The idea gripped Stinchcomb, who has a background in both archaeology and geology. After seeing Ruddiman lecture on his theory, “I kept asking myself, if people could have altered the climate that early, what else have they done?” he recalls.
Yet another proposal for Year Zero came from a London-based group of scientists and geologists called the Anthropocene Working Group. They suggested the epoch began in the 1950s, when pollutants, plastic and — most notably — radioactive compounds from atomic explosions began accumulating in remote corners of the planet.
The debate over Year Zero intensified. In 2009, Stinchcomb decided to settle the debate the old-fashioned way — with a shovel and a trowel — and began exploring the pits in Lehigh Valley.
Three years later, at the annual meeting of the Geological Society of America, Stinchcomb presented his theory to a standing-room-only crowd: Scientists can map out anthropogenic events captured in sediments in the earth, he said. The events would need to have a clear anthropogenic origin, like the layer of coal in the Lehigh River Valley.
Mapping anthropogenic events from the beginning of the Holocene to today would create a timeline of human impacts on Earth. If anthropogenic events cluster around a particular time period, that would be a strong contender for Year Zero, Stinchcomb told the crowd.
'Ask Me in a Million Years'
Some geologists, however, think it is too early in our species’s history to declare human dominance over the Earth. University of Cambridge stratigrapher Philip Gibbard, an expert on the Quaternary period encompassing the past 2.6 million years, points out that a pandemic could decimate the population.
With enough evidence from around the world, the debate over the human age could be settled once and for all.
Cities would fall and buildings would crumble back into sediment, he says. The climate would reset after a few millennia. The rock record would contain evidence of civilization, but it would only be a brief spike, contained wholly within the Holocene.
To Gibbard, talk of a new Human Age is a bit premature. “Ask me in a million years,” he says.
Stinchcomb gets Gibbard’s point of view. After all, the layer of coal that Stinchcomb and his colleagues have excavated is very recent compared with the 4.6 billion-year history of the planet.
“I think we have impacted the planet to a degree that is widespread and measurable,” he says. “[But] we are definitely not masters of this planet. We are still very much a species vulnerable to natural changes.”
Stinchcomb wants to see more scientists map localized anthropogenic events to create a “basket” of markers. With enough evidence from around the world, the debate over the Human Age could finally be settled.
Back in the Lehigh Valley, Stinchcomb follows the river upstream. He comes across a pile of clamshells and broken wine bottles. He plunges a long rod with a scoop at the end, called a split-spoon, into the ground, and brings up red brick. There had been a home here, probably when a coal town thrived nearby. Today, some red dust and debris are all that’s left. It was a minuscule moment in time, already taken over by the forest.