The above image compares brain structures from various species. Of particular interest to me is the comparison between mammals and birds. In PZ Myers words:
In mammals, the neocortex is central to higher level thinking. The comparable structure in birds is called the hyperpallium, or Wulst (German for “bulge”). The fascinating thing is that the cellular organization of these two areas with similar functions and perhaps similar roles in generating consciousness are very different.How do these anatomically different structures allow for similar mental phenomena?
Emory and Clayton stated: "Cognition in corvids and apes must have evolved through a process of divergent brain evolution with convergent mental evolution. This conclusion has important implications for understanding the evolution of intelligence, given that it can evolve in the absence of a prefrontal cortex." For more, read Avian Brain and Senses, part of an online course in ornithology.
Humans, great apes, corvids, dolphins, and elephants all display similar traits for intelligence. Since birds are included in this list, we can conclude that intelligence can result from very different brains. Inevitably I am led to wonder which form of cellular organization is more or less optimal for achieving the functions it serves. Of course, in terms of evolution, that may simply mean reproduction.