Any explanation of how natural cognition may manifest in an organism is constrained by the biological conditions in which its genes survives from one generation to the next.[3] And since by Darwinian theory the species of every organism is evolving from a common root, three further elements of cognitive biology are required: (i) the study of cognition in one species of organism is useful, through contrast and comparison, to the study of another species’ cognitive abilities;[4] (ii) it is useful to proceed from organisms with simpler to those with more complex cognitive systems,[5] and (iii) the greater the number and variety of species studied in this regard, the more we understand the nature of cognition.[6]