Middle Pleistocene Homo in the Levant: Our understanding of the origin, distribution, and evolution of early humans and their close relatives has been greatly refined by recent new information. Adding to this trend, Hershkovitz et al. have uncovered evidence of a previously unknown archaic Homo population, the “Nesher Ramla Homo ” (see the Perspective by Mirazon Lahr). The authors present comprehensive qualitative and quantitative analyses of fossilized remains from a site in Israel dated to 140,000 to 120,000 years ago indicating the presence of a previously unrecognized group of hominins representing the last surviving populations of Middle Pleistocene Homo in Europe, southwest Asia, and Africa. In a companion paper, Zaidner et al. present the radiometric ages, stone tool assemblages, faunal assemblages, and other behavioral and environmental data associated with these fossils. This evidence shows that these hominins had fully mastered technology that until only recently was linked to either Homo sapiens or Neanderthals. Nesher Ramla Homo was an efficient hunter of large and small game, used wood for fuel, cooked or roasted meat, and maintained fires. These findings provide archaeological support for cultural interactions between different human lineages during the Middle Paleolithic, suggesting that admixture between Middle Pleistocene Homo and H. sapiens had already occurred by this time. Science , abh3169 and abh3020, this issue p. 1424 and p. 1429 ; see also abj3077, p. 1395

Clinical grade Alzheimer's disease (AD) is only described in humans. Recent imaging studies in early AD patients showed that the parietal areas display the most prominent metabolic impairments. So far, neuroimaging studies have not been able to explain why the medial parietal regions possess this hub characteristic in AD. Paleoneurological and neuroanatomical studies suggest that our species, Homo sapiens, has a unique and derived organization of the parietal areas, which are involved in higher cognitive functions. Combining evidence from neuroimaging, paleontology, and comparative anatomy, we suggest that the vulnerability of the parietal lobe to neurodegenerative processes may be associated with the origin of our species. The species-specific parietal morphology in modern humans largely influenced the brain spatial organization, and it involved changes in vascularization and energy management, which may underlie the sensitivity of these areas to metabolic impairment. Metabolic constraints and anatomical evolutionary changes in the medial parietal regions of modern humans may be important in early AD onset. Taking into account the species-specific adaptations of the modern human parietal areas and their association with AD, we hypothesize that AD can be the evolutionary drawback of the specialized structure of our parietal lobes. The cognitive advantage is associated with increased sensitivity to neurodegenerative processes which, being limited to the post-reproductive period, have a minor effect on the overall genetic fitness. The changes of energy requirements associated with form and size variations at the parietal areas may support the hypothesis of AD as a metabolic syndrome.

Anatomical systems are organized through a network of structural and functional relationships among their elements. This network of relationships is the result of evolution, it represents the actual target of selection, and it generates the set of rules orienting and constraining the morphogenetic processes. Understanding the relationship among cranial and cerebral components is necessary to investigate the factors that have influenced and characterized our neuroanatomy, and possible drawbacks associated with the evolution of large brains. The study of the spatial relationships between skull and brain in the human genus has direct relevance in cranial surgery. Geometrical modelling can provide functional perspectives in evolution and brain physiology, like in simulations to investigate metabolic heat production and dissipation in the endocranial form. Analysis of the evolutionary constraints between facial and neural blocks can provide new information on visual impairment. The study of brain form variation in fossil humans can supply a different perspective for interpreting the processes behind neurodegeneration and Alzheimer’s disease. Following these examples, it is apparent that paleontology and biomedicine can exchange relevant information and contribute at the same time to the development of robust evolutionary hypotheses on brain evolution, while offering more comprehensive biological perspectives with regard to the interpretation of pathological processes.

Traditional and new disciplines converge in suggesting that the parietal lobe underwent a considerable expansion during human evolution. Through the study of endocasts and shape analysis,paleoneurologyhas shown an increased globularity of the braincase and bulging of the parietal region in modern humans, as compared to other human species, including Neandertals. Cortical complexity increased in both the superior and inferior parietal lobules. Emerging fields bridging archaeology and neuroscience supply further evidence of the involvement of the parietal cortex in human-specific behaviors related to visuospatial capacity, technological integration, self-awareness, numerosity, mathematical reasoning and language. Here, we complement these inferences on the parietal lobe evolution, with results from more classical neuroscience disciplines, such as behavioral neurophysiology, functional neuroimaging, and brain lesions; and apply these to define the neural substrates and the role of the parietal lobes in the emergence of functions at the core of material culture, such as tool-making, tool use and constructional abilities.