Can a Neandertal meditate?

Intelligence can be seen as the capacity to coordinate many different skills at once. Indeed, one can have good verbal, spatial, mnemonic or social abilities, but this is not always useful if they do not merge together to generate coherent and balanced behaviours. In this scenario, attention (the ability to maintain that coherent integration in time and space regardless of internal and external distractions) can represent a sort of “limiting factor”. Limiting factor means that, independently from the punctual efficiency of the cognitive process, to be really fruitful, it must be sustained at least for a given amount of time, and focused on a selected amount of space. As pointed out by Henri Poincaré, the main target of our observations are not the things themselves, but instead their relationships. And to see those relationships, you must pay (or, in languages with Latin roots, at least lend) attention.

Most human-specific activities and behaviours strongly depend on a focused and selective attentional capacity. Indeed, the attention system is widely studied in neurobiology and cognitive sciences. The outstanding complexity of our technological and social resources intimately relies on our capacity to select and maintain a proper array of sensorial stimuli, discarding (many) others. It is hence to be expected that attention played a key role in the evolution of the human genus, and in particular of our species. The attention system relies on distinct neural pathways, so we may also expect that the evolution of attention was not linear, and not the same for every hominid taxon. A patchwork and mosaic pattern probably characterized the evolution of our attention system, which is, furthermore, quite sensitive to training, and thus influenced by subtle biocultural feedbacks (including the elusive –but indeed crucial– Baldwin effect).

Despite the importance of attention for our evolution, to date this topic has yet to be investigated in hominid paleobiology. Few scattered comments can be found here and there, but they are based on general statements (largely influenced by folk science, as often happens when fossils are involved) and not on proper scientific evidence. Here, I am pleased to introduce the first perspective review on attention and human evolution, based on a critical assessment of the evidence in paleoneurology and cognitive archaeology.

The article contains two main messages. First, it integrates the fossil record and the archaeological record into the debate regarding the evolution of our attention system. Which is, definitely, necessary to develop consistent theories on human cognition. The review presents issues associated with the evolution of the parietal cortex, lithic technology, social structure, visuospatial integration and working memory. Of course, working with extinct species has inevitably some important limitations, so many hypotheses cannot be tested, and a certain dose of cautious speculation is inevitably required. However, this information is necessary to support or discard specific assumptions or expectations, and to channel targeted and dedicated experimental approaches. This latter point is crucial because, although theoretical considerations are essential, they must be necessarily followed by experimental (and quantitative) approaches.

The second point concerns the ambivalent nature of the parietal cortex, which is involved in antagonistic processes. On the one hand, the parietal lobe is a core element of the attention system. But, at the same time, it is also a central component of the default mode network. In particular, the dorsal region (the precuneus) is largely responsible for somatic and visual integration, and hence crucial for our (unique) capacity to project visual images in the past (memories) and in the future (predictions). This is a great super-power of Homo sapiens but, at the same time, like in many tales from Greek mythology, its damnation. In fact, on the one hand, a large part of our behavioural complexity depends on the capacity of handling past and future simulations. But, at the same time, the same ability generates mind wandering, rambling and recurrent thoughts, and those never-ending ruminations that characterize the pandemics of stress, anxiety and depression typical of most human societies. All philosophical, spiritual and psychological traditions have recognized, ever since, a basic fact: humans do suffer. Indeed, it seems that this is an intrinsic and implicit human condition. Curiously, among those features that “make us humans”, two very specific ones are crying and suicide. The sad primate. This is why such suffering has represented a central topic for many diverse but converging perspectives, ranging from Buddhism to Stoicism, from Patañjali to Schopenhauer. In recent decades, our Western culture has rediscovered the importance of taking care of the present moment to achieve a proper balance with past and future projections through meditative practice and attentional training. This is mostly happening thanks to the principles of mindfulness meditation, which implies a profound training of body cognition, and the management of the transitions between the default mode network (ruminations) and the attention system (sensorial engagement with the present moment).

This perspective review on attention and human evolution does not aim to provide conclusions or firm statements. Instead, its scope is to call attention (literally) to these aspects, and to trigger future discussion (and research) on this topic. Such a view is necessary in order to provide robust theories on our cognitive abilities, but also to provide an evolutionary background to many psychological aspects (and limitations) of our amazing –albeit fragile– human mind.

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Here a share-link to a free download of the paper.
(valid until August 17th, 2022)

Blood flows through South America

This week we have published a survey on the prevalence of craniovascular traits in four South American samples, dated to the late Holocene (3000-200 ybp). The sample includes 70 skulls from the Pampean plains (Buenos Aires), Southern Andes (Salta), Central Patagonia (Chubut) and Southern Patagonia (Tierra del Fuego). These features display a large individual diversity but, in the case of these four samples,  no consistent group-specific differences. Nonetheless, in agreement with many traditional studies in craniology, people from Tierra del Fuego have a peculiar cranial morphology also when the endocranial anatomy is taken into account. There is a feeble association between cranial size and larger mastoid foramina. Also, in artificially deformed skulls, foramina tend to be somehow smaller. But, in general, the effect of cranial size or cranial deformation is, in this case, minor or negligible. There are instead more recurrent differences between South American and European samples, with the former showing more developed posterior vasculature (foramina and meningeal vessels). It remains to be assessed whether these vascular differences might be due to environmental vs random factors, or physiological vs genetic adaptations. Because of the possible involvement of these features in endocranial thermal regulation, altitude or other climatic influences could be an issue. Preceding surveys dealt with these same craniovascular features in European samples and in craniosynostotic skulls. Here a review on these traits.

Brodmann’s net

Network models and network theory are commonly applied in many distinct fields, including social studies, economics, epidemiology, and ecology. Networks are about relationships and, following the principles of system theory from Ludwig von Bertalanffy, relationships are everywhere. A “node” is whatever element of a system (a person, a city, a concept), and an “edge” is whatever kind of relationship (friendship, a railway, or energy flow). Therefore, network models are definitely suited to investigate the anatomical systems too, in terms of their parts and their functional or structural organization. In anatomical network analysis, the network represents the physical and spatial relationships between organs, tissues, bones, muscles, or any other structural element of the body. In the case of human evolution, it is for example interesting to apply such perspective to the topological relationships between skull and brain, as to provide a more comprehensive interpretation of the paleoneurological evidence. The analysis of the topological organization of the anatomical elements allows the identification of spatial constraints, structural modules, or crucial morphological factors that can influence both ontogeny and phylogeny.

In a preliminary study, some years ago, we applied these principles to investigate the Brodmann map, evidencing an interesting integration of the parieto-occipital cortex. Although brain parcellation is, at present, based on much more detailed variables and criteria than the ones available at the times of Brodmann (1909), his cartography is still widely employed in many fields. This is probably because it is simpler than other alternatives, because it partially relies on macroscopic features, because it is a nomenclature shared in neuroscience since one century, and because in some cases (from clinics to paleoneurology) a finer resolution of the brain regions is not necessary, neither feasible. Now, a more comprehensive research article presents a more detailed study on this topic. Results suggest that the posterior cortical regions are more integrated than the anterior ones, and with a more complex topological organization, associated with a certain biological burden. The cingulate cortex acts as a bridge between the anterior and posterior districts. The retrosplenial region displays a complicated spatial situation, with multiple structural influences.

It is interesting to note that network analysis in neuroscience is more frequently employed to study connectivity. Indeed, this impacting field is strongly based on this method, which represent the golden standard of the discipline. In some cases, talking with some colleagues, I have noticed a sort of scepticism toward a network approach that is not taking into account neural connections, and that deals “only” with the spatial relationship. Parochialism? Connectivity provides crucial information on physiological communication, but spatial topology reveals a relevant part of the underlying morphogenetic  organization. After all, most theories on cortical folding point at spatial constraints to explain ontogenetic and phylogenetic changes. There are surely important relationships between the physical arrangement of the brain areas and their connections, but these two aspects tell different stories, that must be then integrated in a unique and comprehensive scenario. This is why it is important to stress the relevance of network models to investigate topology also in the sense of spatial contiguity, as to investigate geometrical or biomechanical factors that may influence brain folds, endocranial packaging, or evolutionary plasticity.

Tool shape and visual attention

One more study on visual exploration patterns associated with Lower Paleolithic stone tools, this time dealing with the influence of the tool morphology. Previous analyses suggested attentional differences while observing choppers and handaxes, and eye scanning patterns that are independent of the visual saliency of the tool features. According to the results from this new eye-tracking study, however, visual attention is somehow influenced by the general morphology of the tool in handaxes, while for choppers the only correlated factor is their weight. Vision represents the first perceptual interaction between brain, body and tool, and it is hence supposed to be a key factor for triggering the evolution of a human-specific prosthetic capacity. All this is part of a wider research on cognitive archaeology and the evolution of visuospatial functions.

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And, a few weeks later, here is another one on how experience can influence visual exploration of these stone tools. We measured visual attention while eye-scanning choppers and handaxes in naïve subjects and archaeologists. The pattern of visual exploration is roughly similar, although archaeologists spontaneously devote more attention to the functional part of the tool (i.e., the tool tip) and to the knapped surface, revealing top-down influences. Interestingly, there are no patent differences in the exploration of the tool base, that is the part dedicated to the grasping (prosthetic) interaction.

Parietal lobe and material culture

This week we have published a review entitled “The parietal lobe evolution and the emergence of material culture in the human genus”, in Brain Structure and Function. The review, written with Alexandra Battaglia-Mayer and Roberto Caminiti, introduces paleoneurology, neuroarchaeology and cognitive archaeology, and then integrates these fields with information from behavioural neurophysiology, functional imaging and neuropsychology. The article will be part of a special issue dedicated to the parietal lobe and the angular gyrus.

Endocranial asymmetry and platyrrhines

One more study on endocranial asymmetries, this time on New World monkeys. Gonzalez and colleagues have analyzed 110 endocasts from 26 species, through landmarks and shape analysis. Some genera display a right-frontal left-occipital petalia, like humans and apes, while others have the opposite pattern. There is anyhow a pronounced intra-specific variability and, in the latter case, many specimens display scarce or null asymmetry, or the reverse scheme. Differences in these patterns are somehow associated with group size and home range, while the degree of asymmetry is correlated with brain size. Endocasts can only reveal gross brain asymmetries but, as evidenced by the authors, they can provide information when the study of the brain itself is not feasible (like in paleontology, or for living species for which brain samples are not available). This study shows that general brain asymmetries may be different for close related phylogenetic species, are influenced by socio-ecological factors, and have a patent allometric component. So there is no single trend, and evolutionary generalizations should be considered with caution. Interestingly, Alouatta keeps on behaving distinctly from the rest of the atelids, as does for most features of its skull and brain. Here more posts on brain asymmetries.

Visual attention and cognitive archaeology

Investigating the perceptual relationships between body, brain and technology is crucial to understand the peculiar evolution of the human cognitive capacities. In this sense, attention is a key factor and, as primates, visual inputs are our first and more comprehensive sensorial cues to the outer world. After our first paper on eye-tracking and Paleolithic tools, this week we have published a study on visual attention and saliency with images of choppers and handaxes. The study includes one on-line experiment based on remote selection of features, and one eye-tracking experiment based on the detection of pupil behaviour. Images of choppers and handaxes trigger different patterns of visual exploration, in terms of dwell time and fixation counts, partially influenced by morphological dimensions. The knapped surface is more explored than the raw surface, and the tip (the functional region) is more explored than the base (the grasping region). Interestingly, these patterns of visual exploration are not associated with saliency maps, as defined according to the discontinuities in colour, geometry, and texture of the pictures. This study was part of a collaboration with Timothy Hodgson, at the Lincoln University. Here a post from his blog, with a nice video showing eye fixations on stone tools.

Gona, Ethiopia

After an accurate digital reconstruction, we have now published a comprehensive metric analysis of two crucial fossils from Gona, Ethiopia, namely DAN5/P1 (1.5 million years) and BSN12/P1 (1.3 million years). These fossils (here the original description) display traits which are shared by Homo erectus and other early human species. DAN5 shows a general affinity with the Dmanisi fossils, as well as with KNM-ER 1813. Such similarity is probably due to the fact that, in these early humans, a large part of the cranial morphological variation is allometric, and therefore scarcely informative in terms of phylogenetic differences. Indeed, these skulls have a very small overall size. Other features (like the midline keeling or the angular torus) support an interpretation of these specimens as early African H. erectus. The analysis evidences an evolutionary trend in brain expansion, but no patent effects of sexual dimorphism. The study was coordinated by Karen Baab. Here a Share Link for 50 days’ free access to the article, valid until January 27th, 2022.

The cranial functional axis

The head is a complex biomechanical system, formed by a delicate network of soft and hard tissues. Furthermore, its functional and structural relationships extend to the whole body, influencing crucial adaptations ranging from breathing to locomotion. Modern humans are characterized by large parietal bones, at least in part associated with the enlargement of the parietal cortex. Such parietal expansion tilts the orientation of the brain that, in turn, is expected to influence the orientation of the head. In a new geometric morphometric analysis, we investigate the relationships between frontal bone, parietal bone, orbits and cranial base, in a sample of adult modern humans, to test whether and how the size of the parietal region is correlated with the morphological features of the orbital block. Results suggest that the dimension of the parietal bone exerts an influence on the orientation and rotation of the orbital region, but not on its form. In this case, we should hence consider the conceptual and evolutionary differences between a strict morphological integration (a reciprocal influence on shape) and a topological integration (a reciprocal influence on position). This survey supports further the hypothesis that an expansion of the parietal region in modern humans could have involved or required a rearrangement of the head functional axis, namely a rotation of the facial block and changes in the face vs braincase spatial organization. More info in The Skull Box.

Eyes and tools

This week, we present a new research line for the lab, we have been developing in the last couple of years: visual attention and cognitive archaeology. After our previous surveys on haptics and Lower Paleolithic stone tools, we have now begun to investigate how early human technology influences our visual exploration patterns, by using eye-tracking to analyze the schemes of saccades and fixations according to the dwell time and fixation counts. We analyzed the pattern of visual exploration in choppers and handaxes, through vision-only or associated with hand manipulation. The two tool types trigger different visual exploration patterns. In general, the central region of the tool is the more explored one, followed by the tool tip. The knapped region triggers more visual attention than the raw cortex. We found no differences in the visual exploration patterns when the tool is handled, or between males and females. Beyond the central issue of visual attention and cognition, this research line has two main wider targets. The first one is to promote experimental and quantitative approaches in cognitive archaeology, a field that is still largely based on theoretical perspectives but rarely brought into labs and stats. Quantification is mandatory to evaluate theories and hypotheses according to falsification criteria and experimental procedures.  The second aim deals with theories on extended cognition, trying to understand if, how much, and in what way tools are integrative parts of our cognitive system. If humans have evolved a specialized prosthetic capacity, cues of its visuospatial and body integration functions should be still detectable in the changes associated with the paleontological and archaeological record.