Aliens Are Likely to Be Intelligent But Not Sentient: What Evolution of Cognition on Earth Tells Us about Extraterrestrial Intelligence

Anna Dornhaus
University of Arizona, USA

SETI – the search for extraterrestrial intelligence – is usually taken to mean the search for alien civilizations, alien people who are like us perhaps in their self-awareness and cognitive ability, but foreign in their biology because of their independent evolutionary origin. But what does this mean exactly? How would we recognize a foreign intelligence, and what is intelligence to begin with? And, assuming life exists on other planets, how likely it is to be intelligent? Biologists typically assume life self-replicates with inheritance, i.e., traits are passed on to offspring. Any such system is subject to evolution by natural selection. Even the most basic evolving life forms acquire traits that allow them to solve problems (ultimately to increase their own reproduction). 

Certain environments lead to the evolution of cognition to solve problems: feeding on a variety of foods commonly leads to the evolution of learning, e.g., honey bees and rats are more generalist feeders and better learners than their close relatives; animals with large home ranges typically evolve learning (of landmarks) to improve orientation, and living in social groups may also lead to evolution of cognitive skills. Indeed some degree of learning is practically universal among animals, and even much more complex skills, such as abstraction, social learning, tool use, cognitive maps, and metalearning (knowing what one knows, or knowing when to learn) are common even among ‘simple’ animals like insects. Thus, these skills are not ‘hard’ to evolve: they must both be frequently under selection, i.e., be useful or even necessary for many animal lifestyles; and their mechanics (e.g., brains) must not be too hard to produce either. However, human-like intelligence is unique on Earth, and we surprisingly know little on why it evolved in humans and not other organisms, or why it evolved at all.

Natural selection to increase individual reproduction seems insufficient as explanation, and perhaps it is: sexual selection, the evolution of an exaggerated trait unnecessary for survival but impressive to potential mates, much like a peacock’s tail or a nightingale’s song, may be the most plausible explanation. If this is true, then we should expect cognitive ability, i.e., learning, memory, abstraction, and many other elements of intelligence to be commonplace in the galaxy as they are among organisms on Earth; but ‘exaggerated’ intelligence as in humans may be a rare accident of chance, as rare as a peacock’s tail. 


Dr. Anna Dornhaus is an Associate Professor at the University of Arizona in the Department of Ecology and Evolutionary Biology. Her research, using empirical and theoretical approaches, focuses on the emergence of collective pattern from individual behavior, using social insect colonies (ants and bees) as model systems. She is particularly interested in the complex interactions that can produce adaptive, sophisticated, robust system-level behaviors with no unique ‘organizing’ unit driving them. Such ‘emergence’ is not only inherent in biology but in many structures relevant to our society, such as power grids, the internet, and in how diseases spread or organizations thrive or fail to do so. She holds graduate degrees (Ph.D. and ‘Diplom’ ~ M.Sc.) from the University of Würzburg, Germany, and worked at the University of Bristol, UK as postdoctoral researcher. She has published more than 90 peer-reviewed articles, and mentored over 100 undergraduate researchers and more than 20 graduate students and postdocs. Her public lectures have gained a total of over 50,000 views on YouTube, and the most recent one explores what evolution on Earth may tell us about the evolution of complex life on other planets.