as a formal epoch in the next two to four years.
"Really, all geological boundaries are human-made constructs—we make decisions about where to have the most pragmatic, useful, recognizable boundary," Zalasiewicz said. "A lot of the geological boundaries do not coincide with the big earth system changes. But in the case of the Anthropocene, it really does."