Exploring Ancient Civilizations: Were We Alone on Earth?
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Chapter 1: The Inquiry Begins
The question of whether Earth hosted civilizations prior to humanity has intrigued many. Schmidt, the director of NASA’s Goddard Institute for Space Studies (GISS), a premier climate science agency, has ventured into this captivating topic.
Last year, I approached GISS with an ambitious idea. As an astronomer delving into global warming through “astronomical observations,” I sought to understand if industrial civilizations on other planets might inadvertently trigger climate changes of their own. My visit was aimed at enhancing my knowledge of climatology and possibly finding collaborators. During my time in Gavin's office, I was caught off guard by a profound question he posed: “How do you know we are the only civilization on our planet?”
His inquiry left me momentarily speechless. I had come prepared to dismiss discussions of “ancient civilization development.” Yet, the civilizations Gavin referred to could have existed millions of years ago. As I contemplated the vast expanse of Earth’s evolutionary history, I felt a sense of temporal disorientation. “Is it possible,” I wondered, “to identify an industrial civilization from the distant past?”
This conversation catalyzed a research project that we recently published in the International Journal of Astrobiology. Although we didn’t recognize it then, Gavin’s insightful question opened doors to understanding not just the Earth's history, but our own trajectory.
We often visualize lost civilizations through crumbled statues and buried ruins, remnants that reflect a few thousand years of history. However, when we extend our gaze back millions of years, the complexity escalates. Evidence of industrial civilizations, such as cities and roads, is trapped within geological records that date back only to the Quaternary period, approximately 2.6 million years ago. The oldest archaeological sites, like those in the Negev Desert, are merely 1.8 million years old, often identified by large rock formations. Any evidence older than the Quaternary has likely succumbed to erosion and transformation into sand. Since Homo sapiens have only been on Earth for about 300,000 years, this raises questions about other species, leading to Gavin's term for this notion: the Silurian hypothesis, inspired by a story involving intelligent beings.
Section 1.1: The Search for Evidence
Could scientists uncover definitive proof that an ancient species constructed an industrial civilization long before ours? Perhaps certain prehistoric animals developed civilizations during the Paleocene epoch, around 60 million years ago. While fossils exist, the proportion of life capable of creating lasting structures is minimal, varying by era and habitat. Thus, it’s conceivable for an industrial civilization, merely 100,000 years old, to be 500 times older than our current one.
Given that all evidence is likely to vanish over millions of years, what remnants might we leave behind?
One way to address this is to consider what traces we would create if our current civilization were to collapse. As our industrial society has become truly global, human activity is leaving diverse markers that future scientists could uncover in 100 million years.
For example, the extensive use of fertilizers feeds billions but also alters the planet's nitrogen cycles. Future researchers may detect nitrogen characteristics embedded in sediment layers. Similarly, our unquenchable demand for rare materials used in electronics has significantly increased their presence on Earth's surface, which could also be reflected in future sedimentary records. Furthermore, the extensive production and use of synthetic substances could leave a geological imprint for millions of years.
And let’s not overlook plastic. Research indicates that growing amounts of plastic waste are accumulating in oceans, rivers, and even remote Arctic regions. Environmental forces break down this plastic into smaller particles, which eventually settle on the ocean floor, creating a distinct layer over vast time scales.
Section 1.2: The Legacy of Civilization
The critical question remains: how long will our civilizational markers endure? Our study suggests that future sediments could indeed bear witness to our existence. Yet, intriguingly, the very factors that signify human civilization may also pose existential threats. The combustion of fossil fuels releases ancient carbon into the atmosphere, altering the ratio of carbon isotopes. This change, known as the Suess effect, has been evident over the past century. Additionally, rising temperatures leave their own isotopic signatures, which future chemists studying Earth's history will likely identify.
The first video titled "What if Humans Are NOT Earth's First Civilization? | Silurian Hypothesis" delves into the implications of this hypothesis, exploring the potential for ancient civilizations to have existed long before ours.
Chapter 2: The Evidence of the Past
Fifty-six years ago, the planet experienced the Paleocene-Eocene Thermal Maximum (PETM), a period when average global temperatures surged 15 degrees Fahrenheit higher than today. This epoch resembled a world devoid of ice, with summer temperatures at the poles nearing 70 degrees Fahrenheit. Scientists studying the isotopic data from the PETM have observed carbon and oxygen ratios that align with those expected from the Anthropocene.
Other historical events, such as the Eocene Layers of Mysterious Origin and significant occurrences during the Cretaceous period, display characteristics reminiscent of our Anthropocene era. However, do these episodes indicate the presence of early non-human industrial civilizations? Probably not. While the PETM may reflect significant fossil carbon emissions, the timing of these changes is crucial. PETM isotope fluctuations occurred over centuries, whereas the Anthropocene is characterized by an unprecedented speed in fossil carbon release.
The geological record may not clearly reflect the brief existence of any early civilizations. The PETM’s patterns often illustrate Earth’s response times, rather than the timing of the initial causes. Consequently, uncovering evidence of ancient events in sediments may necessitate innovative research methodologies. In essence, if one does not look diligently, the evidence may remain hidden.
This notion became particularly apparent in our study. It’s uncommon to publish an article that presents a viewpoint one doesn’t entirely endorse. Neither Gavin nor I advocate for the existence of a Paleocene civilization. However, by contemplating the visibility of an ancient industrial society, we were compelled to consider the potential impacts such a civilization might have had on our planet.
The essence of astrobiological theories regarding climate change lies in understanding that civilization entails harnessing planetary energy for progress. As a civilization matures on a global scale, it inevitably interacts with the integrated planetary systems that sustain life. This holds especially true for our relatively young civilization, still evolving technologically. Recognizing the importance of minimizing environmental impacts through sustainable energy sources could significantly alter our legacy.
Moreover, our research hints at the possibility that other planets may experience cycles of civilization rise and fall driven by fossil fuel consumption. The climate changes these civilizations induce could lead to diminished oceanic oxygen levels, fostering the conditions necessary for fossil fuel formation. In this manner, the rise and decline of civilizations may pave the way for future societies. By posing questions about lost civilizations from ages past, we explore the potential for universal principles shaping the evolution of biospheres across the cosmos.
The second video, "What If Humans Are NOT Earth's First Civilization?" further investigates the implications of this idea, considering the historical precedents and their influence on our understanding of civilization.