stepEvolution :: Evolvable a => 
  Int -> EvOptions a -> EvData a -> Population a -> IO [(a, Double)]
stepEvolution _ _ _ [] = return []
stepEvolution :: Evolvable a => 
  Int -> EvOptions a -> EvData a -> Population a -> IO [(a, Double)]
stepEvolution _ _ _ [] = return []
stepEvolution _ _ _ [] = return []