Russian comparative embryology takes form: a conceptual metamorphosis toward “evo‐devo”

This essay recapitulates major paths followed by the Russian tradition of what we refer to today as evolutionary developmental biology (“evo‐devo”). The article addresses several questions regarding the conceptual history of evolutionary embryological thought in its particularly Russian perspective: (1) the assertion by the St. Petersburg academician Wolff regarding the possible connections between environmental modifications during morphogenesis and the “transformation” of species, (2) the discovery of shared “principles” underlying animal development by von Baer, (3) the experimental expression of Baer's principles by Kowalevsky and Mechnikoff, (4) Severtsov's theory of phylembryogenesis, (5) Filatov's approach to the study of evolution using comparative “developmental mechanics”, and (6) Shmalgausen's concept of “stabilizing” selection as an attempt to elucidate the evolution of developmental mechanisms. The focus on comparative evolutionary embryology, which was established by Kowalevsky and Mechnikoff, still continues to be popular in present‐day “evo‐devo” research in Russia.     

Mort ou persistance du darwinisme ? Regard d’un épistémologue

The article examines why evolutionary biologists have been haunted by the question whether they are “Darwinian” or “non-Darwinian” ever since Darwin's Origin of species. Modern criticisms addressed to Darwinism are classified into two categories: those concerning Darwin's hypothesis of “descent with modification” and those addressed to the hypothesis of natural selection. In both cases, although the particular models that Darwin proposed for these two hypotheses have been significantly revised and expanded, Darwin's general framework has constrained and canalized evolutionary research, in the sense that it has settled an array of possible theoretical choices. Gould's changing attitudes regarding Darwinism is taken as a striking illustration of this interpretation.     

The proximate/ultimate distinction in the multiple careers of Ernst Mayr

Ernst Mayr's distinction between “ultimate” and “proximate” causes is justly considered a major contribution to philosophy of biology. But how did Mayr come to this “philosophical” distinction, and what role did it play in his earlier “scientific” work? I address these issues by dividing Mayr's work into three careers or phases: 1) Mayr the naturalist/researcher, 2) Mayr the representative of and spokesman for evolutionary biology and systematics, and more recently 3) Mayr the historian and philosopher of biology. If we want to understand the role of the proximate/ultimate distinction in Mayr's more recent career as a philosopher and historian, then it helps to consider hisearlier use of the distinction, in the course of his research, and in his promotion of the professions of evolutionary biology and systematics. I believe that this approach would also shed light on some other important “philosophical” positions that Mayr has defended, including the distinction between “essentialism: and “population thinking.”     

Beyond the DP/DSS controversy

Paul Turke's “Which humans behave adaptively, and why does it matter?” shows, if he we are to take him as being representative of “Darwinian social science” in general, that his school of thought has moved surprisingly close to that of its “Darwinian psychology” critics in accepting the importance if not the primacy of the psychological level of explanation in applying evolutionary theory to human behavior. Disagreements continue over whether the adaptiveness of current behavior should be viewed as an occasionally interesting question because of the light it can shed on evolved psychological mechanisms, or whether, as Turke maintains, it is the central question for human sociobiology. In any event, the “vertically integrated approach,” utterly ignored by Turke, incorporates Darwinian Psychology and is far more powerful than is Turke's approach in explicating the relationship between genes and culture, thereby rendering the current debate pointless.     

In memoriam: Napoleon A. Chagnon

Anthropologist Napoleon A. Chagnon was a central figure in the development and foundation of evolutionary approaches to human behavior. We highlight his ethnographic fieldwork, contributions to studies of kinship and marriage, and his foundational role in the development of evolutionary approaches to human behavior. As a holistic anthropologist Chagnon led anthropology toward the integration of cultural and evolutionary theory. Finally, his leadership was central in the foundation of the Human Behavior and Evolution Society.EpigraphRicardo, a Brazilian Protestant missionary who was assisting the scientific team and who has worked with the Yanomami for over 25 years … told me to run and get my camera. “There's going to be a fight,” he said. Then he turned to leave. “Aren't you going to stay?” I asked. “Nah, happens all the time. You stay, you're an anthropologist, should be interesting. Call me if anyone gets hurt.”     

150 Jahre “Biogenetisches Grundgesetz”

150 years “Biogenetic Law” The zoologist Ernst Haeckel is one of the most well‐known, but also one of the most controversial scientists of the late 19th and early 20th centuries. He was one of the earliest Darwinists and a forceful advocate of evolutionary theory. Together with “Darwin's Bulldog” Thomas Henry Huxley, Haeckel was a central figure in the early history and popularization of Darwinism. But his name is not only a symbol for the disputes about the theory of evolution and its popularization, but also for a campaign for monism, a world‐view or philosophy created by Haeckel himself. Together with Fritz Müller, Ernst Haeckel was one of the first to formulate a “Biogenetic Law”. He also created several concepts and terms still in use in biology today, such as “ontogeny”, “phylogeny”, “ecology”, “cholorogy” and “phylum” in his first, and maybe most important book “General Morphology of Organism”, which was published in 1866, 150 years ago.     

The Williams' legacy: A critical reappraisal of his nine predictions about the evolution of senescence

Williams' evolutionary theory of senescence based on antagonistic pleiotropy has become a landmark in evolutionary biology, and more recently in biogerontology and evolutionary medicine. In his original article, Williams launched a set of nine “testable deductions” from his theory. Although some of these predictions have been repeatedly discussed, most have been overlooked and no systematic evaluation of the whole set of Williams' original predictions has been performed. For the sixtieth anniversary of the publication of the Williams' article, we provide an updated evaluation of all these predictions. We present the pros and cons of each prediction based on recent accumulation of both theoretical and empirical studies performed in the laboratory and in the wild. From our viewpoint, six predictions are mostly supported by our current knowledge at least under some conditions (although Williams' theory cannot thoroughly explain why for some of them). Three predictions, all involving the timing of senescence, are not supported. Our critical review of Williams' predictions highlights the importance of William's contribution and clearly demonstrates that, 60 years after its publication, his article does not show any sign of senescence.     

Das Triplett aus zwei Monophyla und einem Paraphylum als Baustein des phylogenetischen Systems

The triplet consisting of two monophyletic taxa and one paraphyletic taxon as constructive element of the phylogenetic system Evolution has produced very many novelties (apomorphies). Most of them are small and relatively inconstant, these are more or less indicative of the phylogenetic relationships between closely related species. They cannot be the constitutive character of a supraspecific taxon that exists since a long time and comprises many diversified species. Such a taxon of higher rank can only be characterized by an improbable, rare novelty that has developed only once and has been preserved in all descendent species. Two consecutive apomorphies of this persistent type (‘fixed apomorphies’) characterize three supraspecific taxa, the triplet “A”, “B” and “A minus B” (Fig. 1). The group “A minus B” is rejected in Hennig's theory because it is ‘paraphyletic’, but it is not an artefact created by the systematicist. It is an inevitable mathematical consequence of the differentiatison of the group “B” within the group “A”. Being the result of a subtraction, it is necessarily associated with the two monophyletic partners in the triplet, as it is delimited on one side by the synapomorphy of the group “A”, of which it is a part, and on the other side by the autapomorphy of the separate group “B”. Traditional classifications often include paraphyletic groupings that are inconsistent with phylogenetics, e. g. the Reptilia and the Apterygota. The fault in such cases is that these groups are extended beyond the limits of a triplet and cover more than a single interval between consecutive monophyletic taxa. Paraphyletic groups are admitted in the phylogenetic system only for bridging the gaps in our cladistic information. According to HENNIG'S theory, all supraspecific taxa should be arranged two by two as sister-groups originating from one ancestral species and comprising all descendents of that species. The fixed evolutionary novelties which characterize higher supraspecific taxa are, however, rare and scattered. It is highly improbable that they have developed in sister species, therefore the taxa marked by them cannot be sister-groups (except in very rare cases). In HENNIG'S earlier papers, e. g. in his system of Lepidoptera (1953: 46–49), the alleged ‘sister-groups' are, in reality, the groups “B” and “A minus B” of a triplet (see Fig. 2). In his revised concept (1957 and later), two autapomorphic groups which are most closely related in the recent fauna (“B” and “C” in Fig. 3) are called ‘sister-groups’. But these have originated independently from different ancestors in a plesiomorphic complex of extinct species and are more closely related to parts of this complex than to each other. True sister-groups (“Bx” and “Cx” in Fig. 4) would be formed if these related plesiomorphic species were included, but this extension of the ’backward‘ border of the taxon is not justified by synapomorphy (in the terms of logic, it is a ’metabasis‘), and it would make the classification of fossil species impossible, unless these show at least one synapomorphy with either “B” or “C”. In the system of the recent fauna the sister-groups are identical with the autapomorphic groups, because the plesiomorphic species are extinct. The natural system based on synapomorphies and autapomorphies is the triplet-system as outlined in Figure 6. It is not a new type of classification, but its theoretical foundation was missing, and precise instructions were needed for its use in phylogenetics. The information obtained by HENNIG'S method is entirely preserved in this system and can be retrieved from it, and both recent and extinct species can be classified together. The disadvantage of the triplet-system is that it contains twice as many taxa as HENNIG'S classification. This complexity will limit its use in the practice of taxonomy, but it may be simplified by transforming the system into a sequence of paraphyletic taxa terminating in a single monophylum.     

Evolutionary theory and systematics: relationships between process and patterns

The relevance of the Modern Evolutionary Synthesis to the foundations of taxonomy (the construction of groups, both taxa and phyla) is reexamined. The nondimensional biological species concept, and not the multidimensional, taxonomic, species notion which is based on it, represents a culmination of an evolutionary understanding. It demonstrates how established evolutionary mechanisms acting on populations of sexually reproducing organisms provide the testable ontological basis of the species category. We question the ontology and epistemology of the phylogenetic or evolutionary species concept, and find it to be a fundamentally untenable one. We argue that at best, the phylogenetic species is a taxonomic species notion which is not a theoretical concept, and therefore should not serve as foundation for taxonomic theory in general, phylogenetics, and macroevolutionary reconstruction in particular. Although both evolutionary systematists and cladists are phylogeneticists, the reconstruction of the history of life is fundamentally different in these two approaches. We maintain that all method, including taxonomic ones, must fall out of well corroborated theory. In the case of taxonomic methodology the theoretical base must be evolutionary. The axiomatic assumptions that all phena, living and fossil, must be holophyletic taxa (species, and above), resulting from splitting events, and subsequently that evaluation of evolutionary change must be based on a taxic perspective codified by the Hennig ian taxonomic species notion, are not testable premises. We discuss the relationship between some biologically, and therefore taxonomically, significant patterns in nature, and the process dependence of these patterns. Process-free establishment of deductively tested “genealogies” is a contradiction in terms; it is impossible to “recover” phylogenetic patterns without the investment of causal and processual explanations of characters to establish well tested taxonomic properties of these (such as homologies, apomorphies, synapomorphies, or transformation series). Phylogenies of either characters or of taxa are historical-narrative explanations (H-N Es), based on both inductively formulated hypotheses and tested against objective, empirical evidence. We further discuss why construction of a “genealogy”, the alleged framework for “evolutionary reconstruction”, based on a taxic, cladistic outgroup comparison and a posteriori weighting of characters is circular. We define how the procedure called null-group comparison leads to the noncircular testing of the taxonomic properties of characters against which the group phylogenies must be tested. This is the only valid rooting procedure for either character or taxon evolution. While the Hennig -principle is obviously a sound deduction from the theory of descent, cladistic reconstruction of evolutionary history itself lacks a valid methodology for testing transformation hypotheses of both characters and species. We discuss why the paleontological method is part of comparative biology with a critical time dimension ana why we believe that an “ontogenetic method” is not valid. In our view, a merger of exclusive (causal and interactive, but best described as levels of organization) and inclusive (classificatory) hierarchies has not been accomplished by a taxic scheme of evolution advocated by some. Transformational change by its very nature is not classifiable in an inclusive hierarchy, and therefore no classification can fully reflect the causal and interactive chains of events constituting phylogeny, without ignoring and contradicting large areas of corroborated evolutionary theory. Attempts to equate progressive evolutionary change with taxic schemes by Haeckel were fundamentally flawed. His ideas found 19th century expression in a taxic perception of the evolutionary process (“phylogenesis”), a merger of typology, hierarchic and taxic notions of progress, all rooted in an ontogenetic view of phylogeny. The modern schemes of genealogical hierarchies, based on punctuation and a notion of “species” individuality, have yet to demonstrate that they hold promise beyond the Haeckel ian view of progressive evolution.     

How to Rethink Evolutionary Theory: A Plurality of Evolutionary Patterns

Nature has recently depicted the empirical advancements of the theory of evolution as a confrontation between “reformists”, that claim for an urgent rethinking of the standard neo-Darwinian approach including so far neglected factors and processes, and “conservatives” who reply “all is well” about the current evolutionary research programme based on genetic variation and natural selection. The fight is mainly around genetic reductionism, but it seems inconclusive. Reformists stress very important factors, but they are still missing a coherent proposal about the architecture of the future extended evolutionary theory. Conservative react defensively, relying just on non-essential add-ons to the old and stable neo-Darwinian core. We analyze the debate and we propose an interpretation. Evolutionary biology is a rapidly expanding field. The bone of contention is how to update and extend the central core of the Darwinian legacy. We propose here the idea that what is happening in the field today is a development of the evolutionary research programme, whose structure is composed of a set of compatible and integrated evolutionary patterns. Evolutionary biology has been extended over its history by the inclusion of more and more patterns, rather than by revision to core theory. Niles Eldredge’s “Hierarchy Theory” is an example of global structure (meta-theory) aiming at incorporating and unifying the currently observed evolutionary patterns.     

On the concept of limited polygyny: A reply to Frost

The main thrust of Frost's comment on my article (MacDonald 1990) is that polygyny is “limited” or nonexistent among human societies with the exception of those in Subsaharan Africa and New Guinea. The issue raised is an important one for an evolutionary account of human societies. Resource polygyny follows naturally from the evolutionary theory of sex. Roughly, males are expected to benefit much more than females by having multiple mates, so that under certain ecological conditions, males are expected to compete for females as a limiting resource. I argue here that an evolutionary/ ecological approach is not incompatible with supposing that there are ecological circumtances in which polygyny is absent or highly limited. The point is that these conditions did not occur in the populations of Western Europe, so that there is no ecological reason to suppose that the polygyny which did occur was limited in any interesting sense. There are, however, non-ecological reasons which might have limited polygyny, and these will be considered as well.     

So what is a species anyway? A primatological perspective

Since Darwin's time, the question “what a species” has provoked fierce disputes and a tremendous number of publications, from short opinion papers to thick volumes. 1 The debates covered fundamental philosophical questions, such as: Do species exist at all independently of a human observer or are they just a construct of the human mind to categorize nature's organismic diversity and serve as a semantic tool in human communication about biodiversity? 2 - 4 or: Are species natural kinds (classes) or individuals that are “born” by speciation, change in course of time, and finally “die” when they go extinct or diverge into new species? 5 - 8 Also included was the problem of species as taxa (taxonomic) versus species as products of the speciation process (evolutionary). 9 More pragmatic issues arose, such as: How can we reliably delineate and delimitate species? 10 , 11 The great interest in what a species is reflects the importance of “species” as fundamental units in most fields of biology, especially evolutionary biology, ecology, and conservation. 2 , 12 - 14     

Darwin,the amphibians,and the natural selection

A critical review of Darwin's publications shows that he did not dissert much about amphibians, in comparison with the other tetrapods. However, in “A Naturalist's Voyage round the World”, Darwin described for the first time several amphibian species and was surprised by their peculiar way of life, terrestrial or euryhaline. These amphibian observations around the world led Darwin to discuss evolutionnary notions, like developmental heterochronies or evolving convergences, and later to illustrate his famous natural selection theory. This is confirmed, for example, by the publication of “On the Origin of Species” where Darwin ironically questioned creation theory, trying to explain the absence of amphibians on oceanic islands. Lamarck also considered amphibians as relevant material to illustrate his theory of acquired character heredity. These historical uses of lissamphibians as evolutionary models have been mostly realized before any amphibian fossil discovery, i.e. out of a palaeontological context.     

Paraphyly,ancestors, and the goals of taxonomy: A botanical defense of cladism

Cronquist (1987) criticizes cladism for its rejection of paraphyletic groups, which he would retain if he feels they are “conceptually useful.” We argue that paraphyletic higher taxa are artificial classes created by taxonomists who wish to emphasize particular characters or phenetic “gaps,” and that formal recognition of such taxa conveys a misleading picture of common ancestry and character evolution. In our view, classifications should accurately reflect the nested hierarchy of monophyletic groups that is the natural outcome of the evolutionary process. Such systems facilitate the study of evolution and provide an efficient summary of character distributions. Paraphyletic groups, such as “prokaryotes,” “green algae,” “bryophytes,” and “gymnosperms,” should be abandoned, as continued recognition of such groups will only serve to retard progress in understanding evolution. Contrary to Cronquist’s (1987) assertions, cladistic theory is not at odds with standard views on speciation and the existence of ancestors. Groups of interbreeding organisms can continue to exist after giving rise to descendant species, and there are several ways in which such groups, whether extant or extinct, can be incorporated into cladistic classification. In contrast, paraphyletic higher taxa are neither cohesive (integrated by gene flow) nor whole, do not serve as ancestors, and are unacceptable in the phylogenetic system. Fossils may be of great value in assessing phylogenetic relationships and are readily accommodated in cladistic classification. Cladistic studies are helping to answer major questions about plant evolution, and we anticipate increased efforts to develop a truly phylogenetic system.     

Ecological theatre and the evolutionary game: how environmental and demographic factors determine payoffs in evolutionary games

In the standard approach to evolutionary games and replicator dynamics, differences in fitness can be interpreted as an excess from the mean Malthusian growth rate in the population. In the underlying reasoning, related to an analysis of “costs” and “benefits”, there is a silent assumption that fitness can be described in some type of units. However, in most cases these units of measure are not explicitly specified. Then the question arises: are these theories testable? How can we measure “benefit” or “cost”? A natural language, useful for describing and justifying comparisons of strategic “cost” versus “benefits”, is the terminology of demography, because the basic events that shape the outcome of natural selection are births and deaths. In this paper, we present the consequences of an explicit analysis of births and deaths in an evolutionary game theoretic framework. We will investigate different types of mortality pressures, their combinations and the possibility of trade-offs between mortality and fertility. We will show that within this new approach it is possible to model how strictly ecological factors such as density dependence and additive background fitness, which seem neutral in classical theory, can affect the outcomes of the game. We consider the example of the Hawk–Dove game, and show that when reformulated in terms of our new approach new details and new biological predictions are produced.     

Quelques apports à la théorie de l’Évolution,de la « Synthèse orthodoxe » à la « Super synthèse évo-dévo » 1970–2009 : un point de vue

Some contributions to evolutionary theory, from the “orthodox” Synthesis to the “Evo-devo Super synthesis” 1970–2009: A point of view. The “Modern Synthesis” of evolutionary biology coalesced and revitalized evolutionary theory beginning in the 1930s. It stressed the explanatory power of natural selection and gradual change to account for the processes that govern natural populations today, as well as patterns in the history of life. In the past 40 years, the synthesis has been challenged on various fronts ranging from paleontology to developmental biology, systematics, biogeography, and molecular and developmental biology. Several of its central propositions have been modified and expanded as a result. How well the synthesis continues to be effective will depend on its continued ability to test its central propositions and the efficacy of its central mechanisms, particularly on the basis of new evidence from emerging fields of study.     

OPTIMALITY THEORY,GOMPERTZ' LAW,AND THE DISPOSABLE SOMA THEORY OF SENESCENCE

The “disposable soma” theory for the evolution of senescence suggests that senescence arises from an optimal balancing of resources between reproduction and somatic repair. Dynamic programming models are constructed and analyzed to determine the optimal relationship between reproduction, diversion of resources from repair, and added senescent mortality. Of particular interest is the relationship between the repair-reproduction trade-off and the form of the mortality-rate-versus-age curve predicted. The models analyzed in the greatest detail assume that the relationship between reproduction and added senescent mortality does not change with age. These suggest that mortality should increase at an increasing rate with age, but may approach a linear rate as mortality becomes very high. General results are derived for the shape of the mortality curves early and late in the senescing part of the life span, and mortality curves for specific trade-off functions are illustrated. An exponential increase in death rate with age (Gompertz' Law) corresponds to only one of many possible relationships between reproduction and aging. The “Law” is unlikely to hold generally if the disposable soma theory accounts for a large fraction of the observed senescent increase in mortality with age. However, support for the generality of Gompertz' Law is weak, and other theories have not produced an evolutionary explanation for the law. The disposable soma theory is consistent with some of the exceptions to Gompertz' Law that have been observed.     

Testing evolutionary models of senescence: traditional approaches and future directions

From an evolutionary perspective, the existence of senescence is a paradox. Why has senescence not been more effectively selected against given its associated decreases in Darwinian fitness? Why does senescence exist and how has it evolved? Three major theories offer explanations: (1) the theory of mutation accumulation suggested by PB Medawar; (2) the theory of antagonistic pleiotropy suggested by GC Williams; and (3) the disposable soma theory suggested by TBL Kirkwood. These three theories differ in the underlying causes of aging that they propose but are not mutually exclusive. This paper compares the specific biological predictions of each theory and discusses the methods and results of previous empirical tests. Lifespan is found to be the most frequently used estimate of senescence in evolutionary investigations. This measurement acts as a proxy for an individual’s rate of senescence, but provides no information on an individual’s senescent state or “biological age” throughout life. In the future, use of alternative longitudinal measures of senescence may facilitate investigation of previously neglected aspects of evolutionary models, such as intra- and inter-individual heterogeneity in the process of aging. DNA methylation data are newly proposed to measure biological aging and are suggested to be particularly useful for such investigations.     

Selektion und Evolutionstheorie: Müssen »altdarwinistische Dogmen« durch eine kritische Evolutionstheorie ersetzt werden?

Some authors (mainlyBonik, Gutmann, andPeters) have tried to revise current evolutionary concepts, fraught — in their opinion — with “1paleodarwinistic dogmas”. Some points of their theories are reviewed critically in the present paper: (1) Evolution is of course inimaginable without selection, but an “internal selection” eliminating misshaped embryos has nothing to do with evolution. This is stabilizing selection which reduces genetic variation and would even block evolutionary change completely if it was perfect. When this kind of internal selection was “neglected” by earlier authors, this cannot be qualified as paleodarwinistic dogmatism being in contradiction with the premises of evolutionary theory. — (2) Energetic rationalisation of organisms is certainly an important factor in selection but not an absolute law explaining everything about evolution. There are many adaptive processes resulting in less “economic” formations; e.g. heavy armors like those of tortoises, ankylosaurs, and stegosaurs. Among others, protective functions justify a certain waste of energy. — (3) Comparing organisms with technical machines provides an interesting analogy, but again this cannot be considered as the only possible approach for evolutionary models. »Maschinenanalogie« combined with a generalized »internal selection« (i.e. with the nature of adaptive changes determined by the internal construction of organisms) leads inevitably to an underestimation of selective pressures resulting from the ecologic and biocoenotic context. The simple fact of diverging evolutionary lineages shows that the same species (“machine”) can be improved in different ways under the influence of different external factors.     

Natural decision theory: A general formalism for the analysis of evolved characteristics

Classical Decision Theory, a mature and highly developed theory of rational choice, can be applied within evolutionary biology to the question of what traits an organism ought “rationally” to adopt, given that it wants to maximize its fitness. In this way the powerful formalism of decision theory can be brought to bear on the problem of how to predict which characters will be favored by natural selection, or to explain why certain characters have been so favored.Under some circumstances the classical theory of decision can be applied as it stands to an evolutionary problem simply by substituting an appropriate measure of biological fitness for the decision-theoretic concept of “utility”. Under other circumstances, however, it is necessary to extend the classical rules of decision in certain new directions. The result is a family of decision calculi of which the classical is only one. The name “Natural Decision Theory” is proposed for this extended class of biologically relevant decision methods.The decision tree method of diagramming an evolutionary decision situation is illustrated for the classical and three non-classical decision criteria, and is suggested as a potential means of gaining new insights into evolutionary forces.