One of the challenges of searching for life in the Universe is that there is no single universal biosignature that could reveal its presence. Even if we could tell the difference between chemicals produced by living organisms and those from non-living sources like volcanoes, we're still making the assumption that alien life would resemble life on Earth. A new paper proposes that missions search for “energy-ordered resource stratification” which only happens when both self-replication and ecological competition are present.