How did the Chinese get the Pekin to come out white if it is decended from the Mallard?

Question

How did the Chinese get the Pekin to come out white if it is decended from the Mallard?

Answer 1

I think it has something to do with the fact that they are domesticated.  

Answer 2

by choosing the birds that had more white patches on them till the birds were more and more white (mallards have white parts on them anyway and they vary from bird to bird although they look identical). people seem to like white animals because u can easily identify them and distinguish them from wild ones. its evolution controlled by man and not by the natural processes