This is called Paedomorphism (thanks Wikipedia) through Neoteny. Humans are a very good example of it.
Or cats (though I'm not sure about this one). See how Tiger/Lion cubs behave like regular cats? Moderate aggressiveness, meowing, etc?
Which is defined by the humans in this case.
> Your Chi-Pom-Poodle-Terrier isn't an evolutionary step for the canine.
Any change is an 'evolutionary step'. You're thinking in dangerously telelogical and moralizing terms.
This is called Paedomorphism (thanks Wikipedia) through Neoteny. Humans are a very good example of it.
Or cats (though I'm not sure about this one). See how Tiger/Lion cubs behave like regular cats? Moderate aggressiveness, meowing, etc?