From motion to emotion: The evolving brain

The cardiocentric view that all thoughts and feelings resided in the heart, supported especially by Aristotle, dominated Western culture for most of the ancient era. Some of its legacy is preserved in the way we communicate our feelings today – take romantic love, and its association with red hearts; or courage, which in many languages derives from the Latin word for heart ('cor', which also meant 'mind' or 'intelligence'); or even learning and knowing, which in English are often said to happen by heart.

Today we know that emotion and cognition reside inside our skull, and not beneath our ribcage. As the cognitive and emotional powerhouse of the body, we might assume that the brain principally evolved to enable thoughts and feelings. The first thing I learnt from Evolutionary Neuropsychology is that the evolutionary history of the brain, from the comb jellies of 700 million years ago to modern animals and Homo Sapiens, is first and foremost a history of movement.

Coolidge explains that in basic marine multicellular organisms, moving allowed for enhanced feeding and replication. In the first terrestrial animals, moving enhanced reproductive opportunities and defence against predation. Among the first hominins, more sophisticated movements were likely responsible for the development of the first stone tools (hey there, Homo Habilis) as well as the ability to walk and run on two legs, abandon arboreal life, and hunt in groups (enter Homo Erectus). Over millennia, natural selection favoured random genetic mutations, allowing for a set of brain features which were more attuned to motor ancestral demands. That ultimately led to increased environmental fitness – the process we normally call 'adaptation'. 

In essence, as Coolidge often remarks, 'brains are for movement'. But how did they find their way to our modern emotional and cognitive systems? How did brains go from motion to emotion? Coolidge describes the concept of 'exaptation', the co-opting of pre-existing adaptations to serve novel fitness-enhancing purposes. Think of feathers – initially adapted for thermoregulation (we now know dinosaurs had them, much to the dismay of 90s kids like me brought up on Jurassic Park), but later exapted in birds to facilitate flight. Exaptation likely led the brain to co-opt pre-existing motor adaptations to serve more sophisticated emotional and cognitive purposes. 

For instance, the parietal lobes' original adaptation is thought to have been the integration of sensory information to promote movements in a physical environment. The parietal region in modern humans is deeply involved with consciousness and awareness of self and others. It is possible that early parietal functions (where to be and where to go?) were later exapted into a more abstract and metaphorical dimension of movement (who am I and where am I going?). Similarly, the frontal lobes are believed to have originally adapted to direct simple purposeful movements, like grasping and grabbing. With the advent of hominins, these areas may have been exapted to allow for higher levels of motor direction, involving more refined planning and executive skills, as well as the metaphorical grasping of abstract concepts. 

It occurred to me that language and etymology may also come to our aid in understanding this process. The words 'motion' and 'emotion' are deeply interconnected: from the Latin movēre ('to move') and e(x) movēre ('to move out' or 'to move away' – from a place, situation, threat). Etymologically, 'emotion' itself could perhaps be viewed as some form of 'lexical exaptation' of a basic action verb to signify a higher metaphorical form of movement – in English like many other languages, we describe things as emotionally moving.

Personal linguistic reflections aside, Evolutionary Neuropsychology provides a brief fascinating exploration of how the main cortical and subcortical regions may have evolved. An interesting chapter on paleopsychopathology – the potential evolutionary meaning of mental disorders – is also included. However, the flow of the book is at times disrupted by what seems to be confusion over its intended audience as an introductory volume. It includes very basic introductions to the origins of life, neuroanatomy, and the theory of evolution, but also detail on the current empirical evidence which feels suited for a lengthier, more specialist monograph. Ultimately, it succeeds at being a steppingstone into the field, but its pages at time feel just as dense and convoluted as the grey matter it intends to unravel. 

-       Reviewed by Dr Nicolò Zarotti, trainee clinical psychologist, University of East Anglia