United by feelings
A sufficient account of the evolution of mind must go deeper than our power of propositional thinking – our rarefied ability to manipulate linguistic representations. We will have to understand a much older capacity – the power to feel and respond appropriately. We need to think about consciousness itself as an archaeologist thinks about layers of sedimentary strata. At the lower layers, we have basic drives that prod us (and other animals) out into the environment for the exploitation of resources. Thirst, lust, fear and so on are triggers in evolutionarily earlier regions of the brain that stimulate vertebrates toward satisfaction and a return to homeostasis (physiological balance). At the lowest primary level, fear, for example, is radical. Under threat, the fearful animal voids its bowels, and a surge of activity in the amygdala and hypothalamus readies it for defence or escape.
The brain of mammals creates a feedback loop between these ancient affective systems and the next layer up – the experiential learning and conditioning that the creature undergoes. At this secondary level, fear (to continue our example) becomes more specific – rats are afraid of light, while humans are afraid of the dark. Same fear system, different threats. And, finally, in humans, another feedback loop exists between the neocortical ‘rational’ cognitive processes and the aforementioned subcortical triggers and learning systems. At this top level, the tertiary level, fear is enmeshed with higher-level conceptual and narrative thinking. Ruminations and thoughts, underwritten by language, symbols, executive control and future planning constitute this tertiary level, though they are energised by the lower-level emotion. At this third level, we arrive at uniquely human emotions, such as those elaborate and ephemeral feelings so beautifully articulated by introspective literary savants such as Henry James, Fyodor Dostoyevsky and, in the case of horror, Edgar Allan Poe.