Scientists want to change the anthropocentric perspective we have in the search for extraterrestrial life and include types of communication used by other species.
Long before scientists discovered that other stars in the Universe harbor their own planetary systems, humanity was already contemplating the existence of life beyond Earth. As our technology matured and we began to monitor the night sky at multiple wavelengths (i.e. radio waves), this curiosity became a genuine scientific pursuit.
In the 1960s, a scientific field dedicated to the search for advanced life (similar to ours) emerged: Search for Extraterrestrial Intelligence (SETI). Since then, several SETI surveys have been conducted to look for possible signs of technological activity (also known as “technosignatures”).
To date, most of this research has looked for signs of possible radio transmissions, including the most ambitious SETI project to date: Breakthrough Listen. Other surveys included looking for thermal emissions that could be alien megastructures. So far, these searches have not found decisive evidence of technosignatures or advanced life. According to a new study led by Arizona State University’s (ASU) School of Earth and Space Exploration (SESE), humanity’s efforts to search for extraterrestrial intelligence (SETI) to date may have been limited by an anthropocentric bias.
The team also included researchers from ASU’s Beyond Center, the School of Complex Adaptive Systems (SCAS), and the Biodesign Center for Biocomputing, Security, and Society. Additional contributions were made by scientists at the Santa Fe Institute, the BioFrontiers Institute, and several departments at the University of Colorado. The description of their findings is being reviewed for publication in the Proceedings of the National Academy of Sciences (PNAS) Nexus.
“Like Ourselves”
As the team notes in their paper, the Search for Extraterrestrial Intelligence (SETI) has been a search for the familiar. In essence, we have been looking for signs and technosignatures that mirror our current stage of development technological. For example, Project Ozma was based on humanity’s own development of radio communications, which by the 1960s had progressed to the point where our signals could be detected from space. This approach is not without merit, given that radio signals can be transmitted over vast cosmic distances.
Not so much, Earth has become less “radiophonic” in subsequent decades, thanks to the development of satellite communications, the internet and other transmission technologies that do not depend on radio. Therefore, looking for radio transmissions is equivalent to looking for evidence of advanced civilizations during a brief period of technological development. In recent years, SETI researchers have expanded the range of possible technosignatures to include optical transmissions (lasers), neutrinos, gravitational waves (GOs) and other exotic ideas.
Unfortunately, our efforts are further hampered by the fact that we do not have prior knowledge of what to look for. “Traditionally, SETI straddles two extremes: an anthropocentric search for human-like technosignatures and an anomaly-based search for signals that deviate from known astrophysics,” co-author and SESE PhD candidate Estelle Janin explained to Universe Today in an email. “Since we don’t know whether intelligence is likely to will feel familiar or inherently ‘strange’the field needs more robust theoretical frameworks that identify generalizable features of life and intelligent communication without requiring complete prior knowledge or any assumptions.”
As an alternative approach, she and her team recommend broadening the search to include non-human species and their respective communication methods. As they explain, the main focus of both SETI and the emerging field of Messaging for Extraterrestrial Intelligence (METI) is the identification of signals that can be universally understood. Specifically, the team used firefly communication patternswhich consist of evolved flashes distinct from their visual backgrounds. This broadening of perspective also addresses another persistent problem in SETI research: the way in which “intelligence” is poorly defined. Janin said:
Communication is a fundamental feature of life in all lineages and manifests itself in a wonderful diversity of forms and strategies. Taking non-human communication into account is essential if we want to broaden our intuition and understanding of what extraterrestrial communication could be like and what a theory of life should explain. This also keeps the search empirically grounded: instead of relying solely on undefined anomalies, we can start from what life on Earth has been shown to do — not restricted to humans — and ask what aspects might reflect more universal and generalizable regularities, based on evolution and natural selection.
Methods
As they summarize in their article, fireflies produce periodic sequences of flashes during the mating season, which are specific to each species. When several species of fireflies are present in the same place at the same time, their flash patterns allow members of the same group to distinguish between other species, minimizing the risk of predation. The study is based on a firefly communication model that simulates the evolution of flash sequences over several generations. Next, the researchers examined how this signaling could influence the detectability of an extraterrestrial intelligence (ETI) amid space noise.
They also developed a own model that generated an evolved signal distinct from the background noise of natural pulsar signals. The resulting signal minimized energy consumption in a way that mimics the way firefly flash patterns maximize distinctiveness while minimizing the risk of attracting predators. The team selected pulsars because they are common throughout our galaxy and produce highly ordered emissions at regular intervals. This is why, when they were first discovered in 1967, many in the astronomical community thought they might constitute transmissions from an extraterrestrial intelligence (ETI), and why many today consider them “navigation lights” viable.
They were also chosen because pulsars provide an appropriate analogy for firefly behavior and offer a practical, observable background against which ETI signals could be distinguished. In this sense, its approach preserves the strategy of seeking life “like us”but expands the meaning of this by examining communication throughout Earth’s biosphere. It also takes advantage of advances made in the study of animal communication and digital bioacoustics, Janin said, which have not yet been applied to SETI efforts and life detection:
Our study is intended to be a thought-provoking experiment and an invitation for SETI and animal communication research to engage more directly and build more systematically on each other’s discoveries. More broadly, remote sensing astrobiology often has difficulty in track the progress of biologyparticularly with regard to understanding and integrating the full diversity of Earth’s living systems, and tends to focus more on questions related to the nature of astrophysical data than on the properties of the life it seeks to infer.
Results
The model consisted of a background of 158 pulsars within a search area of 5 kiloparsecs (~16,300 light years) centered on Earth. The pulsars were generated using data from the Australian National Telescope Database (ATNF). Then, artificial signals modulated based on different relationships between dissimilarity and energy costs were added. The “pulse” and “flash” profiles were grouped based on on/off states, with an average flux density being used as a threshold. Multiple permutations were performed in this configuration, considering different energy levels.
The results showed that most pulsars have much higher energy costs (between 84% and 99.78%) than optimized artificial signals. The model also incorporated energetic constraints along with dissimilarity, allowing us to compare how each influences the structure of the output sequence. As Janin summarized:
“We showed that extraterrestrial signals do not need to be complex or semantically decipherable to be recognized; rather, its inherent structure can be identified as a product of selection and evolution, uniquely and robustly implying the presence of life. This approach challenges SETI to consider the Earth’s biosphere in its entirety and to adopt less anthropocentric methods, grounded in the ubiquitous structural properties of life and communication.”
The research is part of a growing chorus dedicated to expanding the scope of SETI to include more exotic technologies, life forms and forms of communication. As SETI technology and instruments become increasingly sophisticated, the possible structures (i.e., what we should look for) also increase. In the not-too-distant future, there may be SETI projects dedicated to looking for “side effects of directed energy propulsion and communication, quantum communications and neutrino signals, using everything from radio antennas and infrared telescopes to solar gravitational lenses”.
“Studying non-human signaling can keep SETI empirically grounded while also expands our expectations about how extraterrestrial communication might manifest,” said Janin. “Using firefly flashes as an example of signals evolutionarily optimized to stand out in their environmental context, we argue that SETI should delve into animal communication and digital bioacoustics — fields that have advanced rapidly but remain loosely linked to life detection efforts.”
