Palaeoneurology is fascinating but is a debated field in relation with the complex nature of the analysed material. The brain never fossilises, leaving scientists with only the shallow imprints that it creates on the internal cranial surface. However, the correspondence between these records of convolutional patterns and details of the surface of the brain remains to be demonstrated in living humans. Only then can we apply this knowledge to study hominin fossils brain organisation and cognition.
To do so, we will investigate for the first time the correlation between the shape of the brain and that of the endocast within a sample of modern humans using MRI acquisitions, including some with a specific sequence (ultrashort echo time, UTE) that allows the characterisation of bone tissues. Comparison of morphometric data and anatomical traits between the brain and the endocast will be done using state-of-the-art quantification methodologies and will include an examination of cerebral asymmetry patterns in order to address functionally related traits. Once we have acquired a better understanding of these aspects within our own species, we will be able to use this model to address the shape of the brain/endocast in selected samples of well-preserved Homo erectus and Neandertals, as well as of unique specimens that are crucial for characterising important and debated hominins species. A last goal is to reconstruct Homo erectus brains and Neandertal brains and to approach the variation during growth in these species. We propose an original and integrative study, built around 4 scientific tasks. Each of these tasks is related to a broad scientific objective, while the whole project will allow us to test several scientific questions in anthropological, neuroanatomical and human sciences.
Our project aims at exploring the anatomical substrate of human cognition during the course of hominin evolution using new and multidisciplinary developments in imaging methodologies and complementary data on living humans. From a methodological standpoint, pluridisciplinarity, and more importantly interdisciplinarity, are strong components of the project, and an essential condition to achieve the scientific objectives. Originality in methods and analytical procedures are crucial to overcome difficulties or limitations encountered in the past or to access information that was not studied or previously unavailable. The preservation of the fossils may be a drastic limit, particularly for the endocast. A specific methodology has been developed to evaluate taphonomic alteration, distortion, completeness and any influence on the possibilities of research within the analytical framework of the project. These aspects will be exhaustively studied for each specimen and we will publish detailed descriptions to facilitate and improve the quality of future research by other scientists. In the task Virtual data acquisition and management: fossil, MRI on living humans, ethics and diffusion, we will addresses several methodological aspects at the crossroad of several scientific fields and a true pluridisciplinary approach is implemented. Complementary MRI acquisitions on living humans will be crucial for the later application of the obtained data for neuroanatomical studies of fossil hominins. We have also to deal with crucial questions about the preservation of the fossil hominin record. So, we have defined optimal approaches for the scanning of the fossils, both to allow best scientific studies and to permit their preservation, but also in the context of open science.
The production of an average model for the difference between the endocast and the brain is expected for the end of year 2. Then, a precise characterisation of the variation in detailed anatomical features will be the final result at the end of semester 5. The complete and detailed description of the endocasts of fossil hominins, following validated methodologies, the 3D reconstruction of their brain and comparison with our sample of living humans will be crucial to describe our respective cerebral specificities. These results will highly improve our knowledge on the anatomy of key fossil specimens and will also help to understand the anatomical differences between H. erectus, Neandertals and H. sapiens and variations in respective modalities of growth and development. All the expected results will improve our knowledge on the relationship between candidate species (H. erectus, H. heidelbergensis, H. rhodesiensis…) to the H. neanderthalensis/ H. sapiens clade and those two large-brain hominins. The last scientific task 4 will yield a synthesis of the results obtained in tasks 2 and 3. The detailed and complementary approach of quantified departures from symmetry will be crucial to discuss the possible relationships between brain and skull (including paranasal pneumatisation) asymmetry. We will be able to decipher the expression of functionally related biological asymmetries (shown as directional asymmetry variations) and environmental effects through developmental instability (shown as fluctuating asymmetry) among the available different samples for geographic diverse populations of H. sapiens and different species of great apes. Those results, confronted to the variation observed in fossil hominins, will document our knowledge of the evolution of the hominid brain, and therefore on the generally supposed link between form and function, at the end of PaleoBRAIN.
Our project will allow us to reconstruct for the first time H. erectus brains and Neandertal brains, as well as their respective growth pattern, taking into account the specificities of these species. Understanding brain morphology and ontogeny of extinct hominins will also enhance the understanding of the emergence of the specific organisation of the H. sapiens brain. The approach is unprecedented, so the results will be new for each discipline and will allow for major advances. Pluridisciplinarity, and also interdisciplinarity, will be strong components of PaleoBRAIN and an essential condition to achieve the scientific objectives. Originality in the methods and analytical procedures will be crucial to overcome difficulties detected in previous studies and to access new information. Interactions between anatomy/anthropology and computer science/mathematics will allow for major developments in anthropology, enlarging the field of possibilities in anatomical sciences far beyond the scope of the field of the PI. Indeed, neurosciences will be reinforced by bringing original information on a long time scale about the specificities of the human brain. Clarifying the timing of the appearance of the anatomical substrate related to functional brain specialisations may also help us better understand a wide range of seemingly unrelated issues such as human normal variation and pathologies related to bilateral variation, comparative research, developmental neurobiology of the brain, and the origins of human language. Finally, our results will contribute to the debate about the specificities of living humans. Indeed, documenting the anatomy and its relationship with the notion of cognition in our predecessors will help to clarify what makes us human. Moreover, it will document our shared characteristics and differences with other hominin species, of course in terms of anatomy, but also for future perspectives about interpretations in cognitive skills.
The question of the correspondence between cerebral and endocranial features is crucial for applications in palaeoneurology and has never been addressed. To do so, the PaleoBRAIN project will investigate for the first time the correlation between the shape of the brain and that of the intracranial cast within a sample of modern humans using MRI (for Magnetic resonance imaging) acquisitions, including some with a specific sequence that allows the characterisation of bone tissues. This input will be decisive for detailed study of neurological information from fossil humans. We will then reconstruct for the first time H. erectus brains and Neandertal brains, as well as their respective growth pattern, taking into account the specificities of these species. Understanding brain morphology and ontogeny of extinct hominins will also enhance the understanding of the emergence of the specificities of the brain of our species, Homo sapiens. A more specific objective is to investigate patterns of variation and of correlation between brain and cranial asymmetries. We will be able to decipher the expression of functionally related biological asymmetry (shown as directional asymmetry variations) and environmental effects through developmental instability (shown as fluctuating asymmetry) among the available different samples for geographic diverse populations of Homo sapiens and different species of great apes. Those results, confronted to the variation observed in fossil hominins, will document our knowledge of the evolution of the hominid brain and therefore on the generally supposed link between form and function at the end of PaleoBRAIN. Pluridisciplinarity and interdisciplinarity are strong components of PaleoBRAIN and an essential condition to achieve the scientific objectives. Moreover, this project is deeply engaged in a policy of open science: all the virtual imaging datasets produced during the project will be made available for scientific research to other scientists.
Monsieur Antoine Balzeau (Histoire naturelle de l'Homme préhistorique)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ICM INSTITUT DU CERVEAU MOELLE EPINIERE
EHU/UPV / paleontology
HNHP Histoire naturelle de l'Homme préhistorique
Help of the ANR 361,125 euros
Beginning and duration of the scientific project: February 2021 - 48 Months