I'm not sure if my following comments/observations belong here or in the general thread or the ideas/discussion thread. If desired I'll repost there.
I'm on a northern small continent/large island (about 20 good city sites, or 25 city sites if I wanted to maximize land space). On this land mass, there are no elephants, no cows, no bison, co camels, no llama and no donkeys (although there are 2 horses). I encountered 1 barbarian donkey very early on (via Wanderer) and was damn lucky to subdue it. If I hadn't, I would now be completely unable to produce the animal assitant workers. As it is I can only build them in one city. This is extremely annoying.
I see no reason why subdued animals couldn't be a buildable unit so that farms/flocks/herds/kennels could be established in other cities. Yes, I realize that would obsolete the 'National #### breader' buildings, but I think you could just change what they do instead.
Additionally, I think there should be more animal assisted workers (Musk Ox, Water buffalo, *HORSE* come to mind). Perhaps there could even be some differences between them. Horse and Elephants might work faster, but take more to build (Horses are expensive/valuable) or in maintenance (elphants obviously).
Secondly, this land mass produced an overabundance of lynx and red fox, a decent amount of moose, eagles, hawks, wolverines and skunks. A few pigeons, a few snakes, one couple horses, one donkey and one musk ox (on a single tundra hill); and not a single other type of animal... including no wolves of any sort. Seems a bit silly... particularly the no wolves/dire wolves.