If it doesn't help, and uses more energy, then it won't get kept unless it's an inevitable side effect of something helpful. That was my only basis for "larger (of same type) => more intelligence".
I don't really know anything about this topic. My claim is essentially a tautology that may not have much practical application.
Some trivia (not directly related to my original claim) I found at http://en.wikipedia.org/wiki/Brain_size:
[brain size vs. body size in mammals] follows a power law, with an exponent of about 0.75
the "average" brain of mammals taken as a whole, but each family (cats, rodents, primates, etc) departs from it to some degree, in a way that generally reflects the overall "sophistication" of behavior.
Primates, for a given body size, have brains 5 to 10 times as large as the formula predicts
If it doesn't help, and uses more energy, then it won't get kept unless it's an inevitable side effect of something helpful.
That's true. But something helpful done by the brain isn't necessarily involved with intelligence.
We have a sample of one modern human civilization, but there are some hints on how likely it was to happen.
Major types of hints are:
Data for:
Data against:
To me it looks like life, animals with nervous systems, Upper Paleolithic-style Homo, language, and behavioral modernity were all extremely unlikely events (notice how far ago they are - vaguely ~3.5bln, ~600mln, ~3mln, ~200k or ~600k, ~50k years ago) - except perhaps language and behavioral modernity might have been linked with each other, if language was relatively late (Homo sapiens only) and behavioral modernity more gradual (and its apparent suddenness is an artifact). Once we have behavioral modernity, modern civilization seems almost inevitable. Your interpretation might vary of course, but at least now you have a lot of data to argue for your position, in convenient format.