stepEvolution n evo datum pop = do
  next <- oneStep evo datum pop
  stepEvolution (n-1) evo datum next 
stepEvolution n evo datum pop = do
  next <- oneStep evo datum pop
  stepEvolution (n-1) evo datum next 
stepEvolution n evo datum pop = do
  next <- oneStep evo datum pop
  stepEvolution (n-1) evo datum next 