We're big dog fans here at the NEMO office -- that's no surprise. Check out this interesting segment Dogs Decoded that recently aired on PBS.
You'll have to battle through some of the leaps of logic that the show makes (can dogs really be the only animal to understand pointing, or have we just not done the research on cats, dolphins, octopi, horses?). But it is worth the 30 minutes or so to get to the second half of the show where they describe results of an ongoing 50+ year research experiment on fox domestication in Russia.
The total segment is about an hour long, so bookmark this for a time when you can sit down and digest it all.