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Thinking about Intelligence in the Universe: A Review

Kathryn Denning and Lori Marino


The very short version  (n.b. the long version is forthcoming)

There is a venerable scientific tradition of speculation about intelligence in the universe. Much of this speculation derived from ancient ideas concerning the order of the cosmos, or from assumptions of universal uniformity which justify extrapolation from the observables of Earth. This tradition substantially predated the theory of biological evolution and the recognition that human intelligence evolved, and that other animals also have minds.

In recent decades, there has been a striking diversity of scientific opinion concerning (a) the possibility of extraterrestrial life, and (b) the possibility that if extraterrestrial life exists, some of it could be intelligent.

In the absolute absence, so far, of any detections of extraterrestrial life, commitments ranging from the theoretical to the theological have heavily influenced such scientific opinions. The roles of chance and necessity, contingency and convergence, and various forms of order and directionality, etc., continue to be much-debated.

Astronomy’s search for signatures of extraterrestrial technology (and thus, indirectly, intelligent life) has been underway for over 50 years, as has exobiological/astrobiological research which focuses primarily upon the origins and early evolution of life on Earth, and the possibilities for microbial life in our solar system. Exoplanet searches and astrochemistry have also proceeded as highly successful parts of this larger research program. However, the middle ground – the vast territory between the emergence of life, and the emergence of interstellar transmission capability – has received rather less attention.

The evolution of complex life, and the forms of intelligence evident in Earth’s biota have, of course, been major research foci in the biological sciences, but the translation of research in this area into the astrobiological domain has been comparatively minimal to date.  There have consistently been efforts by some scientists engaged in the search for extraterrestrial life to include consideration of the evolution of complexity and intelligence, but overall, such efforts have tended to be overshadowed and derailed by tensions between some evolutionary biologists/palaeontologists and molecular biologists, and different reasoning styles in physicists/astronomers and biologists. Too often, discussions have tended to devolve into stalemates concerning the probability of complex extraterrestrial life – and thus, the pursuitworthiness or legitimacy of searching for it.  Existing research that might inform some crucial questions about the evolution of intelligence on Earth has not been well-integrated into the discussion, and potential avenues for empirically-grounded research into intelligence within an astrobiological framework have not often been pursued.

However, we can choose to start a new discussion, which preserves the valuable threads of previous conversations about intelligence in the universe, but does not perpetuate the well-entrenched divides from previous decades, or anthropocentric biases.

Contemporary astrobiology is only partly about the search for life elsewhere, or reckonings of what novel forms of life could theoretically exist in conditions on other worlds. Astrobiological research now substantially focuses upon fully mapping the diversity of life that exists, and has existed, here on Earth: the full characterization of life on this world. It is this aspect of astrobiology into which the study of intelligence can be generatively integrated. If we bypass previous preoccupations with probability estimates and extrapolations, and work from the actual data here on Earth, what can we learn about the many aspects of intelligence? If we start from the knowledge, hard-won and still sinking in, that human intelligence is trivially unique at best, and that all life displays intelligence of some kind, how can we then re-draw the history of intelligence on Earth?  If we begin with what we know today about the different forms of intelligence on Earth and their evolutionary trajectories, what new questions can we then ask? If we actively consider present methodological limits and how to push past them, and options for integrating multiple realms of data, what hitherto-intractable questions could we tackle?  If we use new theoretical frameworks concerning the nature and evolution of life itself, what research might we pursue?

What don’t we know about intelligence?



Kathryn Denning

Associate Professor, Anthropology,

York University, Toronto, Ontario, Canada

Lori Marino

Senior Lecturer, Psychology,

Emory University, Atlanta, Georgia, USA


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