Cyclic Behavior in Gene-Culture Coevolution Mediated by Phenotypic Plasticity in Language

Adaptive Phenotypic Plasticity: Target or By-Product of Selection in a Variable Environment?

Phenotypic plasticity may evolve rapidly, enabling a population’s persistence in the face of sudden environmental change. Rapid evolution can occur when there is considerable genetic polymorphism at selected loci. We propose that balancing selection could be one of the mechanisms that sustain such polymorphism for plasticity. We use stochastic Monte Carlo simulations and deterministic analysis to investigate the evolution of a plasticity modifier locus in structured populations inhabiting favorable and adverse environments, i.e. patchy habitats. We survey a wide range of parameters including selective pressures on a target (structural) locus, plasticity effects, population sizes, and migration patterns between demes including periodic or continuous bidirectional and source-sink dynamics. We find that polymorphism in phenotypic plasticity can be maintained under a wide range of environmental scenarios in both favorable and adverse environments due to the balancing effect of population structure in patchy habitats. This effect offers a new plausible explanation for the rapid evolution of plasticity in nature: Phenotypic plasticity may rapidly evolve from genetic variation maintained by balancing selection if the population has experienced immigration from populations under different selection regimes.

Cultural evolution has been proposed as the mechanism by which human languages’ distinct features emerge. One of such features is structure, which is regarded as an optimal solution to the competing pressures for simplicity and expressivity in language learning and use. A recent experimental iterated learning study (Kirby et al., 2015) shows that structure can emerge from an unstructured language under these competing pressures, by implementing both a learning and a communication task in a transmission chain setup. However, as most iterated learning experiments, it was run on a written modality, which might be problematic if the aim is to drive conclusions about language in general—writing is not language’s default modality and was not present in early stages of language evolution. The present study carried out a partial replication of the aforementioned experiment, contrasting a written condition (analogous to the original) with a spoken condition, in order to test for possible modality effects. Results for the written condition did not replicate those in Kirby et al. (2015) in any of the measures, suggesting that motivational factors could have played a crucial role in the previous findings. This hinders the interpretations of modality effects and suggests the need of further work.

Evidence of selection on phenotypic plasticity and cost of plasticity in response to host-feeding sources in the major Chagas disease vector Triatoma infestans

Culture consists of behavior. The units are practices shared by members of a group and acquired as a result of membership in the group. Although it is common to define the units of culture as abstractions, such as culturgens or memes, these abstractions in no way help to explain a group’s practices. Instead, they only direct research away from the context and consequences that result in transmission of a practice from one group member to another. If culture is to be described as an evolutionary process, one must have a sufficiently general definition of “evolutionary process” to allow genetic evolution and cultural evolution to be examples. This may be accomplished by defining an evolutionary process as composed of variation (within a pool of replicators), transmission (by copying), and selection (by differential transmission). The replicators of cultural evolution are practices, which are units of operant behavior (i.e., behavior under control of consequences and context). Practices are transmitted from individual to individual by imitation and instruction. Instruction may be understood with the concept of a rule, which is a verbal discriminative stimulus (i.e., a verbally created context). Instruction consists of rule-giving, which results in rule-following on the part of the instructee. New rules come into a culture frequently as a result of rule-making, the generation of new rules on the basis of non-social stimuli. Selection in cultural evolution occurs because imitation and instruction of competing practices have differential consequences in the long run, consequences that impact reproductive potential. Since such long-term consequences have little effect on behavior, an adaptive practice (i.e., one that pays in the long run, called “self-control”) is strengthened in the short-term by social reinforcers delivered by rule-givers. A behavioral analysis focuses on environmental events that are observable and, so, susceptible to research. The postulating of fictitious inner entities, whether they be memes, “devices,” or “modules,” only impedes understanding of culture and cultural evolution. Natural selection, because it is short-sighted and opportunistic, may be expected to produce mechanisms that aid and abet valuable behavioral functions. The key to understanding cultural evolution lies in understanding practices in the light of their environmental contexts and short- and long-term consequences.

Phenotypic plasticity – the ability of organisms to express variable forms in response to environmental cues – is increasingly appreciated for its roles in a variety of phenomena, from population persistence in the face of climate change to sparking evolutionary innovations. Plasticity itself clearly has genetic foundations, whereby the genome provides instructions for a typically physiological response. As a result, physiology becomes the proximate developmental mediator between the environment and an individual’s phenotypic expression. This chapter, focusing mostly on endocrine systems, reviews the (1) relationship between physiology and plasticity; (2) approaches that have been used to examine the role of physiological divergence in the evolution of plasticity; (3) ways in which physiology can potentially constrain or facilitate the evolution of plasticity; and (4) how the evolution of physiological mechanisms can promote subsequent trait evolution or even speciation. Characterizing the physiological mechanisms underlying plasticity in a comparative framework will yield a clearer picture of how plastic phenotypes evolve and promote the diversification of traits.

Cultural change constitutes a Darwinian evolutionary process, comprising the three Darwinian principles of variation, selection and inheritance. Yet cultural evolution is not identical to genetic evolution: the sources of variation, the forms of selection and the modes of inheritance found in cultural evolution may be very different to those found in genetic evolution. Here, I review research conducted in the last 30 years that has built a Darwinian theory of cultural change by borrowing the rigorous, quantitative methods developed by biologists to explain biological evolution, yet simultaneously acknowledging the differences between cultural and genetic evolution. I argue that the quantitative nature of Darwinian methods (e.g. statistical analysis, formal models, laboratory experiments) has resulted in a significantly better understanding of cultural phenomena than many traditional non-evolutionary, non-scientific approaches to cultural change in the social sciences and humanities. Evolutionary theory also provides a synthetic framework within which different branches of the social sciences and humanities may be integrated, equivalent to the “evolutionary synthesis” that integrated the biological sciences in the early 20th century.

The 21st century will be the century of biology, and evolutionary biology will be the linchpin. Yes, this is a bold statement, but it is certainly in keeping with Dobzhansky's famous dictum about evolution. Dobzhansky was one of the major architects of the Modern Synthesis. This book by Schlichting and Pigliucci (SP the Final Synthesis is just gathering steam. Note that these dates are just rough guides and not meant to imply that significant work did not occur outside those periods. What is critical is that within these periods the relevant disciplines all become focussed on the same research program. We are now in the midst of this final joining of biological disciplines. This joining, if history is a guide, will take the next couple of decades. This joining will be driven from the evolutionary side. It is the evolutionary side within which the disciplines are linked by a synthetic theory. The molecular side is primarily linked by a shared set of techniques and a viewpoint that centers all questions ultimately on DNA sequences. Because the evolution side is much more theory driven, that is where synthetic concepts tend to arise. This book by S&P is an excellent example of such theorydriven synthesis. Also, if truth be told, as a whole evolutionary biologists tend to have a larger perspective than those in many other biological disciplines. Looking back on the Modern Synthesis is useful for the task ahead (Mayr and Provine, 1980). In particular, if we learn anything from that episode in our history, we

Developmental systems theory (DST) expands the unit of replication from genes to whole systems of developmental resources, which DST interprets in terms of cycling developmental processes. Expansion seems required by DST's argument against privileging genes in evolutionary and developmental explanations of organic traits. DST and the expanded replicator brook no distinction between biological and cultural evolution. However, by endorsing a single expanded unit of inheritance and leaving the classical molecular notion of gene intact, DST achieves only a nominal reunification of heredity and development. I argue that an alternative conceptualization of inheritance denies the classical opposition of genetics and development while avoiding the singularity inherent in the replicator concept. It also yields a new unit—the reproducer—which genuinely integrates genetic and developmental perspectives. The reproducer concept articulates the non-separability of “genetic” and “developmental” roles in units of heredity, development, and evolution. DST reformulated in terms of reproducers rather than replicators preserves an empirically interesting distinction between cultural and biological evolution.

Although the study of adaptation is central to biology, two types of adaptation are recognized in the biological field: physiological adaptation (accommodation or acclimation; an individual organism's phenotype is adjusted to its environment) and evolutionary–biological adaptation (adaptation is shaped by natural selection acting on genetic variation). The history of the former concept dates to the late nineteenth and early twentieth centuries, and has more recently been systemized in the twenty‐first century. Approaches to the understanding of phenotypic plasticity and learning behavior have only recently been developed, based on cellular–histological and behavioral–neurobiological techniques as well as traditional molecular biology. New developments of the former concepts in phenotypic plasticity are discussed in bacterial persistence, wing di‐/polymorphism with transgenerational effects, polyphenism in social insects, and defense traits for predator avoidance, including molecular biology analyses. We also discuss new studies on the concept of genetic accommodation resulting in evolution of phenotypic plasticity through a transgenerational change in the reaction norm based on a threshold model. Learning behavior can also be understood as physiological phenotypic plasticity, associating with the brain–nervous system, and it drives the accelerated evolutionary change in behavioral response (the Baldwin effect) with memory stock. Furthermore, choice behaviors are widely seen in decision‐making of animal foragers. Incorporating flexible phenotypic plasticity and learning behavior into modeling can drastically change dynamical behavior of the system. Unification of biological sciences will be facilitated and integrated, such as behavioral ecology and behavioral neurobiology in the area of learning, and evolutionary ecology and molecular developmental biology in the theme of phenotypic plasticity.

Species that compete for the same resource may undergo ecological character displacement (CD), where the phenotype of each species evolves to deviate from its optimum in the absence of competition. As natural habitats are rarely static, interspecific competition is likely to occur in environments that fluctuate over time. Such environmental fluctuations can in turn cause the evolution of phenotypic plasticity for traits mediating the competition. However, the interplay of environmental fluctuations, evolution of plasticity, and character displacement, has been little investigated. We use a quantitative genetic model to study theoretically how a randomly fluctuating environment and evolution of plasticity influence the outcome of ecological CD between 2 competing species. We show that environmental fluctuations make the conditions for CD more stringent, requiring stronger competitive selection relative to stabilizing selection. This occurs because environmental fluctuations reduce the average population size and thereby competition intensity. Evolving plasticity can restore CD by buffering the impact of environmental fluctuations through phenotypic tracking, to a degree that depends on environmental predictability. Somewhat paradoxically, competition that favors phenotypic divergence among species can cause convergence in plasticity, when this reduces the load caused by fluctuations in phenotypic divergence. Our results shed light on how competition and plasticity influence the evolution of the fundamental niche in a fluctuating environment.

The environmental variables hypothesized to cause behavioral adaptation are distributed across a wide array of spatial scales, from local variation in factors such as food sources and territorial encounters to regional or continental variation in factors such as seasonality and the presence of predators. Geographic variation in behavior, the topic of this book, is just one of the potential evolutionary responses to environmental variation. Because behavioral divergence among populations generated by disparate natural selection can be counterbalanced by the homogenizing influence of gene flow, adaptive geographic variation can evolve only if the spatial scale of variation in natural selection is greater than the scale of gene flow (Endler 1977, Slatkin 1978). If geographic variation does not evolve because the spatial scale of selection is smaller than the scale of gene flow, populations may instead evolve adaptive phenotypic plasticity (Bradshaw 1965); the expression, by a single genotype, of different fitness-enhancing phenotypes in different environments. Because the same evolutionary processes operating on different spatial scales can generate behavioral geographic variation, behavioral phenotypic plasticity, or geographic variation in phenotypic plasticity, I devote this chapter to development of a hierarchical perspective tor studying environmental variation and behavioral evolution. This perspective emphasizes the shared evolutionary processes and research methodologies common to different levels of spatial variation, such as the balance of gene flow, natural selection, and genetic drift, the relationship between environmental patch size and local adaptation, and the effects of historical contingencies and genetic constraints on behavioral adaptation and phenotypic plasticity. In what follows, I review behavioral research in two unrelated taxa to illustrate the range of possible evolutionary responses to different patterns of environmental variation. First, I discuss different spatial scales of adaptation in the climbing behavior of deer mice (Peromyscus maniculatus) and provide a hierarchical analysis of the effects of natural selection, genetic drift, and gene flow. Second, I discuss diet-induced phenotypic plasticity in the feeding behavior of acridid grasshoppers (Melanoplus femurrubrum and M. sanguinipes) and the evolution of behavioral norms of reaction in response to local spatial and temporal variation in plant environments.

The selective past of populations is presumed to affect the levels of phenotypic plasticity. Experimental evolution at constant temperatures is generally expected to lead to a decreased level of plasticity due to presumed costs associated with phenotypic plasticity when not needed. In this study, we investigated the effect of experimental evolution in constant, predictable and unpredictable daily fluctuating temperature regimes on the levels of phenotype plasticity in several life history and stress resistance traits in Drosophila simulans. Contrary to the expectation, evolution in the different regimes did not affect the levels of plasticity in any of the traits investigated even though the populations from the different thermal regimes had evolved different stress resistance and fitness trait means. Although costs associated with phenotypic plasticity are known, our results suggest that the maintenance of phenotypic plasticity might come at low and negligible costs, and thus, the potential of phenotypic plasticity to evolve in populations exposed to different environmental conditions might be limited.

This article was inspired by some works of Belyaev in which he discussed the biosocial human nature, and is dedicated to the 100 year anniversary of Belyaev’ birth. The main views and theories of the human nature and the main paths of genome and culture evolution during anthropogenesis are overviewed. The views of the leading past and present world-wide scientists on the basic principles of the genome-culture interactions are discussed. The seeming contradictions between “geneticists” and “sociologists” are resolved due to the development of the concept of co-evolution of the genome and culture. The evolution of genes and culture is a whole, but not separate processes. During their evolution, humans modify and reconstruct their sociocultural environment. The new environment creates new selection vectors and forms new ways and directions for genetic evolution. In response to the culture development, the genetic determination of human cognitive processes also changed. A good example of the co-evolution of culture and the genome is the development of human speech, the voice and mimic apparatus of communication. The vital importance of the new possibilities for social communication in human populations disposes to the fixation of genetic features that facilitate such communication. At the early stages of human evolution, the areas of the cerebral cortex that were responsible for the development of speech expanded and reorganized. The point of genome-culture co-evolution is well illustrated by niche construction theory. It is emphasized that the evolution of culture, which is widely regarded as a non-biological phenomenon, is quite similar in all its respects to the Darwinian process, as a result of which a sociocultural environment that is adaptive for a given community is formed through selection and transmission in a series of generations. In fact, we are talking about epigenetic inheritance in the evolution of culture and morality. The review details the views and theoretical concepts of geneticists, sociologists, social psychologists, anthropologists, behaviorists and ethologists in explaining the phenomenon of human evolution. Some contradictions caused by different rates of evolution of culture and genome are considered. In conclusion, it is shown that Belyaev’s interpretation of the biosocial nature of humans finds confirmation in modern studies by geneticists, sociologists and psychologists.

There are numerous children and adolescents throughout the world who are either diagnosed with speech and language disorders or manifest any of them as a result of another disorder. Meanwhile, since the emergence of language as an innate capability, the question of whether it constitutes a behaviour or an innate ability has been debated for decades. There have been several theories developed that support and demonstrate the biological foundations of human language. Molecular evidence of the biological basis of language came from the FOXP2 gene, also known as the language gene. Taking a closer look at both human language and biology, biolinguistics is at the core of these inquiries—attempting to understand the aetiologies of the genetics of speech and language disorders in children and adolescents. This paper presents empirical evidence based on both scientometrics and bibliometrics. We collected data between 1935 and 2022 from Scopus, WOS, and Lens. A total of 1570 documents were analysed from Scopus, 1440 from the WOS, and 5275 from Lens. Bibliometric analysis was performed using Excel based on generated reports from these three databases. CiteSpace 5.8.R3 and VOSviewer 1.6.18 were used to conduct the scientometric analysis. Eight bibliometric and eight scientometric indicators were used to measure the development of the field of biolinguistics, including but not limited to the production size of knowledge, the most examined topics, and the most frequent concepts and variables. A major finding of our study is identifying the most examined topics in the genetics of speech and language disorders. These included: gestural communication, structural design, cultural evolution, neural network, language tools, human language faculty, evolutionary biology, molecular biology, and theoretical perspective on language evolution.