I often reach a fitness about 100% or 80% within the first 60 generations. I don't understand why the fitness often drops radically in the following generations (7 to 15%).

I know that high fitness is kind of luck very often but shouldn't it stay at a certain level after about 120 generations or so? 

If the goal of the game is to develop an train a creature, it seems not logical to me that creatures regulary reach their best fitness around 30 to 60 generations and then things get much worse again and stay there.

Maybe someone could help me?

Thanks!

Greets