Are we missing the universe's 'noosignatures'? Astrobiology has long been divided between the search for biosignatures and technosignatures, leaving a vast middle ground unexplored. This gap in our understanding is the focus of a new paper, 'Signs and Signatures of Intelligence', by astrobiologist Julia DeMarines. The paper introduces the concept of noosignatures, which are traces of intelligence left on a medium, and proposes a new research framework called noosemiotics. These noosignatures can be physical, like stone tools, or signal-based, like complex animal communication, but they must remain detectable as the product of intelligence. The paper suggests using Assembly Theory to measure the 'assembly index' of an object, which is the number of joining operations required to construct it from basic elemental components. This index can be used to determine if an object could have arisen by random chance or required a mind to create it. Earth has examples of noosignatures, such as the Lomekwian assemblage and agricultural impacts on the nitrogen cycle, which would pass this test. The beauty of this idea is that it captures the worlds that developed intelligence but failed to sustain a cooperative planetary civilization. These noosignatures might be the only evidence of intelligence on these worlds. However, the concept is still new and has many kinks to work out. Noosignatures decay over time and natural self-organization can be hard to distinguish from noosignatures. Assembly Theory is still in its infancy when dealing with macroscale archaeological structures, and relatively few scientists have explored this problem. The paper suggests that astrobiologists should start to view astrobiological signatures as a continuum rather than a graph with two distinct peaks. This could lead to the discovery of planets where life falls into this middle category. In my opinion, this is an exciting development in astrobiology, as it opens up new possibilities for understanding the evolution of intelligence in the universe. It also raises deeper questions about the nature of intelligence and the challenges of sustaining a cooperative civilization. Personally, I think that the search for noosignatures is a crucial step in the search for extraterrestrial life, and it is an area that deserves more attention from the scientific community.
