What Makes Us Human

One of the major challenges in current science is to understand the emergence of modern humans, who have cognitive capacities which in a biological context are extraordinary. How could this have happened in anatomically modern humans, that is, in a species which had apparently already evolved to its current genotype (or close to it)? It is a species in which further major changes in brain structure and organisation did not occur. Yet this transition in cognitive capacities gave to this single species the potential to transform the natural world.

The emergence of modern humans with their extraordinary cognitive capacities is to be ascribed to a particular type of cognitive computational process: sustained non-routine multi-level operations. These operations are required for the common denominator of the cognitive capacities specific to modern humans: abstract projectuality.

What makes humans different from animals?

Modern humans have a range of cognitive capacities which are unique to them. We call them h-capacities. For many of these capacities it is possible to recognize some degrees of protocapacities in animals and, especially, primates.

Assigning protocapacities to hominins is more controversial due to the limited information provided by archeological material. What is most critical is to specify them by contrast with the capacities of pre-modern humans such as Homo ergaster, Homo erectus, and Homo Neanderthalensis. However, since the cognitive capacities of modern humans are themselves not easy to characterise, let’s simply consider the capacities of modern humans by contrast with other animals, in particular primates. Here is a brief, incomplete, list to illustrate their diversity:

1. Language

A greatly discussed basic human capacity, with a complex underlying structure which goes far beyond any communication system used by other animals. There is widespread agreement that some form of protolanguage developed relatively early in human evolution. However, there are major disagreements as to whether there was then a single critical step in attaining a modern language facility such as the acquisition of recursion or speech or a whole sequence of critical steps.

2. Tools and instruments

Tools and instruments are designed to realise, amplify, optimise, and extend their natural capacities. This ability goes far beyond that shown in the rudimentary use of tools by monkeys and primates, for instance, in using bones or stones to break nuts or sticks to capture ants.

3. Signs, signals and other homomorphic representations

Humans have the ability to visually represent aspects of reality for a particular purpose such as indicating something for subsequent use. For example, a bifurcation or a cross can be used to indicate the correct direction or route, an ability that eventually will develop to provide representations such as plans or maps.

4. Dynamic concepts

Humans have the ability to conceive of dynamic entities, to use ideas of forces, or more generally to conceive of causes for events and of the consequences of actions. This allows humans to analyse nature by isolating characteristics, identifying regularities and recognizing relevant causes and effects. These capacities could be considered as an implementation of what Vygotsky and Luria (1930) called the basic characteristic of humanity: the constant search for a why.

5. Aesthetic sense

It enables other capacities to be sublimated for a further function. Poetry and literature are generated from language, painting, sculpture, and plastic arts from schematic representations, music from vocalisation, dance from action and so on.

6. Meta-representation

Humans are capable of using representations not only of directly perceived things but also as a second or higher-level interpretation of “mental, public or abstract” entities (see here).

7. Algorithmic capacity

Modern humans have an efficient algorithmic capacity, providing the basis of logical operations, and eventually of arithmetic, geometry, and mathematics.

8. Categorisation and organisation

Even traditional societies have complex systems for organising their knowledge, as for instance what they know of the properties of animals and plants.

9. Theory of mind

A more controversial candidate for an h-capacity is theory-of-mind or mentalising. It is known that primates, in particular, are able to perceive the attitudes or intentions of others of their species. The extra human component is the ability to make inferences based on the abstracted mental state of the other, not just on a database of the representations of specific behaviour using their statistical relationships to compute possible actions. This depends on the development of a cognitive process – the ‘expression raiser’ (EXPRAIS) – which makes the human aspects of theory-of-mind derive from meta-representation, discussed above.

10. Anticipatory planning

Human behaviour is often directed towards the attainment of some explicitly represented future state-of-affairs. This capacity has been called “mental time-travel into the future”. Humans can also set themselves imagined goals not closely related to their current situation and current needs. By contrast, it has been argued that even chimpanzees cannot represent a goal without a means of achieving it. More generally, animals cannot anticipate future needs or drive states. Also, the capacity develops in relation to theory-of-mind but is not directly dependent on language.

How did we become special?

What is critical about even this short list is the variety of specific cognitive processes involved in the different capacities. Any common denominator would need to be abstract. However, is there any reason to associate developments in any of these capacities with the evolution of modern humans per se?

Brain volume relative to body weight steadily increased in the homo lineage by a factor of about two from 2 million years ago to the origins of anatomically modern humans, generally identified with Homo sapiens. Such humans evolved in Africa roughly around 160–200 thousand years ago, spreading later through the world.

There was however a considerable gap in time before any behavioural consequences of the anatomical change became apparent. There is, however, a general consensus that by 50–35 kya in the Upper Palaeolithic in Europe and the Late Stone Age in Africa, a range of activities took place which have been characterised as “modern human behaviour”. There are however different views on how cognitive abilities developed over this period, and thus when and where the acquisition of modern human behavioural capacities took place.

One school proposes that following a gradual development from 200 kya, a rather rapid change to fully modern human behaviour happened around the transition from Middle to Upper Palaeolithic. A rival school proposes a more gradual and slower development over a few tens of thousands of years and possibly from the advent of Homo sapiens.

But what could explain the emergence of a very varied set of h-capacities in an already evolved brain? Such a mechanism would not only provide possible causes for the transition, but it would also situate it as following a slower but continuous cognitive development in hominins. The critical stage responsible for the transition in the development of all h-capacities is the attainment of a key basic human capacity: abstract projectuality.

Concrete projectuality

Other animals also engage in complex actions that lead to satisfaction of a need at some future time. This can even involve predominantly innate structures, as in bees and ants, when conscious choice presumably does not occur. At a higher level, animals may use complex routines to achieve specific goals, for instance, in hunting and mothering. At an even higher level, an animal like a gorilla uses highly complex, well-learned routines to achieve a specific goal, such as eating nettle leaves.

This type of complex behaviour is called concrete projectuality. The animal is generally aiming to achieve a well-learnt objective; given this motivational context, the behaviour is triggered by specific stimuli or by a memory of a closely related event. In doing so, it will operate with a limited number of parameters, representing the position of a prey, characteristics of the terrain, and so on.

Abstract projectuality

Humans, by contrast, are able to set objectives which do not stem directly from immediate representations of their current perceptual world and motivational systems, but imply instead a representation abstracted from immediate reality.

Both the goals and the steps taken to realise them need to be specified on the basis of a limited set of pertinent parameters; they determine an abstract space in which operations and objectives are represented. Pertinence is not ‘natural’ but is determined by the process envisaged. The limited number of parameters – as compared to the infinite number of parameters of reality – allows intentional recursive computation to be produced that can be sustained in time, may branch in a variety of subroutines and may use logical or algorithmic operations.

In carrying out the project, the relevant parameters may need to be reassessed, and even its objectives redefined. To be effective, such a process of reassessment or redefinition would require an extra level of abstraction in which the elements manipulated are metarepresentations of the elements or processes of the preceding stage.

More specifically, we hold a process requiring abstract projectuality to have a number of properties:

  1. The process can be protracted – potentially very protracted – in time. Moreover, it can be suspended and continued later.
  2. It does not need to be triggered by direct sensory stimuli.
  3. Mental effort is usually required in establishing, controlling and implementing projects.
  4. It aims to attain goals that may be novel or require the production of new strategies and does not consist merely in reproducing an already well-known procedure. In other words, the procedure required cannot be reduced to a “memory organisation packet”, namely a well-learned, routine program such as that we employ when we to go to work each morning.
  5. It involves the potential for fluent non-routine thought.
  6. It involves abstraction. In other words, it operates with a limited number of pertinent parameters abstracted from reality.
  7. In the course of the process, all characteristics may be modified.

How did we achieve abstract projectuality?

Many cognitive scientists assume that language was the original modern human capacity and that the abstract organization and the communication systems it allows generated the other h-capacities. Others have argued that the ability to produce meta-representations was a precursor to modern language abilities. In the abstract projectuality framework, all h-capacities have a common causal root. The existence of a novel mode of processing (latching) is not however equivalent to its concrete realisation in the social context of early modern humans. Undoubtedly, the powerful communication between individuals that language allows could have played a major role in the epidemic of new h-capacities that occurred.

A novel computational capacity – that for sustained multi-level operations allowed by latching – sees the basic human capacity as (potentially infinite) recursion, the ability of an operation to ‘‘call’’ another operation of the same type. This is required in the evolution of a number of critically human skills, including but not limited to language. Moreover, the way that the products of two operations can coalesce in the operation of another has considerable similarities with the basic “minimalist” concept of merge in modern linguistics.

The relevant brain mechanism for these processes is the fronto-polar cortex, a crucial structure for human emergence. A drastic and rather sudden macro-change without sudden drastic micro-ones (phase transition view). Evolutionary biologists are familiar with rather rapid and unforeseen transformations in organs or structures that were prepared by natural selection for a different function. This is called exaptation.

The neural changes are dependent upon processes that occur well after birth and are affected by many cultural and child-rearing factors. The strong evolutionary increase in brain connectivity from rats to hominids becomes a crescendo due to epigenetic influences, and so opens to the environment the genetic envelope.

What distinguishes Us

In the end, what has distinguished man’s evolution is the establishment of brain mechanisms that, in addition to assessing the direct response that an event or action provoked, also accounted for subsequent events and possible implications.

Men began to notice that the effects of their actions were not necessarily immediate or clearly evident, and consequently began to modify the instinctive and irrational fear that derives from the “sense of loss” of an apparently unsuccessful act.

In one word: projectuality.


[F.O. – adapted from Amati and Shallice (2007)]
Thanks to E.M. for the inspiration
Featured image: Piet Mondrian, Evolution (1911)

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