Today we see many shapes and sizes of dogs, from big dogs that weigh more than most people to little tiny dogs that can fit inside a handbag. There are long nosed dogs and very short nosed dogs. Skinny dogs and fat dogs. We love them all.
All of these changes in shape are fine, but the changes in behavior are what is really important. None of us would want a wolf as a pet; mainly because they would rather attack us and be free than be our best friend. But Rock, up there in the picture, was a big old sweetheart. He was also very afraid of the dark.
There are also some other changes that scientists are just now discovering in dogs. The shapes of their brains has changed dramatically. Not just to one particular shape, but to many different shapes. Most dogs' brains have slowly moved forward over their long, human influenced evolution. Their olfactory bulb, which is what influences how they smell things, has also moved; and farther for some dogs than others.
We all think of dogs as being super smellers, but that isn't necessarily true for all dogs anymore. Some dogs are much better than others. I myself would much rather depend on a bloodhound for sense of smell than maybe a poodle.
Who knows what other differences have been inadvertently created with our manipulation of this creature of nature. There may be positive or negative consequences. But at least we know that the main consequences are that dogs are our best friends.
To read another article, which is also a bit more scientific, go here: Dogs' Brains Reorganized by Breeding