They've already talked (and showed) quite a bit about how stuff like animals, trees, ships etc are done. Essentially what they're doing is building a base model

They've already talked (and showed) quite a bit about how stuff like animals, trees, ships etc are done. Essentially what they're doing is building a base model (a prototype, I guess) for everything that is then changed with something like the sliders in any character creator, but more extreme. So from the "cat" base model you'd get house cats, lions, leopards, tigers etc from that, in addition to really wild things.