The Cylons were created by man.
They were the product of a desire to make life easier on Kobol. At first, they were simple robots. Toys. Conversation pieces at parties for the rich and trendy.
The Cylons became more advanced. Began to work the mines. Do the hard and dangerous work Man no longer wished to do.
And when the poeple of the Twelve Colonies of Kobol decide to war against each other, the Cylons began to do their fighting and killing for them too. The Cylons were the greatest soldiers the planet had ever seen. Smart. Fast. Deadly. They made decisions without waiting for orders.
And then the day came when the Cylons decided to kill their masters.
Oh wait...wrong planet can't possibly happen here.