For more than sixty years, humanity has been searching the cosmos for evidence of extraterrestrial intelligence.
While our efforts have been limited, and the results less than encouraging, that may be about to change. With thousands of exoplanets discoveries in the last two decades alone and next-generation telescopes becoming available, major breakthroughs are expected to happen soon. These surveys will be a chance to test various theories that have been advanced over the years.
In particular, astrobiologists hope to spot signatures associated with life and biological processes (aka. biosignatures) and technological activity (technosignatures), the latter of which are considered to be indications of intelligence. However, there are significant questions about what forms intelligence may take. According to new research led by the University of Rochester, the search for extraterrestrial intelligence (SETI) should be broadened to look for signs of "planetary intelligence."
The research consisted of Adam Frank, who is the Helen F. and Fred H. Gowen Professor of Physics and Astronomy at the University of Rochester, and his colleagues David Grinspoon at the Planetary Science Institute and Sara Walker at Arizona State University. The paper that describes their findings, titled "Intelligence as a planetary scale process," recently appeared in the International Journal of Astrobiology.
Typically, studies of intelligence tend to treat the phenomenon as a property of individuals. When it comes to humans, intelligence is demonstrated primarily by social behaviors, as demonstrated by our complex political, economic, and personal interactions — which are currently global in reach. However, there is considerable evidence that intelligence is also a property of collectives, as demonstrated by social insects, slime molds, and even viruses and microorganisms.
When it comes to the Search for Extraterrestrial Intelligence (SETI), studies have tended towards this anthropocentric bias. In short, we assume that other forms of intelligence will be individual and not collective.
"Humans have had a very particular view that intelligence only meant using tools and developing technology," Frank told Universe Today by email. "We have now come to see that many of the most important parts of intelligence — in terms of cognitive activity — are already present in the biosphere and often in distributed forms like social insects or even forests and microbial communities."
For the sake of their study, the team considered whether or not intelligence can operate on a planetary scale and whether this transition has already occurred for humanity. This required considering several theories that have been proposed in the past few decades, which are associated with the emergence of biogeochemistry, Earth systems' science, and astrobiology as fields of study. Of particular interest are the concepts of the Noosphere and the Gaia Hypothesis.
The former theory is attributed to Vladimir Vernadsky, a 19th-century scientist who founded the fields of geochemistry and biogeochemistry and also proposed the concept of a biosphere. Taking this a step further, Vernadsky conceived of a cognitive equivalent of a biosphere consisting of the collective cognitive activity of every living being. He referred to this as the "Noosphere," derived from the Greek word for mind ('noos').
The Gaia Hypothesis, originally proposed by chemist James E. Lovelock and biologist Lynn Margulis, asserts that Earth and its biological systems behave as a single huge entity that maintains conditions favorable to life. In the same vein, Frank and his colleagues considered how the emergence of intelligence might represent a planetary-scale transition — i.e., something that doesn't happen on a planet but to a planet.
Finally, they considered humanity's influence on planet Earth and how (since the industrial age) it has become the single-greater factor in planetary evolution — hence why many refer to the current geological epoch as the "Anthropocene." With these theorems as a foundation, the team then considered what a planetary transition would look like. In the end, they crafted a four-stage system to describe the evolution of planetary intelligence, Earth's past, and possible future).
Stage one in the system is an "Immature Biosphere," which describes Earth's climate and atmosphere during the early Archaean Era (about 3.5 billion years ago) when the atmosphere was composed largely of carbon dioxide and methane, and the first life forms began to appear. Stage two, the Mature Biosphere, began after the transition known as the Great Oxygenation Event (about 2.4 billion years ago) occurred, which corresponds with the emergence of complex life forms.
Stage Three, "Immature Technosphere," refers to the modern era where human technological behavior led to increased levels of CO2 and the introduction of chlorofluorocarbons (CFC) into the atmosphere. Stage Four, "Mature Technosphere," is a theoretical state where intelligent species can live sustainably with their planet — i.e., where the "technosphere" is fully integrated with the biosphere.
"Our idea was that as planets with life evolve, they can pass through a series of stages that can increase that life's capacity to maintain itself, to be sustainable for long periods," Frank told Universe Today. "So there is first a passage from an immature to a mature biosphere — [meaning that] the feedback loops of planetary intelligence have been established and are working. The same could happen for a technosphere."
According to this system, humanity is currently in Stage Three because our technology is degrading the planet's capacity to maintain a technosphere. To ensure our survival, we must ensure that the transition to a Mature Technosphere occurs. When applied to exoplanets and the possibility of life beyond Earth, this system presents some fascinating opportunities for SETI research.
"Any alien civilization we find is likely to be older than us," Frank added. "That means it will have learned how to bring its technosphere into what we called the mature state. So if we can understand what the properties of that mature state look like, we might have a better chance of knowing what 'technosignatures' we should be looking for."
In the near future, scientists hope to use next-generation telescopes like James Webb to search for possible technosignatures. These include indications of industrial activity in the form of excess CO2, CFCs, and other industrial pollutants. Similarly, research that helps define what a Mature Technosphere might look like can offer solutions for climate change here at home. At present, it is not clear how humanity can avert the ecological disaster and mass extinctions that are anticipated.
"We seem to be at a loss to be able to see how our global technological civilization can avoid the climate crisis it's generating," Frank said. "By looking at the history of the biosphere and how it developed the kinds of dense feedback loops that we call Planetary Intelligence, and that allowed it to persist for so long, we are hoping to see how we might guide the technosphere into a mature state such that it can also persist for a long time."
As always, the search for extraterrestrial life and civilizations requires that we take a harder look at ourselves and how living systems operate here on Earth. In so doing, we are not only able to expand the scope of SETI research (thereby increasing the odds that we will find that we are not alone) but deepen our appreciation of Earth and the nature of life.