Natural selection -- where certain traits give a population of a species a better chance of survival and reproduction under given environmental conditions -- doesn't result only from "natural" pressures. The problem of antibiotic overuse resulting in resistant bacteria is well-known, but Darwinian results from human activities may be showing up in an entirely new realm: cod. According to a subscriber-only article in this week's Financial Times (complete version is available in a Google Cache), researchers at the Institute for Applied System Analysis in Austria report a steady decline in north-east Arctic cod sizes over the past 60 years. They link this to fishing guidelines which mandate only the largest fish can be kept when caught; smaller ones are more likely to be thrown back, and therefore are more likely to pass along their genes. Changes to fishing rules -- specifying a maximum size as well as a minimum -- could reduce this selection pressure, but without countervailing pressure to make being large more survivable than being small, increases will happen much more slowly.