MY sister got her yorkie at 6 weeks old. She does a lot of lunging and biting too. The vet told her that her dog was on the aggressive side. But, I don't know if that has anything to do with the age she brought her home or if its just personality. Did you meet the puppy's parents? What were their personalities like? I personally don't know if age has anything to do with it. There are alot of people on here that have conflicting opinions. My breeder let my puppy wean himself. I took him home at 11 weeks and he has been a great little dog. You could always consider hiring a trainer if you continue to have problems
