{"id":311002,"date":"2018-04-16T11:21:07","date_gmt":"2018-04-16T15:21:07","guid":{"rendered":"http:\/\/www.rochester.edu\/newscenter\/?p=311002"},"modified":"2022-04-25T21:00:32","modified_gmt":"2022-04-26T01:00:32","slug":"astrobiology-we-think-were-the-first-advanced-earthlings-but-how-do-we-really-know-311002","status":"publish","type":"post","link":"https:\/\/www.rochester.edu\/newscenter\/astrobiology-we-think-were-the-first-advanced-earthlings-but-how-do-we-really-know-311002\/","title":{"rendered":"We think we\u2019re the first advanced earthlings\u2014but how do we really know?"},"content":{"rendered":"

Imagine if, many millions of years ago, dinosaurs drove cars through cities of mile-high buildings. A preposterous idea, right? Over the course of tens of millions of years, however, all of the direct evidence of a civilization\u2014its artifacts and remains\u2014gets ground to dust. How do we really know, then, that there weren\u2019t previous industrial civilizations on Earth that rose and fell long before human beings appeared?<\/p>\n

It\u2019s a compelling thought experiment, and one that Adam Frank, a professor of physics and astronomy at the University of Rochester, and Gavin Schmidt, the director of the NASA Goddard Institute for Space Studies, take up in a paper published in the International Journal of Astrobiology<\/em>.<\/a><\/p>\n

\u201cGavin and I have not seen any evidence of another industrial civilization,\u201d Frank explains. But by looking at the deep past in the right way, a new set of questions about civilizations and the planet appear: What geological footprints do civilizations leave? Is it possible to detect an industrial civilization in the geological record once it disappears from the face of its host planet? \u201cThese questions make us think about the future and the past in a much different way, including how any planetary-scale civilization might rise and fall.\u201d<\/p>\n

In what they deem the \u201cSilurian Hypothesis,\u201d Frank and Schmidt define a civilization by its energy use. Human beings are just entering a new geological era that many researchers refer to as the Anthropocene, the period in which human activity strongly influences the climate and environment. In the Anthropocene, fossil fuels have become central to the geological footprint humans will leave behind on Earth. By looking at the Anthropocene\u2019s imprint, Schmidt and Frank examine what kinds of clues future scientists might detect to determine that human beings existed. In doing so, they also lay out evidence of what might be left behind if industrial civilizations like ours existed millions of years in the past.<\/p>\n

Human beings began burning fossil fuels more than 300 years ago, marking the beginnings of industrialization. The researchers note that the emission of fossil fuels into the atmosphere has already changed the carbon cycle in a way that is recorded in carbon isotope records. Other ways human beings might leave behind a geological footprint include:<\/p>\n