Meganalyses

In the last decades, computed and digital methods are providing amazing tools for anatomy, a field that is enjoining new challenges, but most of all a field that is rediscovering many old – unresolved – questions. In general, macroscopic anatomy still suffers from a profound lack of basic knowledge, and we don’t know the functions and variability of many morphological features, including for our own species. That’s why every small information, in this sense, can be outstanding. The current bubble of science marketing, however, is not sufficiently fuelled by small or isolated chunks of information, and it requires “sexy” scoops and massive products. As a result, in the gold rush to financial support and social recognition, researchers and institutions are aiming at providing, in one single article, the largest amount of data. Such huge studies often involve never-ending lists of methods and techniques that no single person can entirely control and guarantee (sometimes with patent consequences in their technical reliability or scientific interpretation). Paradoxically, because the product must be easily sold to the information agencies, it must also be fast and short. As a consequence, many of those entangled methods and results end up buried and forgotten in remote supplementary files, or quickly mentioned in a synthetic figure caption. Many of those little pieces of these mega-analyses (like a correlation plot, an average, a group comparison, a regression parameter, a coefficient of variation or a punctual observation) are crucial, illuminating and revealing, but they serve to a greater campaign, and must be sacrificed as minor passages for the sake of the big scoop. As transitory and secondary parts of the game, they will pass unnoticed, undiscussed, and uncomprehended. What a pity!

Electrodermal hands

After our first research article on stone tool manipulation and electrodermal reaction, here a second one on the effect of hand size and morphology. Females display larger electrodermal variation and higher peaks than males in both arousal and attention, but they also have smaller hands. So, the different electrodermal reaction to tool manipulation could be due to an allometric effect associated with hand size. Accordingly to our results, this is not the case, and these electrophysiological differences during haptic exploration are instead real sex differences, due to biological or cultural factors. By the way, the length and width of the palm are the hand variables with more sexual dimorphism, while the thumb length is the one showing less sexual differences. For a general review on body cognition and cognitive archaeology, you can also see this article on hand-tool interaction, recently published in a  Current Topics in Behavioral Neurosciences volume dedicated to the Processes of Visuospatial Attention and Working Memory.

Brains Through Time

A Natural History of Vertebrates …

Skulls and brains

A recent study by José Luis Alatorre Warren and colleagues supplies one of the very few analyses on both skull and brain morphology from the same individuals, in humans, chimpanzees, and gorillas. They analyzed the shape variation of the brain and skull separately, and then at the same time. The study describes the spatial relationships between brain and skull, and the differences between species. The study confirms once more that there is a limited correspondence between cerebral and cranial anatomical boundaries and references. According to their results, the most striking difference between humans and chimpanzees is, in the former, a spatial change of the frontal lobe regions associated with language. They also found a larger parietal cortex in humans when compared with apes but, according to the model they use, these differences would be not so remarkable as suggested by most of the preceding studies. However, their geometrical model is very comprehensive and it includes many distinct and independent elements of the brain and of the skull, that are melted and averaged when all their coordinates are superimposed together. In these cases, punctual or local differences are spread onto the whole global variation, and can be hardly detected. Namely, these extensive shape registrations are excellent to analyze general covariation patterns, but can be tricky when trying to identify the contribution of local regions or of specific anatomical elements in a heterogeneous and multifactorial anatomical complex.

In my opinion, the article suffers, unfortunately, some important conceptual limitations. There is a confusion between Ralph Holloway’s theories on parietal evolution in australopiths (largely based on the position of the lunate sulcus) and my own ones on parietal evolution in modern humans (based on the size and proportions of the parietal lobe). It seems obvious to say, but we are dealing with distinct taxa (australopiths and modern humans) and distinct processes (early hominid evolution and late human specialization), and therefore there is no reason to look for common factors or mechanisms. For example, when taking into account the possibile influence of posture on brain shape, the evolution of bipedalism may be an issue for australopiths or early Homo, but not when comparing modern humans with Neandertals. Also, there seems to be a constant misunderstanding between parietal cortex enlargement (which involves parietal lobe absolute and relative size) and brain globularization (which refers to the rounded shape of the brain). It should be clear that these features can be influenced by (and due to) different factors, although they concern the same anatomical regions. Finally, there is a frequent confusion (and miscitation) between papers and results on parietal bones, and papers and results on parietal lobes. So, in my opinion, we are dealing with a study which supplies an amazing analysis, but a problematic discussion of the results. I think this study would have seriously benefited from a more cautious interpretation of the numerical outputs, and a more careful integration of the literature. Nonetheless, this exceptional database is there, and I hope it will supply in the future more information on the spatial relationships between brain and braincase.

Gánovce

The natural endocranial cast of Gánovce was found in 1926 in Slovakia, and dated to 105 ka. Although the surface is damaged, the endocast is pretty complete, and has some bony fragments of the braincase encrusted on the surface. Cranial capacity is approximately 1320 cc, and the endocast has a clear Neandertal appearance, with flat parietal lobes, projecting occipital lobes, and wide frontal lobes. Between the 40s and the 60s, Emanuel Vlček provided many comprehensive studies of the cast, including shape analyses based on superimposition criteria and outlines, histological and chemical surveys, and radiological considerations. However, the endocast is scarcely known because most of the articles were published in Czech and Slovak. We have now published a JASs report to briefly summarize the information available on this fossil, providing further metrics, new comments on the craniovascular features, and a digital reconstruction after tomographic scan.

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And here the curious story of … the Circle of Gánovce!
The natural history of an endocast …

 

Mind and Brain

Amazing special volume in Cortex: The Evolution of the Mind and the Brain. The issue is edited by Michel Thiebaut de Schotten and Karl Zilles, and it includes reviews articles and research reports on neuroanatomy, primatology, ecology, social cognition, networks, cytoarchitecture, neuroimaging, handedness, brain size and cortical folding. A great collection of papers and authors, indeed!

Paleoneurology at UCCS

At the end of August we will begin a renewed online course in Human Paleoneurology at the Center for Cognitive Archaeology of the University of Colorado Colorado Springs. Here a post introducing the course, and the information on registration and credits.