When discussing the changing sense of reality around 1900 in the cultural arts the lexicon of early modernism reigns supreme. This essay contends that a critical condition for the possibility of many of the turn of the century modernist movements in the arts can be found in exchange of instruments, concepts, and media of representation between the sciences and the arts. One route of interaction came through physiological aesthetics, the attempt to ‘elucidate physiologically the nature of our Aesthetic feelings’ and (...) explain how works of art achieve their effects. Physiological aesthetics provided the terms for new formalist languages of art and criticism, and in some instances suggested optimistic, even utopian, possibilities for art to remake human individuals and societies.Keywords: Physiology; Psychology; Evolution; Aesthetics; Modernism; Art history. (shrink)

Galatea, or the Future of Darwinism W Russell Brain Originally published in 1927 "A brilliant exposition…of the evolutionary hypothesis." The Guardian "Should prove invaluable…" Literary Guide This non-technical but closely-reasoned book is a challenge to the orthodox teaching on evolution known as Neo-Darwinism. The author claims that although Neo-Darwinian theories can possibly account for the evolution of forms, they are quite inadequate to explain the evolution of functions. 88pp ************** Daedalus or Science and the Future J (...) B S Haldane Originally published in 1924. "The essay is brilliant. Sparkling with wit and bristling with challenges." British Medical Journal "Predicts the most startling changes." Morning Post This volume examines the future of scientific research from religious, philosophical social and economic standpoints. 94pp Automaton, or the Future of Mechanical Man H Stafford Hatfield Originally published in 1928 "It is impossible to do justice to his volume in a brief review…"Daily Herald At the time of original publication mankind’s chief inventions had been extensions of his senses or limbs. This work prophesies the dawn of an era in which substitutes will gradually be found even for the human brain. 96pp Gallio or the Tyranny of Science J W N Sullivan Originally published in 1927 "So packed with ideas it is not possible to give any adequate résumé of its contents." Times Literary Supplement "Remarkable monograph…devastating summary of materialism…" Spectator An attack on the values which science is so successfully imposing upon civilization. 90pp. (shrink)

This target article presents a plausible evolutionary scenario for the emergence of the neural preconditions for language in the hominid lineage. In pleistocene primate lineages there was a paired evolutionary expansion of frontal and parietal neocortex (through certain well-documented adaptive changes associated with manipulative behaviors) resulting, in ancestral hominids, in an incipient Broca's region and in a configurationally unique junction of the parietal, occipital, and temporal lobes of the brain (the POT). On our view, the development of the POT (...) in our ancestors resulted in the neuroanatomical substrate consistent with the ability for representations in modality-neutral association cortex and, as a result of structure-imposing interaction with Broca's area, the hierarchically structured Evidence from paleoneurology and comparative primate neuroanatomy is used to argue that Homo habilis (2.5–2 million years ago) was the first hominid to have the appropriate gross neuroanatomical configuration to support conceptual structure. We thus suggest that the neural preconditions for language are met in H. habilis. Finally, we advocate a theory of language acquisition that uses conceptual structure as input to the learning procedures, thus bridging the gap between it and language. (shrink)

Hypotheses regarding the selective pressures driving the threefold increase in the size of the hominid brain since Homo habilis include climatic conditions, ecological demands, and social competition. We provide a multivariate analysis that enables the simultaneous assessment of variables representing each of these potential selective forces. Data were collated for latitude, prevalence of harmful parasites, mean annual temperature, and variation in annual temperature for the location of 175 hominid crania dating from 1.9 million to 10 thousand years ago. We (...) also included a proxy for population density and two indexes of paleoclimatic variability for the time at which each cranium was discovered. Results revealed independent contributions of population density, variation in paleoclimate, and temperature variation to the prediction of change in hominid cranial capacity (CC). Although the effects of paleoclimatic variability and temperature variation provide support for climatic hypotheses, the proxy for population density predicted more unique variance in CC than all other variables. The pattern suggests multiple pressures drove hominid brain evolution and that the core selective force was social competition. (shrink)

Striedter's accessible concept-based book is strong on the macroevolution of brains and the developmental principles that underlie how brains evolve on that scale. In the absence of greater attention to microevolution, natural selection, and sexual selection, however, it is incomplete and not fully modern on the evolution side. Greater biological integration is needed.

Biological evolution and technological innovation, while differing in many respects, also share common features. In particular, implementation of a new technology in the market is analogous to the spreading of a new genetic trait in a population. Technological innovation may occur either through the accumulation of quantitative changes, as in the development of the ocean clipper, or it may be initiated by a new combination of features or subsystems, as in the case of steamships. Other examples of the latter (...) type are electric networks that combine the generation, distribution, and use of electricity, and containerized transportation that combines standardized containers, logistics, and ships. Biological evolution proceeds, phenotypically, in many small steps, but at the genetic level novel features may arise not only through the accumulation of many small, common mutational changes, but also when distinct, relatively rare genetic changes are followed by many further mutations. In particular, capabilities of biologically modern man may have been initiated, perhaps some 150 000 years ago, by one or few accidental but distinct combinations of modules and subroutines of gene regulation which are involved in the generation of the neural network in the cerebral cortex. It is even conceivable that it was one primary genetic event that initiated the evolution of biologically modern man, introducing some novel but subtle feature of connectivity into the cerebral cortex which allowed for meta-levels of abstraction and upgraded modes of information processing. This may have set the stage for the evolution of integrated but diverse higher capabilities such as structured language, symbolic thought, strategic thought, and cognition based empathy. (shrink)

Principles of Brain Evolution (Striedter 2005) places little emphasis on natural selection. However, one cannot fully appreciate the diversity of brains across species, nor the evolutionary processes driving such diversity, without an understanding of the effects of natural selection. Had Striedter included more extensive discussions about natural selection, his text would have been more balanced and comprehensive.

Allometric analyses suggest that there are some developmental constraints on brain evolution. However, when one compares animals of similar body size, these constraints do not appear to be very tight. Moreover, the constraints often differ between taxonomic groups. Therefore, one may ask not only what causes developmental constraints but also how (and why) these constraints might be altered (or circumvented) during the course of evolution.

The DSM-III, DSM-IV, DSM-IV-TR and ICD-10 have judiciously minimized discussion of etiologies to distance clinical psychiatry from Freudian psychoanalysis. With this goal mostly achieved, discussion of etiological factors should be reintroduced into the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. A research agenda for the DSM-V advocated the "development of a pathophysiologically based classification system". The author critically reviews the neuroevolutionary literature on stress-induced and fear circuitry disorders and related amygdala-driven, species-atypical fear behaviors of clinical severity in adult (...) humans. Over 30 empirically testable/falsifiable predictions are presented. It is noted that in DSM-IV-TR and ICD-10, the classification of stress and fear circuitry disorders is neither mode-of-acquisition-based nor brain-evolution-based. For example, snake phobia and dog phobia are clustered together. Similarly, research on blood-injection-injury-type-specific phobia clusters two fears different in their innateness: 1) an arguably ontogenetic memory-trace-overconsolidation-based fear and 2) a hardwired fear of the sight of one's blood or a sharp object penetrating one's skin. Genetic architecture-charting of fear-circuitry-related traits has been challenging. Various, non-phenotype-based architectures can serve as targets for research. In this article, the author will propose one such alternative genetic architecture. This article was inspired by the following: A) Nesse's "Smoke-Detector Principle", B) the increasing suspicion that the "smooth" rather than "lumpy" distribution of complex psychiatric phenotypes may in some cases be accounted for by oligogenic transmission, and C) insights from the initial sequence of the chimpanzee genome and comparison with the human genome by the Chimpanzee Sequencing and Analysis Consortium published in late 2005. Neuroevolutionary insights relevant to fear circuitry symptoms that primarily emerge overconsolidationally are presented. Also introduced is a human-evolution-based principle for clustering innate fear traits. The "Neuroevolutionary Time-depth Principle" of innate fears proposed in this article may be useful in the development of a neuroevolution-based taxonomic re-clustering of stress-triggered and fear-circuitry disorders in DSM-V. Four broad clusters of evolved fear circuits are proposed based on their time-depths: 1) Mesozoic circuits hardwired by wild-type alleles driven to fixation by Mesozoic selective sweeps; 2) Cenozoic circuits relevant to many specific phobias; 3) mid Paleolithic and upper Paleolithic circuits ; 4) Neolithic circuits. More importantly, the author presents evolutionary perspectives on warzone-related PTSD, Combat-Stress Reaction, Combat-related Stress, Operational-Stress, and other deployment-stress-induced symptoms. The Neuroevolutionary Time-depth Principle presented in this article may help explain the dissimilar stress-resilience levels following different types of acute threat to survival of oneself or one's progency. PTSD rates following exposure to lethal inter-group violence are usually 5-10 times higher than rates following large-scale natural disasters such as forest fires, floods, hurricanes, volcanic eruptions, and earthquakes. The author predicts that both intentionally-caused large-scale bioevent-disasters, as well as natural bioevents such as SARS and avian flu pandemics will be an exception and are likely to be followed by PTSD rates approaching those that follow warzone exposure. During bioevents, Amygdala-driven and locus-coeruleus-driven epidemic pseudosomatic symptoms may be an order of magnitude more common than infection-caused cytokine-driven symptoms. Implications for the red cross and FEMA are discussed. It is also argued that hospital phobia as well as dog phobia, bird phobia and bat phobia require re-taxonomization in DSM-V in a new "overconsolidational disorders" category anchored around PTSD. The overconsolidational spectrum category may be conceptualized as straddling the fear circuitry spectrum disorders and the affective spectrum disorders categories, and may be a category for which Pitman's secondary prevention propranolol regimen may be specifically indicated as a "morning after pill" intervention. Predictions are presented regarding obsessive-compulsive disorder and "culture-bound" acute anxiety symptoms. Also discussed are insights relevant to pseudoneurological symptoms and to the forthcoming Dissociative-Conversive disorders category in DSM-V, including what the author terms fright-triggered acute pseudo-localized symptoms. Speculations based on studies of the human abnormal-spindle-like, microcephaly-associated gene, the microcephaly primary autosomal recessive gene, and the forkhead box p2 gene are made and incorporated into what is termed "The pre-FOXP2 Hypothesis of Blood-Injection-Injury Phobia." Finally, the author argues for a non-reductionistic fusion of "distal neurobiology" with clinical "proximal neurobiology," utilizing neurological heuristics. It is noted that the value of re-clustering fear traits based on behavioral ethology, human-phylogenomics-derived endophenotypes and on ontogenomics can be confirmed or disconfirmed using epidemiological or twin studies and psychiatric genomics. (shrink)

The article of Finlay et al. is an excellent example of identifying constraints in the development of the brain, and their implications on brain architecture in evolution. Here we further illustrate the importance of constraints by presenting a few examples of how a small number of biophysical mechanisms or even a single life history parameter can have an enormous impact on brain evolution.

How does evolution grow bigger brains? It has been widely assumed that growth of individual structures and functional systems in response to niche-specific cognitive challenges is the most plausible mechanism for brain expansion in mammals. Comparison of multiple regressions on allometric data for 131 mammalian species, however, suggests that for 9 of 11 brain structures taxonomic and body size factors are less important than covariance of these major structures with each other. Which structure grows biggest is largely (...) predicted by a conserved order of neurogenesis that can be derived from the basic axial structure of the developing brain. This conserved order of neurogenesis predicts the relative scaling not only of gross brain regions like the isocortex or mesencephalon, but also the level of detail of individual thalamic nuclei. Special selection of particular areas for specific functions does occur, but it is a minor factor compared to the large-scale covariance of the whole brain. The idea that enlarged isocortex could be a a by-product of structural constraints later adapted for various behaviors, contrasts with approaches to selection of particular brain regions for cognitively advanced uses, as is commonly assumed in the case of hominid brain evolution. (shrink)

The law of coherence helps us understand the physical force behind the increasing complexity of the evolutionary process, from quanta, to cells, to self-awareness and collective consciousness. The coherent electromagnetic field is the inner glue of every system, the "intelligent" energy-information communication that assures a cooperative and synergic behavior to all the components of the system, as a whole, allowing harmonious evolution and unity of consciousness. Neuropsychological experiments show that the different brain areas communicate with more or less (...) coherence according to different states of consciousness: high values are correlated with states of psychophysical integrity and well-being, whereas low values with states of conflict and depression. If we expand isomorphically these brain discoveries, we will have four main general states of coherence: from disgregation to unity, which represents an important element, in the General System Theory, to differentiate between inanimate and animate system, and to understand how billions cells become a single living organism, and then how billions of human beings could eventually generate planetary consciousness. In this light the resolution of the global ecosystem crisis implicates human transformation from a low to a highly coherent state of consciousness. The key to the entire process seems to be the coherent nature of consciousness. (shrink)

Brain evolution is a complex weave of species similarities and differences, bound by diverse rules and principles. This book is a detailed examination of these principles, using data from a wide array of vertebrates but minimizing technical details and terminology. It is written for advanced undergraduates, graduate students, and more senior scientists who already know something about “the brain,” but want a deeper understanding of how diverse brains evolved. The book's central theme is that evolutionary changes in (...) absolute brain size tend to correlate with many other aspects of brain structure and function, including the proportional size of individual brain regions, their complexity, and their neuronal connections. To explain these correlations, the book delves into rules of brain development and asks how changes in brain structure impact function and behavior. Two chapters focus specifically on how mammal brains diverged from other brains and how Homo sapiens evolved a very large and “special” brain. Key Words: basal ganglia; cladistics; development; hippocampus; homology; lamination; mammal; neocortex; neuromere; parcellation; primate. (shrink)

Quartz (2002) argues that some recent findings about the evolution of the brain (Finlay & Darlington, 1995) are inconsistent with evolutionary psychologists’ massive modularity hypothesis. In substance, Quartz contends that since the volume of the neocortex evolved in a concerted manner, natural selection did not act on neocortical systems independently of each other, which is a necessary condition for the massive modularity of our cognition to be true. I argue however that Quartz’s argument fails to undermine the massive (...) modularity hypothesis. (shrink)

A dorsalization mechanism is a good candidate for the evolutionary origin of the isocortex, producing a radial and tangential expansion of the dorsal pallium (and perhaps other structures that acquired a cortical phenotype). Evidence suggests that a large part of the dorsal ventricular ridge (DVR) of reptiles and birds derives from the embryonic ventral pallium, whereas the isocortex possibly derives mostly from the dorsal pallium. In early mammals, the development of olfactory-hippocampal associative networks may have been pivotal in facilitating the (...) selection of a larger and more complex dorsal pallium which received both collothalamic and lemnothalamic sensory information. Finally, although it is not clear exactly when mammalian brain expansion began, fossil evidence indicates that this was a late event in mammaliaform evolution. (shrink)

The cerebral cortex controls our most distinguishing higher cognitive functions. Human‐specific gene expression differences are abundant in the cerebral cortex, yet we have only begun to understand how these variations impact brain function. This review discusses the current evidence linking non‐coding regulatory DNA changes, including enhancers, with neocortical evolution. Functional interrogation using animal models reveals converging roles for our genome in key aspects of cortical development including progenitor cell cycle and neuronal signaling. New technologies, including iPS cells and (...) organoids, offer potential alternatives to modeling evolutionary modifications in a relevant species context. Several diseases rooted in the cerebral cortex uniquely manifest in humans compared to other primates, thus highlighting the importance of understanding human brain differences. Future studies of regulatory loci, including those implicated in disease, will collectively help elucidate key cellular and genetic mechanisms underlying our distinguishing cognitive traits. (shrink)

Rolls shares important data on hunger, thirst, sexuality, and learned behaviors, but is it pertinent to understanding the fundamental nature of emotionality? Important as such work is for understanding the motivated behaviors of animals, Rolls builds a constructivist theory of emotions and primary-process affective consciousness without considering past evidence on specific types of emotional tendencies and their diverse neural substrates.

We review the evidence for the concept of the “initial” or prototype brain. We outline four possible modes of brain evolution suggested by our new findings on the evolutionary status of the dolphin brain. The four modes involve various forms of deviation from and conformity to the hypothesized initial brain type. These include examples of conservative evolution, progressive evolution, and combinations of the two in which features of one or the other become dominant. (...) The four types of neocortical organization in extant mammals may be the result of selective pressures on sensory/motor systems resulting in divergent patterns of brain phylogenesis. A modular “modification/multiplication” hypothesis is proposed as a mechanism of neocortical evolution in eutherians. Representative models of the initial ancestral group of mammals include not only extant basal Insectivora but also Chiroptera; we have found that dolphins and large whales have also retained many features of the archetypal or initial brain. This group evolved from the initial mammalian stock and returned to the aquatic environment some 50 million years ago. This unique experiment of nature shows the effects of radical changes in environment on brain-body adaptations and specializations. Although the dolphin brain has certain quantitative characteristics of the evolutionary changes seen in the higher terrestrial mammals, it has also retained many of the conservative structural features of the initial brain. Its neocortical organization is accordingly different, largely in a quantitative sense, from that of terrestrial models of the initial brain such as the hedgehog. (shrink)

Researchers studying primate brain allometry often focus on departures from allometry more than the allometric relationships themselves because only the former reveal what brain regions and behavioral-cognitive abilities were the focus of selection. Allometric departures for the human brain provide insights into hominid brain evolution and cast doubt on the suggestion that the large human cerebral cortex is a.

First, we clarify the central nature of our argument: our attempt is to apportion variation in brain size between developmental constraint, system-specific change, and change, underlining the unexpectedly large role of developmental constraint, but making no case for exclusivity. We consider the special cases of unusual hypertrophy of single structures in single species, regressive nervous systems, and the unusually variable cerebellum raised by the commentators. We defend the description of the cortex (or any developmentally-constrained structure) as a potential spandrel, (...) and weigh the implications of the spandrel concept for the course of human evolution. The empirical and statistical objections raised in the commentary of Barton are discussed at length. Finally, we catalogue and comment on the suggestions of new ways to study brain evolution, and new aspects of brain evolution to study. (shrink)

The opposition set up between co-ordinated and mosaic brain evolution distracts from the fact that the two go hand-in-hand. Here and elsewhere (Barton & Harvey 2000), I show that the patterns of co- ordinated evolutionary change among brain structures fit a mosaic evolution model. The concept of overarching developmental constraints is unnecessary and is not supported by the data.

Constraint has played a major role in brain evolution, but cannot tell the whole story. In primates, adaptive specialization is suggested by the existence of a covarying visual system, and may explain some residual variation in the constraint model. Adaptation may also appear at the microstructural level and in the globally integrated system of brain, body, life history and behavior.

According to Darwinian thinking, organisms are (for the most part) designed by natural selection, and so are (for the most part) integrated collections of adaptations, where an adaptation is a phenotypic trait that is a specialized response to a particular selection pressure. For animals that make their living in the Arctic, one adaptive problem is how to maintain body temperature above a certain minimum level necessary for survival. Polar bears' thick coats are a response to that selection pressure (surviving in (...) extreme cold). A thick coat makes a positive difference to a polar bear's fitness, since polar bears with very thin coats left fewer offspring than those with thicker coats. The foundational idea ofevolutionary psychologyis that brains are no different from any other organ with an evolutionary function, insofar as brains too are systems shaped by natural selection to solve adaptive problems. Thus brains have a particular functional organization because their behavioural effects tend, or once tended, to help maintain or increase the fitness of organisms with those brains. Prominent evolutionary psychologists (for example: Cosmides and Tooby, 1987; Cosmides and Tooby, 1994 and Symons, 1992) have endorsed the view that the last time any significant modifications were made by natural selection to the human brain's functional architecture, we were hunter-gatherers, inhabiting a world quite different from that which we now inhabit. That world was the Pleistocene epoch, between about 2 million years ago and 10 thousand years ago. On this view, then, the Pleistocene constitutes what evolutionary psychologists often call ourenvironment of evolutionary adaptedness(or EEA), and the information- processing structure and organization of our present-day cognitive architecture is no different from that of our recent huntergatherer ancestors. (shrink)

Wilkins & Wakefield (1995) provide a thoughtful contribution to our understanding of language origins. In this commentary I attempt to define the relationship between object-manipulation and primate brain function further by reviewing research on aimed throwing and the production and use of stone tools by tufted capuchin monkeys (Cebtis apella). I propose that examining the relation between brain function and object-manipulation inCebuswill provide insight into the preconditions of language in our hominid ancestors.

The “hypervigilance, escape, struggle, tonic immobility” evolutionarily hardwired acute peritraumatic response sequence is important for clinicians to understand. Our commentary supplements the useful article on human tonic immobility (TI) by Marx, Forsyth, Gallup, Fusé and Lexington (2008). A hallmark sign of TI is peritraumatic tachycardia, which others have documented as a major risk factor for subsequent posttraumatic stress disorder (PTSD). TI is evolutionarily highly conserved (uniform across species) and underscores the need for DSM-V planners to consider the inclusion of (...) class='Hi'>evolution theory in the reconceptualization of anxiety and PTSD. We discuss the relevance of evolution theory to the DSM-V reconceptualization of acute dissociativeconversion symptoms and of epidemic sociogenic disorder(epidemic “hysteria”). Both are especially in need of attention in light of the increasing threat of terrorism against civilians. We provide other pertinent examples. Finally, evolution theory is not ideology driven (and makes testable predictions regarding etiology in “both directions”). For instance, it predicted the unexpected finding that some disorders conceptualized in DSM-IV-TR as innate phobias are conditioned responses and thus better conceptualized as mild forms of PTSD. Evolution theory may offer a conceptual framework in DSM-V both for treatment and for research on psychopathology. (shrink)

Sir John Eccles, a distinguished scientist and Nobel Prize winner who has devoted his scientific life to the study of the mammalian brain, tells the story of...

Modern biology has not yet come to terms with the presence of many organic codes in Nature, despite the fact that we can prove their existence. As a result, it has not yet accepted the idea that the great events of macroevolution were associated with the origin of new organic codes, despite the fact that this is the most parsimonious and logical explanation of those events. This is probably due to the fact that the existence of organic codes in all (...) fundamental processes of life, and in all major transitions in the history of life, has enormous theoretical implications. It requires nothing less than a new theoretical framework, and that kind of change is inevitably slow. There are too many facts to reconsider, too many bits of history to weave together in a new mosaic. But this is what science is about, and the purpose of the present paper is to show that it can be done. More precisely, it is shown that the whole natural history of the brain can be revisited in the light of the organic codes. What is described here is only a bird’s-eye view of brain macroevolution, but it is hoped that the extraordinary potential of the organic codes can nevertheless come through. The paper contains also another message. The organic codes prove that life is based on semiosis, and are in fact the components of organic semiosis, the first and the most diffused form of semiosis on Earth, but not the only one. It will be shown that the evolution of the brain was accompanied by the development of two new types of sign processes. More precisely, it gave origin first to interpretive semiosis, mostly in vertebrates, and then to cultural semiosis, in our species. (shrink)

The existence of linked regularities in size among brain components across species is, by itself, not a strong argument against the importance of behavioral selection in brain evolution. A careful consideration of hominid brain evolution suggests that brain components can change their scaling relationships over time, and that behavioral selection was likely crucial. The best neuroanatomical index of a given behavioral ability can only be determined empirically, not through comparative analysis of brain anatomy (...) alone. (shrink)

Descartes boldly claimed: "I think, therefore I am." But one might well ask: Why do we think? How? When and why did our human ancestors develop language and culture? In other words, what makes the human mind human? _Evolution of Mind, Brain, and Culture_ offers a comprehensive and scientific investigation of these perennial questions. Fourteen essays bring together the work of archaeologists, cultural and physical anthropologists, psychologists, philosophers, geneticists, a neuroscientist, and an environmental scientist to explore the evolution (...) of the human mind, the brain, and the human capacity for culture. The volume represents and critically engages major theoretical approaches, including Donald's stage theory, Mithen's cathedral model, Tomasello's joint intentionality, and Boyd and Richerson's modeling of the evolution of culture in relation to climate change. The volume contains chapters by: Peter Carruthers; Thierry Chaminade; Philip Chase; Merlin Donald; Peter Gardenfors; Gary Hatfield; Jody Hey; Steven Mithen; April Nowell; Peter Richerson and Robert Boyd; Theodore Schurr; Robert Seyfarth and Dorothy Cheney; Kim Sterelny; and Felix Warneken. ISBN 978-1-934536-49-0. (shrink)

According to Darwinian thinking, organisms are designed by natural selection, and so are integrated collections of adaptations, where an adaptation is a phenotypic trait that is a specialized response to a particular selection pressure. For animals that make their living in the Arctic, one adaptive problem is how to maintain body temperature above a certain minimum level necessary for survival. Polar bears' thick coats are a response to that selection pressure . A thick coat makes a positive difference to a (...) polar bear's fitness, since polar bears with very thin coats left fewer offspring than those with thicker coats. The foundational idea of evolutionary psychology is that brains are no different from any other organ with an evolutionary function, insofar as brains too are systems shaped by natural selection to solve adaptive problems. Thus brains have a particular functional organization because their behavioural effects tend, or once tended, to help maintain or increase the fitness of organisms with those brains. Prominent evolutionary psychologists have endorsed the view that the last time any significant modifications were made by natural selection to the human brain's functional architecture, we were hunter-gatherers, inhabiting a world quite different from that which we now inhabit. That world was the Pleistocene epoch, between about 2 million years ago and 10 thousand years ago. On this view, then, the Pleistocene constitutes what evolutionary psychologists often call our environment of evolutionary adaptedness , and the information- processing structure and organization of our present-day cognitive architecture is no different from that of our recent huntergatherer ancestors. (shrink)