What if we weren't the first advanced civilization on Earth?

Complex life on our planet has existed for at least 400 million years, while primitive life has existed on this planet for more than 3.5 billion years. However, as a species, we only managed to create an industrial civilization about 300 years ago.

That leaves the more than 3 billion years of pre-humanity left unaccounted for - too long a period for the rise and fall of not one but a number of pre-human industrial civilizations that may have been. exist!

Life has existed on this planet for more than 3.5 billion years.

What if an earlier industrial civilization (pre-human) existed on Earth millions of years ago? If so, how can we prove it - or disprove it?

This is the crux of the Silurian Hypothesis, a fascinating thought experiment that emerged in a study published in 2018 in the International Journal of Biology.

In the BBC-produced British science fiction television series 'Doctor Who', an alien species known as Silurians exist - these are technologically advanced anthropomorphic reptiles that live very well. long before humans.

The possibility of life elsewhere in the universe and its resemblance to the Anthropocene - the current geological epoch in which humans have impacted the Earth to the point of no return - has long since led Adam Frank, Professor of astrophysics at the University of Rochester, New York, USA (one of the two authors of the study) to see the need to delve deeper.

'Can any civilization that reaches our level of energy use trigger their own version of climate change? - I was wondering. If there are alien civilizations, will they cause climate change?' - Professor Adam Frank struggled with these questions.

With a stream of thoughts in his mind, Professor Adam Frank went to NASA's Goddard Institute for Space Science (GISS), an advanced climate science facility at Columbia University, New York, USA, and shared his thoughts. with climate researchers.

'I went to Professor Gavin A. Schmidt (a climatologist and Director of GISS), and started talking about geological history millions of years ago,' said Professor Adam Frank excitedly.

Tracing in the Earth's geological record

Homo sapiens (sophisticated humans, modern humans) first appeared on Earth about 300,000 years ago.

The question of whether there was a pre-human civilization led the two professors to decide to look for evidence between 4 million years ago and 400 million years ago. Will they be successful?

Going back hundreds of millions of years to find traces of a potential pre-Homo Sapiens civilization is not easy.

Earth's history through the ages.

'After a few million years, the Earth is pretty much recreated. You won't have any statues, buildings, or anything left. The fossil record is virtually nonexistent because everything would turn to dust. The only evidence will come in the form of chemical traces,' said Professor Adam Frank.

'You would have to look at each rock layer, then try and spot trends - looking for changes in things like carbon or oxygen isotopes. An industrial civilization would release a lot of carbon dioxide into the atmosphere. Plastic or nano particles would also be good traces that an industrial civilization appeared in the past - that's all we need to find out,' he added.

Professors Schmidt and Frank were intrigued by the period of geological history known as the Paleocene-Eocene Thermal Maximum (PETM), because something strange happened on our planet, the way 56 million years ago: Earth's average temperature skyrocketed to minus 9.4 degrees Celsius above what we have today, and the world has become a priceless and temperate place.

They investigated the carbon and oxygen isotope ratios from the PETM and actually saw a spike, but they also saw a decrease in temperature, and all of this over a few hundred thousand years, not at the rate of carbon. currently choking the atmosphere.

Professor Frank says that PETM's chemical differences point to long-term climate change.

They also looked at other "sudden events" over the course of time visible in the geological record, including oceanic anoxic events - when the ocean becomes depleted of oxygen - and extreme events. strains .

Not surprisingly, they are also not indicative of an industrial civilization.

Applying the philosophy of "Ockham razor"

In 1324, the English theologian William of Ockham formulated a famous philosophical theory called the 'Ockham Razor', which implied that if a scientific problem were explained by the fewest hypotheses it would become most correct.

'The hypothesis that Earth may have harbored long-extinct industrial civilizations and that such existence could be recorded in the geological record in relation to signs of climate change is very fascinating, however, even the authors find it hard to see it as true," Stephen Holler, an associate professor of physics at Fordham University in New York City, told Popular Mechanics.

In the 14th century, the English philosopher Franciscan and the theologian William of Ockham proposed that the most possible solution to a problem was the simplest solution.

Associate Professor Stephen Holler said: 'That's very likely the case here. We can explain most of the geological record of natural phenomena, so there is no need to cite lost civilizations."

However, if a pre-industrial civilization existed and its extinction was the result of catastrophic climate change caused by industrial activities, then we should heed the warnings by because, as a civilization, we are at the edge.

The Silurian Hypothesis states: "The more sustainable a society is in the way it generates energy and produces resources - the more advanced a society is, so to speak - the smaller the footprint it leaves on the planet. ".

If you're not explicitly looking for something, you probably won't see it.

However, these tracks are likely to translate into some key points in the geological record of that period. For example, the more plastic or persistent synthetic molecules we produce, the more likely future civilizations will find our tracks.

(Our society produces 300 million tons of plastic a year worldwide - roughly equivalent to the weight of the entire population!).

Or, even if we wipe out the face of the Earth with a nuclear disaster, long-lived radioactive particles will remain in the soil tens/hundreds of years later, signaling that we already exist.

Professor Adam Frank said: 'With the Silurian hypothesis, we have clearly outlined the types of signals our civilization will leave if we disappear and someone will search for our civilization in the future. 10 or 20 million years from now'.

But above all, the experiment of the two professors demonstrated certain shortcomings in our current scientific apparatus.

Professor Frank explains: 'In cases where the industrial activity of a previous species was particularly brief, we would not be able to detect it in ancient sediments using the tools and methods we have at our disposal. Currently. If you want to look for evidence of a previous civilization, you have to do research that has never been done before and develop new methods'.

Remember, we're talking about the multimillion-year evolution of complex life.

And although neither Professors Frank nor Schmidt truly believe that an industrial civilization existed before our own, the main takeaway from the Silurian Hypothesis, Professor Frank said, is that if you're not clear Obviously looking for something, you probably won't see it.

According to the Silurian Hypothesis, not pyramids, not skyscrapers, not Styrofoam, not Shakespeare - in the end, we will only be known by a change in rock that marks the beginning of The Anthropocene Era!