"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
In human society we see that good and evil tends to cluster in separate regions, some in places where life is cheap, governments are corrupt and crime is rampant. And we see other places that are much very serene. This is because good and evil both have positive feedback effects. In other words, evil begets evil and good inspires good.
In nature we often see the same thing. There are places where it is very dangerous to be. In these places the plants are toxic and the animals are either aggressive and vicious or suspicious and fearful. On the other hand you see places where animals are quite friendly. I don't believe this is coincidence. I thing the dynamics of good and evil apply to animals as well as humans. Animals in packs or herds have their instincts suppressed by the herd the same as humans have their own evil nature suppressed by religion and society. And these animal herds or human societies are subject to change and actually have a will seperate from that of their components.