Posted by Astrobiology has traditionally focused on two major targets: biosignatures, such as atmospheric oxygen or methane, and technosignatures, including radio signals or large-scale engineering. A new paper by astrobiologist Julia DeMarines argues that this approach overlooks a vast evolutionary middle ground between simple life and technological civilization.
DeMarines proposes noosemiotics, a framework for searching for noosignatures – detectable traces produced by intelligence. These could include physical objects such as tools and architecture, communication systems, or environmental changes caused by intelligent organisms. Importantly, researchers would not need to understand their meaning to recognize them as products of cognition. One possible method for identifying such signatures is Assembly Theory, which measures how many construction steps are required to produce a complex object. Highly complex structures may be less likely to arise through random natural processes.
Earth provides examples of potential noosignatures. Stone tools date back around 3.3 million years, while agriculture began altering the global nitrogen cycle thousands of years before humans developed radio technology.
The concept could expand astrobiology by allowing scientists to search for planets where intelligence evolved without ever developing detectable advanced technology. However, distinguishing artificial structures from natural complexity and determining how long such signatures remain observable are major challenges. Noosignatures could ultimately help scientists view life and intelligence as an evolutionary continuum rather than two separate search categories.
For more details, read the original paper and the full article by Universe Today.
