Degeneracy is a poorly understood process, essential to natural selection. In the 18th and 19th centuries, the concept of degeneracy was commandeered by the colonial imagination. A rigid understanding of species, race, and culture grew to dominate the normative thinking that persisted well into the burgeoning new industrial age. A 20th-century reconfiguration of the concept by George Gamow highlighted a form of intraorganismic variation that is still underexplored. Degeneracy exists in a population of variants where structurally different components perform a (...) similar, but not necessarily identical, function with respect to context. The presence of degeneracy increases a system’s complexity and robustness against perturbations. The loss of a genetic component in biological systems, for example, can be compensated by redundant elements , or by degenerate elements . A historical survey of the use of the term “degeneracy” reveals how and why the processes it once designated, and the mechanisms it now represents, have largely escaped the purview of contemporary science. Despite confusion and general oversight, degeneracy has been characterized by select researchers at the molecular, genetic, and neuronal levels. The concept is a potent analytical tool to understand selection, variation, and transmission. (shrink)

The species-specific organizational property of speech is a continual mouth open-close alternation, the two phases of which are subject to continual articulatory modulation. The cycle constitutes the syllable, and the open and closed phases are segments framescontent displays that are prominent in many nonhuman primates. The new role of Broca's area and its surround in human vocal communication may have derived from its evolutionary history as the main cortical center for the control of ingestive processes. The frame and content components (...) of speech may have subsequently evolved separate realizations within two general purpose primate motor control systems: (1) a motivation-related medial system, including anterior cingulate cortex and the supplementary motor area, for self-generated behavior, formerly responsible for ancestral vocalization control and now also responsible for frames, and (2) a lateral system, including Broca's area and surround, and Wernicke's area, specialized for response to external input (and therefore the emergent vocal learning capacity) and more responsible for content. (shrink)

The purpose of this article is to develop a model of life history theory that incorporates environmental influences, contextual influences, and heritable variation. I argue that physically or psychologically stressful environments delay maturation and the onset of reproductive competence. The social context is also important, and here I concentrate on the opportunity for upward social mobility as a contextual influence that results in delaying reproduction and lowering fertility in the interest of increasing investment in children. I also review evidence that (...) variation in life history strategies is influenced by genetic variation as well. Finally, I show that cultural shifts in the social control of sexual behavior have had differential effects on individuals predisposed to high- versus low-investment reproductive strategies. (shrink)

Despite its importance, the linkage between genetic and cultural evolution has until now been little explored. An understanding of this linkage is needed to extend evolutionary theory so that it can deal for the first time with the phenomena of mind and human social history. We characterize the process of gene-culture coevolution, in which culture is shaped by biological imperatives while biological traits are simultaneously altered by genetic evolution in response to cultural history. A case is made from both theory (...) and evidence that genetic and cultural evolution are inseverable, and that the human mind has tended to evolve so as to bias individuals toward certain patterns of cognition and choice rather than others. With the aid of mathematical models we trace the coevolutionary circuit: The genes prescribe structure in developmental pathways that lay down endocrine and neural systems, imposing regularities in the development of cognition and behavior; these regularities translate upward into holistic patterns of culture, which can be predicted in the form of probability density distributions ; natural selection acts within human history to favor certain epigenetic rules over others; and the selection alters the frequencies of the underlying genes. The effects of genetic and cultural changes reverberate throughout the circuit and are consequently tested with the passage of each life cycle. In addition to modeling gene-culture coevolution, we apply methods from island biogeography and information theory to examine the cultural capacity of the genes, the factors determining the magnitude of cultural diversity, and the possible reasons for the uniqueness of the human achievement. (shrink)

Despite its importance, the linkage between genetic and cultural evolution has until now been little explored. An understanding of this linkage is needed to extend evolutionary theory so that it can deal for the first time with the phenomena of mind and human social history. We characterize the process of gene-culture coevolution, in which culture is shaped by biological imperatives while biological traits are simultaneously altered by genetic evolution in response to cultural history. A case is made from both theory (...) and evidence that genetic and cultural evolution are inseverable, and that the human mind has tended to evolve so as to bias individuals toward certain patterns of cognition and choice rather than others. With the aid of mathematical models we trace the coevolutionary circuit: The genes prescribe structure in developmental pathways that lay down endocrine and neural systems, imposing regularities in the development of cognition and behavior; these regularities translate upward into holistic patterns of culture, which can be predicted in the form of probability density distributions ; natural selection acts within human history to favor certain epigenetic rules over others; and the selection alters the frequencies of the underlying genes. The effects of genetic and cultural changes reverberate throughout the circuit and are consequently tested with the passage of each life cycle. In addition to modeling gene-culture coevolution, we apply methods from island biogeography and information theory to examine the cultural capacity of the genes, the factors determining the magnitude of cultural diversity, and the possible reasons for the uniqueness of the human achievement. (shrink)

One foundational question in contemporarybiology is how to `rejoin evolution anddevelopment. The emerging research program(evolutionary developmental biology or`evo-devo) requires a meshing of disciplines,concepts, and explanations that have beendeveloped largely in independence over the pastcentury. In the attempt to comprehend thepresent separation between evolution anddevelopment much attention has been paid to thesplit between genetics and embryology in theearly part of the 20th century with itscodification in the exclusion of embryologyfrom the Modern Synthesis. This encourages acharacterization of evolutionary developmentalbiology as the marriage (...) of evolutionary theoryand embryology via developmental genetics. Butthere remains a largely untold story about thesignificance of morphology and comparativeanatomy (also minimized in the ModernSynthesis). Functional and evolutionarymorphology are critical for understanding thedevelopment of a concept central toevolutionary developmental biology,evolutionary innovation. Highlighting thediscipline of morphology and the concepts ofinnovation and novelty provides an alternativeway of conceptualizing the `evo and the `devoto be synthesized. (shrink)

This essay attempts to describe the neo-Lamarckian atmosphere that was dominant in French biology for more than a century. Firstly, we demonstrate that there were not one but at least two French neo-Lamarckian traditions. This implies, therefore, that it is possible to propose a clear definition of a (neo) Lamarckian conception, and by using it, to distinguish these two traditions. We will see that these two conceptions were not dominant at the same time. The first French neo-Lamarckism (1879-1931) was structured (...) by a very mechanic view of natural processes. The main representatives of this first period were scientists such as Alfred Giard (1846-1908), Gaston Bonnier (1853-1922) and Félix Le Dantec (1869-1917). The second Lamarckism - much more vitalist in its inspiration - started to develop under the supervision of people such as Albert Vandel (1894-1980) and Pierre-Paul Grassé (1895-1985). Secondly, this essay suggests that the philosophical inclinations of these neo-Lamarckisms reactivated a very ancient and strong dichotomy of French thought. One part of this dichotomy is a material, physicalist tradition, which started with René Descartes but developed extensively during the 18th and 19th centuries. The other is a spiritual and vitalist reaction to the first one, which also had a very long history, though it is most closely associated with the work of Henri Bergson. Through Claude Bernard, the first neo-Lamarckians tried to construct a mechanical and determinist form of evolutionary theory which was, in effect, a Cartesian theory. The second wave of neo-Lamarckians wanted to reconsider the autonomy and reactivity of life forms, in contrast to purely physical systems. (shrink)

In 1920, Eugen Steinach and Paul Kammerer reported experiments showing that exposure to high temperatures altered the structure of the gonad and produced hyper-sexuality in "heat rats," presumably as a result of the increased production of sex hormones. Using Steinach's evidence that the gonad is a double gland with distinct sexual and generative functions, they used their findings to explain "racial" differences in the sexuality of indigenous tropical peoples and Europeans. The authors also reported that heat induced anatomical changes in (...) the interstitial cells of the gonad were inherited by the heat rats' descendants. Kammerer used this finding to link endocrinology to his long-standing interest in the inheritance of acquired characteristics. The heat rats supported his hypothesis that the interstitial cells of the double gland were the mechanism of somatic induction in the inheritance of acquired characteristics. The Steinach-Kammerer collaboration, Kammerer's use of Steinach's "puberty gland" to explain somatic induction, and his endocrine analysis of symbiosis reveal Paul Kammerer's late career attempt to integrate endocrinology and genetics with the political ideals of Austrian socialism. With them he developed a bioethics that challenged the growing reliance on race in eugenics and instead promoted cooperation over competition in evolution. I relate his attempt to the controversies surrounding the interstitial cells, to the status of extra-nuclear theories of heredity, and to Kammerer's commitment to Austromarxist social reforms during the interwar period. (shrink)

It has long been recognized that cancer onset and progression represent a type of reversion to an ancestral quasi‐unicellular phenotype. This general concept has been refined into the atavistic model of cancer that attempts to provide a quantitative analysis and testable predictions based on genomic data. Over the past decade, support for the multicellular‐to‐unicellular reversion predicted by the atavism model has come from phylostratigraphy. Here, we propose that cancer onset and progression involve more than a one‐off multicellular‐to‐unicellular reversion, and are (...) better described as a series of reversionary transitions. We make new predictions based on the chronology of the unicellular‐eukaryote‐to‐multicellular‐eukaryote transition. We also make new predictions based on three other evolutionary transitions that occurred in our lineage: eukaryogenesis, oxidative phosphorylation and the transition to adaptive immunity. We propose several modifications to current phylostratigraphy to improve age resolution to test these predictions. Also see the video abstract here: https://youtu.be/3unEu5JYJrQ. (shrink)

Arbuscular mycorrhiza (AM), a type of plant‐fungal endosymbiosis, and nodulation, a bacterial‐plant endosymbiosis, are the most ubiquitous symbioses on earth. Recent findings have established part of a shared genetic basis underlying these interactions. Here, we approach root endosymbioses through the lens of the homology and modularity concepts aiming at further clarifying the proximate and ultimate causes for the establishment of these biological systems. We review the genetics that underlie interspecific signaling and its concomitant shift in genetic programs for either partner. (...) Also, through the comparative analysis of genetic modules shared by AM and nodulation symbioses, we identify fundamental nodes in these networks, suggesting the elemental steps that may have permitted symbiotic adaptation. Here, we show that this approach, allied to recent technical advances in the study of genetic systems architecture, can provide clear testable hypotheses for the advancement of our understanding on the evolution and development of symbiotic systems. (shrink)

Segregated neural circuits that effect particular domain-specific behaviors can be differentiated from neuroanatomical structures implicated in many different aspects of behavior. The basal ganglionic components of circuits regulating nonlinguistic motor behavior, speech, and syntax all function in a similar manner. Hence, it is unlikely that special properties and evolutionary mechanisms are associated with the neural bases of human language.

Ernst Haeckel formulated his biogenetic law, famously stating that ontogeny recapitulates phylogeny, in 1872. The Russian evolutionist Alexei Sewertzoff, and the Swiss-born zoologist Adolf Naef were among those who revised Haeckel’s law, thus changing the course of evolutionary theory and of developmental biology. Although Sewertzoff and Naef approached the problem in a similar way and formulated similar hypotheses at a purely descriptive level, their theoretical viewpoints were crucially different. While Sewertzoff laid the foundations for a Darwinian evolutionary morphology and is (...) regarded as a forerunner of the modern synthesis, Naef was one of the most important figures in “idealistic morphology”, which is usually seen as a type of anti-Darwinism. Both Naef and Sewertzoff aimed to revise Haeckel’s biogenetic law and came to comparable conclusions at the empirical level. This paper is an attempt to explain how their fundamentally different theoretical backgrounds influenced their views on the relationship between ontogeny and phylogeny. (shrink)

In this paper we argue that an operational organism concept can help to overcome the structural deficiency of mathematical models in biology. In our opinion, the structural deficiency of mathematical models lies mainly in our inability to identify functionally relevant biological characters in biological systems, and not so much in a lack of adequate mathematical representations of biological processes. We argue that the problem of character identification in biological systems is linked to the question of a properly formulated organism concept. (...) Lastly, we demonstrate how a decomposition of an organism into independent characters in the context of a specific biological process--such as adaptation by means of natural selection--depends on the dynamical properties and invariance conditions of the equations that describe this process. (shrink)

It is very curious that C.G. Jung has had so little influence upon the anthropology of consciousness. In this paper, the reasons for this oversight are given. The archetypal psychology of Jung is summarized and shown to be more complex and useful than extreme constructivist accounts would acknowledge. Jung's thinking about consciousness fits very well with a modern neuroscience view of the psyche and acts as a corrective to relativist notions of consciousness and its relation to the self.