Visuospatial behaviours

After the perspective paper on visuospatial cognition and human evolution, and the review on visuospatial integration and the fossil record, we have now published a review article on visuospatial behaviors in archaeology. Here, we introduce and discuss parietal cortex evolution, embodiment, tool use and tool making, wayfinding, and the association between physical, chronological, and social spaces. A main target of cognitive archaeology is to test whether modern human cognition is due to a specific prosthetic capacity that enhances the functional relationships between body and technology, offloading brain functions and outsourcing information process to the enviroment. Something similar happens to … spiders! This chapter is part of a book dedicated to the Evolution of Primate Social Cognition (Springer).

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Newborn folding

Amazing study this one on neonate cortical folding! They analyzed almost 600 newborn brains with an automated method based on surface and curvature and, according to the results, the adult folding scheme is already expressed after birth. This means that most folding mechanisms act before birth. Taking into account that the brain then undergoes a dramatic increase in size, we can probably say that size-related effects may be important but indeed not determinant, for the final sulcal scheme. There could be allometric influences in brain folding but, if a neonate already displays the adult cortical pattern, this means that other early non-allometric factors are involved. Here a post on this study. And, a recent review by Van Essen and colleagues on brain development and evolution, addressing the issue of cortical folding.

Goodbye, Mr. Gene …

Luigi Luca Cavalli-Sforza (25 January 1922 – 31 August 2018)

 

Parietal cortex

In November 2017 Ashley Morhardt organized a Karger Workshop at Hyattsville (USA), entitled “From fossils to function: integrative and diverse approaches to vertebrate evolutionary neuroscience“. The workshop was included in the activities of the J. B. Johnston Club, and papers are  now published in Brain Behavior and Evolution. My contribution is a review on the evolution of the parietal cortex in the human genus. Articles will be freely accessible for the next six months. Have a look!

Neanderthal’s visual cortex

A recent study published by Antonio García Tabernero addresses issues about the morphology of the occipital lobes in Neanderthals. It is an anatomical description of a new occipital fragment from El Sidrón, and a morphological analysis of the Neanderthal occipital variation. Neanderthals display more occipital asymmetries than other hominids, including in the vascular pattern of the venous sinuses. They have been also hypothesized to have larger occipital cortex when compared with modern humans. It remains to be evaluated whether differences in the occipital lobe morphology can suggest distinct functional capacity, and here is a stimulating article right on this topic. However, it should be considered the possibility that occipital proportions in Neanderthals are not a derived feature, but a plesiomorph human (Homo) condition, being modern humans the ones who depart from this scheme.

Electrodermal archaeology

After all those surveys on parietal lobes and parietal evolution, some years ago we began investigating some functions particularly associated with the parietal cortex, and generically labeled as visuospatial integration. Some visuospatial behaviors can be inferred in fossils, according to anatomical and archaeological evidence. In my lab, we are interested in aspects bridging cognition, body, and tools. In a recent paper published in Progress in Brain Research we have applied electrodermal analysis to investigate the cognitive response during a haptic experience with stone tools. Electrodermal signals have been employed here to evaluate changes in emotion and attention during stone tool manipulation, as to evidence whether different tools exert different cognitive responses when handled. New methods for cognitive archaeology!

 

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The paper is part of a volume entitled “Cerebral Lateralization and Cognition: Evolutionary and Developmental Investigations of Behavioral Biases“, edited by Gillian Forrester, William Hopkins, Kristelle Hudry and Annukka Lindell.

Naledi

Ralph Holloway and colleagues have just published a paleoneurological study of Homo naledi. They used seven cranial portions from at least five individuals to provide a general view of an endocast of this species. The study is comprehensive and very detailed, indeed. It turns out that, despite the very small endocranial volume (about 500 cc), the brain general organization is very similar to all the other human species. Beyond some particular features in Neanderthals and modern humans, all human (Homo) species display the same general sulcal pattern. If there were differences in their sulcal organization, these should have been pretty minor or hardly recognizable on an endocast, at least according to what we can test with the small samples generally available in paleoanthropology. So, it is not surprising that Homo naledi has a Homo brain form. But the interesting thing is the association between a human brain morphology and a small brain size, as suggested by this current study. If true, we have two main conclusions. First, our brain cortical complexity and our large brain size are two independent features. They have evolved together in many cases, but not in others. Second, our human cortical folding scheme is not simply an allometric (scaled) version of the apes’ one. Cortical folding is largely influenced by mechanical factors, most of all size-related effects, so one could think that our brain morphology, although distinct from apes, is a secondary consequence of having a big brain. The results presented in this study suggest that this is not the case. We humans have a specific cortical organization and, furthermore and additionally, a big brain too. Reasonably, both features have an influence on our cognitive capacities.

Of course, these results must be confirmed on a larger perspective. Remember that here we don’t have a “brain”, but some scattered endocranial surfaces of a few specimens. That’s not sufficient to reach detailed and reliable conclusions on the brain itself, not to say on cognition. Also, the species Homo naledi (and its chronology) is at present strictly associated with one specific site and needs further corroboration from a wider geographical scenario before supporting firm or generalized statements. Its striking feature is the very small brain size. In this sense, it is worth noting that we often use to mention “average” values, sometimes forgetting about their associated variation and variability. We modern humans have a normal cranial capacity spanning a range of more than 1000 cc. In this paper, Holloway mentions the case of Homo erectus, spanning from 550 cc to 1200 cc. Therefore, caution is still necessary when interpreting the small brain size of these individuals. Of course, the fact that this species (as the Flores hominid) could have undergone brain size reduction or small brain retention does not point against the importance of brain size and encephalization. According to the available fossil record, most human species bet on big brains. Exceptions are expected, but do not break the rule.

I want to focus on one more aspect of this article. Although the topic was definitely “sexy”, the authors avoided any speculation on cognition or phylogeny. Such attitude is so professional and definitely welcome, thank you!


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