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"The establishment and maintenance of distinct cell identities are ultimately controlled by epigenetic mechanisms: the stable expression of defined transcriptional networks."[1] - M. Albert Basson (2012)
Black, Ira B.
Mnemonic Plasticity To Memory
"Memory must involve the alteration of neuronal function and therefore requires plasticity, a change in state with experience. Moreover, mnemonic plasticity is characterized by (a) codification within the neuron, (b) short onset, (c) long-lasting effects, (d) specificity, (e) a high degree of precision, (f) enhanced effects with repetition, and (g) alteration of neuronal function. Further mechanisms must allow for decay, or the phenomena of forgetting... In fact, neurotransmitter functions, the agents of synaptic communication, undergo relatively long-term changes in response to brief experimental stimuli, and most definitely alter behavior. Transmitters and associated regulatory molecules encode, store, and express environmental information in a highly precise manner, thereby exhibiting mnemonic characteristics. Transmitter metabolism and even phenotypic expression are altered by discrete environmental stimuli. Relatively brief environmental events evoke long-lasting alterations in transmitter function, providing the temporal amplification that is central to mnemonic phenomena (Black 1984). Transmitter metabolism and physiologic effects are precisely governed by specific regulatory molecules, many of which respond to environmental stimuli in a pattern characteristic of memory."[2] - Ira B. Black
Neurotransmission - Regulatory Biology With A Unicellular Prehistory
"Neurotransmission is part of the larger process of information flow and the alteration of function in biological systems. To survive, all cells presumably must be capable of information reception, processing, storage, and communication. These faculties are required for unicellular life as well as life of complex metazoa. Can we gain additional insights by attempting to place neural function in the broader context of biological regulation? More specifically, can we identify effector molecules and symbols in nonneural cells? By examining simple forms, the essential features of molecular transduction may be grasped, devoid of the confounding complexities of higher nervous systems."[3]
"Prof. Cavalier-Smith of Oxford University has produced a large body of work which is well regarded. Still, he is controversial in a way that is a bit difficult to describe. The issue may be one of writing style. Cavalier-Smith has a tendency to make pronouncements where others would use declarative sentences, to use declarative sentences where others would express an opinion, and to express opinions where angels would fear to tread. In addition, he can sound arrogant, reactionary, and even perverse.
On the other [hand], he has a long history of being right when everyone else was wrong. To our way of thinking, all of this is overshadowed by one incomparable virtue: the fact that he will grapple with the details. This makes for very long, very complex papers and causes all manner of dark murmuring, tearing of hair, and gnashing of teeth among those tasked with trying to explain his views of early life."
"Membrane chemistry divides negibacteria into the more advanced Glycobacteria (e.g. Cyanobacteria and Proteobacteria) with outer membrane lipolysaccharide and primitive Eobacteria without lipopolysaccharide (deserving intenser study). It also divides unibacteria into posibacteria, ancestors of eukaryotes, and archaebacteria—the sisters (not ancestors) of eukaryotes and the youngest bacterial phylum. Anaerobic eobacteria, oxygenic cyanobacteria, desiccation-resistant posibacteria and finally neomura (eukaryotes plus archaebacteria) successively transformed Earth. Accidents and organizational constraints are as important as adaptiveness in body plan evolution."[4]
Thomas Cavalier-Smith (2010)
Phylogenetic Fashions & Long Neglected Facts
"Great advances in knowledge and understanding of organismal history have been made, but some fashions, attitudes and dogmas have spread more widely and dominated other viewpoints more than their scientific merits justify. The significance of the stasis of ancestral body plans over billenia and the non-uniformity of evolutionary modes and rates is insufficiently appreciated. Much discussion has been among students of recently derived branches of the tree (Hennig insects; Mayr birds) or among those whose focus is biochemistry or computer algorithms, rather than organisms and the needs and principles of taxonomy. I offer the perspective of a biologist especially interested in unicellular organisms, ancestral groups and in explaining the major transitions of life, perhaps more conscious than most of flaws in some aspects of recent phylogenetic fashions."[4]
Thomas Cavalier-Smith (2010)
From Nematocysts to Post Synaptic Cleft
"The larger larvae of true sponges provided a novel, hitherto unexploited, food for predators. One stem sponge lineage, I suggest, evolved nematocysts to catch and digest them, thereby becoming the ancestor of coelenterates (Cnidaria, Ctenophora), a clade on the best multigene trees. Nematocyst discharge of ECM anchors the aboral pole of settling cnidarian planula larvae just as do secretory flask cells at the aboscular pole (similarly anterior when swimming) of sponge larvae. Flask cells are the only larval sponge cell type to coexpress the majority of post-synaptic protein homologues, so I suggest, evolved directly into nematocytes by evolving capsular/tube minicollagens and cnidoin elastomer that facilitates their nanosecond discharge."[5] - Thomas Cavalier-Smith (2017)
Evolving Animals From Multicellularity
"Evolving multicellularity is easy, especially in phototrophs and osmotrophs whose multicells feed like unicells. Evolving animals was much harder and unique;"[6] - Thomas Cavalier-Smith (2017)
Multicellularity Evolves In Two Ways - Naked and Walled Cells
"Multicellularity evolves in two ways. Naked cells, as in animals and slime moulds, evolve glue to stick together. Walled cells modify wall biogenesis to inhibit the final split that normally makes separate unicells, so daughters remain joined. The ease of blocking that split allowed almost every group of bacteria, fungi and plants (and many chromists) to evolve multicellular walled filaments, more rarely two-dimensional sheets, most rarely three-dimensional tissues. Tissues require more geometric control of daughter wall orientation, as in embryophyte green plants and chromist brown algae; both can grow longer than blue whales. Evolving tissues is selectively harmful to many walled multicells whose filaments are best for reproductive success. Almost all multicells retain unicellular phases (eggs, sperm, zygotes), so adhesion is temporally controlled and developmentally reversible—except for purely clonal vegetatively propagating plants or ‘colonial’ invertebrates (evolutionarily transient) the only organisms that are never unicellular."[7] - Thomas Cavalier-Smith (2017)
Trophic Continuity
"Evolving animals was much harder and unique; probably only one pathway via benthic ‘zoophytes’ with pelagic ciliated larvae allowed trophic continuity from phagocytic protozoa to gut endowed animals."[6] - Thomas Cavalier-Smith (2017)
"Don't be distracted by politics. This is serious. We cannot let America become a nation of conspiracy theories and thug violence."[8]
Liz Cheney (2022)
Chomsky, Noam
Eighteen quotes from Noam Chomsky's The Responsibility of Intellectuals
"With respect to the responsibility of intellectuals, there are still other, equally disturbing questions. Intellectuals are in a position to expose the lies of governments, to analyze actions according to their causes and motives and often hidden intentions. In the Western world, at least, they have the power that comes from political liberty, from access to information and freedom of expression. For a privileged minority, Western democracy provides the leisure, the facilities, and the training to seek the truth lying hidden behind the veil of distortion and misrepresentation, ideology and class interest, through which the events of current history are presented to us...[9]
IT IS THE RESPONSIBILITY of intellectuals to speak the truth and to expose lies. This, at least, may seem enough of a truism to pass over without comment. Not so, however. For the modern intellectual, it is not at all obvious...[9]
‘In addition to this growing lack of concern for truth, we find, in recent published statements, a real or feigned naivete about American actions that reaches startling proportions...[9]
But it is an article of faith that American motives are pure, and not subject to analysis... Although it is nothing new in American intellectual history—or, for that matter, in the general history of imperialist apologia—this innocence becomes increasingly distasteful as the power it serves grows more dominant in world affairs, and more capable, therefore, of the unconstrained viciousness that the mass media present to us each day. We are hardly the first power in history to combine material interests, great technological capacity, and an utter disregard for the suffering and misery of the lower orders. The long tradition of naiveté and self-righteousness that disfigures our intellectual history, however, must serve as a warning...[9]
Is the purity of American motives a matter that is beyond discussion, or that is irrelevant to discussion? Should decisions be left to “experts” with Washington contacts—even if we assume that they command the necessary knowledge and principles to make the “best” decision, will they invariably do so? And, a logically prior question, is “expertise” applicable—that is, is there a body of theory and of relevant information, not in the public domain, that can be applied to the analysis of foreign policy or that demonstrates the correctness of present actions in some way that psychologists, mathematicians, chemists, and philosophers are incapable of comprehending?...[9]
American aggressiveness, however it may be masked in pious rhetoric, is a dominant force in world affairs and must be analyzed in terms of its causes and motives. There is no body of theory or significant body of relevant information, beyond the comprehension of the layman, which makes policy immune from criticism. To the extent that “expert knowledge” is applied to world affairs, it is surely appropriate—for a person of any integrity, quite necessary—to question its quality and the goals it serves. These facts seem too obvious to require extended discussion...[9]
I do not doubt that these attitudes are in part a consequence of the desperate attempt of the social and behavioral sciences to imitate the surface features of sciences that really have significant intellectual content. But they have other sources as well. Anyone can be a moral individual, concerned with human rights and problems; but only a college professor, a trained expert, can solve technical problems by “sophisticated” methods. Ergo, it is only problems of the latter sort that are important or real. Responsible, non-ideological experts will give advice on tactical questions; irresponsible, “ideological types” will “harangue” about principle and trouble themselves over moral issues and human rights, or over the traditional problems of man and society, concerning which “social and behavioral science” has nothing to offer beyond trivalities. Obviously, these emotional, ideological types are irrational, since, being well-off and having power in their grasp, they shouldn’t worry about such matters.[9]
At times this pseudo-scientific posing reaches levels that are almost pathological...[9]
There is much more that can be said about this topic, but, without continuing, I would simply like to emphasize that, as is no doubt obvious, the cult of the experts is both self-serving, for those who propound it, and fraudulent. Obviously, one must learn from social and behavioral science whatever one can; obviously, these fields should be pursued as seriously as possible. But it will be quite unfortunate, and highly dangerous, if they are not accepted and judged on their merits and according to their actual, not pretended, accomplishments. In particular, if there is a body of theory, well-tested and verified, that applies to the conduct of foreign affairs or the resolution of domestic or international conflict, its existence has been kept a well-guarded secret...[9]
To anyone who has any familiarity with the social and behavioral sciences (or the “policy sciences”), the claim that there are certain considerations and principles too deep for the outsider to comprehend is simply an absurdity, unworthy of comment...[9]
When we consider the responsibility of intellectuals, our basic concern must be their role in the creation and analysis of ideology...[9]
It seems fairly obvious that the classical problems are very much with us; one might plausibly argue that they have even been enhanced in severity and scale. For example, the classical paradox of poverty in the midst of plenty is now an ever-increasing problem on an international scale. Whereas one might conceive, at least in principle, of a solution within national boundaries, a sensible idea of transforming international society to cope with vast and perhaps increasing human misery is hardly likely to develop within the framework of the intellectual consensus that [Daniel] Bell describes...[9]
THUS IT WOULD SEEM NATURAL to describe the consensus of Bell’s intellectuals in somewhat different terms from his. Using the terminology of the first part of his essay, we might say that the Welfare State technician finds justification for his special and prominent social status in his “science,” specifically, in the claim that social science can support a technology of social tinkering on a domestic or international scale. He then takes a further step, ascribing in a familiar way a universal validity to what is in fact a class interest: he argues that the special conditions on which his claim to power and authority are based are, in fact, the only general conditions by which modern society can be saved; that social tinkering within a Welfare State framework must replace the commitment to the “total ideologies” of the past, ideologies which were concerned with a transformation of society. Having found his position of power, having achieved security and affluence, he has no further need for ideologies that look to radical change. The scholar-expert replaces the “free-floating intellectual” who “felt that the wrong values were being honored, and rejected the society,” and who has now lost his political role (now, that is, that the right values are being honored)...[9]
It is easy for an American intellectual to deliver homilies on the virtues of freedom and liberty, but if he is really concerned about, say, Chinese totalitarianism or the burdens imposed on the Chinese peasantry in forced industrialization, then he should face a task that is infinitely more important and challenging—the task of creating, in the United States, the intellectual and moral climate, as well as the social and economic conditions, that would permit this country to participate in modernization and development in a way commensurate with its material wealth and technical capacity...[9]
A GOOD CASE CAN BE MADE for the conclusion that there is indeed something of a consensus among intellectuals who have already achieved power and affluence, or who sense that they can achieve them by “accepting society” as it is and promoting the values that are “being honored” in this society. It is also true that this consensus is most noticeable among the scholar-experts who are replacing the free-floating intellectuals of the past...[9]
IF IT IS THE RESPONSIBILITY of the intellectual to insist upon the truth, it is also his duty to see events in their historical perspective...[9]
Recent history shows that it makes little difference to us what form of government a country has so long as it remains an “open society,” in our peculiar sense of this term—that is, a society that remains open to American economic penetration or political control...[9]
QUITE OFTEN, THE STATEMENTS of sincere and devoted technical experts give surprising insight into the intellectual attitudes that lie in the background of the latest savagery."[9]
Noam Chomsky (1967)
Universals Of Human Nature
"If we do not like what we see when we look into the mirror honestly, we have every opportunity to do something about it."[10]
Noam Chomsky (2005)
Darwin, Charles
"I have called this principle, by which each slight variation, if useful, is preserved, by the term of natural selection."[11] - Charles Darwin
“The very essence of instinct is that it's followed independently of reason.”[12] - Charles Darwin
Deuchar, Elizabeth M.
Diffusion in Embryogenesis[13] - A Reply to Francis Crick
"Sir - As an embryologist who started work during the heyday of 'fields' and 'gradients', I suppose I ought to be grateful to Dr. Francis Crick for allowing me a nostalgic look back on these long-discredited concepts which he has now resurrected - or should I say canonized - with the double halo of his own reputation and some elegant mathematics (Nature, 225, 420; 1970). There is, however, one point that he appears to overlook: the extreme rarity with which sheer diffusion processes occur in living systems. Twenty years ago my better-informed colleagues told me about active transport and permeases. Ever since then, if materials diffused in and out of my experimental embryos, I have regarded that as a sign that they are dying or dead. A sheet of frozen-dried tissue, extended between source and sink, might fit Dr. Crick's formulae, but - alas - it would not differentiate!"[14]
- Yours faithfully, Elizabeth M. Deuchar
Dobzhansky, Theodosius
Theodosius Dobzhansky
In the Light of Evolution...
"Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts some of them interesting or curious but making no meaningful picture as a whole."[15]
The Immune System as an Ideal Model for Studying Evolution in a Selective System
"Two major developments have profoundly altered immunological research in the last decade: the theory of clonal selection and the chemical analysis of antibody structure... As a result of these developments, it has become clear that the central problem of immunology is to understand the mechanisms of selective molecular recognition in a quantitative fashion. Aside from evolution itself, there are few such well-analyzed examples of selective systems in biology or in other fields for that matter. For this reason, the immune system provides a unique opportunity to analyze the problem of selection under defined and experimentally measurable conditions that have so far been hard to achieve in other Eukaryotic systems. It is fortunate that the characteristics of the molecules and cells mediating selection in the immune response are known or can be known, and above all, that the time scale of the selective events is well within that required for direct observation and experimentation."[16]
Gerald M. Edelman (1974)
Recognition and Memory in the Immune and Nervous Systems
"[I]t is not difficult to see that both the brain and the immune system are recognition systems. Both can recognize and therefore distinguish positively among different objects in a set (in the one case via sensory signals, in the other via molecular complementarity between the shapes of antigens and the combining sites of antibodies). By positive recognition I mean that they do not merely exclude an object by subjecting it to a match with a fixed pattern, but rather that they can name or tag an object uniquely. This is a much more powerful kind of recognition than the exclusive one embodied, say, in the construction of a combination lock. Furthermore, both systems have the capacity to store a recognition event ("memory" and "immunological memory") as well as the capacity to forget."[17]
Pre-existing Diversity is the Engine of Adaptive Creativity
"It is clear from both evolutionary and immunological theory that in facing an unknown future, the fundamental requirement for successful adaption is preexisting diversity."[18]
Gerald M. Edelman (1978)
The Regulator Hypothesis
"According to the regulator hypothesis, the genes force adhesion molecules (CAMs) are expressed in schedules that are prior to and largely independent of those for cytodifferentiation. The expressed CAMs act as regulators of the overall patterns of those morphogenetic movements that are essential for inductive sequences or early milieu-dependent differentiations. It is proposed that, during evolution, natural selection eliminates those organisms in which variants of CAM gene expression or of morphogenetic movements or of both result in interruptions in the inductive sequence. Under this assumption, more than one (but not all) combinations of these two variables will lead to stabilization of the order of inductive sequences and of the body plan in a variety of species. Moreover, small variations in the pattern of action of regulatory genes for CAMs in those organisms that are not selected against could lead to large changes in animal form within relatively short periods of evolutionary time."[19]
Gerald M. Edelman (1984)
The Requirements of a Selection Theory
"[T]he abstract general requirements on any selection theory are (1) a source of diversification leading to variants, (2) a means for effective encounter with or sampling of an independent environment that is not initially categorized in any absolute or predetermined fashion, and (3) a means of differential amplification over some period of time of those variants in a population that have greater adaptive value."[20]
"The key idea may be summarized roughly as follows: These molecules link cells into collectives whose borders are defined by CAMs of different specificity. The binding properties of cells linked by the CAMs are dynamically controlled by the cells themselves as a result of signals exchanged between collectives. Cell binding in turn regulates cell motion and further signalling, and thus the ensuing forms. Control of the expression of CAM genes by the specific biochemistry affecting CAM regulatory genes at particular morphologic sites assures constancy of form in a species. But because the main function of CAMs is to regulate dynamic cellular processes and not specify cell addresses exactly, variability is also introduced during development."[21]
Gerald M. Edelman (1987)
Perceptual Categorization
"An individual animal endowed with a richly structured brain must also adapt without instruction to a complex environment to form perceptual categorizations or an internal taxonomy governing its further responses to its world"[22]
Gerald M. Edelman (1987)
Essential Components Of TNGS
"The essential components [of the TNGS theory] are (1) the existence of a source of connectional diversity during ontogeny; (2) a set of selection rules for changes in synaptic efficacy within synaptic populations leading to selection and additional variations; (3) the existence of functional reentrant circuits between maps to provide spatiotemporal continuity; (4) the parallel arrangements of such maps to yield classification couples or n-tuples for sampling of independent attributes; and (5) the final construction of global mappings containing motosensory ensembles that are the smallest units capable of perceptual categorization. If our assumptions about the need for any one of these major components are falsified, the theory will be severely weakened."[23]
Gerald M. Edelman (1987)
The Central Features Of TNGS
"A central feature of the theory of neuronal group selection is that the mechanisms leading to the formation of both the primary and secondary repertoire are epigenetic: while bounded by genetic constraints, events occurring at both developmental and experiential stages of selection lead to increases with time in both the heterogeniety and spatial diversity of cells and cellular structures. Such events depend upon the prior occurrence of other events in time courses that are long compared with those of intracellular events, and the cells involved exhibit interactive and cooperative spatial orderings that could not have been stored directly in the genetic code."[24]
Gerald M. Edelman (1987)
Transmitter Logic
"...instead of dividing input into only two classes - excitatory and inhibitory - and thinking of neuronal operations in Boolean terms, we might rather consider a kind of 'transmitter logic' in which each transmitter (in association with its post-synaptic partners) can lead to characteristic modifications of synapses receiving only certain other transmitters and located only on certain other parts of the dendritic tree."[25] - Gerald M. Edelman (1987)
Topobiology
"Topobiology - The study of the place-dependent regulation of cells resulting from interactions of molecules at the cell surfaces with those of other cells or substrates. In the context of this book, such place-dependent molecular interactions can regulate the primary processes of development and lead to changes in morphology by epigenetic means. The fundamental problem of topobiology is to determine how cells of different types are ordered in time or place during development to give species-specific tissue pattern and animal form."[26]
Gerald M. Edelman (1988)
The Developmental Genetic Question
"How does a one-dimensional genetic code specify a three-dimensional animal?"[27]
Gerald M. Edelman (1988)
The Evolutionary Question
"How is an answer to the developmental genetic question (q.v.) reconciled with the relatively rapid changes in form occurring in relatively short evolutionary times?"[28]
Gerald M. Edelman (1988)
The Morphoregulatory (MR) Hypothesis
"The Morphoregulatory (MR) Hypothesis - A hypothesis linking control of epigentic primary processes to a set of genetic elements (morphoregulatory, historegulatory, and selector genes) in order to account for morphogenesis. The linkage occurs via morphoregulatory proteins acting in CAM cycles and SAM modulatory networks. If confirmed this hypothesis would provide the basis for an answer to the developmental genetic question (q.v.)."[29]
Gerald M. Edelman (1988)
Prelinguistic Conceptual Categorization
"The conceptual categorization that emerges prior to language is obviously richer than perceptual categorization but is also enormously enhanced by language. Nonetheless, concepts are about the world..."[30]
Gerald M. Edelman (1989)
Memory in a Somatic Selection System
"Each memory reflects a system property within a somatic selection system. And each property serves a different function based upon the evolution of the appropriate neuroanatomical structure. These higher-order systems are selective and are based on the responses to environmental novelty of populations of neuronal groups arranged in maps. They are recognition systems."[31]
"I have made a distinction, which I believe is a fundamental one, between primary consciousness and higher-order consciousness. Primary consciousness is the state of being aware of things in the world - of having mental images in the present. But it is not accompanied by any sense of a person with a past and future. ...higher-order conciousness involves the recognition by a thinking subject of his or her own acts or affections. It exhibits direct awareness - the non-inferential or immediate awareness of mental episodes without the involvement of the sense organs or receptors."[32]
"There are, grossly speaking, two kinds of nervous system organization that are important to understanding how consciousness evolved. These systems are very different in their organization, even though they are both made up of neurons. (...) The two systems, limbic brain-stem and thalamocortical, were linked during evolution. The later-evolving cortical system served learning behavior that was adaptive to increasingly complex environments."[33]
"The first [type of nervous system] is the brain stem, together with the limbic (hedonic) system, the system concerned with the appetite, sexual and consummatory behavior, and evolved defensive behavior patterns. It is a value system; it is extensively connected to many different body organs, the endocrine system, and the autonomic nervous system. (...) It will come as no surprise that the circuits in this limbic-brain stem system are often arranged in loops, that they respond relatively slowly (in periods ranging from seconds to months), and that they do not consist of detailed maps. They have been selected during evolution to match the body, not to match large numbers of unanticipated signals from the outside world. These systems evolved early to take care of the bodily functions; they are systems of the interior."[34]
"The thalamocortical system consists of the thalamus and the cortex acting together, a system evolved to receive signals from the sensory receptor sheets and to give signals to voluntary muscles. It is very fast in its responses (taking from milliseconds to seconds), although its synaptic connections undergo some changes that last a lifetime. (...) Unlike the limbic-brain stem system, it does not contain loops so much as highly connected layered structures with massively reentrant connections. In many places these are topographically arranged. The cerebral cortex is a structure adapted to receive a dense and rapid series of signals from the world through the sensory modalities simultaneously - sight, touch, taste, smell, joint sense (feeling the position of your extremeties). It evolved later than the limbic-brain stem system to permit increasingly sophisticated motor behavior and the categorization of world events."[35]
Rejection Of Computational Models, Codes, & Point-to-point Wiring
"One conclusion we can draw (...) is that, while there are close similarities in certain regions, there are no absolutely specific point-to-point connections in the brain. The microscopic variability of the brain at the finest ramifications of its neurons is enormous, making each brain unique. These observations provide a fundamental challenge to models of the brain based on instruction or computation."[36]
Gerald M. Edelman (1998)
The Ubiquity of Degeneracy in Biological Systems
"Degeneracy, the ability of elements that are structurally different to perform the same function or yield the same output, is a well known characteristic of the genetic code and immune systems. Here, we point out that degeneracy is a ubiquitous biological property and argue that it is a feature of complexity at genetic, cellular, system, and population levels. Furthermore, it is both necessary for, and an inevitable outcome of, natural selection."[37]
" Every gun that is made, every warship launched, every rocket fired signifies, in the final sense, a theft from those who hunger and are not fed, those who are cold and are not clothed.
This world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children. The cost of one modern heavy bomber is this: a modern brick school in more than 30 cities. It is two electric power plants, each serving a town of 60,000 population. It is two fine, fully equipped hospitals. It is some fifty miles of concrete pavement. We pay for a single fighter plane with a half million bushels of wheat. We pay for a single destroyer with new homes that could have housed more than 8,000 people.
This is, I repeat, the best way of life to be found on the road the world has been taking. This is not a way of life at all, in any true sense. Under the cloud of threatening war, it is humanity hanging from a cross of iron."[38]
Dwight D. Eisenhower (1953)
Hall, Brian K.
The Neural Crest as a Fourth Germ Layer And Vertebrates as Quadroblastic Not Triploblastic
"...[N]eural crest cells are not a homogenous population of cells, but rather a collective of populations of cells. Although they overlap in the neural crest, some of these cell populations have been separate since the origin of the vertebrates almost 500 million years ago... [N]eural crest cells transform to mesenchyinal cells and migrate away from the developing brain and spinal cord, migrating as discrete populations of cells. Similar populations of cells can be observed across the vertebrates, i.e.. they have been conserved throughout vertebrate evolution. The neural crest gives rise to so many different cell types - more types than arise from mesoderm - that the neural crest can be regarded as a fourth germ layer, one that is unique to vertebrates and that allowed many distinctive vertebrate tissues to arise."[39]
"We are now faced with the fact, my friends, that tomorrow is today. We are confronted with the fierce urgency of now. In this unfolding conundrum of life and history, there is such a thing as being too late. Procrastination is still the thief of time. Life often leaves us standing bare, naked, and dejected with a lost opportunity. The tide in the affairs of men does not remain at flood -- it ebbs. We may cry out desperately for time to pause in her passage, but time is adamant to every plea and rushes on. Over the bleached bones and jumbled residues of numerous civilizations are written the pathetic words, "Too late." There is an invisible book of life that faithfully records our vigilance or our neglect."[40]
Martin Luther King Jr. (1967)
Krishnamurti, Jiddu
Freedom From The Known
"Man has throughout the ages been seeking something beyond himself, beyond material welfare - something we call truth or God or reality, a timeless state - something that cannot be disturbed by circumstances, by thought or by human corruption."[41] -
Jiddu Krishnamurti (1969)
Mackie, George O.
Neuroid Conduction Facilitates Rapid Response
"In hydromedusae and siphonophores neuroid conduction occurs in the exumbrellar ectoderm and subumbrellar endoderm, the two layers being linked as a transmission pathway for excitation going to ectodermal smooth muscle systems. The "crumpling" behavior of medusae is transmitted by this system, but nervous components may be involved in the generation of the full response. Reverse locomotion in physonectid siphonophores (e.g., Nanomia) involves activation of neuroid pathways. In the siphonophore Hippopodius, neuroid conduction in the exumbrella is coupled to luminescent and blanching reactions. Neuroid conduction in all these forms provides a rapid and efficient method of information transfer. It is typically associated with the spread of protective and locomotory responses and is general rather than local in effect. The more complex and local responses are believed to be organized by the nervous system."[42] - G.O. Mackie (1970)
Porges, Stephen
In Mammals... There Are Two Vagal Motor Systems
"There are two vagal motor systems. One vagal system is the vegetative vagus, which originates in the dorsal motor nucleus [DMNX] and is associated with passive reflexive regulation of visceral functions. The other vagal system is the smart vagus, which originates in [the Nucleus Ambiguus] NA and is associated with the active processes of attention, motion, emotion, and communication. These two systems are neuroanatomically distinct, have different ontogenetic and phylogenetic origins, and employ different adaptive strategies."[43]
Polyvagal Contributions to Mammalian Consciousness
"The Polyvagal Theory proposes that the evolutionary shift resulting in both a NA that is distinct from the DMNX and the development of special visceral efferents changed the role of the vagus... The special visceral efferent pathways from the NA create an active voluntary motor system associated with the conscious functions of attention, motion, emotion, and communication, and, thus, a smart vagus"[43]
The Social Engagement System: Phylogenetic Origins of Behavioral and Autonomic Components
"The Phylogenetic origin of the behaviors associated with the social engagement system is intertwined with the phylogeny of the autonomic nervous system. As the striated muscles, via special visceral efferent pathways, evolved into a behavioral system that regulated social engagement behaviors, there was a profound shift in neural regulation of the autonomic nervous system. Phylogenetically, these changes in both somatomotor and visceromotor regulation are observed in the transition from reptiles to mammals. As the muscles of the face and head evolved into an ingestion (i.e., nursing) and social engagement system, a new component of the autonomic nervous system (i.e., a myelinated vagus) evolved that was regulated by a brainstem nucleus, which was also involved in the regulation of the striated muscles of the face and head (i.e. nucleus ambiguus). This convergence of neural mechanisms resulted in an integrated social engagement system with a synergism between behavioral and visceral features of social engagement. Thus, activation of the somatomotor components would trigger visceral changes that would support social engagement, while modulation of visceral state would either promote or impede social engagement behaviors... Moreover, activation of the social engagement system dampens the neural circuits including the limbic structures that support fight, flight, or freeze behaviors."[44]
The Vertebrate as a Dual Animal: Somatic and Visceral
"In many regards the vertebrate organism, whether fish or mammal, is a well-knit unit structure. But in other respects there seems to be a somewhat imperfect welding, functionally and structurally, of two somewhat distinct beings: (1) an external, "somatic," animal, including most of the flesh and bone of our body, with a well organized nervous system and sense organs, in charge, so to speak, of "external affairs," and (2) an internal, "visceral," animal, basically consisting of the digestive tract and its appendages, which, to a considerable degree, conducts its own affairs, and over which the somatic animal exerts but incomplete control."[45]
The Functional Welding of the CNS to the ENS - The Autonomic Nervous System
"To sum up the phylogenetic suggestions gained from a consideration of the structure of the nervous system in living vertebrates, high and low, and of their chordate and protochordate "ancestors," one tends strongly to gain the impression that the remote "visceral" ancestral form had a simple superficial nerve net and, at some early stage, acquired a visceral nerve net as well; that, with the development of the "somatic" animal, there developed the central nervous system, with segmental nerves including a ventral root of somatic motor type and a distinct dorsal root at first composed merely of somatic sensory neurons; but that there was a strong tendency for the somatic animal to attempt neural control over the visceral animal, first perhaps, by a direct connection with the important visceral muscles of the pharynx, later by an attempt to dominate the gut by autonomic fibers, originally by way of dorsal nerve roots, running to the postganglionic neurons, which represent elements of the original gut nerve net. The development of visceral centers in brain and cord was associated with this attempt at domination of the visceral by the somatic animal. But, as we are ourselves aware, the integration of the visceral animal into the dominant nervous system of our somatic being is still far from perfect."[45]
The Functional Welding of the CNS to the ENS - Gaining Control
"It is not unreasonable to speculate on the possibility that: The ancestor of the vertebrates may have had, like many invertebrate types, an essentially independent visceral nerve net; that the development of the autonomic system represents an attempt by the central nervous system at gaining control over visceral activity; and that possibly in the peculiar two-neuron system seen here, the post-ganglionic neurons may be representatives of the original visceral nerve net system, the pre-ganglionics representatives of attempts at domination by the central nervous system."[45]
Evolution of the Pharyngeal Arch Cartilages and the Striated Visceral Musculoskeletal System
"In every vertebrate there is a set of well-developed striated muscles associated with the anterior part of the digestive tract, most notably the pharynx. In fishes there is an important series of muscles, lying along the walls of the pharyngeal region, which effect opening and closing of the gill slits. In jaw-possessing fishes there are powerful muscles associated with jaw movements; it is universally agreed that the jaws represent a modified and enlarged series of gill bars, and these jaw muscles are clearly a special part of the pharyngeal series.In tetrapods the jaw muscles remain prominent, but the gills are lost; much of the original gill musculature disappears, but a few small muscles persist in the throat and ear region, the trapezius muscle system of the neck is a further persistent relic, and in mammals the muscles of expression are an outgrowth of the same set of muscles."[45]
"Evolutionary speculation constitutes a kind of metascience, which has the same intellectual fascination for some biologists that metaphysical speculation possessed for medieval scholastics. It can be considered to be a relatively harmless habit, like eating peanuts, unless it assume the form of an obsession; then it becomes a vice."[46]
Roger Y. Stanier (1970)
Tang, Weiyi & Bronner, Marianne E.
Neural Crest Questions
"Thus, there are many interesting unanswered questions about neural crest development. For example, how do migrating neural crest cells interact with each other, both molecularly and mechanically? How are lineage decisions coupled with migration, and how do neural crest cells interact with the rapidly developing surrounding tissue? As neural crest cells have stem cell properties, what is their degree of fate restriction versus multipotency to form diverse cell types? How does this vary along the rostrocaudal body axis? In the adult, do neural crest-derived cells participate in tissue repair? "[47] - Weiyi Tang and Marianne E. Bronner (2020)
