Posts Tagged 'Neandertals'

Ontogenetic dilemma

Ponce de Leon et al 2016

Marcia Ponce de León and colleagues have published a comprehensive shape analysis on modern human and Neandertal early ontogenetic endocranial changes, as Philipp Gunz and his team did back in 2010. Interestingly, results are different. The previous study from the Max Planck Institute concluded that only modern humans have a species-specific postnatal stage in which the braincase bulges (globularization stage). In contrast, this new analysis, coordinated by Christoph Zollikofer, suggests that after birth Neandertals and modern humans share a similar pattern of endocranial shape change. In this case, any endocranial difference between these two species must occur before birth. The discrepancy between the two studies may be due to differences in the samples (which, recognizing the good samples used in these analyses, would reveal a problematic instability of most paleoanthropological studies) or to differences in the reconstructions of the specimens (which, recognizing the good experience of both teams, would reveal a problematic instability of most paleoanthropological studies). Nonetheless, we must also take into account that both articles rely on very complex statistical and algebraic passages, and methodological biases should not be ruled out. After all, also paleontology deals with the same limits of any science: we do not work with skulls or brains, but with models made of variables and parameters. Models that work well in some cases, and do a worse job in some others, depending on the questions involved. In this new study, the fact that endocranial shape differences between Neandertals and modern humans are prenatal is used to state that there are no cognitive differences between the two species. Of course, cognition is more than shape, so the relationship between the timing of these changes (before or after birth) and the statement on cognition is not particularly straight. Inferences on cognition should be made on multiple evidence, dealing with something that goes well beyond a surface analysis.

Diploic veins

Rangel de Lazaro et al 2015Diploic channels run within the vault bones, and are therefore protected from external agents. This condition makes them an interesting topic in paleontology, archaeology, and forensics. At the same time, such secluded position has hampered detailed studies on their morphology, variations, and functions. In 1999 Hershkovitz and colleagues published a first pioneering survey on these “elusive” anatomical elements. This week we publish a segmentation procedure to visualize these channels after computed tomography, applying this method to modern humans and Neandertals. The diploic network displays a marked individual variability. It is frequently connected with the meningeal system at the pteric area, and with the emissary and venous systems at the occipital area. As for the meningeal arteries, also the diploic vasculature is apparently more complex in modern humans than in other hominids, mostly at the parietal area. Taking into account the large size of the parietal lobes and bones of our species, it is likely that such vascular development can be associated with metabolic and thermal functions. Beyond the large diploic channels, this vascular system counts with a widespread network of microvessels, which should be carefully investigated in the future.

Amud

Amano et al 2015 - AmudA new reconstruction of the Neandertal skull and endocast of Amud has been published by a team coordinated by Naomichi Ogihara, at the Keio University (Yokohama). They applied mathematical models to align the surfaces of the original fossil fragments (surface extrapolation). Thin-plate spline was then used to integrate the available anatomy from Amud with other Neandertals, namely La Chapelle-aux-Saints 1 and Forbes’ Quarry 1 (shape interpolation). Modern skulls were used to smooth all together. This new reconstruction shows a skull that is shorter and wider than the former one. The basicranial areas, largely missing in this specimen, were the most difficult parts to interpolate, because of their complex morphology influenced by different independent factors. Amud is dated to 50-70 ka, with a massive cranial capacity: around 1740 cc.

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.

Three hands for the Neandertals

Lozano et al 2008Together with Marina Lozano (IPHES), this week we have published a JASs Forum on a speculative hypothesis concerning the use of the mouth in support to praxis and handling in Neandertals and their ancestors, as evidenced through the analysis of their dental marks. This behaviour, very common in Homo neanderthalensis and Homo heidelbergensis, is not so frequent in modern hunter-gatherer. According to the theory of extended mind, cognition is the result of the interaction between brain and environment as mediated by the experience of the body. The main “ports” of such interface are the eye (input, from the world to the brain) and the hand (output, from the brain to the world). Modern human brain displays a peculiar dilation of the deep parietal areas, which are particularly involved in visuo-spatial integration, which includes the management of the eye-hand system, the integration with memory, and the integration with frontal executive functions. Hence, we suggest that the necessity of a further additional element (the mouth) may be necessary when the standard anatomical elements are not sufficient to integrate the body relationships with the cultural complexity. A mismatch between the biological substrate (neural system/body interface) and cultural substrate (complex tools and behaviours) could have been the backstage of a risky involvement: the mouth as integrative body support. The investment is not safe, considering the importance of the mouth in different and relevant functions, and it sounds like an extreme solution. Neandertals do not show a similar enlargement of the parietal areas, when compared with Homo sapiens. Although we ignore the exact relationship between brain form and function, the fact that these areas are crucial for visuo-spatial integration is, at least, intriguing. Needless to say, a possible mismatch between neural and cultural systems in Neandertals should not be interpreted as an “intermediate” condition between archaic and modern forms, but else as a lack of proper coordination associated, as far as we know, with an evolutionary blind alley.

The hypothesis has been commented by Lambros Malafouris, Marco Langbroek, Thomas Wynn, Fred Coolidge, and Manuel Martin-Loeches. Next issues to be considered: details of the hand anatomy and hand management, early modern humans associated with Mousterian tools, and functional behaviours in those modern populations that use mouth and teeth for praxis. Hypotheses in cognitive archaeology are necessarily speculative. But we can try nonetheless to supply multidisciplinary evidence to integrate paleoneurological and archaeological data, providing at least a logical framework. In this case the next step is clear: to evaluate further this hypothesis we have to investigate more visuo-spatial behaviours in these extinct forms.

[You can download here the whole forum]

Dynamics of learning

Dynamics of Learning 2014The talks from the Tokyo meeting on learning processes in Neanderthals and modern humans are now published in two books by Springer. The first volume is on cultural perspectives, the second volume is on cognitive and physical perspectives. Cultural anthropologists, paleontologists, archaeologists, sociologists, medical doctors, and psychologists collaborate in a joint project coordinated by several Japanese universities and research institutions (like the Kochi University of Technology and the Keio University) to evaluate whether differences in learning abilities may have influenced the competition between modern humans and Neanderthals. In volume two there is a review of mine on Neanderthals’ paleoneurology, presenting the current information we have on the anatomical and morphological endocranial changes associated with the Neanderthal lineage. The paper evidences structural constraints and functional limits which may have characterized the spatial organization of the Neanderthal braincase.

Models in paleoneurology

Pithsight 2013 (EBruner)Paleoneurology gets new tools. By using living species, Eiluned Pearce and colleagues look for correlations between neural and non-neural anatomical elements, and then apply their results to fossils. This approach opens up an incredibly large set of new research lines. They find a correlation between orbit size and visual cortex which, after a delicate series of normalization processes, suggests that Neandertals had larger visual areas of the brain. At the expense of the parietal ones. This new information seems to provide further support for the hypothesis of relative dilation of the parietal lobes in our species. The long chain of numerical transformations the authors applied to control any possible scaling factor is really efficient and successful. Evidently it also introduces many assumptions and estimations which call for caution when dealing with strict interpretations of the final outputs. Also, we know that only in modern humans and Neandertals the prefrontal brain areas lie on the orbital roof, generating complex constraints between brain and eyes that may produce departures from the schemes of other species. Nonetheless, with these limits in mind, we must recognize that this study supplies new and fresh ideas to our field, and relevant new information on Neandertals. It is also useful in reminding us once more that different lineages may undergo different cognitive evolution, which in the case of the brain means improving or demoting different behavioural skills. This recalculation of the different cortical areas in fossil hominids also supplies new estimations of parameters associated with primates’ biology and social structure, such as the average group size.

Many people are warning against “paleo-phrenology”, but this should not be the case. This is a correlation study. A theory can explain a correlation or fail to do it, but the correlation is there, and it can reveal underlying information. Caution is recommended, but this is always recommended in science. It is strange how we are critic against a lots of details for complex models in evolution, yet we accept overly simplistic alternatives like those associating cognition with a single molecule or gene …

A comment on National Geographic.


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