Is information a selectable trait?
There is little doubt in scientific circles that--counting from the origin of life towards today--evolution has led to an increase in the amount of information stored within the genomes of the biosphere. This trend of increasing information on average likely holds for every successful line of descent, but it is not clear whether this increase is due to a general law, or whether it is a secondary effect linked to an overall increase in fitness. Here, we use "digital life" evolution experiments to study whether information is under selection if treated as an organismal trait, using the Price equation. By measuring both sides of the equation individually in an adapting population, the strength of selection on a trait appears as a "gap" between the two terms of the right-hand-side of the Price equation. We find that information is strongly selected (as it encodes all fitness-producing traits) by comparing the strength of selection on information to a weakly selected trait (sequence length), as well as to a neutral marker. We observe that while strength of selection on arbitrary traits can vary during an experiment (including reversing sign), information is a selectable trait that must increase in a fixed environment.