Social brain

Lucy to LanguageI think Herbert Spencer was totally right stressing that humans are the ultimate problem of biology and the initial factor of sociology. Robin Dunbar’s Social Brain Hypothesis integrates information from many different fields to provide a comprehensive perspective on human brain evolution and its associated social context. Like gas molecules, it looks like individuals are not predictable in terms of behaviour but groups, indeed, are. The larger the group, the more the social responses and dynamics can be predicted by apparently simple rules, often based onto our primatological nature. Our brain biology supplies opportunities and constraints to our social networks. This book “Lucy to Language: the Benchmark Papers“, puts together about twenty review articles published in the last decade on the social brain hypothesis. This topic is definitely relevant and promising for every approach in evolutionary anthropology. This month I have published a review on this book, introducing issues in paleoneurology and cognitive archaeology which can be important to integrate these perspectives with evidence from the fossil record.

Visuospatial evolution

Descartes - Meditations metaphysiques 1641Visuospatial integration is essential in handling, tooling, simulation, and many specific tasks which are supposed to be crucial for human evolution. However, it may be even more important for theories on extended cognition, taking into account the relevance in coordinating the relationships among brain, body, and environment. This is something directly associated with concepts like embodiment, material engagement, and brain-artefact interface. And this is pretty intriguing when considering that the upper and medial parietal areas, which are major functional nodes of visuospatial integration, show a remarkable enlargement only in Homo sapiens. Together with Atsushi Iriki (Riken Brain Institute), we have now published a review trying to interlace all these issues: Extending mind, visuospatial integration, and the evolution of the parietal lobes in the human genus. We have tried to integrate topics in neurobiology, paleoneurology, cognitive archaeology, and comparative primatology, to understand why and how visuospatial integration may have been important, in our genus and in our species, for enhancing material engagement and embodying capacities. This article will be part of an issue of Quaternary International dedicated to the importance of “Material dimensions of cognition”. At the same time, the Journal of Anthropological Sciences is now publishing a second forum on the “three hands” of the Neandertals. The hypothesis of a mismatch between visuospatial functions and cultural complexity in this human species is further discussed with comments by Leee Overmann, Enza Spinapolice, Joseba Rios Garaizar, Ariane Burke, Carlos Lorenzo, and Duilio Garofoli. All the papers of the forum are free to download.

Prize!

Journal of Anatomy Bruner et al 2014

Journal of Anatomy Best Paper Prize 2014”  to Bruner E., Rangel de Lázaro G., de la Cuétara JM., Martín-Loeches M., Colom R. & Jacobs HIL. 2014. ‘Midsagittal brain variation and MRI shape analysis of the precuneus in adult individuals’,  Journal of Anatomy, Volume 224, Issue 4, April 2014, pp 367-376,  as the most outstanding article published during 2014! The prize is awarded by the Anatomical Society. Thanks!!!

Continuity

Humanchimp_2015Since the earliest hypotheses on human evolution there is major issue on continuity vs discontinuity. Charles Darwin suggested that only a matter of degree separates human and non-human species, also in the cognitive sense. From the opposite side, many biologists (mostly those involved in molecular sciences) are constantly looking for unique features, single changes that can switch the light on. The fact that there is still no agreement or evidence giving definitive support to any of the two perspectives may suggest that the debate is simply oriented toward an unfruitful direction. If there is still no good answer, maybe it is because there is a bad question. Is a faster car faster just because it supports higher speed or because it is differently designed? Both. What about evolutionary “shifts” based on the same processes? Are they a continuous or a discontinuous phenomenon? Both. Brain evolution is particularly sensitive to the continuity vs discontinuity debate. Is there a real biological frontier between continuity and discontinuity? It looks like a fractal loop and any change is, after all, a discontinuity in something. In paleontology, continuity is often a matter of appearance concerning the homogeneity of the fossil record, which gives a partial and largely incomplete view of the variation. Paleontology is furthermore based on a specific biological component – morphology – which may not necessarily have a linear correspondence with the underlying evolutionary processes. What if continuity and discontinuity are just in our head, in our eyes, in the form we perceive reality, in the form we analyze reality? We need fixed categories to decompose the scene and then recompose it by searching for relationships. Maybe this necessity is a limit, or maybe it is an advantage. But we think through categories. Evolution does not.

Warping brains

Ogihara et al 2015The team coordinated by Naomichi Ogihara has published an analytical review on computed reconstruction of fossil crania and interpolation of their brain morphology. The article presents and discusses the applications of biomedical imaging in paleontology, including technical and algebraic details. Automated assembling of fossil fragments is approached following geometric similarity, fracture surfaces, pattern matching, smoothness, and anatomical correspondence. Skulls, endocasts, and brains are integrated mixing information from computed tomography and magnetic resonance, and spatial deformation functions are used to interpolate brain morphology in fossil species. This is a very useful paper both for the technical issues and for general perspectives in digital anatomy and computed morphometrics in paleoneurology. Additional information on this topic can be found in the paper by Gunz and colleagues on virtual reconstruction and in the review by our team on functional craniology.

Brain ontogeny

Hublin et al 2015After that recent article on endocasts, the team from the Max Planck Institute has now published one more review, this time on brain ontogeny and life history. This paper introduces issues concerning encephalization, energy budget, birth, maturation, ecology, and culture. It provides also many general perspectives on hominid paleoneurology, resuming much paleontological evidence published in the last decade. It is a good and effective recompilation of literature and concepts, integrating morphometrics, development, and evolution. It is part of a special issue dedicated to brain, birthweight and the immune system.

Precuneus and surface

Bruner et al 2015One year ago we showed that a main source of variation among adult human brains is due to the proportions of the precuneus. This seems to be a stand-alone feature, not integrated with other patent morphological changes of the brain form. The spatial pattern associated with the dilation/contraction of the precuneus is particularly similar to the parietal bulging characterizing the brain of our species in evolutionary terms. Now we have published a study of the anatomical factors associated with this shape change, namely an analysis of the whole precuneal volume (cortical surface and cortical thickness) in a sample of adult humans. The results suggest that the observed changes of precuneal shape and proportions are associated with actual changes in precuneal surface area. Therefore, it is a matter of absolute cortex volume, and not just of relative size. There are no differences in cortical thickness. The precuneal volume increases with positive allometry as brain size increases (that is, it increases more than the rest of the brain, as brains get bigger), but the individual differences – as well as the differences between hemispheres – are important. What is the cellular reason of such morphological variation? Number of neurons, connections, or other components?

Interestingly, such marked anatomical variation seems not influencing any standard psychometric variable. It can be hypothesized that traditional psychometric performances are not adequate to quantify the functions of the precuneus. This is likely most of all when taking into consideration its importance in the default mode network, which functions are not easy to capture with task-based metrics.


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  • JA Best 2014
    “Journal of Anatomy Best Paper Prize 2014”  to Bruner E., Rangel de Lázaro G., de la Cuétara JM., Martín-Loeches M., Colom R. & Jacobs HIL. 2014. Midsagittal brain variation and MRI shape analysis of the precuneus in adult individuals,  Journal of Anatomy, Volume 224, Issue 4, April 2014, pp 367-376,  as the most outstanding article […]

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