You mean to tel me this was accidental?
No, it was not "accidental".
I remember an experiment with fish. A scientist put the same fish in different tanks.
1: Tanks with large pebbles + no predators.
2: Tanks with small pebbles + no predators.
3: Tanks with large pebbles + predators.
4: Tanks with small pebbles + predators.
In the tanks with no predators the skin of the fish slowly evolved to be more prominent. The males which were noticed the most got to breed the most. In the tanks with predators the prominent fish got eaten more often. Over time the fish in the tanks with large pebbles ended up with large spots, and the ones in the tanks with small pebbles evolved small spots.
It's random mutation that generates the changes, but what you must remember is that LOTS of animals die, far more than are born! The ones which survive have a slight edge over the others and then pass that edge on to their children. But then their children are slightly mutated, lots of those die, so the ones with the slight edge again survive to reproduce. This cycle means that the pattern is guided by the environment, the closer you are to something useful the more you breed.
Another experiment with wolves has been running for decades in Siberia. Only the most docile were permitted to breed. Over time not only did they become very tame but their features became more puppy-like, their ears floppy, and their coats started to produce different patterns making them look like collie dogs.
If you are not familiar with how selection works watch my video:
http://www.youtube.com/watch?v=QCQoyJAiMooHopefully that will make it easier to understand.