Thanks. I can see that. However, I wonder if the study included fish and arachnids? :) At some point a line was drawn based on taxonomical definitions. It seems to me, the question is not whether or not animals sacrifice gut for brain, but whether 'gut for brain' was a niche that humans filled, or if the inverse change of the two was coincidence. It doesn't seem to be possible to answer that question by analogy unless all species included in the data set could explore the niche to begin with. Glad that I'm not an evolutionary biologist. :)At the same time I'm also weary of special pleading. The "refuting" paper noted that for the expensive tissue hypothesis to remain viable we must propose unique mechanisms operating in humans, which Occam's Razor doesn't like.
No, the study only included mammals. However they - and others - note that the expensive tissue hypothesis does seem to be in play in fish (such as the artificial selection study I mentioned in the post; where fish who were "evolved" to have big brains also developed a smaller gut) and a few other groups. Of course, if we're debating over whether or not data from other mammals is applicable to humans then data from fish surely suffers from the same flaws and then some! Last time I checked they didn't have fire either!