Is it normal for a male puppy to hump? 12 weeks of age? Or should I select another dog.
This kind of behavior is pretty common, especially in male puppies - but females do it too!
It's generally considered to be a dominant behavior, and personally I have noticed that the puppies/dogs that exhibit this trait do seem to be of a more dominant nature. However, don't confuse dominance with aggression, they're not the same.
Discourage this behavior in your puppy with a firm "no" and redirect his attention to his toys, or another activity. Many puppies go through stages where they 'hump' like this, and it can get worse during adolescence. Make sure you're consistent in correcting him.
As this is likely an early sign of a dominant nature, be sure to work with your puppy at home and teach him basic obedience commands. Also, enroll him in a puppy/basic obedience class to help you both communicate better and give him valuable socialization experience.
I don't think you need to choose another puppy because of this humping behavior, it's just one of those annoying/frustrating things that puppies do - like chewing, biting/nipping and so on.
However, if you feel strongly about this, or are concerned about other aspects of his personality/temperament, then I would talk it over with the breeder.
Best of luck!