PERSON
Sara Imari Walker
American astrobiologist and theoretical physicist (b. 1978),
Davies's principal collaborator on the
algorithmic origins of life, whose work on assembly theory and the physics of information provides the mathematical foundation for understanding life as informational architecture.
Sara Imari Walker is an astrobiologist and theoretical physicist at Arizona State University whose collaboration with Paul Davies has produced some of the most rigorous contemporary work on the boundary
between physics, information theory, and biology. Her research focuses on the question of what makes matter alive—not as a philosophical puzzle but as a problem in physics with testable consequences. The 2013 paper 'The Algorithmic Origins of Life,' co-authored with Davies, argued that life is distinguished by its informational architecture rather than its chemistry, and that the transition from non-living to living is marked by the
emergence of top-down causation. Walker's subsequent development of assembly theory—a quantitative framework for measuring complexity by the minimum number of steps required to construct an object—has provided empirical tools for detecting life and intelligence in systems where traditional biochemical markers may not apply.
In The You On AI Field Guide
Walker's trajectory into astrobiology was unconventional. She studied physics and chemistry at