The precuneus is still an elusive element of the brain. It is the result of an anteroposterior functional gradient integrating body perception and vision, and a dorsoventral gradient integrating this visuospatial frame with episodic memory and autonoetic projections. The body is used as a sort of metric unit to “travel” through physical, chronological, mnemonic, and social spaces. It is like the “homunculus” we throw on Google Maps to explore a virtual environment, and run through imagined pixel-based landscapes. Namely, the precuneus is a key node for mental imaging, consciousness, and self-construction.

This week, we have published a still-missing study on this key cortical region: ontogeny. We have analyzed shape and size variations in the precuneus from birth to early adulthood. Here are the main results. First, its growth is largely associated with general brain growth, mostly in the first two years after birth, reaching a plateau before five years of age. Second, during this early period, there are only minor shape changes, which include a bit of dorsal extension. Therefore, the expansion of the precuneus (and its contribution to dorsal brain bulging) is distributed through the pre- and postnatal stages, although the former period is probably more relevant, in this sense. Third, the outstanding individual diversity can be detected in all age groups, since birth. This is particularly important, because it means that this pronounced diversity must originate prenatally, influenced by intrauterine or genetic factors. Fourth, although the precuneus dorsal extension represents the main feature involved in its variations, there are multiple factors involved in its morphology, likely due to the many topological influences of the neighboring regions. Fifth, the dorsal and ventral regions of the precuneus are not much integrated, as they belong to distinct morphological modules. The dorsal region fades into the superior parietal lobule, and should probably be interpreted as its hidden deep part. The ventral region fades instead into the posterior cingulate and retrosplenial areas, without a clear boundary. This separation is also relevant when dealing with aging. The subparietal sulcus could probably be used as a conventional and operational reference to separate these two morphological blocks. It is hence mandatory to keep these two regions separated, when analyzing structural and functional features of the posteromedial parietal cortex.

The precuneus displays a noticeable diversity in adult humans, mostly in its longitudinal proportions. These variations are due to differences in cortical surface area. Nonetheless, its variability also concerns the vertical extension, and the sulcal patterns. The main focus of diversity is localized in its dorsal and anterior region, the one most involved in somatic awareness. It is much more expanded in humans, when compared with apes. Probably, it is also more expanded in Homo sapiens, when compared with extinct hominids. Such evolutionary change could have occurred recently, say in the last 50-100 thousand years. The precuneus is also a hot target for neurodegeneration, possibly because of its functional and structural complexity. You can find a list of posts on the precuneus right here.

What is left? Well, surely many details, but the main mystery is still the complex (and unclear) association between anatomical and cognitive variability.

In a detailed perspective review, Giovanni Federico and colleagues have recently presented a comprehensive proposal to disclose the neural structure supporting the human technological cognitive skills. Their model integrates those cortical regions associated with causal reasoning, semantic cognition, visuospatial skills, sensorimotor knowledge, and social learning. The journal (Cognitive Neuroscience) is collecting commentaries on this article, and the ongoing discussion is indeed stimulating. My commentary has now been published too, dealing with technological evolution, embodiment, extended mind, and cognitive archaeology. In my brief comment, I frame technological cognition within the hypothesis of a specialized prosthetic ability, which I have been proposing in several papers (e.g., Frontiers in Psychology 2019; Brain Structure and Function 2023), and in the recent book on body cognition and visuospatial integration. In my opinion, the great challenge to investigate human technological cognition is to understand how cognitive integration and extension do work. This would probably require a shift of attention from tool-making and tool-using to a previous and neglected step: tool-sensing. About human evolution and cognitive archaeology, I stress the necessity to rely on clear definitions, and experimental approaches. Finally, I discuss possible drawbacks: the fact that technological extension is a derived natural specialization of humans, does not mean that it is free from risks, limitations, or downsides. In this context, I recommend (once more) reading an old-and-gold book by Konrad Lorenz: The Waning of Humaneness. A technocratic society has pros and cons, mostly when evolutionary success and individual well-being come into conflict. Here you can find a dissemination article (in Spanish) on this topic.

Apparently, Georges-Louis Leclerc, Comte de Buffon, was a sort of hero of his time: noble in spirit, wise, brilliant, attractive, generous, uninterested in fame, supporting folk science and dissemination, his outstanding and pioneering achievements spanned many distinct fields of science and culture. He strongly supported human rights and equality. He proposed that “evolution” (the term was coined after an English translation of his transformism) was the mechanism generating the observed biological diversity. He was continuously encrypting and adjusting his inconvenient statements to swing between the restrictions of religious censorship and prosecution. He thought that taxonomy is a matter of conventional and useful naming, aimed at interpreting nature within the subjective vision of human culture. He died accompanied by the glory of his name. Carl Linnaeus lived a tricky life. Arrogant and deceitful, racist, classist, and sexist, obsessed, greedy for power and social recognition, and only competent in botany.  He thought that species are the product of God’s creation, and that he was here to reveal His plans. He aged and died tragically, leaving behind resentment and oblivion. You can read the whole story in this amazing book, a book that any biologist should read (and, here, a perspective summary). Then came the French Revolution, and human emotions reshaped, once more, history. Buffon represented the (complex and complicated) old aristocracy. Linnaeus, the (easier and simpler) new European frontiers. And the twist of fate did happen: the great hero forgotten and prohibited, and the shady botanic resurrected and gloriously mythologized. That’s how it works, those simple twists of fate. Buffon and Linnaeus were both born in 1707. They never met.

After three hundred years, things have developed further. Our current knowledge in taxonomy has definitely improved. Nonetheless, the roots are still fragile: no one knows what a species is. We have plenty of definitions, hundreds of mathematical models, thousands of papers and meetings on this topic, but no agreement. In some fields, things have been blurred further by mixing taxonomy with social, political, or personal interests. In paleoanthropology, naming species all too often means naming fossils, a sensible market for fossil hunters. More than ten years ago, I proposed to see taxonomy as a cognitive tool, more than a biological fact. Tools for thinking. I am still convinced this can be a good (in the sense of useful) approach and, beyond the disagreements, a complementary and transversal interpretation.

I have recently found this stimulating and motivating perspective review on taxonomy and Homo heidelbergensis, written by Sheela Athreya and Allison Hopkins in 2021. A very welcome lecture, indeed. The paper explores the limitations of a typological approach in a post-typological culture. In line with my above-mentioned proposal, they cite Marks 1997 on taxonomy and systematics: this is a cognitive task and, specifically, a cultural one. And Ernst Mayr, who reminded paleontologists, back in 1950, that “the formal application of generic and specific names simulates a precision that often does not exist”. A delicate warning in a field where naming (or even nicknaming!) fragments is a key business. Athreya and Hopkins also call (contra Groves) for a helpful stability in taxonomy, acknowledging its key function: communication. Consistency and clarity are also appreciated. Interestingly, they propose ethnobiology as a compass for identifying why and how we naturally name animals and plants. Western classifications are largely intellectual, while native cultures have a strong utilitarian component. Intellectual categories are more devoted to the storage and retrieval of information, while utilitarian terminology is mainly oriented to communication. Utilitarian approaches may look more arbitrary when compared with intellectual ones, but this is probably a mirage: as the story of Linnaeus clearly shows, the presumed objectivity of a real intellectual taxonomy is an illusion, entangled in a messy admixture of expectations, conceptual biases, methodological influences, and historical caprices. The many endless disputes in paleoanthropology are also an easy example that falsifies the hypothesis of an unblemished systematics. Naming things is always a contextual exercise, embedded in the actual ecology of the species (humans) that self-appointed the charge of naming. In this sense, ethnobiology can offer, at least, some frank clues to recalibrate our pedantic taxonomic competitions. I think that someone else before proposed a similar approach, even supporting the use of the local vernacular names instead of Western academic artificial labels. Oh yes, his name was … Buffon!