Multi-trait convergent trends in the evolution of brains and cognition

Our target article proposed that vertebrates, cephalopod mollusks, and euarthropods independently converged onto high levels of brain and cognitive complexity and that this macroevolutionary trend was coupled with and facilitated by the acquisition of a small set of pivotal traits, used in visuomotor control of three-dimensional and targeted movements. In response to commentaries that challenged our working premise and conclusions, we (1) use the concept of aggregate complexity to define brain and cognitive complexity and dispel misconceptions about anthropocentric bias, (2) call attention to the explanatory value and power of convergence as an important evolutionary concept, (3) highlight certain architectural and organizational features of the nervous system as scaffolds for the evolutionary expansion of behavioral and cognitive complexity, and (4) consider the phylogenetic distribution of phenomenal consciousness in relation to our findings. We also try to foster a greater appreciation for cognition as a process that involves whole animals as aggregate systems and that requires an extended repertoire of laws and principles to understand its evolution.