I am no expert on either dog or human breeding (having reproduced only twice, non-selectively)but my bet would be that physical traits would be not much more difficult than in dogs. However, dogs have traditionally also been bred for certain behavioural traits which is much more difficult in humans.Either way, there is a big difference in man's best friend and your friend's best man.

Neatly side-stepping any delusions of policital correctness, aliens that want humans as "pets" would select those humans that never make the mental changes that occur at adolescence - in short those with mental illnesses. This would keep the pet human in a permanent mental state of that of a child - which, for those that work in the care of adults with mental illnesses is how many of these individuals are (physically adult, mentally child). The more traditional term would probably be "retarded", however we're more delicate these days and recognise the many different types and facets of these illnesses and conditions.These carefully selected pet humans would have to be inter-bred to ensure that they all develop these problems, so we're looking for a genetic disorder. Once complete it should be possible to develop a reasonably healthy stock of such human pets that never mentally develop into adolescents, let alone adults. As a result, the alien masters won't have the problems of humans getting ideas above their station, challenging for dominance and other problems that make some animals unsuitable for being pets.This is pretty much the same case to that of human pet dogs - they've been bred to never mentally pass the adolescent stage and therefore don't challenge their human masters for "leadership of the pack". Wolves (and other wild dogs), on the other hand, do reach the adult state of dog-hood and as a result typically make lousy pets.

This one made me chuckle.As has already been stated, Aliens actually wanting a human as a pet? – It's an interesting concept, though in the unlikelihood any intelligent extraterrestrial would require a pet amongst all its "holodeck VR video games" and "techno toys" your gadget crazed boy-friend could only dream about, they'd need to completely re-engineer the "pet" so it could survive in space with them.Radiation does bad things to DNA, though Earth does harbour radiation resilient life-forms, it's likely they'd have to cross any Earth bound life form with their own genetic make-up. This is assuming that any space fairing alien can splice DNA as they see fit, and that they themselves have some sort of DNA.Human bones and vascular systems deteriorate in a weightless environment, so they might remove these completely. - Realistically, I think we're looking at complete custom build here.I'm not convinced they'd want a retarded pet though. Surely, this would be no fun for an owner who is obviously looking for a challenge (they chose a human pet after all!). - If they're really masochistic, they'll opt for a human teenager!!If they need to "breed" at all, it would have to work over several human lifetimes, though arguably, they might want to tweak the "pet's" life-span to best fit their requirements. Personally, I'd much prefer a "Tribble"(http://en.wikipedia.org/wiki/Tribble);)

You just have to look at the huge range of different types of human already avaliable to see that an alien breeder could expect an excellent and varied range of human pets. Think of all the different types of skin, eye, hair colours, different shapes and sizes. From dark hairy giants to pale hairless waifs. With a bit of selective breeding the already exsisting variations in characteristics could be significantly enhanced to produce a set of human breeds every bit as extrodinary looking in their differences and those of dogs.Breeding programes, however, might be a little more tricky that with dogs, as humans tend to be rather more selective in their choices of partner....

The concept of human selective breeding is treated in the "Dune" series by Frank Herbert and i agree with him that due to the relatively long life span of an species like us (compared to that of a dog or cat) I would say that the time lapses involved would be far greater than the ones involved in other pet breedings.I think as well that these breedings would mean loads of reproductions in family related members, that would enhance the possibility of genetic disorders along with the desired features that were intended to breed.If I was an alien and I wanted to breed the best humans by conventional breeding techniques I would aim for the less developed countries as a source, as most of the medical advances weve made allowed a greater amount of "worse genetically stocked" humans to live.