Expands an inquiry to animals at large, investigating the evolution of experience with the assistance of far-flung species. Godfrey-Smith shows that the appearance of the first animal body form well over half a billion years ago was a profound innovation that set life upon a new path.

In lieu of an abstract, here is a brief excerpt of the content:Reviewed by:Metazoa: Animal Life and the Birth of the Mind by Peter Godfrey-SmithMichael BrownMetazoa: Animal Life and the Birth of the Mind BY PETER GODFREY-SMITH New York: Farrar, Straus and Giroux, 2020Carrying forward the project he began in Other Minds (2016), Peter Godfrey-Smith aims in Metazoa (2020) to cast light on the problem of consciousness by inviting meditation on the minds of our distant deep-sea cousins. To (...) elaborate on the Nagelian question of what it’s like to be a bat, he asks what it is like to be a crab, a shrimp, or a cephalopod. One will not find here the dense and fine-grain argumentation that is characteristic of academic monographs, but instead a freer exploration of ideas ranging from marine biology, to philosophy of mind, to animal psychology. Godfrey-Smith’s more modest goal is not to argue definitively for a single viewpoint, but to acclimate the reader to the challenging conceptual-shift he calls gradualism—namely, “the idea that in evolution, minds and experience come slowly into view, rather than appearing in a single move” (262).In the place of a barrage of observational data or dense philosophical argumentation, Godfrey-Smith paints a rich picture of the underwater environment, describes his personal interactions with the creatures that live there, and invites the reader to reflect on their activities and the cognition behind them. In this capacity, he walks a fine line—not anthropomorphizing the creatures, but presenting their actions as mentally agnostic as possible—to let the reader consider how much mental unity there might be, or how much self-or other-awareness may or may [End Page 130] not be present behind the beady mollusk eyes. Nevertheless, he strives to acquaint us with creatures we otherwise might not engage with. The several drawings of the animals and settings Godfrey-Smith discusses throughout the book aid this goal, as well as eight pages of vibrant photographs featuring several of the book’s “characters.”Because minds are things formed over time, Godfrey-Smith takes us through the first fossil evidence of animals in the Ediacaran, the appearance of shrimp-like ancestors in the Cambrian, the vast increase in size of the Ordovician, and the appearance of the octopus and dinosaurs of the Mesozoic. Yet, minds also develop under pressure and conditions of their environment, so Godfrey-Smith takes us on his dives to consider what environmental conditions led to the development of these submarine minds. As such, the text inventively winds its way across dimensions of space, time, and a variety of academic disciplines.In advancing the gradualist thesis, Godfrey-Smith entertains the Aristotelian notion of continuity between life and mind, as opposed to Descartes’ firm dualism. In this way, as noted in chapter 2, when a cell establishes its boundaries and controls the traffic of ions in and out, it becomes a kind of self. This leads him to a discussion of the glass sponge, multicellular but structurally simple, and yet a “collector and curator of biological light,” referring to its ability to channel light like a fiber optic cable (47). Chapter 3 considers the cnidarians—corals, in particular—in which the first signs of animal action appear. This action, like grasping, requires the appearance of a nervous system, and this increased complexity seems to give rise to agency, and more particularly, subjecthood. Chapter 4 invites us to consider the crab to guide reflections on early animal sensation. Of particular interest to this investigation are signs of feeling pain, such as the release of painkillers and the tending of wounds. Surprisingly, scientists find such behavior in shrimp. Chapter 5 returns to more philosophical considerations, attempting to stitch up false dichotomies of self-awareness and other-awareness, and activity and passivity, to name a couple. This sets the stage for chapter 6’s examination of the mysterious mix of mental unity and disunity in the octopus. With a decentralized nervous system, each arm seems to have a mind of its own, yet the creature nevertheless acts to unified purposes. Godfrey-Smith considers the resemblance to split-brain cases in humans, and the copresence of unified and disunified experience in... (shrink)

With historical hindsight, it can be little questioned that the view of protozoa as unicellular organisms was important for the development of the discipline of protozoology. In the early years of this century, the assumption of unicellularity provided a sound justification for the study of protists: it linked them to the metazoa and supported the claim that the study of these “simple” unicellular organisms could shed light on the organization of the metazoan cell. This prospect was significant, given the (...) state of cytology circa 1910. In the wake of the major gains made in understanding nuclear division in the last two decades of the nineteenth century, cytology was suddenly confronted with many, seemingly less penetrable, problems. Several aspects of nuclear organization still remained unexplained, and recent research had revealed the presence in the cytoplasm of structures whose functions in cell life were unknown. Classical methods of cytology, relying on descriptive, morphological analysis, seemed ill equipped to resolve these questions.Hertwig's program for protozoology, grounded in the assumption of the fundamental unity of organization in protozoa and metazoa, offered a potential means for investigating these and other problems of cell theory. Linked to mainstream cytology, protozoology was advocated as a means of experimentally investigating key biolobical processes — reproduction, metabolism, and organelle morphology and physiology — less accessible in higher organisms. Protozoa were hailed as prime experimental organisms, in which cell structure and function could be more easily studied. Unlike the metazoan cell, they could be subjected to controlled experiments in which the external environment was modified and the effects monitored. Protozoa offered, in other words, a promising experimental means by which to investigate the cell — its structures and its processes.The success of this program within Germany was soon apparent. In contrast to the rather neglected state of the discipline in 1900, protozoology began to be recognized as more than a somewhat obscure area of study for specialists. In practical terms, this translated into greater numbers of students attracted to the field, increased institutional support for the discipline, and its elevation in status within the biological sciences as new developments, particularly in connection with medical applications, began to draw attention to the field.64The unicellular hypothesis also promoted the internal development of the science. It provided a rationale for introducing the various techniques used in cytology, embryology, physiology, and the new field of biochemistry as suitable research tools for protozoology as well. This vastly extended the research possibilities and facilitated the understanding of, among other things, protozoan organization, modes of reproduction, and evolutionary relationships. The new experimental grounding of the discipline in turn fitted in well with developments in biology at large: in contrast to the descriptive methodology that had predominated in the nineteenth century, this new experimental program placed protozoology at the forefront of the early twentieth-century movement to make biology an experimental science comparable to physics and chemistry.Yet the criticism of the unicellular hypothesis can also be seen as having served a valuable function within the development of the discipline. It focused attention on the study of protists as organisms in their own right, not simply as models for metazoan cells. More generally, it helped to remind biologists of the particular evolutionary assumptions that supported this conception. Dobell and other British critics pointed out, among other things, the association between the theory of recapitulation and the interpretation of protozoa as unicellular organisms. At the time when the recapitulation theory and the germ-layer doctrine were in decline, it was important to stress how these evolutionary ideas also entered into the contemporary concepts of subsidiary specialties. This was as true for protozoology as it was for cell theory itself. The chromidial theory, in its various guises, and the binuclearity hypothesis did in fact contain elements of recapitulationist reasoning, and they were open to criticism for the same kind of overly speculative theorizing that characterized this evolution theory. Dobell's critique forced protozoologists and cell theorists alike to review the theoretical postulates guiding their investigations.In the absence of further historical studies, it is hard to evaluate the consequences of this debate in later years. The issue was not whether protozoa were the precursors of metazoa — both sides accepted this. They disagreed over which particular protozoon had served as the ancestral form, and this, in turn, influenced their stance on the question of unicellularity. The situation is little changed today. Because the former question is still an open one, the latter remains so too. Both of the models for the origin of multicellular organisms — colonies of ciliates versus multinucleate protists — are still presented as possible mechanisms in modern textbooks of evolution. Unable to judge the dispute in terms of the ultimate validity of the competing conceptions, the historian requires other criteria. It perhaps becomes more important to evaluate the issues in the context of the internal and external stimulus they provided the discipline.65 In these terms, and from the present historical vantage point, Hertwig's research program for protozoology, based upon the unicellular hypothesis, appears to have been a successful one. (shrink)

For over a century, Haeckel's Gastraea theory remained a dominant theory to explain the origin of multicellular animals. According to this theory, the animal ancestor was a blastula‐like colony of uniform cells that gradually evolved cell differentiation. Today, however, genes that typically control metazoan development, cell differentiation, cell‐to‐cell adhesion, and cell‐to‐matrix adhesion are found in various unicellular relatives of the Metazoa, which suggests the origin of the genetic programs of cell differentiation and adhesion in the root of the Opisthokonta. (...) Multicellular stages occurring in the complex life cycles of opisthokont protists (mesomycetozoeans and choanoflagellates) never resemble a blastula. Here, we discuss a more realistic scenario of transition to multicellularity through integration of pre‐existing transient cell types into the body of an early metazoon, which possessed a complex life cycle with a differentiated sedentary filter‐feeding trophic stage and a non‐feeding blastula‐like larva, the synzoospore. Choanoflagellates are considered as forms with secondarily simplified life cycles. (shrink)

Animal Studies Journal 2021 10: [Review] Peter Godfrey-Smith. Metazoa: Animal Life and the Birth of the Mind. New York: Farar, Straus and Giroux, 2020. 336 pp.

We propose that the sudden emergence of metazoans during the Cambrian was due to the appearance of a complex genome architecture that was capable of computing. In turn, this made defining recursive functions possible. The underlying molecular changes that occurred in tandem were driven by the increased probability of maintaining duplicated DNA fragments in the metazoan genome. In our model, an increase in telomeric units, in conjunction with a telomerase-negative state and consequent telomere shortening, generated a reference point equivalent to (...) a non-reversible counting mechanism. (shrink)

It is desirable that the antecedents of existing, highly specialised, evolutionary mechanisms in animals be sought. The study of the lower Metazoa and especially of their simpler reproductive processes suggests that asexual reproduction is the primitive evolutionary mechanism from which the more advanced sexual mechanisms have evolved. A study of the metagenetic cycles of Coelenterata and Platyhelminthes seems to throw much light upon their prophylogeny and indicates that: Such cycles seem to provide the closest possible recapitulatory parallelism between phylogeny (...) and ontogeny. The Hydrozoa are ancestral to the other classes of Coelenterata. The polypoid adult is more primitive than the medusoid adult. The sporocysts, rediae and scolices represent the more primitive types of adults in their respective ontogenies and phylogenies.On avance la théorie qu'il y a eu une évolution des mécanismes évolutionnaires depuis les stades primitifs jusqu'aux stades avancés. D'après cette théorie les premières étapes dans l'évolution des Métazoaires inférieurs se sont effectuées par la reproduction asexuelle avant que les mecanismes sexuels très spécialisés se soient manifestés.Des preuves à l'appui de cette théorie découlent: de la rencontre actuelle d'une reproduction asexuelle chez des animaux, avec l'indication que sa simplicité est, dans la plupart des cas, originelle, et des cycles d'évolution des Coelentérés et Platyhelminthes qui sont métagénésiques. Leurs cycles peuvent s'interpréter comme partant de stades reproductifs asexuels pour évoluer vers des formes se reproduisant sexuellement.On croit que les organismes ne pouvant se reproduire que sexuellement sont plus avancés que ceux qui peuvent se reproduire asexuellement, ou à la fois sexuellement et asexuellement.Cette théorie a d'importantes implications pour l'étude de la métagenèse, de la récapitulation et de la phylogénie chez les Métazoaires inférieurs; elle exemplifie, dans l'étude de ces phénomènes, la nouvelle orientation qu'on a appelée Prophylogénie.In dieser Arbeit wird eine Theorie entwickelt, die besagt, dass eine Fortentwicklung der Evolutionsmechanismen von primitiven zu fortgeschrittenen Stufen besteht. Dieser Theorie nach haben sich die niedrigeren Metazoen ursprünglich nur ungeschlechtlich entwickelt und fortgepflanzt. Erst später haben sich die höchst spezialisierten geschlechtlichen Mechanismen entwickelt.Belege für diese Theorie sind: Noch heute kommt die geschlechtslose Fortpflanzung in Tieren vor, was dafür spricht, dass ihre Einfachheit in den meisten Fällen ursprünglich ist. Die Lebenskreisläufe der Metagenetischen Coelenteraten und Platyhelminthen lassen sich interpretieren als bestehend aus ursprünglich ungeschlechtlichen Fortpflanzungsstufen, die jedoch später in Formen mit geschlechtlicher Fortpflanzung übergehen.Es wird behauptet, dass Organismen mit nur geschlechtlicher Fortpflanzung weiter fortgeschritten sind als solche mit nur ungeschlechtlicher oder mit sowohl ungeschlechtlicher als auch geschlechtlicher Fortpflanzung.Diese Theorie ist wichtig für das Studium der Metagenese, Rekapitulation und Phylogenie in den niedrigen Metazoen und veranschaulicht die Prophylogenie, d.h. die neue Methode im Studium dieser Erscheinungen. (shrink)

In the period 1875-1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), (...) an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end. (shrink)

Metazoa are one of the great monophyletic groups of organisms. They comprise several major groups of organisms readily recognizable based on their anatomy. These major groups include the Bilateria (animals with bilateral symmetry), Cnidaria (jellyfish, corals and other closely related animals), Porifera (sponges), Ctenophores (comb jellies) and a phylum currently made up of a single species, the Placozoa. Attempts to systematize the relationships of these major groups as well as to determine relationships within the groups have been made for (...) nearly two centuries. Many of the attempts have led to frustration, because of a lack of resolution between and within groups. Other attempts have led to “a new animal phylogeny”. Now, a study by Dunn et al.,1 using the expresssed sequence tag (EST) approach to obtaining high‐throughput large phylogenetic matrices, presents an “even newer” animal phylogeny. There are two major aspects of this study that should be of interest to the general biological community. First, the methods used by the authors to generate their phylogenetic hypotheses call for close examination. Second, the relationships of animal taxa in their resultant trees also prompt further discussion. BioEssays 30:1043–1047, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

One of the most interesting challenges facing paleobiologists is explaining the Cambrian explosion, the dramatic appearance of most metazoan animal phyla in the Early Cambrian, and the subsequent stability of these body plans over the ensuing 530 million years. We propose that because phenotypic variation decreases through geologic time, because microRNAs (miRNAs) increase genic precision, by turning an imprecise number of mRNA transcripts into a more precise number of protein molecules, and because miRNAs are continuously being added to metazoan genomes (...) through geologic time, miRNAs might be instrumental in the canalization of development. Further, miRNAs ultimately allow for natural selection to elaborate morphological complexity, because by reducing gene expression variability, miRNAs increase heritability, allowing selection to change characters more effectively. Hence, miRNAs might play an important role in shaping metazoan macroevolution, and might be part of the solution to the Cambrian conundrum. (shrink)

The origin of metazoa implies the passage from an eukarote protozoan to a protozygote ancestor of a metazoan zygote. The most probable hypothesis is that of a symbiotic origin of the first zygote by association of two protists one signifying a spherical oocell and the other a flagellated spermatozoan; this could be the first step of the metazoan ontogenesis and therefore also of the phylogenesis. The genesis can also be explained by two haploid genomes NX NY, three gametes (two (...) spermatozoa and one ovule), NX apparently being able to create both forms, and two zygotes. A double symbiosis, a chromosomic crossing-over and a selective expulsion can prove it. (shrink)

A half-billion years ago, a few species of single-celled protozoa stumbled irreversibly from loose social interaction into a tight, specialized interdependence. They became multi-celled metazoa, and human beings are one sort. Metazoa greatly transcend their constituent cells in lifetime, abilities, experiences and even materials (like bone). New kind of beings emerged out of the interactions of the old.

Peter Godfrey-Smith’s Metazoa and Joseph LeDoux’s The Deep History of Ourselves present radically different big pictures regarding the nature, evolution and distribution of consciousness in animals. In this essay review, I discuss the motivations behind these big pictures and try to steer a course between them.

The somatic mutation theory has been the prevailing paradigm in cancer research for the last 50 years. Its premises are: (1) cancer is derived from a single somatic cell that has accumulated multiple DNA mutations, (2) the default state of cell proliferation in metazoa is quiescence, and (3) cancer is a disease of cell proliferation caused by mutations in genes that control proliferation and the cell cycle. From this compelling simplicity, an increasingly complicated picture has emerged as more than (...) 100 oncogenes and 30 tumor suppressor genes have been identified. To accommodate this complexity, additional ad hoc explanations have been postulated. After a critical review of the data gathered from this perspective, an alternative research program has been proposed. It is based on the tissue organization field theory, the premises of which are that carcinogenesis represents a problem of tissue organization, comparable to organogenesis, and that proliferation is the default state of all cells. The merits of these competing theories are evaluated herein. BioEssays 26:1097–1107, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

This study focuses on the concept of a 'model organism' in the biomedical sciences through an historical and philosophical examination of research with the nematode Caenorhabditis elegans. I explore the choice of C. elegans in the mid-1960s, showing a rich context existed within which the organism was selected as the focus for a molecular biological research program, including an experimental life prior to Sydney Brenner's work. I argue that this choice can be seen as an obvious outcome of what was (...) a complex search procedure, and that the success of the 'worm project' depended not only on organismal choice but also on the conceptual and institutional framework at the Laboratory of Molecular Biology in Cambridge within which it was pursued. Examination of C. elegans work in the late 1960s through the early 1980s illuminates several additional theses. Although development and behavior were the general areas of interest for the project, the original goals and proposed methodology were extremely vague. As the project evolved, which investigations proved to be tractable using the worm depended not only on which methodologies were fruitful but also on the interests and skills of early workers. Much of the power of C. elegans as a model organism can be traced historically to the investment of resources which resulted in an unprecedented, complete description of the organism, and represented a return to a more naturalistic biological tradition. In light of the historical study, I develop a philosophical analysis of C. elegans as a model organism through exploration of the three kinds of modeling with the worm: modeling of structures, processes, and information. I expand the notion of a descriptive model, arguing that C. elegans is best understood as a prototype of the metazoa, and that C. elegans as a model organism has been not only heuristically valuable, but also essential to this research project particularly in its pre-explanatory stages. I conclude by suggesting that more investigation of descriptive prototypes such as those in the worm project must be done to capture important aspects of the biomedical sciences that will be neglected if explanatory models are the sole focus in the philosophy of science. (shrink)

Theories of the genetics underlying punctuated equilibrium (PE) have been vague to date. Here the developmental gene hypothesis is proposed, which states that: 1) developmental regulatory (DevReg) genes are responsible for the orchestration of metazoan morphogenesis and their extreme conservation and mutation intolerance generates the equilibrium or stasis present throughout much of the fossil record and 2) the accumulation of regulatory elements and recombination within these same genes—often derived from transposable elements—drives punctuated bursts of morphological divergence and speciation across (...) class='Hi'>metazoa. This two‐part hypothesis helps to explain the features that characterize PE, providing a theoretical genetic basis for the once‐controversial theory. Also see the video abstract here https://youtu.be/C-fu-ks5yDs. (shrink)

In the last few years, an understanding has emerged of the developmental mechanism for the consistent internal left–right structure, termed situs, that characterises vertebrate anatomy. This involves largely vertebrate‐conserved (i.e. ‘phylotypic’) gene expression cascades that encode ‘leftness’ and ‘rightness’ in appropriate tissues either side of the embryo's midline soon after gastrulation. Recent evidence indicates that the initial, directional symmetry breaking that initiates these cascades utilises mechanisms that are conserved or at least closely related in different vertebrate types. I describe a (...) scenario whereby the capacity for directional modification of an otherwise bilateral body plan can be viewed as an adaptive innovation rather closely connected with vertebrate origins, enabling optimal ‘design’ for very active lifestyles. But an alternative scenario, while retaining the view that situs and indeed other vertebrate functional lateralisations are deeply adaptive, proposes that they originated in the co‐optation of left–right developmental information inherited from a very early stage in metazoan diversification. It is proposed that a remote chordate ancestor lost its original or ‘ur‐bilaterian’ symmetry to pass through an altogether non‐symmetrical stage, and that the vertebrate dorsoventral midline plane is not descended from that original one. I review the considerable evidence in favour of this scenario, and discuss its wider implications for directional asymmetries across the Metazoa. BioEssays 26:413–421, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

In gonad‐bearing animals gametogenesis can be divided into three main phases. During embryonic development the primordial gem cells move towards the gonadal primordia. A long, intra‐gonadal phase follows during which the germ cells grow and differentiate. Mature germ cells are finally released from the gonads and brought to the exterior. Thus, germ cells are successively motile, non‐motile and motile again. This complex life history is given here a simple evolutionary interpretation. The basic assumption is that primitive Metazoa already had (...) germ cells, but no gonads to harbour them. Higher animals acquired gonads, which sequestered the germ cells, thus creating the temporary confinement experienced by germ cells in most present‐day Metazoa. This evolutionalry scheme may explain why several steps of germ cell differentation are totally or partially independent of the gonads. These steps presumably existed in primitive, gonad‐free Metazoa, and conserved their autonomy in higher animals. (shrink)

The Crustacea present a variety of body plans not encountered in any other class or phylum of the Metazoa. Here we review our current knowledge on the complement and expression of the Hox genes in Crustacea, addressing questions related to the evolution of body architecture. Specifically, we discuss the molecular mechanisms underlying the homeotic transformation of legs into feeding appendages, which occurred in parallel in several branches of the crustacean evolutionary tree. A second issue that can be approached by (...) the comparative study of Hox genes and their expression in the Crustacea bears on the homology of the abdomen. We discuss whether the so‐called “abdominal” tagma of the crustaceans is homologous to the abdomen of insects. In addition, the homology of the abdomen between malacostracan and non‐malacostracan crustaceans has also been questioned. We also address the question of the molecular developmental basis of the apparent lack of an abdomen in barnacles. We discuss these issues in relation to the problem of constraint versus adaptation in evolution. BioEssays 25:878–887, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

Before going further, it will be helpful to consider briefly the notion that novelty per se is a fundamental human need. Experiments with human beings, as well as with animals, indicate that the maintenance of normal, successful behavior depends upon an adequate level of incoming stimulation—or, as some have put it, of novelty.2 But lumping all novelty together is misleading. At least three kinds of novelty need to be distinguished. Some novel patterns arise out of, or represent, changes in the (...) fundamental rules governing the organization of musical processes and structures. By significantly weakening our comprehension of the musical relationships presented—undermining not only our understanding of what is past but our ability to envisage what is to come—such systemic change seriously threatens our sense of psychic security and competent control. Far from being welcome, the insecurity and uncertainty thus engendered is at least as antipathetic, disturbing, and unpleasant as stimulus privation. Novel patterns may also result from the invention of a new strategy that accords with prevalent stylistic rules. Though they may initially seem to threaten existing competencies, the function and significance of novel strategies within the larger set of stylistic constraints can usually be grasped without too much delay or difficulty. For a while the tensions produced by strategic innovation may seem disturbing. But in the end, when our grasp of the principles ordering events is confirmed and our sense of competency is reestablished and control is reinforced, tension is resolved into an elation that is both stimulating and enjoyable. Most novel patterns—original themes, rhythms, harmonic progressions, and so forth—involve the innovative instantiation or realization of an existing strategy or schema .3 Novelties of this kind not only enhance our sense of control—a feeling that we know how things really “work”—but provide both the pleasure of recognition and the joy of skillfully exercising some competency. We enjoy novelty—the stimulation of surprise, the tension of uncertainty—as long as it can be accommodated within a known and understandable set of constraints. When the rules governing the game are abrogated or in doubt—when comprehension and control are threatened—the result is usually anger, anguish, and desperation.These responses to novelty are consequences of fundamental and poignant verities of the human condition: the centrality of choice in human behavior. Because only a minute fraction of human behavior seems to be genetically specified, choice is inescapable.While in lower organisms, behavior is strictly determined by the genetic program, in complex metazoa the genetic program becomes less constraining, more “open” as Ernst Mayr puts it, in the sense that it does not lay down behavioral instructions in great detail but rather permits some choice and allows for a certain freedom of response. Instead of imposing rigid prescriptions, it provides the organism with potentialities and capacities. This openness of the genetic program increases with evolution and culminates in mankind.4The price of freedom is the imperative of choice. Human beings must choose were to sow and when to reap, when to work and where to live, when to play and what to build. Intelligent, successful choices are possible only if alternative courses of action can be imagined and their consequences envisaged with reasonable accuracy. 2. For further discussion, see my Music, the Arts, and Ideas , p. 50.3. Rules are transpersonal but intracultural constraints—for instance, the pitch/time entities established in some style, as well as grammatical and syntactic regularities. Strategies are general means for actualizing some of the possibilities that are potential in the rules of the style. The rules of a style are relatively few, while the number of possible strategies may, depending upon the nature of the rules, be very large indeed. The ways of instantiating a particular strategy are, if not infinite, at least beyond reckoning.4. François Jacob, The Possible and the Actual , p. 61. See also Stephen Jay Gould, Ever Since Darwin , p. 257. (shrink)

DNA repair is important in such phenomena as carcinogenesis and aging. While much is known about DNA repair in single‐cell systems such as bacteria, yeast, and cultured mammalian cells, it is necessary to examine DNA repair in a developmental context in order to completely understand its processes in complex metazoa such as man. We present data to support the notion that proliferating cells from organ systems, tumors, and embryos have a greater DNA repair capacity than terminally differentiated, nonproliferating cells. (...) Differential expression of repair genes and accessibility of chromatin to repair enzymes are considered as determinants in the developmental regulation of DNA repair. (shrink)

The establishment of distinct cellular identities was pivotal during the evolution of Metazoa, enabling the emergence of an array of specialized tissues with different functions. In most animals including vertebrates, cell specialization occurs in response to a combination of intrinsic (e.g., cellular ontogeny) and extrinsic (e.g., local environment) factors that drive the acquisition of unique characteristics at the single‐cell level. The first functional organ system to form in vertebrates is the cardiovascular system, which is lined by a network of (...) endothelial cells whose organ‐specific characteristics have long been recognized. Recent genetic analyses at the single‐cell level have revealed that heterogeneity exists not only at the organ level but also between neighboring endothelial cells. Thus, how endothelial heterogeneity is established has become a key question in vascular biology. Drawing upon evidence from multiple organ systems, here we will discuss the role that lineage history may play in establishing endothelial heterogeneity. (shrink)

In the evolution of the vertebrates and probably a few other animals (Metazoa), biological values have been translated (subjectivized) into affective experience that necessarily involves the consciousness of external objects/events (as different from one’s body), which is tantamount to the origins of subjectivity. Mammals, birds and other vertebrates are experiencing subjects even though their negative and positive experience greatly vary in scope. Some mammals are capable of vicarious experience and may act as empathic agents, and some of them, at (...) least the great apes, use true reflective self-consciousness and thus perceive themselves as agents, which generates attributive feelings. The balance of positive and negative experience determines the intrinsic value of (an individual) life. Every subjective life is autotelic in striving to maximize this balance. A subjective life may also have a social value that is measured in terms of the impact on intrinsic values of other lives. The social value of life is contingent upon an agency, that is, conscious intentional actions that impact intrinsic value of other lives. The difference between the social value of a subjective life and an instrumental value of an individual comes down to the difference between agent causation and event causation. The moral agency refers to a subcategory of agent causation that involves the awareness of impact on another subject’s wellbeing (interests). The moral agency is at present known only in the hominids (including the chimpanzees) which understand causality and use reflective self-consciousness, which in turn enables them to perceive themselves as agents and attribute to themselves responsibility. The moral agency originated as a motivational mechanism of reciprocity execution , and thus as an adaptation for group life, which is why it favors ingroup members and often promotes norms that harm other groups. The human moral agency is frequently used by third parties to implement group norms that are based on ideologies (religious or secular) and may actually harm both group members and the entire groups. Any received, bioculturally evolved morality is unlikely to be good in either absolute or universal sense. Therefore, the moral capacity alone does not make a human life categorically more valuable, even if human motivation were dominated by moral agency (which is true only of some people). The life of a vertebrate has, therefore, two values, intrinsic and social. Each can be negative or positive, and may vary to a large extent independently of the other, whereby a joint value of a subjective life cannot be sensibly assessed and compared without prior assessments of the intrinsic and social component separately. In the absence of objective reasons to rate the intrinsic value of a human life as categorically higher than that of other mentally advanced mammals, and in consideration of the observed range of social values of human lives, some of which approach zero and some are highly negative (lower than any thinkable negative values of non-human lives), the doctrine of extraordinary and inalienable (innate) human „dignity” is groundless and unethical, as it leads to a depreciation of the lives of non-human subjects, and often preempts the need to impart a real social value to one’s own life. (shrink)

Many marine invertebrates have the ability to combine tissues with conspecifics and form chimeras. This ability is usually accompanied by the presence of a polymorphic self/non-self recognition system that allows integration of closely related individuals, but blocks interactions between those more distantly related. The presence of a discriminatory allorecognition system suggests that there are costs and benefits to chimerism that are correlated to relatedness, but the nature of these costs and benefits is still poorly understood. Interestingly, allorecognition is found throughout (...) the animal kingdom, with examples in nearly all the multicellular phyla; however, the role of allorecognition in these different species is not always clear. In addition, the molecular mechanisms underlying allorecognition in different species are not related, suggesting a unique origin for each species. This brings up the question as to whether there is a universal need for self/non-self recognition processes among the metazoa, or if these systems evolve in response to different selective pressures. We are studying allorecognition and chimerism in the colonial ascidian, Botryllus schlosseri. Allorecognition takes place at the tips of the extracorporeal vasculature, and can result in a parabiosis, or a rejection reaction that blocks vascular fusion. Fusion has both hypothesized benefits as well as well-documented costs. This article will focus on characterizing the costs and benefits of fusion and chimerism in Botryllus, and put them into the broader context of the role of allorecognition in the metazoa. (shrink)

Considering the enormous diversity of living organisms, representing mostly untapped resources for studying ecological, ontogenetic and phylogenetic patterns and processes, why should evolutionary biologists concern themselves with the remains of animals and plants that died out tens or even hundreds of millions of years ago? The reason is that important new insights into some of the most vexing evolutionary questions are being revealed at the interfaces of palaeontology, developmental biology and molecular biology. Attempts to synthesise information from these disciplines, however, (...) often encounter their greatest hurdles in considerations of the radiation of the Metazoa. Ongoing challenges relate to the origins of body plans, the relationships of the metazoan phyla and the timing of major evolutionary radiations. Palaeontology not only has its own unique contributions to the study of evolutionary processes, but provides a lynchpin for many of the emerging techniques. BioEssays 22:1142–1152, 2000. © 2000 John Wiley & Sons, Inc. (shrink)