Are we missing the universe's 'noosignatures?'

Astrobiology has long been split into two camps: a search for "biosignatures" and a search for "intelligence." These look for very different things, but they also leave a huge gap in between. It took 3.5 billion years for us to go from the first microbe to a civilization that sent radio waves into the cosmos. Detecting life in between those stages is a relatively untouched aspect of astrobiology-which is also the focal point of a new paper, "Signs and Signatures of Intelligen...