Transgressive Hybrids as Hopeful Monsters

The origin of novelty is a critical subject for evolutionary biologists. Early geneticists speculated about the sudden appearance of new species via special macromutations, epitomized by Goldschmidt’s infamous “hopeful monster”. Although these ideas were easily dismissed by the insights of the Modern Synthesis, a lingering fascination with the possibility of sudden, dramatic change has persisted. Recent work on hybridization and gene exchange suggests an underappreciated mechanism for the sudden appearance of evolutionary novelty that is entirely consistent with the principles of modern population genetics. Genetic recombination in hybrids can produce transgressive phenotypes, “monstrous” phenotypes beyond the range of parental populations. Transgressive phenotypes can be products of epistatic interactions or additive effects of multiple recombined loci. We compare several epistatic and additive models of transgressive segregation in hybrids and find that they are special cases of a general, classic quantitative genetic model. The Dobzhansky-Muller model predicts “hopeless” monsters, sterile and inviable transgressive phenotypes. The Bateson model predicts “hopeful” monsters with fitness greater than either parental population. The complementation model predicts both. Transgressive segregation after hybridization can rapidly produce novel phenotypes by recombining multiple loci simultaneously. Admixed populations will also produce many similar recombinant phenotypes at the same time, increasing the probability that recombinant “hopeful monsters” will establish true-breeding evolutionary lineages. Recombination is not the only (or even most common) process generating evolutionary novelty, but might be the most credible mechanism for sudden appearance of new forms.     

The acquisition of conscience and Developmental Systems Theory

Summary Proponents of Developmental Systems Theory (DST) argue that it offers an alternative to current research programs in biology that are built on the historic disjunction between evolutionary and developmental biology. In this paper I illustrate how DST can be used to account for the acquisition of an important component of moral agency, conscience. Susan Oyama, a major proponent of DST, has set moral issues outside the compass of DST. Thus, I examine her reasons for restricting DST to non-moral matters, and argue that they are not decisive. On the positive side, I argue that DST not only is compatible with attempts to describe and explain moral agency but also aids us in understanding it. In particular, I show how DST can provide a fruitful perspective for viewing some significant current findings and theories in moral developmental psychology about the acquisition of conscience. The familiar dichotomies resisted by DST, those between genes and environment, inherited and acquired, innate and learned, and biological and cultural, have also plagued human developmental psychology, including moral development. By bringing a DST perspective to the study of moral development, I illustrate how a DST perspective might offer a promising way to reconceive that phenomenon, and provide some insights into how further work in understanding the development of moral agency might proceed. Thus, I hope to contribute to the current efforts of proponents of DST to integrate developmental and evolutionary considerations.     

Neither Adaptive Thinking nor Reverse Engineering: methods in the evolutionary social sciences

In this paper I argue the best examples of the methods in the evolutionary social sciences don’t actually resemble either of the two methods called “Adaptive Thinking” or “Reverse Engineering” described by evolutionary psychologists. Both AT and RE have significant problems. Instead, the best adaptationist work in the ESSs seems to be based on and is aiming at a different method that avoids the problems of AT and RE: it is a behavioral level method that starts with information about both the trait in question and knowledge of the EEA. I describe some examples from the literature, and suggest how a behavioral level ESS might still contribute to the discovery and understanding of human psychology. Finally, I describe some remaining problems for adaptationist reasoning of this kind.     

Rebuilding ships while at sea—Character individuality,homology, and evolutionary innovation

How novel traits originate in evolution is still one of the most perplexing questions in Evolutionary Biology. Building on a previous account of evolutionary innovation, I here propose that evolutionary novelties are those individualized characters that are not homologous to any characters in the ancestor. To clarify this definition, I here provide a detailed analysis of the concepts of “character individuality” and “homology” first, before addressing their role for our understanding of evolutionary innovation. I will argue (1) that functional as well as structural considerations are important for character individualization; and (2) that compositional (structural) and positional homology need to be clearly distinguished to properly describe the evolutionary transformations of hierarchically structured characters. My account will therefore integrate functional and structural perspectives and put forward a new multi-level view of character identity and transformation.     

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.     

Vygotsky's Crisis: Argument, context, relevance

Vygotsky’s The Historical Significance of the Crisis in Psychology (1926–1927) is an important text in the history and philosophy of psychology that has only become available to scholars in 1982 in Russian, and in 1997 in English. The goal of this paper is to introduce Vygotsky’s conception of psychology to a wider audience.I argue that Vygotsky’s argument about the “crisis” in psychology and its resolution can be fully understood only in the context of his social and political thinking. Vygotsky shared the enthusiasm, widespread among Russian leftist intelligentsia in the 1920s, that Soviet society had launched an unprecedented social experiment: The socialist revolution opened the way for establishing social conditions that would let the individual flourish. For Vygotsky, this meant that “a new man” of the future would become “the first and only species in biology that would create itself.” He envisioned psychology as a science that would serve this humanist teleology.I propose that The Crisis is relevant today insofar as it helps us define a fundamental problem: How can we systematically account for the development of knowledge in psychology? I evaluate how Vygotsky addresses this problem as a historian of the crisis.     

Beyond neo-Darwinism--an epigenetic approach to evolution

We argue that the basic neo-Darwinian framework—the natural selection of random mutations—is insufficient to account for evolution. The role of natural selection is itself limited: it cannot adequately explain the diversity of populations or of species; nor can it account for the origin of new species or for major evolutionary change. The evidence suggests on the one hand that most genetic changes are irrelevant to evolution; and on the other, that a relative lack of natural selection may be the prerequisite for major evolutionary advance.Contrary to the neo-Darwinian view, we point out that the variations of the phenotype, on which natural selection could act, do not arise at random; they are produced by interactions between the organism and the environment during development. We propose, therefore, that the intrinsic dynamical structure of the epigenetic system itself, in its interaction with the environment, is the source of non-random variations which direct evolutionary change, and that a proper study of evolution consists in the working out of the dynamics of the epigenetic system and its response to environmental stimuli as well as the mechanisms whereby novel developmental responses are canalized.We postulate that “large” evolutionary changes could be the result of the canalization of novel developmental responses which arose from environmental challenges under conditions of relaxed natural selection, and moreover, that the canalization of novel developmental responses might involve cytoplasmic inheritance or maternal effects at least in the initial stages.     

Causal mechanisms of evolution and the capacity for niche construction

Ernst Mayr proposed a distinction between “proximate”, mechanistic, and “ultimate”, evolutionary, causes of biological phenomena. This dichotomy has influenced the thinking of many biologists, but it is increasingly perceived as impeding modern studies of evolutionary processes, including study of “niche construction” in which organisms alter their environments in ways supportive of their evolutionary success. Some still find value for this dichotomy in its separation of answers to “how?” versus “why?”questions about evolution. But “why is A?” questions about evolution necessarily take the form “how does A occur?”, so this separation is illusory. Moreover, the dichotomy distorts our view of evolutionary causality, in that, contra Mayr, the action of natural selection, driven by genotype-phenotype-environment interactions which constitute adaptations, is no less “proximate” than the biological mechanisms which are altered by naturally selected genetic variants. Mayr’s dichotomy thus needs replacement by more realistic, mechanistic views of evolution. From a mechanistic viewpoint, there is a continuum of adaptations from those evolving as responses to unchanging environmental pressures to those evolving as the capacity for niche construction, and intermediate stages of this can be identified. Some biologists postulate an association of “phenotypic plasticity” (phenotype-environment covariation with genotype held constant) with capacity for niche construction. Both “plasticity” and niche construction comprise wide ranges of adaptive mechanisms, often fully heritable and resulting from case-specific evolution. Association of “plasticity” with niche construction is most likely to arise in systems wherein capacity for complex learning and behavioral flexibility have already evolved.     

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.     

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.     

A theoretical investigation of the role of social transmission in evolution

This paper contains an investigation of the interaction between protocultural processes in animals, generated by social learning and the processes of biological evolution. It addresses the question of whether mechanisms of social learning and transmission can play an evolutionary role by allowing learned patterns of behavior to spread through animal populations, in the process changing the selection pressures acting on them. Simple models of social transmission and gene-meme coevolution are developed to investigate three hypotheses related to the role of social transmission in animal evolution. Simulations using the models suggest that social transmission would have to be particularly stable and be associated with estremely strong selection, if it were to result in the fixation of alleles. A more likely hypothesis is that social transmission might allow animals to respond adaptively to novelty in their environment, rendering a genetic response unnecessary, or only partially necessary. Socially transmitted traits appear to spread sufficiently rapidly, relative to changes in gene frequency, that it would be quite feasible for a socially transmitted response to an environmental change to occur, preempting a genetic response. Social transmission is probably more likely to slow down evolutionary rates than to speed them up through changing selection pressures. However, cultural and evolutionary processes are likely to interact in complex ways, and a “behavioral drive” effect cannot be ruled out.     

Evolutionary remnants as widely accessible evidence for evolution: the structure of the argument for application to evolution education

Evolution education, in both schools and informal education, often focuses on natural selection and the fit of organisms through natural selection to their environment and way of life. Examples of evidence that evolution has occurred are therefore often limited to a modest number of classic but exotic cases, with little attention to how one might apply principles to more familiar organisms. Many of these classic examples are examples of adaptation; adaptation to local environments is, however, an outcome that could in principle also be explained by supernatural creation or design. A frequent result is the perception among the public is that examples of evolution are rare, and that the existence of well-adapted organisms may just as easily be explained metaphysically. We argue that among categories of evidence of evolution accessible to non-specialists in any environment, the most compelling evidence of common ancestry consists of remnants of evolutionary history evident in homologous features, particularly when those homologies are related to lack of fit of organisms to their way of life (“vestiges”) or to better fit that involves complicated combinations of parts usually assigned other functions (“contrivances”). Darwin emphasized the critical nature of this argument from imperfections, and it has been part of traditional catalogs of “evidence for evolution” for more than a century. Yet while remnants of history are widely used as a category of evidence for evolution, their utility in education of comparative anatomy to document body parts passed on through descent is underemphasized in evolution education at all levels. We explore the use of evolutionary remnants to document common ancestry and evidence for evolution, for application to evolution education.     

On stony ground: Lithic technology,human evolution,and the emergence of culture

Culture is the central concept of anthropology. Its centrality comes from the fact that all branches of the discipline use it, that it is in a way a shorthand for what makes humans unique, and therefore defines anthropology as a separate discipline. In recent years the major contributions to an evolutionary approach to culture have come either from primatologists mapping the range of behaviors, among chimpanzees in particular, that can be referred to as cultural or “proto‐cultural” ¹, ² or from evolutionary theorists who have developed models to account for the pattern and process of human cultural diversification and its impact on human adaptation. ^3–5.     

Logical-Semantic Analysis and the Development of L.S. Vygotsky's Ideas About “Units” and “Elements” of Psychological Systems

Based on an analysis of L.S. Vygotsky's concepts of “units” and “elements” of psychological systems, this article highlights five of their attributes. It shows that these attributes are logically symmetrical, since in their wording they can be converted into one another by negation or by replacing some words with their opposites. This suggests that the concepts of the “unit” and “element” of a system are different poles of one theoretical construct of the activity of human psychology. Thus methods for the study of psychological systems by breaking them down into elements or by separating them into units can be seen as complementary. The article describes differences among the concepts of “unit,” “minimal unit,” and “cell” of a psychological system. It reviews several problems that are solvable using the “method of units,” as well as some concepts of the theory of psychological systems that are understood as holistic, conceptual, and active processes and/or results of human interaction with the world. Among the examples of such systems are “systems of psychological functions” (according to Vygotsky), as well as separate activities (according to A.N. Leontiev), human actions and operations (interactions with the world on the level of objects and mental or physical means). The “component” of a psychological system is defined as any “something” that in some sense belongs to or is included in human interaction with the world. A component that belongs to the system is called an “element” of it, but a component that is included in the functioning and development of the system is called a “part” of it. The article presents the mathematical and psychological foundation of these definitions. It identifies and discusses the substantial (independently existing) components of psychological systems and their attributes (properties and conditions). It describes the relationships between them using the bipolar theoretical constructs “part-element” and “substantial-attributive” component of a system.     

Differences in evolutionary history translate into differences in invasion success of alien mammals in South Africa

Attempts to investigate the drivers of invasion success are generally limited to the biological and evolutionary traits distinguishing native from introduced species. Although alien species introduced to the same recipient environment differ in their invasion intensity – for example, some are “strong invaders”; others are “weak invaders” – the factors underlying the variation in invasion success within alien communities are little explored. In this study, we ask what drives the variation in invasion success of alien mammals in South Africa. First, we tested for taxonomic and phylogenetic signal in invasion intensity. Second, we reconstructed predictive models of the variation in invasion intensity among alien mammals using the generalized linear mixed‐effects models. We found that the family Bovidae and the order Artiodactyla contained more “strong invaders” than expected by chance, and that such taxonomic signal did not translate into phylogenetic selectivity. In addition, our study indicates that latitude, gestation length, social group size, and human population density are only marginal determinant of the variation in invasion success. However, we found that evolutionary distinctiveness – a parameter characterising the uniqueness of each alien species – is the most important predictive variable. Our results indicate that the invasive behavior of alien mammals may have been “fingerprinted” in their evolutionary past, and that evolutionary history might capture beyond ecological, biological and life‐history traits usually prioritized in predictive modeling of invasion success. These findings have applicability to the management of alien mammals in South Africa.     

Cost–benefit analysis of social/cultural learning in a nonstationary uncertain environment: An evolutionary simulation and an experiment with human subjects

Social/cultural learning is an effective way to reduce uncertainty about the environment, helping individuals adopt an adaptive behavior cheaply. Although this is evident for learning about temporally stable targets, such as acquisition of a skill in avoiding toxic foods, the utility of social/cultural learning in a temporally unstable environment is less clear, since knowledge acquired by social learning may be outdated. This paper addresses the adaptive value of social/cultural learning in a nonstationary environment both theoretically and empirically. We first conducted an evolutionary computer simulation that extended Henrich and Boyd's [Evol. Hum. Behav. 19 (1998) 215.] model of cultural transmission, with the following results. When individual learning about the nonstationary environment is costly, a mixed equilibrium emerges in the population, where members who engage in costly individual learning and members who skip the information search and free-ride on other members' search efforts coexist at a stable ratio. Such a “producer–scrounger” structure qualifies effectiveness of social/cultural learning severely, especially “conformity bias” when using social information. We then tested these propositions by an experiment implementing a nonstationary uncertain environment in a laboratory. The results supported our thesis. Implications of these findings and some future directions are discussed.     

The hierarchical basis of serial homology and evolutionary novelty

Given the pervasiveness of gene sharing in evolution and the extent of homology across the tree of life, why is everything not homologous with everything else? The continuity and overlapping genetic contributions to diverse traits across lineages seem to imply that no discrete determination of homology is possible. Although some argue that the widespread overlap in parts and processes should be acknowledged as “partial” homology, this threatens a broad base of presumed comparative morphological knowledge accepted by most biologists. Following a long scientific tradition, we advocate a strategy of “theoretical articulation” that introduces further distinctions to existing concepts to produce increased contrastive resolution among the labels used to represent biological phenomena. We pursue this strategy by drawing on successful patterns of reasoning from serial homology at the level of gene sequences to generate an enriched characterization of serial homology as a hierarchical, phylogenetic concept. Specifically, we propose that the concept of serial homology should be applied primarily to repeated but developmentally individualized body parts, such as cell types, differentiated body segments, or epidermal appendages. For these characters, a phylogenetic history can be reconstructed, similar to families of paralogous genes, endowing the notion of serial homology with a hierarchical, phylogenetic interpretation. On this basis, we propose a five-fold theoretical classification that permits a more fine-grained mapping of diverse trait-types. This facilitates answering the question of why everything is not homologous with everything else, as well as how novelty is possible given that any new character possesses evolutionary precursors. We illustrate the fecundity of our account by reference to debates over insect wing serial homologs and vertebrate paired appendages.     

Is exploration a metric for information gathering? Attraction to novelty and plasticity in black-capped chickadees

Animals can learn about the value of resources and predation risk by exploring novel environments or exploring novel stimuli in their regular environments. Still, there is a disconnect in the way that exploration has been defined and measured; exploration is defined in terms of information acquisition, while measured in terms of movement speed and diversity of contacted items in a novel environment. If exploration is indeed a measurement of information gathering, fast explorers should seek to reduce uncertainty about their environment more than slow explorers. Exploration speed has also been linked to behavioral plasticity, where fast explorers move fast but collect less detailed information, thereby forming routines and expressing less plasticity than slow explorers. We test these two hypotheses by comparing exploration in a novel environment to individuals' attraction to novelty and behavioral plasticity. Our results support the view that exploration is a measurement of information-gathering tendencies as fast explorers were more likely to collect novel information, which should reduce uncertainty further than sampling familiar information sources, compared with slower explorers. Furthermore, faster explorers switched to sampling novel information more quickly than slow explorers when the value of the familiar option decreased, opposing the widely held view that faster explorers present more routine-like behavior. By providing familiar and novel foraging options in close spatial contiguity, we demonstrate an attraction to novelty in faster explorers that cannot be confounded by activity rate, thereby suggesting that these individuals seek to reduce uncertainty. In conclusion, our results support the biological validity of the term “exploration” through its association with information gathering.