The way that I've phrased this outside of lesswrong (where people don't typically know what priors are) is: "In the absence of empirical data, things which are evolutionarily novel should be treated as guilty until evidence proves them innocent, whereas things which are evolutionarily familiar should be treated as innocent until evidence proves them guilty."

"Prior" captures the connotation that this is only a provisionary belief until more evidence surfaces in one neat word.