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Kosha Dholakia An Introduction to Paleoneuropsychology

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Executive Functions of the Frontal Lobes and the Evolutionary Ascendancy of

Homo Sapiens

In this article, the evolution of modern thought is attributed to a cluster of cognitive abilities –

collectively termed as executive function – that can be measured through the archaeological

evidence available. While the role of development of neural capacity for language and

“symboling” (Klein 2000) or abilities of internal representation that enable external mental

rehearsal (Shepard 1997) cannot be ignored, as the ability to articulate and successfully

communicate complex ideas is fundamental for implementation of a large number of significant

actions, it is evident that the very inception of a complex thought is of far greater importance.

For example, the colonization of Sahul, which required the use of watercraft, required both – the

processing of complex variables for inception of such an idea, as well as efficient

communication for the implementation of the same. However, as the evolutionary models

mentioned above lack a common identifiable measure across eras, they are comparatively weak.

Complex human behaviour requires an ability to select a context specific action in the face of

strong, yet context – inappropriate responses as well as an inhibition of impulses seeking instant

gratification (Pennington & Ozonoff 1996, 54). Thus, the domain of executive functions

responsible for complex thought, while distinct from cognitive domains, has to overlap with

domains like attention, reasoning and also with working memory, language, sensation and

perception. However, there has to be a significant overlap between the executive function like

sequential memory and the central executive. Thus, apart from executive functions, development


of working memory would also play an important role in determining the evolution of complex

thought through human history.

The neural substrates of the frontal lobes make it ideal candidate as a domain due to its

extensive and reciprocal connections to a number of subcortical as well as cortical regions. To

validate this domain, the proof of heritability of these executive functions of the frontal lobe –

indirect and direct – needs to be examined thoroughly. The indirect proof, which stems from the

deficits suffered in ADHD, backed by the substantial proof of its heritability is conclusive. The

direct proof from the study of monozygotic and dizygotic twins, where their parents rated their

executive functions on a standardized scale across varying situations is also conclusive,

assuming that the parents’ observations were accurate. Thus, as executive function seems to be

highly heritable, it can be supported by archaeological evidence to trace the evolution of modern

thought.

Many Palaeolithic activities like making of barbed bone projectiles, foraging and colonization

require use of the executive functions mentioned above. As mentioned above, colonization

required development of watercraft, which required planning, organization, sequential memory

and working memory. Setting a date for evidence of modern thought in the Palaeolithic era is

more difficult, as different evidence puts it between 40,000 to 60,000 years ago. For example,

technologies of inhibition, while prevalent during the Mesolithic era, are hard to find in the

Palaeolithic. However, Middle Palaeolithic foraging can be considered, as it would require tasks

of inhibition. Barbed bone points from the Congolese site of Katanda dated by ESR may be a

100,000 years old. There is no doubt that modern thought existed in the Mesolithic and the

Neolithic era, but pin pointing the origin of modern thought in Palaeolithic era is difficult, but

arguably 40,000-60,000 years ago. There is conclusive lack of proof for archaeological evidence


for executive function among the traces left by Neanderthals as well as the early anatomically

modern humans from South Africa which makes the inception of modern thought firmly

independent from skeletal changes. However, this increases the probability of a change at the

genetic level.

It is highly probable that these executive functions contributed in the rapid development of

human culture about 60,000 to 30,000 years ago. It is also likely that natural selection favoured

executive functions as they would facilitate the necessary abstraction required for thought

experiments, as opposed to overt trials and overt errors. This ability to predict an outcome would

work favourably for increasing the odds of survival.

Even though executive functions can be seen as a metaphor based on the study of patients with

mental disorders. But since these functions are clearly heritable, and the archaeological evidence

supports their role in a shift of complexity of human actions, in my opinion, the development of

cluster of cognitive abilities, combined with working memory may be responsible for the

inception of modern human thought.

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