That was S. J. Gould’s model—in Life’s Grandeur. Assuming that a trait like brain size behaves as though it is a neutral trait seems pretty loopy, though. Now we have enormous data centres to explain, the “random drift” model is surely no longer worth entertaining.
A random walk away from no brain by a large number of lineages would also give you a constantly increasing upper bound on brain size.
That was S. J. Gould’s model—in Life’s Grandeur. Assuming that a trait like brain size behaves as though it is a neutral trait seems pretty loopy, though. Now we have enormous data centres to explain, the “random drift” model is surely no longer worth entertaining.