A candidate for a future evolutionary suicide might be cod. Cod is caught as fish by humans. The fish do not weigh as much as they used to, mostly because they do not survive long enough. They do, however, mature earlier. Although this means the number of eggs per female fish is reduced, its effect depends rather on the extent of overfishing. Data suggests that when fishing is controlled, cod numbers return to their former level. This was the lesson of World War II, when cod fishing in many areas was greatly reduced, and pre-war cod numbers recovered.