That is, they are probably good evidence for some emotions in animals, but fairly useless in their current incarnation as to whether it was naturally occurring. Interestingly, it's entirely possible (and likely, IMO) that they exhibited some of this behavior originally due to their social nature, and this is what causes humans to start the process of domestication in the first place (not that it was likely a decision like that).
What's really interesting is how quickly changes, both behavioral and physical happen during domestication (and how quickly domestication works, possibly on the order of a decade or so)[1].
Years ago I had a lurcher, raised from a pup. One day I noticed that if you spoke to him in a stern manner - even if he had done absolutely nothing wrong he would hang his head low and look up at you, and put his tail between his legs as if he was guilty of something bad and wanted to look contrite.
It seems to me that it may be a long ago learned, now instinctive, behaviour to react that way to a particular tone of human voice.
On that note, I'll leave you with this, which is wonderful: https://www.reddit.com/r/HFY/comments/4rkdit/text_we_didnt_s...
Well, that was a good reason why we initially liked them, but the last few millennia of genetic modification through selective breeding to alter their behavior and appearance for our benefit hasn't hurt either...