Robust monomer-distribution biosignatures in evolving digital biota
  Because organisms synthesize component molecules at rates that reflect those molecules' adaptive utility, we expect a population of biota to leave a distinctive chemical signature on their environment that is anomalous given the local (abiotic) chemistry. We observe the same effect in the distribution of computer instructions used by an evolving population of digital organisms, and characterize the robustness of the evolved signature with respect to a number of different changes in the system's physics. The observed instruction abundance anomaly has features that are consistent over a large number of evolutionary trials and alterations in system parameters, which makes it a candidate for a non-Earth-centric life-diagnostic 
Evan D. Dorn and Christoph Adami
q-bio.BM q-bio.PE