Murky Science

Here below an update (April 22, 2024) on the situation of Investigación y Ciencia, the Spanish version of Scientific American. Springer Nature bought the magazine, then closed the journal and … deleted all the archives. Almost fifty years of publications. Gone. Science and marketing have different interests. Apparently, Springer Nature does not have the deep commitment to science it claims to have in its attractive web pages. The brazenness of such open hypocrisy suggests a feudal system. Probably, we should begin planning a direct boycott of those companies promoting a murky business with science. And, in this sense, researchers may have a crucial role. Here the update, from the former editorial team at Investigación y Ciencia and Mente y Cerebro:

“Shortly after the publication of this open letter in April 2023, the science magazine Mètode, published by the University of Valencia, offered to host the complete digital archive of http://www.investigacionyciencia.es on its own website to make it freely available to the public. It was a non-profit initiative that didn’t involve the appropriation of any publishing rights, as it would have preserved all licenses held by Springer Nature—the publishing group that owned Investigación y Ciencia and Mente y Cerebro, the one that decided to close them in 2023, and the legal owner of their digital archive, which has since remained inaccessible.

Although Springer Nature initially seemed receptive to Mètode’s offer and took the first steps to assess its technical and legal feasibility, shortly after the company abruptly ended talks.

Since then, and throughout the last year, Springer Nature and Scientific American have ignored all our attempts to resume the issue—without ever responding to our requests, or without ever explaining their rejection of a proposal that, once the archive had been transferred, would have entailed zero costs for them and would have given 500 million Spanish speakers free access to a scientific and cultural heritage of more than 21,000 articles and half a century of history.

During this time we have become aware of some individual initiatives to provide access to the print archive of Investigación y Ciencia. While we certainly welcome such efforts, they are unrelated to our original request—the full and official release by Springer Nature of the entire archive of all magazines (Investigación y Ciencia, Mente y Cerebro, Temas, Cuadernos and Especial), as well as the thousands of science news and blog articles published over the years at www.investigacionyciencia.es.

With its silence, Springer Nature has chosen to ignore a non-profit and extremely credible proposal that would have been of enormous benefit to the global Spanish-speaking community. A proposal that was supported by 11 scientific institutions, by more than 550 scientists and science communication professionals, and by more than 11,000 signatories at change.org.

We would like to express our most sincere thanks to all of them, as well as to the science magazine Mètode, the Spanish Association of Science Communication and, of course, to the countless readers and authors who, for 47 years, made possible one of the most impactful science communication projects in the Spanish-speaking world.”

Microforamina

Some endocranial vascular elements can leave their traces on the neurocranial bones, and their morphology can be hence investigated in fossils, as well as in archaeological or forensic samples. The term craniovascular traits is generally employed to describe grooves, imprints, and channels shaped by these arteries and veins. These features are often associated with macroscopic vessels, like the middle meningeal artery, the venous sinuses, the diploic veins, or the emissary foramina. However, the braincase also displays a myriad of very small vessels, bridging the diploic layer of the vault bones and the endocranial space. These small vessels might be important for thermal regulation. However, to date, information on their morphology and distribution is lacking. Very recently, it has been hypothesized that these vessels are crucial for the brain immunological response and inflammation, connecting the neurocranial bone marrow with the cerebral tissues. These passages (including their perivascular space) can be employed by leukocytes or even infectious agents to cross the arachnoid barrier. This interchange, triggering tissue repair, inflammation, and clearance, is crucial in pathological conditions ranging from stroke to Alzheimer’s Disease.

These microvessels leave the traces of their passages through the endocranial surface as tiny channels, that we have called microforamina. We have now published the first anatomical survey to describe the distribution of these passages in a sample of modern human skulls. These microforamina are principally distributed on the dorsal surface of the braincase, and in particular along the course of the major venous sinuses. Similarly, this distribution matches the position of the dorsal bridging veins, which are also involved in the same flow between diploic and cerebral spaces. In contrast, the parietal squama, often associated with the larger diploic channels, is not particularly dense in microvessels. Adults have more vessels than children, although after maturity there is no correlation between the number of vessels and age. Apparently, females might have more vessels than males. It is worth noting that this survey deals with the channels visible with standard medical tomography, with a lumen size generally larger than 0.5 mm. Microtomographic analyses will be necessary to investigate the amount and distribution of smaller vessels.

Some years ago, we described these microforamina in the parietal bone from Gran Dolina, Atapuerca, dated to 800ka. More recently, these passages have also been described in Neandertals. Indeed, these features should be officially included in the package of the craniovascular traits, and investigated in fossil hominids, in different geographic or historical samples, and in distinct pathological conditions.

The Evolutionary Roots of Human Brain Diseases

Amazing congress, the past week in Luxembourg, on The Evolutionary Roots of Human Brain Diseases. A book will soon be available. The evolutionary approach, when employed in medicine, can supply different perspectives and alternative interpretations of disease and pathology. On the one hand, a phylogenetic view can reveal complementary ways we can investigate specific biological mechanisms. At the same time, the evolutionary framework can change the concept of disease itself, at biological, cultural, and social levels. However, we are the product of evolution and, accordingly, everything is inevitably linked to evolution. Therefore, when asking about the evolutionary background of a pathological condition, we should probably clarify more precisely what we are looking for. In fact, we can identify at least four interpretations of the possible relationships between evolution and medicine.

The first and more general one is to consider that pathology deals with something that “has evolved”. For example, wings are an evolutionary specialization of birds, produced by natural selection, so if a bird crashes against a rock or a tree and dies we can state this is for evolutionary reasons. Similarly, our blood biochemistry is the result of biological selection, so any blood pathology will be linked to some evolutionary features. This is probably a too-wide interpretation of the relationships between evolution and disease, and could not add much to the perspective. Comparative biology (comparing humans with other species) can shed light on the derived traits of our species but, per se, this is only a first step to investigating possible links between natural selection and pathology. I mean, detecting that birds have wings is crucial to understanding why they can die crashing against rocks, and this implies that crashing is an evolutionary drawback of natural selection. But, probably, this can be a bit too general, albeit mandatory and necessary to understand the problem. The same example of birds’ wings can apply to cells or molecules of our amazing brain: whatever evolutionary feature, gene, or trait, ancestral or derived, is susceptible to damage. And, if it is a human-only feature, we are probably dealing with a human-only vulnerability.

A second general perspective deals with those features in which evolution may have approached some limits or constraints, generating problems. Those who fly high can fall very far. Many biological systems may reach a high level of complexity. In some cases, excessive complexity may generate failures. In other cases, the biological organization suffers functional or structural limits, which can cause drawbacks. These cases are of special interest to medicine, and they deal directly with the potentialities and limitations of our adaptive background. An evolutionary interpretation of these causes and consequences can surely add to the scientific and medical view.

The third situation is even more specific: when a pathological condition is the result of a targeted selective force. In this case, the pathology is the consequence of a specific selective change. A negative trait can be for example associated with a very good one, and they are selected together (antagonistic pleiotropy). Or, the trait is negative for the individual (pathology, suffering, etc.) but positive for evolution (it increases the reproductive success and the distribution of the species). This latter case is particularly interesting for many psychological aspects or psychiatric conditions, in which detrimental individual well-being is associated with social and reproductive achievements.

Finally, there is a fourth possible situation: when the environment does change too much, and the species is no longer adapted to the new conditions. This is a frequent case for humans, in which cultural and technological changes are so fast that can trespass the limit of our adaptive plasticity. This case is sometimes called “evolutionary mismatch”.

These last two conditions (namely a conflict between evolutionary and individual needs, and the decoupling between evolutionary background and environment) are probably the two core situations of evolutionary medicine. Indeed, as always, the boundaries between the four situations are blurred, and the harmful consequences (which we call “pathology”) may be due to an admixture of different factors. Nonetheless, these simplified categories are useful to define what kind of relationships we are considering when dealing with the interaction between evolution and disease. We should anyway take into account that, nonetheless, if the pathological condition does not affect the species’ success, the problem is not phylogenetic. Namely, all too often the “mismatch” is not evolutionary at all but, instead, personal. The interests of evolution (reproductive success) and the interests of the individual (a healthy, happy, and fulfilled life) are, frequently, in competition. At least in the long run, the house always wins and, in this case, the house is natural selection. On the short range, instead, our individual well-being is our own responsibility.

Archaeological bias

There are still disagreements on whether the increase in cultural complexity through our recent evolutionary history has been gradual or exponential, progressive or abrupt. But no one doubts it was outstanding. Technological and social complexity reveal cognitive complexity, because the boundaries of these three elements are definitely blurred and, at most, conventional. Nonetheless, the shadow of the taphonomic bias sheds worries on the most optimistic views, and caution is necessary when dealing with the pompous phylogenetic ego of our species. The absence of evidence may not be the evidence of absence. The lack of complex cultural and technological remains associated with extinct human species may be an artifice of time: the more the antiquity, the less the probability of maintaining a representative record of a past culture. At a glance, it looks like this chronological bias may have contributed, but not generated, the remarkable archaeological differences between Homo sapiens and other fossil hominids. Many early and archaic humans have been now investigated in detail for a century or more, and unexpected discoveries have only concerned local or minor differences, very relevant to understand the evolution and ecology of a species, but not to question the exceptional cognitive specialization of Homo sapiens. Most archaic and early species of the genus Homo, after all, are still associated with long periods of stasis, namely, a remarkable lack of changes when considered in a proper geographical and chronological range. In sum, the taphonomic bias may influence our perception of an extinct culture, but it is nonetheless highly improbable that H. erectus or H. heidelbergensis were using pen drives or riding bicycles.

Then, we have the special case of Neandertals, which had a brain size and a chronology very similar to H. sapiens. Modern humans and Neandertals shared a common origin, and then evolved for a similar period, at the same moment. In this case, a taphonomic bias is unlikely to explain the apparent cultural differences between the two species, mostly when dealing with the period (the last 50ka) in which the records of complex behavior for H. sapiens become increasingly abundant. However, the frequency and complexity of a behavior are key parameters to speculate on the cognitive skills of extinct populations and, therefore, we should try to understand whether the loss of cultural evidence might be an issue or not.

Despite the importance that taphonomic bias may have in prehistory, in general, it is treated like a ghost, an uncertain quantity of loss, an incommensurable confounding agent that, depending upon personal expectancy, may or may not influence substantially the corresponding conclusions. In a recent study, instead, Robert Kelly and colleagues investigated this topic quantitatively, modeling the factors involved to consider the fluctuations of the archaeological record associated with the last 50 ka. According to their model, the answer is: no, the taphonomic bias does not apparently bias so much. A welcome, nice, and elegant approach that reminds us of the necessity, in science, to quantify and measure. Quantifications and measures can be right or wrong, but they are nonetheless compulsory to bring the debate to a valuable common ground of discussion, beyond speculations and personal opinions.

However, the story is more complex than that, because our science is the product of our mind, with its cognitive, historical, economic, and social packages of preconceptions. The taphonomic bias is only one factor that might skew information we rely on. For example, what about  “research bias”? Robert Kelly, who is an anthropologist at the University of Wyoming, has kindly provided his contribution to this post, by replying to a couple of questions.

1. What is a “research bias” in archaeology?

Reply: Research bias comes in two forms: positive and negative. No matter what field of research you work in, from archaeology to zoology, you know that are certain areas that generate greater interest and consequently more research than others. These are the “glory fields” that can increase the likelihood of grants, publication, and public attention. This is positive research bias. In North American archaeology, the archaeology of the earliest human occupation, the Clovis culture (~13,200 to 12,900 cal BP) generates a level of attention that is the opposite of the short length of its time period. And those sites that possibly pre-date Clovis, that are possibly 14,000, 16,000, 30,000 years or even older, generate enormous public attention and guarantee publication in Nature or Science. The investigation of pre-Clovis-aged sites, in fact, has attracted several multi-million-dollar private endowments (and yet, we still have no definitive answer as to when the western hemisphere was first colonized. I have strong opinions on this question that are best left for another discussion!).  In the Old World, the study of Neanderthals and Middle Paleolithic sites attracts more attention than sites of some other ages or associations. And there is negative bias: there are fields that interest fewer researchers usually because there is one period of time that is “glory field”.” For example, US archaeologists who work in the southwest strongly focus on the pueblo period (roughly post AD 700) and nearly ignore the Archaic period (which follows the Clovis period but is prior to the maize-horticulture pueblo period).

Both kinds of bias become problematic as our fields of inquiry move into the era of “big data” because we need to show that peaks or gaps in our data mean something other than research bias, otherwise we obviously risk errors in interpretation. For example, my colleagues and I have compiled a radiocarbon database of the continental US. Plotting those data (now >110,000 dates) on a map by county (land divisions within states), there are some counties that have no radiocarbon dates in our database. Is that because no one ever lived in those places prehistorically? That’s most likely wrong. Negative research bias is the most likely reason: for whatever reason, archaeologists have done less field research in those counties, and/or the research they did do, did not generate radiocarbon dates (or we failed to locate those dates in our literature searches).

How can this problem be avoided? In the US and Europe, this problem is partly mitigated by the legal requirement to conduct archaeological studies prior to construction. In the US, this is known as the field of Cultural Resource Management, and it is a response to federal (and some state and local) legislation that required, under certain circumstances, that archaeological survey and testing be conducted, and larger excavations be undertaken where they are deemed necessary. This field is required by law to concern itself with whatever it encounters, not just what the practitioners deem interesting. The problem is also mitigated by analyzing datasets with your “eyes open” to the problem and using methods that can overcome this bias. For example, we are currently analyzing spatial and temporal trends in the US by combining radiocarbon dates in terms of large watersheds, partly so that counties with no dates are overwhelmed in analysis by those that do.

2. Are there other confounding factors that might be relevant in archaeology?

Reply: Yes! Another confounding factor is discovery bias, which can also have negative and positive forms. The nature of the record left behind may bias an archaeologist to discover sites of a particular age and to not find sites of other ages. For example, Clovis peoples hunted some “megafauna,” large beasts such as mammoths, mastodons, and possibly horses, camels, and giant ground sloths. (All of these animals became extinct in the western hemisphere at the end of the Pleistocene, about 12,900 years ago.) Many Clovis-age sites have been found by lay persons, who, while out walking, notice large bones, too large to be domesticated cattle or modern bison, protruding from the side of an arroyo or stream cutbank. In fact, my colleagues and I are working on a Clovis site in my home state of Wyoming that was found in exactly such a fashion. Some archaeologists suggest that this method has biased our discovery to sites with the bones of megafauna, and consequently, has biased our interpretation of Clovis subsistence toward heavy dependence on megafauna. Maybe that’s a function of discovery bias. (One archaeologist said “Clovis hunters probably killed one mammoth in their lifetimes and never stopped talking about it!”). Sites that leave behind physically significant ruins, such as Maya temples or, in the American southwest, 800-room pueblos, are easier to locate than small, temporary hunter-gatherer camps consisting of a few ephemeral hearths and a scatter of stone tool manufacture waste flakes and shattered animal bone, all of which are more quickly buried than a three-story, stone-walled pueblo).

And Mother Nature can hide sites. Sites can become deeply buried, e.g., along floodplains, and the older the site the more deeply buried it can be. Obviously, this can bias the archaeologist to find young sites rather than old sites. Archaeologists can walk over them, and our standard discovery tools – augers or even backhoes – may still not reach the appropriate depth. Construction projects also may not excavate sufficiently deep to make inadvertent discoveries.

***

I am sincerely grateful to Robert Kelly for his kind availability, and to Petra Jelinek for calling my attention to these topics.

The psychological assessment of extinct minds

This week, I have published a comprehensive perspective review on cognitive archaeology in the Journal of Comparative Neurology. The article introduces fields bridging prehistory and neuroscience, like paleoneurology and neuroarchaeology. Successively, the relationship between fossils and cognition is discussed following the principles of cognitive archaeology, and the application of psychological models to those behaviors relevant to human evolution. It is important to consider that evolution is based on multiple independent lineages, which make linear, gradual, and progressive changes unlikely. Therefore, the traditional view considering fossil species as “something less” than modern human standards, might be seriously biased. Each species has a distinct combination of mental abilities, and this is probably true also when dealing with extinct taxa and their mind: fossil hominids might have had cognitive skills that we have lost, or never evolved. The cognitive landscape can be, in this sense, influenced by differences in quantity (increasing/decreasing specific skills) and quality (presence/absence of specific skills). In this sense, the simple presence of a specific behavior in the archaeological record is not sufficient to reveal the expression of common cognitive patterns. The frequency of the behavior is crucial, because of the importance of distinguishing occasional vs. habitual responses and adaptations. The complexity of the behavior must also be considered, to avoid generalizations that can hide consistent cognitive changes.

The review then deepens into the fronto-parietal system, working memory, visuospatial cognition, and attention. Following perspectives on embodiment, the importance of the body is discussed in terms of consciousness and self. Haptic, psychomotor, and kinesthetic abilities have mechanical and cognitive aspects, with blurred boundaries with many other broad and narrow skills. At present, we still miss proper conceptual and psychometric tools to investigate their actual roles and influences. Social and technological aspects are also further introduced. Attention, as a cognitive limiting factor, is then particularly discussed, taking into consideration that modern human has a social and technological system that suggests recent evolutionary enhancements in executive, top-down, and focused attentional skills. Many of our cognitive and cultural achievements are probably due to the fact that our attention is intentional, sustained, and conscious.

Finally, the role of the parietal cortex in the narrative of the self is presented. The precuneus, which is much larger in Homo sapiens when compared with other primates and, probably, with extinct hominids, is interpreted as a “beamer” of our storyline, integrating body and visual imaging. The outstanding imaging capacity of our species has, anyway, a drawback: an out-of-control mind wandering through past memories, future expectations, and ruminations, leading to that ontological suffering described by multiple philosophical traditions. If this vulnerability is due to a mismatch between attentional and visual skills, competing for the same neural and cognitive resources, such suffering must be interpreted as a human universal, following the principles of human ethology. Subsequently, I introduce the subsystem model of John Teasdale, employed in Mindfulness-Based Cognitive Therapy (MBCT) and based on two different forms of reasoning: holistic intuitive (based on perception) and conceptual (based on phonological and imaging resources). The former is largely developed on on-line somatic and attentional factors, while the latter is based on off-line information, working memory, and the default network. We can hence wonder whether different hominids might have relied on distinct combinations of the two subsystems.

The review ends with a call for experimental and quantitative methods in cognitive archaeology. Experimental psychology can supply, in this sense, efficient tools and perspectives. Sometimes, experimental approaches are criticized in cognitive archaeology because of the employment of “modern minds” to make experiments, forgetting that, usually, apes are used as models for human evolution, macaques are used as models for the human brain, and mice and worms are used as models for the human medicine. Science works with models. In this case, a human (H. sapiens) is used as a model for other humans. Not that bad! A second common criticisms deal with the fact that theories and hypotheses in archaeology cannot be proven. This is true, as it is for any other field of science. Selection of hypotheses is based on available data, in physics, ecology, or molecular biology. That’s how science works. As a final remark, the review stresses the importance of somatic, social, and technological elements when investigating cognition, in particular when dealing with a human primate.

BSAF – Prehistory and neuroscience

Brain Structure and Function’s New Collection:
PREHISTORY AND NEUROSCIENCE

Evolutionary anthropology must necessarily integrate information from extinct and extant species, investigating the natural history of the human genus in terms of phylogenetic processes and outputs. Brain evolution is a key aspect of such natural history. In this sense, studies on non-human primates can supply large samples and detailed variables, but living taxa represent parallel, independent, and derived lineages, neither ancestral nor primitive to the genus Homo. Instead, fossil species can supply direct evidence of the changes associated with our evolutionary pathway. Of course, this line of study imposes its own limitations in terms of samples and specific variables that can be analysed. Within this framework, different disciplines are currently trying to bridge prehistory and neuroscience. Paleoneurology deals with brain anatomy in fossil species, considering the morphogenetic relationships between brain and skull, and analysing brain form variations through digital morphometric models. Neuroarchaeology investigates brain functions associated with behaviours inferred from the archaeological record, largely through brain imaging and neurobiological correlates. Cognitive archaeology evaluates psychological models associated with specific behavioural abilities crucial to human evolution, employing methods from experimental psychology and cognitive sciences. Because neuroanatomical and behavioural information from fossil species is scant and fragmentary, consistent hypotheses on brain biology and cognitive abilities in extinct hominids must rely on multiple, parallel, and independent sources of evidence. This new collection of Brain Structure and Function welcomes original articles, reviews, and perspectives papers, presenting topics in these three fields, integrating paleoanthropology and archaeology with neuroanatomy, neurobiology, and psychology.

A pipeline to study hominoid brain evolution

A large team led by Angela Friederici has now published a methodological article to describe a pipeline to investigate brain evolution, integrating anatomical and behavioral information from living and extinct species. To analyze correlations between brain structure and function, post-mortem brain imaging and histology in non-human primates are matched with (pre-mortem) behavioral data. Such correlations can be extrapolated to fossil endocasts. In living primates, shape analysis is employed to localize endocranial surface features, then matched with the sulcal pattern of the corresponding brain. Adult skulls are micro-CT scanned with a resolution of 90 μm. Results are, indeed, promising and exciting, revealing a very good correspondence between endocranial imprints and cortical elements. According to the authors, “almost all brain sulci leave unambiguous impressions in the endocranial cavity”. Major differences between endocranial and brain form are due to brain shrinking (mostly in the vertical dimension) after extraction, and removal of the connective tissues and cerebrospinal fluid. I guess the absence of blood pressure is another crucial factor. In the paper, language is finally used as an example to discuss how this pipeline can be employed to investigate cognitive functions that are key features in human evolution.

The large number of people, institutions, and methods necessary to handle this pipeline reminds us that approaches like this one are, indeed, very difficult to organize. Technical outputs, methodological issues, and their final interpretations represent an intricate network of variables and parameters, which require much caution when coming to the final inferences and conclusions. Nonetheless, the publication of this article also suggests that such comprehensive and efficient approaches are, at present, already available. And this is definitely the very good news.

This article represents a very useful and efficient tutorial on current comparative neuroanatomy, in particular when dealing with traditional aspects associated with evolutionary anthropology. We must anyway remark (once more) two relevant points. First, in this field, comparative approaches with humans and apes are essential. However, we should not forget that living apes are derived taxa, not ancestral ones. Furthermore, they are specialized for a kind of environment profoundly different from the one in which humans evolved. Their striking differences in cranial architecture add one more crucial problem, when they are used as models in human paleoneurology and, in general, for human brain or cognitive evolution. The second point deals with the fact that we keep focusing on human evolution as the main target of research. This is undeniably a priority, no doubt. But it should not be the only target. Apes biology and evolution are also amazing topics, to which we should probably pay more attention. And, in this case, we should probably avoid taking humans as models when investigating their peculiar derived traits.

Happy New Theme!

Hi folks, and happy new year! After more than ten years working fine, one week ago my blog suddenly crashed. Faced with a lack of support from the WordPress team, it took some days (and the help of good friends – special thanks to Rafa!) to understand that there was an issue with the Theme, gone out-of-date. Theme changed, issue resolved. Welcome to the new design! Some minor formatting problems will be fixed on the way. This unexpected failure of the platform reminds us that the Internet is a huge ocean, in which powerful cybernetic currents can carry information far as well as make it disappear, quickly, into the waves (see for example the recent dramatic experience with the Spanish version of Scientific American!). This blog was opened on January 1, 2012. So, after a dozen years of posting (193 posts, at present), welcome to the new version of the Paleoneurology blog. Please visit also our lab blog: The Skull Box.

Human altriciality and brain development

A new study by Gomez-Robles and colleagues investigates altriciality in humans and other 140 mammals, comparing and correlating body, brain, and gestation metrics, within a very broad phylogenetic context. Human infants are “helpless”, especially in their first year of life. Traditional theories suggest that this feature, so much apparent in our species, may be due to metabolic or obstetric constraints associated with our specialized brain. Of course, other mammals have evolved altriciality, so a major question concerns whether this trait, in humans, is associated with specific (human-only) factors. According to the correlation models presented in this comprehensive survey, it turns out that our altriciality might be due to changes in our postnatal development, which results in a specialized pattern of myelination. Such changes are likely related to neuroplasticity, a crucial factor in human evolution, that can have bridged social and technological features in our own lineage. Results are then extrapolated to fossil hominids although, in this case, uncertainties remain on the possibility of relying on consistent estimations for their brain, body, and gestation values, in terms of means and ranges. The topic is surely central to evolutionary anthropology, taking into account that brain plasticity represents a limiting factor for cognitive, social, and cultural complexity.

Brain casts

This week, we have published a very welcome article for paleoneurology, on the accuracy of the identification of brain sulcal imprints on endocranial casts. The study, led by Nicole Labra and Antoine Balzeau (Muséum National d’Histoire Naturelle, Paris), compares the endocast identification of major sulci supplied from 14 different researchers with the folding scheme of the corresponding real brain from one adult modern human. Results shows that the reliability is not that bad, but suffers important limitations. There are many discrepancies between observers. As usually, the inferior brain regions display clearer sulcal imprints, probably because of the gravity and because of the spatial interaction with the facial and basal elements of the skull. There are some systematic errors in localizing the frontal, parietal, and occipital boundaries, and many endocranial imprints have no relationship with brain folding.

When working with fossil species, the endocranial casts are the only proxy we have to make inferences on brain morphology. Therefore, the information they can supply is, albeit scarce and uncertain, surely useful and necessary. A proper knowledge of these limitations is hence crucial for enhancing the reliability of the field. In paleoneurology, we need to integrate information from living and fossil species. Sulcal imprints on endocasts can be identified directly (as traces on the surface) or indirectly (using other cortical elements as spatial references), namely by investigating local features within a wider anatomical context. Furthermore, endocasts should be always studied with their skulls, because many morphological changes in the brain form may not be due to primary cerebral variations, but just secondary adjustments to intrinsic and extrinsic spatial constraints.

What could we do to deal with the limitations described in this study? First, we have to take into account that these limitations and uncertainties are more critical when dealing with single specimens. Unfortunately, paleoneurology has a long tradition, in this sense. The compulsive need to provide concluding statements on single fossils (a need often associated with academic marketing and personal prestige) can generate an excess of speculations. Instead, working on samples (many specimens) and trends (multivariate statistics) can average mistakes and uncertainties, providing more consistent and reliable results. The same is true for the observers: having many, is better than having just one. More eyes, more opinions, more experience. With all this in mind, at last, there is the golden rule: in paleontology (and in science in general), a reasonable probability is better than a false truth. Namely, caution is, at best, highly recommended. Such caution begins when using terms and concepts. For example, in paleoneurological articles, endocast should be used instead of brain, and boss or depression instead of gyrus and sulcus.

In paleoneurology, sulcal references are, indeed, necessary. Cranial landmarks can be seriously misleading when investigating brain morphology and evolution because their spatial relationships with brain regions are modest or even null. After all, it is not surprising that paleoneurological analyses based on cranial references often come to the conclusion that brain form is … a matter of cranial form! Surface analysis can help, but it considers the endocast as an undifferentiated object, a sort of balloon, with no anatomical elements or boundaries. The absence of information on homology is interpreted by the algorithms as an absence of homology, and all the local differences are then spread, shared, and averaged through all the anatomical system. A good alternative is using surface analysis by anchoring the geometrical model to some anatomical references. After all, sulcal references are necessary to investigate changes in brain proportions, which is a key aspect in neurobiology.

Whatever the method, we should anyway keep in mind the main message: paleoneurology is about anatomy, not cognition or behavior. Inferences on cognition and behavior should be provided according to multiple and independent sources of information, well beyond the evidence associated with a faint and uncertain furrow of the endocranial space.