The functional regions of the brain which subserve physical agony, the "pain centres", and the mainly limbic substrates of emotion, appear in phylogenetic terms to be remarkably constant in the vertebrate line. The neural pathways involving serotonin, the periaquaductal grey matter, bradykinin, dynorphin, ATP receptors, the major opioid families, substance P etc all existed long before hominids walked the earth. Not merely is the biochemistry of suffering disturbingly similar where not effectively type-identical across a wide spectrum of vertebrate (and even some invertebrate) species. It is at least possible that members of any species whose members have more pain cells exhibiting greater synaptic density than humans sometimes suffer more atrociously than we do, whatever their notional "intelligence".