Developmental Constraints

Primatology tells that about seven million years ago a split began in primate evolution, a split that led to chimpanzee and human lineages (the pan-homo split). During these millions of years our human lineage has developed performances that our chimpanzee cousins do not possess, like reflective self-consciousness and language. We present here an evolutionary scenario that proposes a rationale for the pan-homo split. It is based on a pre-human anxiety that may have barred access to self-consciousness for the chimpanzee lineage. (...) The starting point of the scenario is the capability that had our pre-human ancestors for an elementary identification with conspecifics. We consider that the evolution of that capability has led to self-consciousness when identifications with conspecifics brought our ancestors to represent their own entities as existing as conspecifics were represented. But the same identification process also took place with suffering or endangered conspecifics. And this has produced a huge anxiety increase, source of important mental sufferings that our ancestors had to limit (ESPP 2021). Our hypothesis is that different modes of anxiety limitation have led to the pan-homo split. On one side the chimpanzee lineage would have limited an unbearable mental suffering by stopping the development of identification with conspecifics, and by this also stopping a possible evolution toward self-consciousness. Such anxiety limitation process would have led to today chimpanzees which possess a very limited consciousness of themselves. On the other side our human lineage would have successfully developed anxiety limitation tools like caring, pleasure, anticipation, communication and imitation. And these tools have accelerated the evolution of our lineage toward our human mind. The proposed pan/homo process complements an existing evolutionary scenario for self-consciousness that has positioned anxiety management as a key contributor to the build-up of our human minds (ASSC 25). Such overall perspective makes anxiety management a major source to many of our motivations and mental states, much more than assumed so far. Continuations are proposed for a better understanding about our modes of anxiety limitation (including evil behaviors), and also to introduce a possible evolutionary nature of phenomenal consciousness. -/- . (shrink)

Historically, the empirical study of phenotypic diversification has fallen into two rough camps; (1) "structuralist approaches" focusing on developmental constraint, bias, and innovation (with evo-devo at the core); and (2) "adaptationist approaches" focusing on adaptation, and natural selection. Whilst debates, such as that surrounding the proposed "Extended" Evolutionary Synthesis, often juxtapose these two positions, this review focuses on the grey space in between. Specifically, here I present a novel analysis of structuralism which enables us to take a more nuanced look (...) at the motivations behind the structuralist and adaptationist positions. This makes clear how the two approaches can conflict, and points of potential commensurability. The review clarifies (a) the value of the evo-devo approach to phenotypic diversity, but also (b) how it properly relates to other predominant approaches to the same issues in evolutionary biology more broadly. (shrink)

Throughout the recent history of research at the intersection of evolution and development, notions such as developmental constraint, evolutionary novelty, and evolvability have been prominent, but the term ‘developmental bias’ has scarcely been used. And one may even doubt whether a unique and principled definition of bias is possible. I argue that the concept of developmental bias can still play a vital scientific role by means of setting an explanatory agenda that motivates investigation and guides the formulation of integrative explanatory (...) frameworks. Less crucial is a definition that would classify patterns of phenotypic variation and unify variational patterns involving different traits and taxa as all being ‘bias.’ Instead, what we should want is a concept that generates intellectual identity across various researchers, and that unites the diverse fields and approaches relevant to the study of developmental bias, from paleontology to behavioral biology. I point to some advantages of conducting research specifically under the label of ‘developmental bias,’ compared to employing other, more common terms such as ‘evolvability.’. (shrink)

In identifying intrinsic molecular chance and extrinsic adaptive pressures as the only causally relevant factors in the process of evolution, the theoretical perspective of the Modern Synthesis had a major impact on the perceived tenability of an ontology of dispositional properties. However, since the late 1970s, an increasing number of evolutionary biologists have challenged the descriptive and explanatory adequacy of this “chance alone, extrinsic only” understanding of evolutionary change. Because morphological studies of homology, convergence, and teratology have revealed a space (...) of possible forms and phylogenetic trajectories that is considerably more restricted than expected, evo-devo has focused on the causal contribution of intrinsic developmental processes to the course of evolution. Evo-devo’s investigation into the developmental structure of the modality of morphology – including both the possibility and impossibility of organismal form – has led to the utilisation of a number of dispositional concepts that emphasise the tendency of the evolutionary process to change along certain routes. In this sense, and in contrast to the perspective of the Modern Synthesis, evo-devo can be described as a “science of dispositions.” This chapter discusses the recent philosophical literature on dispositional properties in evo-devo, exploring debates about both the metaphysical and epistemological aspects of the central dispositional concepts utilised in contemporary evo-devo and addressing the epistemological question of how dispositional properties challenge existing explanatory models in evolutionary biology. (shrink)

Nach neodarwinistischem Verständnis der Evolution entstehen neue Organismen letztlich durch rein zufällige Mutationsprozesse auf genetischer Ebene. Ihre Überlebenschancen werden dann durch die jeweilig herrschende Umwelt begünstigt oder unterdrückt. Die Evolution ist demnach nur vom reinen Zufall geleitet. Neuere Einsichten aus Entwicklungsbiologie (EvoDevo) und Epigenetik haben unsere Sicht der Evolutionsabläufe jedoch deutlich erweitert. Dabei kommt der Umwelt eine lenkende Rolle zu, der reine Zufall verliert an Bedeutung. Damit lässt sich naturwissenschaftliches Verständnis wieder besser mit herkömmlichen Schöpfungsbildern versöhnen.

The concept of developmental constraint was at the heart of developmental approaches to evolution of the 1980s. While this idea was widely used to criticize neo-Darwinian evolutionary theory, critique does not yield an alternative framework that offers evolutionary explanations. In current Evo-devo the concept of constraint is of minor importance, whereas notions as evolvability are at the center of attention. The latter clearly defines an explanatory agenda for evolutionary research, so that one could view the historical shift from ‘developmental constraint’ (...) towards ‘evolvability’ as the move from a concept that is a mere tool of criticism to a concept that establishes a positive explanatory project. However, by taking a look at how the concept of constraint was employed in the 1980s, I argue that developmental constraint was not just seen as restricting possibilities (‘constraining’), but also as facilitating morphological change in several ways. Accounting for macroevolutionary transformation and the origin of novel form was an aim of these developmental approaches to evolution. Thus, the concept of developmental constraint was part of a positive explanatory agenda long before the advent of Evo-devo as a genuine scientific discipline. In the 1980s, despite the lack of a clear disciplinary identity, this concept coordinated research among paleontologists, morphologists, and developmentally inclined evolutionary biologists. I discuss the different functions that scientific concepts can have, highlighting that instead of classifying or explaining natural phenomena, concepts such as ‘developmental constraint’ and ‘evolvability’ are more important in setting explanatory agendas so as to provide intellectual coherence to scientific approaches. The essay concludes with a puzzle about how to conceptually distinguish evolvability and selection. (shrink)

Reciprocal altruism implies delayed payoffs by definition. It might therefore seem logical to assume that limited memory, calculation, and planning capacities have constrained the evolution of reciprocity in non-human animals. Here I will argue that this is not the case. First, I will show that the emotional track of past interactions is enough to motivate and maintain reciprocity over longer timespans. Second, I will propose a developmental pathway of this system of emotional bookkeeping. In particular, the neuropeptide modulation underlying mother-infant (...) and pair bonding may have been coopted for emotionally mediated reciprocity. Finally, I suggest that similar rewarding mechanisms may motivate indirect reciprocity and cooperation in larger social networks. Therefore, reciprocity can be ultimately conserved in primate lineages, without the need for individuals to keep a detailed account of benefits exchanged. (shrink)

I develop a variant of the constraint interpretation of the emergence of purely physical (non-biological) entities, focusing on the principle of the non-derivability of actual physical states from possible physical states (physical laws) alone. While this is a necessary condition for any account of emergence, it is not sufficient, for it becomes trivial if not extended to types of constraint that specifically constitute physical entities, namely, those that individuate and differentiate them. Because physical organizations with these features are in fact (...) interdependent sets of such constraints, and because such constraints on physical laws cannot themselves be derived from physical laws, physical organization is emergent. These two complementary types of constraint are components of a complete non-reductive physicalism, comprising a non-reductive materialism and a non-reductive formalism. (shrink)

Many apparently complex mechanisms in biology, especially in embryology and molecular biology, can be explained easily by reasoning at the level of the “efficient cause” of the observed phenomenology: the mechanism can then be explained by a simple geometrical argument or a variational principle, leading to the solution of an optimization problem, for example, via the co-existence of a minimization and a maximization problem . Passing from a microscopic level to the macroscopic level often involves an averaging effect that gives (...) birth to a global functional feature . We will illustrate these general principles by building in four different domains of application “a minima” models and showing the main properties of their solutions: extraction of a minimal RNA structure functioning as the first “peptidic machine,” a kind of ancestral ribosome; study of a genetic regulatory network of Drosophila centred on Engrailed gene and expressing successively two genes inside a limit cycle; study of a genetic network regulating neural activity and proliferation in mammals; and study of a simple geometric model of epiboly in zebrafish. (shrink)

Understanding the role mechanistic constraints play in shaping evolution can relieve the tension between the generally accepted intuition that there are no strict laws in biology and empirical findings showing that evolutionary processes are biased toward preferred outcomes. Mechanistic constraints explain why some evolutionary outcomes are more probable than others and allow for predictions in specific lineages. At the same time, mechanistic constraints are neither necessary nor universal in the way laws are traditionally characterized: they remain contingent on the past (...) evolution of the biological mechanisms underpinning them and only constrain the future evolution of the organisms possessing them. (shrink)

Developmental biology is expanding into several new areas. One new area of study concerns the production of adult-onset phenotypes by exposure of the fetus or neonate to environmental agents. These agents include maternal nutrients, developmental modulators (endocrine disruptors), and maternal care. In all three cases, a major mechanism for the generation of the altered phenotype is chromatin modification. Nutrient conditions, developmental modulators, and even maternal care appear to alter DNA methylation and other associated changes in chromatin that regulate gene expression. (...) This brings a new, under-appreciated, dimension of gene regulation into developmental biology, and it also demonstrates the poverty of the nature versus nurture framework for discussing phenotype production. Moreover, while such epigenetic mechanisms undermine genetic determinism, they add a layer of probabilistic biological causality for the maintenance of social inequalities. (shrink)

There is still a great deal of debate over what counts as a constraint and about how to assess experimentally the relative importance of constraints and selection in evolutionary history. I will argue that the notion of a constraint on variation, and thus the selection-constraint distinction, depends on two specifications: (1) what counts as a variant -- constraints limit or bias the production of what? and (2) range of assessment -- over what range of times or conditions is the variation (...) assessed? Specifications 1 and 2 help us to understand empirical work on the relative importance of constraint and selection in evolution. (shrink)

This article reviews the recent reissuing of Richard Owen’s On the Nature of Limbs and its three novel, introductory essays. These essays make Owen’s 1849 text very accessible by discussing the historical context of his work and explaining how Owen’s ideas relate to his larger intellectual framework. In addition to the ways in which the essays point to Owen’s relevance for contemporary biology, I discuss how Owen’s unity of type theory and his homology claims about fins and limbs compare with (...) modern views. While the phenomena studied by Owen are nowadays of major interest to evolutionary developmental biology, research in evo-devo has largely shifted from homology (which was Owen’s concern) towards evolutionary novelty, e.g., accounting for fins as a novelty. Still, I argue that questions about homology are important and raise challenges even for explanations of novelty. (shrink)

Darwin´s Erkenntnis über die Abstammung der Arten durch Mutation und Selektion sind in aller Munde, dass aber darüber im Detail noch viel Unklarheit herrscht, ist weniger bekannt. Es sind Fortschritte der Entwicklungsbiologie, die erst seit wenigen Jahren uns molekulare Erklärungsmuster an die Hand geben, mit denen die Entstehung neuer Arten besser verständlich wird. Es handelt sich um die Aufklärung der Wirkungsweise von Genen und ihren molekularen Produkten, die während der embryonalen Entwicklung von Tier und Mensch dafür sorgen, daß der Organismus (...) sich normal entwickelt. Treten Veränderungen (Mutationen) in einem dieser Mastergene auf, so wird dies zur Missbildung oder gar zum Absterben des betreffenden Embryos führen. Aber in seltenen Fällen kann so auch eine neue Tierart begründet werden. Gerade im Darwin-Jahr werden die Lehrbücher zur Evolutionsbiologie um ein wesentliches Kapitel erweitert. Es ist mit EvoDevo überschrieben und will damit ausdrücken, daß Evolutionary Theory ohne Developmental Biology keinen Sinn macht. Die bisherigen Lücken im Verständnis des Evolutionsgeschehens und die neue Sicht von EvoDevo wird im Folgenden dargestellt werden. (shrink)

One current version of the internalism/externalism debate in evolutionary theory focuses on the relative importance of developmental constraints in evolutionary explanation. The received view of developmental constraints sees them as an internalist concept that tend to be shared across related species as opposed to selective pressures that are not. Thus, to the extent that constraints can explain anything, they can better explain similarity across species, while natural selection is better able to explain their differences. I challenge both of these aspects (...) of the received view and propose a hierarchical view of constraints. (shrink)

Conrad Hal Waddington was a British developmental biologist who mainly worked in Cambridge and Edinburgh, but spent the late 1930s with Morgan in California learning about Drosophila. He was the first person to realize that development depended on the then unknown activities of genes, and he needed an appropriate model organism. His major experimental contributions were to show how mutation analysis could be used to investigate developmental mechanisms in Drosophila, and to explore how developmental mutation could drive evolution, his other (...) deep interest. Waddington was, however, predominantly a thinker, and set out to provide a coherent framework for understanding the genetic bases of embryogenesis and evolution, developing his ideas in many books. Perhaps his best-known concept is the epigenetic landscape: here a ball rolls down a complex valley, making path choices. The rolling ball represents a cell’s development over time, while the topography represents the changing regulatory environment that controls these choices. In its later forms, the role of each feature in the landscape was controlled by the effects of sets of interacting genes, an idea underpinning contemporary approaches to systems biology. Waddington was the first developmental geneticist and probably the most important developmental biologist of the pre-molecular age. (shrink)

Morphogenesis is a key process in developmental biology. An important issue is the understanding of the generation of shape and cellular organisation in tissues. Despite of their great diversity, morphogenetic processes share common features. This work is an attempt to describe this diversity using the same formalism based on a cellular description. Tissue is seen as a multi-cellular system whose behaviour is the result of all constitutive cells dynamics. Morphogenesis is then considered as a spatiotemporal organization of cells activities. We (...) show how this formalism relies on Reaction–Diffusion/Positional Information approach and how it permits to generalize its modelling possibilities. Three quite different applications for concrete morphogenetic processes are presented. The first one is a model for epithelial invagination, the second is a model of cellular differentiation by local cell–cell signalling. The last example is the secondary radial growth of conifer trees. From the mathematical point of view, different modelling tools are used according to the specificity of each process. (shrink)

By linking the concepts of homology and morphological organization to evolvability, this paper attempts to (1) bridge the gap between developmental and phylogenetic approaches to homology and to (2) show that developmental constraints and natural selection are compatible and in fact complementary. I conceive of a homologue as a unit of morphological evolvability, i.e., as a part of an organism that can exhibit heritable phenotypic variation independently of the organism’s other homologues. An account of homology therefore consists in explaining how (...) an organism’s developmental constitution results in different homologues/characters as units that can evolve independently of each other. The explanans of an account of homology is developmental, yet the very explanandum is an evolutionary phenomenon: evolvability in a character-by-character fashion, which manifests itself in phylogenetic patterns as recognized by phylogenetic approaches to homology. While developmental constraints and selection have often been viewed as antagonistic forces, I argue that both are complementary as they concern different parts of the evolutionary process. Developmental constraints, conceived of as the presence of the same set of homologues across phenotypic change, pertain to how heritable variation can be generated in the first place (evolvability), while natural selection operates subsequently on the produced variation. (shrink)

Bei der Suche nach dem rätselhaften Ursprung des Phänomens „Leben“ wird hier zunächst die zelluläre Ebene betrachtet. Im Grundaufbau zeigen alle Zellen viel Konstantes, aber gleichzeitig stellt jede Zelle ein einmaliges Individuum dar. Leben von Zellen gibt es nur als gegenseitiges Wechselspiel mit ihrer jeweiligen Umwelt. Das Genom (die Gesamtheit aller Gene) bleibt ab der Befruchtung in jeder Zelle eines Individuums konstant. Aber auch die Verwirklichung der Gene braucht eine „molekulare Umwelt“, besonders die vom Muttertier vorbereitete Umwelt im Zytoplasma des (...) Eies. Individualität eines Organismus (z.B. des Menschen) wird also nicht allein vom Genom festgelegt, sondern ist durch Entwicklungsprozesse bedingt (braucht Zeit!). „Leben“ kann (muß?) somit begriffen werden als ein wechselseitiges Kontinuum, welches alle Individuen, alle Spezies und alle Generationen miteinander und ihren Umwelten verbindet. Wie phylogenetisch betrachtet die allererste Zelle aus abiotischen Umständen entstehen konnte, wird hier nicht behandelt. Das Gesagte legt allerdings nahe, dass es nicht Gene waren, die sich eine belebte Welt erschufen, sondern bestimmte (Um-)Welten „erschufen“ sich Gene, die „lebenstauglich“ waren. (shrink)

Background: One of the all-time questions in evolutionary biology regards the evolution of organismal shapes, and in particular why certain forms appear repeatedly in the history of life, others only seldom and still others not at all. Recent research in this field has deployed the conceptual framework of constraints and natural selection as measured by quantitative genetic methods. Scope: In this paper I argue that quantitative genetics can by necessity only provide us with useful statistical sum- maries that may lead (...) researchers to formulate testable causal hypotheses, but that any inferential attempt beyond this is unreasonable. Instead, I suggest that thinking in terms of coordinates in phenotypic spaces, and approaching the problem using a variety of empirical methods (seeking a consilience of evidence), is more likely to lead to solid inferences regarding the causal basis of the historical patterns that make up most of the data available on phenotypic evolution. (shrink)

The research presented in this volume demonstrates that it is no longer reasonable to ask whether or not synesthesia is real--we must now ask how we can account ...

Developments in the sequencing of whole genomes and in simultaneously surveying many thousands of transcription and translation products of specific cells have ushered in a conceptual revolution in genetics that rationally introduces top-down, holistic analyses. This emphasized the futility of attempts to reduce genes to structurally discrete entities along the genome, and the need to return to Johannsen's definition of a gene as 'something' that refers to an invariant entity of inheritance and development. We may view genes either as generic (...) terms for units of inheritance whose referents are pragmatic ad hoc and context-dependent, or as (epistemologically) representing entities of cell functions. It is cellular functions that determine the structural referents along the DNA. Structures that happened to secure specific functions that were essential for or conducive to the survival of cells were selected for. With natural selection being the etiological background of genes as functions, genes obtain again their theoretical role as intervening variables, abstractive variables that purely 'summarize' characters. The importance of DNA sequences is that of all possible phenotypes these are the most basic ones from which we can read off the genotype directly. (shrink)

A new voice in the nature-nurture debate can be heard at the interface between evolution and development. Phenotypic integration is a major growth area in research.

The purpose of this paper is to present a critique of the current view that reduces cancer to a cellular problem caused by specific gene mutations and to propose, instead, that such a problem might become more intelligible, if it is understood as a phenomenon that results from the breakdown of the morphological plan or Gestalt of the organism. Such and organism, in Aristotelian terms, is characterized for presenting a specific morphe or logos (form) and for having a telos (end) (...) to fulfill. A malignant tumor represents an entity separated from both the organic logos and the organic telos. According to the basic postulates of Semiophysics – a blend of Aristotelian physics and Catastrophe Theory developed by René Thom – an organism is a source (original) form individuated by a dominant pregnance that corresponds to its morphogenetic field. Here it is suggested that cancer in aged individuals might result from the progressive exhaustion of developmental constraints that regulate the process of ontogeny, that it is expected to go from the fertilized non-differentiated zygote to the mature fully developed organism, because there is no further point ahead in the developmental pathway past the reproductive age. Cancer in young individuals (before their reproductive maturity) may then be consequence of the premature derangement of such fundamental developmental constraints. In all cases the result is the loss of morphological coherence within the organism. Thus representing a conflict between an organized morphology (the organism) and a part of such a morphology that drifts towards an amorphous state (the tumor). (shrink)

Developmental systems theory is an attempt to sum up the ideas of a research tradition in developmental psychobiology that goes back at least to Daniel Lehrman’s work in the 1950s. It yields a representation of evolution that is quite capable of accommodating the traditional themes of natural selection and also the new results that are emerging from evolutionary developmental biology. But it adds something else - a framework for thinking about development and evolution without the distorting dichotomization of biological processes (...) into gene and non-gene and the vestiges of the ‘black-boxing’ of developmental processes in the modern synthesis, such as the asymmetric use of the concept of information. Phenomena that are marginalized in current gene-centric conceptions, such as extra-genetic inheritance, niche construction and phenotypic plasticity are placed center stage. (shrink)

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)

Shepard's internalization concept is defended against Hecht's criticisms. By ignoring both Shepard's evolutionary perspective and the fact that internalization does not preclude modularization, Hecht advances inconclusive evidence. Developmental research supports Shepard's conclusion that kinematic geometry may be more deeply internalized than physical dynamics. This research also suggests that the internalization concept should be broadened to include representations acquired during ontogeny. [Hecht; Shepard].

Somites are transient structures which represent the most overt segmental feature of the vertebrate embryo. The strict temporal regulation of somitogenesis is of critical developmental importance since many segmental structures adopt a periodicity based on that of the somites. Until recently, the mechanisms underlying the periodicity of somitogenesis were largely unknown. Based on the oscillations of c-hairy1 and lunatic fringe RNA, we now have evidence for an intrinsic segmentation clock in presomitic cells. Translation of this temporal periodicity into a spatial (...) periodicity, through somite formation, requires Notch signaling. While the Hox genes are certainly involved, it remains unknown how the metameric vertebrate axis becomes regionalized along the antero–posterior (AP) dimension into the occipital, cervical, thoracic, lumbar, and sacral domains. We discuss the implications of cell division as a clock mechanism underlying the regionalization of somites and their derivatives along the AP axis. Possible links between the segmentation clock and axial regionalization are also discussed. (shrink)

Lorenz proposed in his (1935) articulation of a theory of behavioral instincts that the objective of ethology is to distinguish behaviors that are “innate” from behaviors that are “learned” (or “acquired”). Lorenz’s motive was to open the investigation of certain “adaptive” behaviors to evolutionary theorizing. Accordingly, since innate behaviors are “genetic”, they are open to such investigation. By Lorenz’s light an innate/acquired or learned dichotomy rested on a familiar Darwinian distinction between genes and environments. Ever since Lorenz, ascriptions of innateness (...) have become widespread in the cognitive, behavioral, and biological sciences. The trend continues despite decades of strong arguments that show, in particular, the dichotomy that Lorenz invoked in his theory of behavioral instincts is literally false: no biological trait is the product of genes alone. Some critics suggest that the failure of Lorenz’s account shows that innateness is not well-defined in biology and the practice of ascribing innateness to various biological traits should be dropped from respectable science. Elsewhere (Ariew 1996) I argued that despite the arguments of critics, there really is a biological phenomenon underlying the concept of innateness. On my view, innateness is best understood in terms of C.H. Waddington’s concept of “canalization”, i.e. the degree to which a trait is innate is the degree to which its developmental outcome is canalized. The degree to which a developmental outcome is canalized is the degree to which the developmental process is bound to produce a particular endstate despite environmental fluctuations both in the development’s initial state and during the course of development. The canalization account differs in many ways to the traditional ways that ethologists such as Konrad Lorenz originally understood the concept of innateness. Most importantly, on the canalization account the distinction between innate and acquired is not a dichotomy, as Konrad Lorenz had it, but rather a matter of degree difference that lies along a spectrum with highly canalized development outcomes on the one end and highly environmentally sensitive development outcomes on the other end. Nevertheless, I justified the canalization account on the basis of a set of desiderata or criteria that I suggested falls-out of what seemed uncontroversial about Lorenz’s account of innateness (briefly): innateness is a property of a developing individual, innateness denotes environmental stability, and innate-ascriptions are useful in certain natural selection explanations (more below). From that same set of desiderata I argued (in my 1996) that neither the concept of heritability nor of norms of reactions—two concepts from population genetics—suffice to ground innateness. In this essay, I wish to provide further support of the canalization account in two ways. First, I wish to better motivate the desiderata by revisiting a debate between Konrad Lorenz and Daniel Lehrman over the meaning and explanatory usefulness of innate ascriptions in ethology. Second, I wish to compare my canalization account of innateness with accounts proposed by contemporary philosophers, one by Stephen Stich (1975), another by Elliott Sober (forthcoming), and a third by William Wimsatt (1986). (shrink)

This book deals with embryology although it is not a book on embryology. It is in itself like a developing embryo and at a difference of textbooks it does not pretend to be an introduction to any particular scientific discipline. This work was born from a fascination about forms and it is the draft of a morphological process: the account of a form coming into being, the form of an as yet unnamed but emerging science. A new science of qualities (...) in which the natural phenomena are understood as wholes, as complex entities, possessing integral properties that are non-reducible to discrete or quantifiable magnitudes. This book is like a jump into the future of science but also it is a return in time in order to find the founder of science. The first thinker that blended speculative thought with the direct observation of facts. This book is a return to the organism, to purpose and meaning, a return to Aristotle. (shrink)

The recent discovery of a phenomenon of craniofacial growth, called craniofacial contraction, throws a new light on the process of hominization. The main interest of this discovery lies in a growth principle combining the different craniofacial units, that is to say, the neurocranium, the chondrocranium and the splanchnocranium. Until recent years, these different parts were considered as neighbouring element without any morphogenic or morphodynamic connection. But now, we know that the morphogenesis of the base of the skull governs that of (...) the face. This basicranial morphogenesis is the occipital flexion. It generates morphogenic correlations with the face since embryogenesis. The ontogenic pathway of this phenomenon is the craniofacial contraction. It concerns embryonic dynamics connected with the spatial development of the embryonic neural system, the neural tube. These morphodynamics are common to each primate species, but they are differenciated by the amplitude of the embryonic contraction. We ask ourself the question: is hominization of the neurocephalic embryogenesis, that is the craniofacial contraction, plausible over a very long period, with gradual and chaotic evolutionary pathways, or, on the contrary, is the complexity of such an embryonic phenomenon, a limiting factor generating determined and predictible ontogenic thresholds? The study of extant and fossil primate skulls demonstrates that species are organized around 6 levels of embryonic contraction, which, starting from 60 millions years, evolve from the less to the most contracted skull. Among each ontogenic level, living and fossil species develop from the same embryonic system but between both levels, the embryos suddenly are reorganized. Therefore, I have defined an evolutive ontogenic unity, that is the fundamental ontogenesia. The cephalic pole has a fundamental ontogenesis, meaning that, beyond the diversities, we can see the same contraction in many living and extinct species. The ontogenic diversities are the result of the microevolution and are not predictible. In such a perspective, the ontogenic morphodynamics evolve with chaotic trajectories. But, between two embryonic levels, or two fundamental ontogeneses, evolutionary modalities are different. Eventually, from 60 millions years to XXth century, we observe the same phenomenon than during human ontogenesis; hominization of the cephalic pole is a craniofacial contraction. The evolutive pathway is stable, whatever the number of thresholds, the cranial shape changes but the ontogenic trajectory is preserved. This is a macroevolution because the embryonic system is reorganized. The logics of the phenomenon are an increasing dynamization, the human ontogenesis is the more unstable and the longer morphodynamics to stabilize the craniofacial contraction. To conclude, hominization is an iteration of an ontogenic process when embryos reach successive dynamic thresholds. The attractors are neither static, periodic, nor chaotic because the successive ontogenic trajectories are themselves in a stable evolutive trajectory, and the results with increasing contraction, complexified neocortical tissues and cephalocaudal reorganization are predictible. During hominization, irreversibility and innovations do not emerge with chaotic determinism, but with harmonic determinism in association with the correlations established between the embryonic tissues. When the system is destabilized, the embryonic systems do not forget the previous ontogenic pattern, on the contrary, they develop the pattern with new dynamical conditions. This sort of phenomenon is not described in the sciences of complexity. In the present case, we are in front of many millions years and the necessity to propose new concepts such as a new familly of attractors, namely the harmonic attractors. (shrink)

The so-called "adaptationism" of mainstream evolutionary biology has been criticized from a variety of sources. One, which has received relatively little philosophical attention, is developmental biology. Developmental constraints are said to be neglected by adaptationists. This paper explores the divergent methodological and explanatory interests that separate mainstream evolutionary biology from its embryological and developmental critics. It will focus on the concept of constraint itself; even this central concept is understood differently by the two sides of the dispute.

Observed biological growth curves generally are sigmoid in appearance. It is common practice to fit such data with either a Verhulst logistic or a Gompertz curve. This paper critically considers the conceptual bases underlying these descriptive models.The logistic model was developed by Verhulst to accommodate the common sense observation that populations cannot keep growing indefinitely. A justification for using the same equation to describe the growth of individuals, based on considerations from chemical kinetics (autocatalysis of a monomolecular reaction), was put (...) forward by Richardson, but met with heavy criticism as a result of his erroneous derivation of the basic equation (Snell, 1929). It errs on the side of over-simplicity (Priestley & Pearsall, 1922). Von Bertalanffy (1957) subsequently based a justification on the assumption that, as a first approximation, the rates of catabolism and anabolism may be assumed to be proportional to weight and power (still vacant places, between the maximal possible and the already accumulated population sizes. This point of view was fiercely challenged by Nicholson (1933), Milne (1962), Smith (1954) and Rubinov (1973). And indeed, what is meant by vacant places has never become entirely clear. Finally Lotka (1925) devised a third leading approach by just truncating a Taylor expansion around zero of the differential law for autonomous growth after the second degree term. (shrink)

Ethical behavior — the conscious attempt to act in accordance with an individually-owned morality — is the product of an advanced stage of the maturing process. Three models of ethical growth derived from research in human development are applied to issues of business ethics.