Non-mental aspects of encephalisation: The forebrain as a playground of mammalian evolution

Neo-darwinian theory holds that changes in mammalian and avian body morphology follow behavioral adaptation. The problem then is to explain how random mutations can result in a sufficiently rapid reorganization of the most complex biological system —common sense would predict that the CNS is the slowest to evolve. This paper attempts a parsimonious explanation which predicts that the accumulation of genetic variation is most likely in CNS systems ranking high in the functional hierarchy of the brain, and that thetop-ranking systems are the preferred initial targets after increased selective pressure. They thus serve as a matrix for subsequent canalized selection which leads to a comparatively rapid, top-to-bottom reorganization of the CNS, providing a neuronal framework for the evolution of body morphology.     

On the validity of Freud's dream interpretations

In this article I defend Freud's method of dream interpretation against those who criticize it as involving a fallacy-namely, the reverse causal fallacy-and those who criticize it as permitting many interpretations, indeed any that the interpreter wants to put on the dream. The first criticism misconstrues the logic of the interpretative process: it does not involve an unjustified reversal of causal relations, but rather a legitimate attempt at an inference to the best explanation. The judgement of whether or not a particular interpretation is the best explanation depends on the details of the case in question. I outline the kinds of probabilities involved in making the judgement. My account also helps to cash out the metaphors of the jigsaw and crossword puzzles that Freudians have used in response to the 'many interpretations' objection. However, in defending Freud's method of dream interpretation, I do not thereby defend his theory of dreams, which cannot be justified by his interpretations alone.     

Morphological and functional diversity in therizinosaur claws and the implications for theropod claw evolution

Therizinosaurs are a group of herbivorous theropod dinosaurs from the Cretaceous of North America and Asia, best known for their iconically large and elongate manual claws. However, among Therizinosauria, ungual morphology is highly variable, reflecting a general trend found in derived theropod dinosaurs (Maniraptoriformes). A combined approach of shape analysis to characterize changes in manual ungual morphology across theropods and finite-element analysis to assess the biomechanical properties of different ungual shapes in therizinosaurs reveals a functional diversity related to ungual morphology. While some therizinosaur taxa used their claws in a generalist fashion, other taxa were functionally adapted to use the claws as grasping hooks during foraging. Results further indicate that maniraptoriform dinosaurs deviated from the plesiomorphic theropod ungual morphology resulting in increased functional diversity. This trend parallels modifications of the cranial skeleton in derived theropods in response to dietary adaptation, suggesting that dietary diversification was a major driver for morphological and functional disparity in theropod evolution.     

The Use of Functional and Adaptive Criteria in Phylogenetic Systematics

SYNOPSIS. The controversy over whether functional data can contributeto phylogenetic inference has grown in recent years. Steps canbe taken toward its resolution if the relevance of functionaldata is judged for each component of phylogenetic analysis.These components are (1)recognizing of basic taxa (species orsupraspecific taxa), (2) formulating hypotheses of homologyfollowed by character analysis, (3) evaluating character phylogeny,(4) formulating phylogenetic hypotheses, and (5) evaluatingalternative phylogenetic hypotheses. It can be shown that functionaldata do not play a necessary or unique role in any of thesecomponents of phylogenetic analysis. Arguments to the contraryhave failed to provide a rigorous, repeatable methodto incorporatefunctional data; proponents of a functional approach to phylogeneticreconstruction rely too often on subjective, authoritarian argumentation. Students of functional evolutionary morphology frequently havefailed to understand the kinds of information necessary to studyor apply the causal process of adaptation via natural selection.This information, required by the very nature of the theoryitself, includes knowing the pattern of heredity of the phenotypiccharacters being studied, relating intrapopulational phenotypicvariability to variation in fitness, and knowing a sufficientamount about population structure to specify the componentsof natural selection. Studies within functional evolutionarymorphology are not designed to satisfy these requirements. Functionalevolutionary morphology uses the concepts of adaptation andnatural selection axiomatically, and thus such studies contributenothing to our understanding of the evolutionary process becausehypotheses about that process are not being evaluated. Thisalso suggests that, if functional evolutionary morphology wishesto engage in analyses of the evolutionary dynamics of the phenotype,a reorientation of its research strategy and goals will be necessary.     

论达尔文医学(Ⅰ)

一切生物功能的设计都用查理士．达尔文的的自然选择理论来解释,是本文中贯彻始终的思想,探讨的中心自然自动所控制所挑选的适应性变化这一概念：我们与病原格斗适应性变化,病原对抗这变而产生的知识性变化。     

论达尔文医学(Ⅱ)

一切生物功能的设计都用查理士·达尔文的自然选择理论来解释,是本文中贯彻始终的思想．探讨的中心是自然选择所挑选的适应性变化这一概念：我们与病原格斗适应性变化,病原对抗这变化而产生的适应性变化,我们为了这些变化必须付出代价而出现的不适应性,以及机体设计和现在的生活环境之间的不适应性,等等．我们希望读者将在对身体的功能以及某些异常情况的进化论解释中得到教益．     

Evolution of leaf form correlates with tropical-temperate transitions in Viburnum (Adoxaceae)

Strong latitudinal patterns in leaf form are well documented in floristic comparisons and palaeobotanical studies. However, there is little agreement about their functional significance; in fact, it is still unknown to what degree these patterns were generated by repeated evolutionary adaptation. We analysed leaf form in the woody angiosperm clade Viburnum (Adoxaceae) and document evolutionarily correlated shifts in leafing habit, leaf margin morphology, leaf shape and climate. Multiple independent shifts between tropical and temperate forest habitats have repeatedly been accompanied by a change between evergreen, elliptical leaves with entire margins and deciduous, more rounded leaves with toothed or lobed margins. These consistent shifts in Viburnum support repeated evolutionary adaptation as a major determinant of the global correlation between leaf form and mean annual temperature. Our results provide a new theoretical grounding for the inference of past climates using fossil leaf assemblages.     

Dietary adaptations in the teeth of murine rodents (Muridae): a test of biomechanical predictions

Functional dental theory predicts that tooth shape responds evolutionarily to the mechanical properties of food. Most studies of mammalian teeth have focused on qualitative measures of dental anatomy and have not formally tested how the functional components of teeth adapt in response to diet. Here we generated a series of predictions for tooth morphology based on biomechanical models of food processing. We used murine rodents (Old World rats and mice) to test these predictions for the relationship between diet and morphology and to identify a suite of functional dental characteristics that best predict diets. One hundred and five dental characteristics were extracted from images of the upper and lower tooth rows and incisors for 98 species. After accounting for phylogenetic relationships, we showed that species evolving plant‐dominated diets evolved deeper incisors, longer third molars, longer molar crests, blunter posteriorly angled cusps, and more expanded laterally oriented occlusal cusps than species adapting to animal‐dominated diets. Measures of incisor depth, crest length, cusp angle and sharpness, occlusal cusp orientation, and the lengths of third molars proved the best predictors of dietary adaptation. Accounting for evolutionary history in a phylogenetic discriminant function analysis notably improved the classification accuracy. Molar morphology is strongly correlated with diet and we suggest that these dental traits can be used to infer diet with good accuracy for both extinct and extant murine species.     

Adaptive speciation and sexual dimorphism contribute to diversity in form and function in the adaptive radiation of Lake Matano's sympatric roundfin sailfin silversides

The utility of traits involved in resource exploitation is a central criterion for the adaptive character of radiations. Here, we test for differentiation in morphology, jaw mechanics and nutrition among species and sexes of Lake Matano's sympatric 'roundfin' sailfin silversides. The three incipient fish species differ significant in several candidate traits for adaptation following ecological selection pressure, corresponding to contrasting jaw mechanics and distinct patterns in food resource use. These findings are consistent with functional adaptation and suggest divergence following alternative modes of feeding specialization. Further, intersexual resource partitioning and corresponding adaptation in jaw mechanics is evident in two of the three incipient species, demonstrating that sexual dimorphism contributes to the ecomorphological and trophic diversity of the emerging radiation. This is, to the best of our knowledge, the first study reporting interspecific as well as intersexual adaptation by alternative modes of form and function in an evolving fish species flock.     

Interspike interval correlations in neuron models with adaptation and correlated noise

The generation of neural action potentials (spikes) is random but nevertheless may result in a rich statistical structure of the spike sequence. In particular, contrary to the popular renewal assumption of theoreticians, the intervals between adjacent spikes are often correlated. Experimentally, different patterns of interspike-interval correlations have been observed and computational studies have identified spike-frequency adaptation and correlated noise as the two main mechanisms that can lead to such correlations. Analytical studies have focused on the single cases of either correlated (colored) noise or adaptation currents in combination with uncorrelated (white) noise. For low-pass filtered noise or adaptation, the serial correlation coefficient can be approximated as a single geometric sequence of the lag between the intervals, providing an explanation for some of the experimentally observed patterns. Here we address the problem of interval correlations for a widely used class of models, multidimensional integrate-and-fire neurons subject to a combination of colored and white noise sources and a spike-triggered adaptation current. Assuming weak noise, we derive a simple formula for the serial correlation coefficient, a sum of two geometric sequences, which accounts for a large class of correlation patterns. The theory is confirmed by means of numerical simulations in a number of special cases including the leaky, quadratic, and generalized integrate-and-fire models with colored noise and spike-frequency adaptation. Furthermore we study the case in which the adaptation current and the colored noise share the same time scale, corresponding to a slow stochastic population of adaptation channels; we demonstrate that our theory can account for a nonmonotonic dependence of the correlation coefficient on the channel’s time scale. Another application of the theory is a neuron driven by network-noise-like fluctuations (green noise). We also discuss the range of validity of our weak-noise theory and show that by changing the relative strength of white and colored noise sources, we can change the sign of the correlation coefficient. Finally, we apply our theory to a conductance-based model which demonstrates its broad applicability.     

TRIBUTE: In Goethe's Wake: Marvalee Wake's conceptual contributions to the development and evolution of a science of morphology

Decrying the typological approach in much of the teaching of morphology, from the outset of her career Marvalee Wake advocated a synthetic, mechanistic and pluralistic developmental and evolutionary morphology. In this short essay, I do not evaluate Wake's contributions to our knowledge of the morphology of caecilians, nor her contributions to viviparity, both of which are seminal and substantive, nor do I examine her role as mentor, supervisor and collaborator, but assess her broader conceptual contributions to the development and evolution of morphology as a science. One of the earliest morphologists to take on board the concept of constraint, she viewed constraint explicitly in relation to adaptation and diversity. Her approach to morphology as a science was hierarchical – measure form and function in a phylogenetic context; seek explanations at developmental, functional, ecological, evolutionary levels of the biological hierarchy; integrate those explanations to the other levels. The explanatory power of morphology thus practised allows morphology to inform evolutionary biology and evolutionary theory, and paves the way for the integrative biology Wake has long championed.     

Craniofacial sexual dimorphism in Alouatta palliata, the mantled howling monkey

Ontogenetic scaling has been hailed as an explanation of the differences in craniofacial morphology between adult males and females of a number of non human primate species. This inference has implications for the evolutionary processes underlying patterns of sexual variation, as several heterochronic processes (rate and time hypo- and hypermorphosis) predict ontogenetic scaling. Primary among species for which ontogenetic scaling of craniofacial dimensions has been claimed is Alouatta palliata , the mantled howling monkey. This study uses a variety of analytical tools to explore the efficacy of ontogenetic scaling as an explanatory paradigm for this classic example. Multivariate analysis captures shape far better than does bivariate analysis. However, multivariate analysis does not support the traditional inference of ontogenetic scaling. Explanations for contradictory results are considered.     

Viewpoints: Feeding mechanics,diet, and dietary adaptations in early hominins

Inference of feeding adaptation in extinct species is challenging, and reconstructions of the paleobiology of our ancestors have utilized an array of analytical approaches. Comparative anatomy and finite element analysis assist in bracketing the range of capabilities in taxa, while microwear and isotopic analyses give glimpses of individual behavior in the past. These myriad approaches have limitations, but each contributes incrementally toward the recognition of adaptation in the hominin fossil record. Microwear and stable isotope analysis together suggest that australopiths are not united by a single, increasingly specialized dietary adaptation. Their traditional (i.e., morphological) characterization as “nutcrackers” may only apply to a single taxon, Paranthropus robustus. These inferences can be rejected if interpretation of microwear and isotopic data can be shown to be misguided or altogether erroneous. Alternatively, if these sources of inference are valid, it merely indicates that there are phylogenetic and developmental constraints on morphology. Inherently, finite element analysis is limited in its ability to identify adaptation in paleobiological contexts. Its application to the hominin fossil record to date demonstrates only that under similar loading conditions, the form of the stress field in the australopith facial skeleton differs from that in living primates. This observation, by itself, does not reveal feeding adaptation. Ontogenetic studies indicate that functional and evolutionary adaptation need not be conceptually isolated phenomena. Such a perspective helps to inject consideration of mechanobiological principles of bone formation into paleontological inferences. Finite element analysis must employ such principles to become an effective research tool in this context. Am J Phys Anthropol 151:356–371, 2013.© 2013 Wiley Periodicals, Inc.     

Active inference unifies intentional and conflict-resolution imperatives of motor control

The field of motor control has long focused on the achievement of external goals through action (e.g., reaching and grasping objects). However, recent studies in conditions of multisensory conflict, such as when a subject experiences the rubber hand illusion or embodies an avatar in virtual reality, reveal the presence of unconscious movements that are not goal-directed, but rather aim at resolving multisensory conflicts; for example, by aligning the position of a person’s arm with that of an embodied avatar. This second, conflict-resolution imperative of movement control did not emerge in classical studies of motor adaptation and online corrections, which did not allow movements to reduce the conflicts; and has been largely ignored so far in formal theories. Here, we propose a model of movement control grounded in the theory of active inference that integrates intentional and conflict-resolution imperatives. We present three simulations showing that the active inference model is able to characterize movements guided by the intention to achieve an external goal, by the necessity to resolve multisensory conflict, or both. Furthermore, our simulations reveal a fundamental difference between the (active) inference underlying intentional and conflict-resolution imperatives by showing that it is driven by two different (model and sensory) kinds of prediction errors. Finally, our simulations show that when movement is only guided by conflict resolution, the model incorrectly infers that is velocity is zero, as if it was not moving. This result suggests a novel speculative explanation for the fact that people are unaware of their subtle compensatory movements to avoid multisensory conflict. Furthermore, it can potentially help shed light on deficits of motor awareness that arise in psychopathological conditions.     

Adaptation and functional integration in primate phylogenetics

In two areas of phylogenetics, contrary predictions have been developed and maintained for character analysis and weighting. With regard to adaptation, many have argued that adaptive characters are poorly suited to phylogenetic analysis because of a propensity for homoplasy, while others have argued that complex adaptive characters should be given high weight because homoplasy in complex characters is unlikely. Similarly, with regard to correlated sets of characters, one point of view is that such sets should be collapsed into a single character-a single piece of phylogenetic evidence. Another point of view is that a suite of correlated characters should be emphasized in phylogenetics, again because recurrence of detailed similarity in the same suite of features is unlikely. In this paper, I discuss the theoretical background of adaptation and functional integration with respect to phylogenetic systematics of primates. Several character examples are reviewed with regard to their functional morphology and phylogenetic signal: postorbital structures, tympanic morphology, fusion of the mandibular symphysis, the tooth comb, strepsirrhine talar morphology, and the prehensile tail. It is clear when considering characters such as these that some characters are synapomorphic of major clades and at the same time functionally important. This appears particularly to be the case when characters are integrated into a complex and maintained as stable configurations. Rather than being simply a problem in character analysis, processes of integration may help to explain the utility of phylogenetically informative characters. On the other hand, the character examples also highlight the difficulty in forming a priori predictions about a character's phylogenetic signal. Explanations of patterns of character evolution are often clade-specific, which does not allow for a simple framework of character selection and/or weighting.     

Thyroid rhythm phenotypes and hominid evolution: a new paradigm implicates pulsatile hormone secretion in speciation and adaptation changes

Thyroid hormones (THs, T(3)/T(4)) are essential central regulators that link many biological tasks, including embryonic and post-natal growth, reproductive function, and the behavioral and physiological responses to stress. Recently I proposed a novel theory to explain the role of THs in vertebrate evolution. Here I review the concept and discuss its ability to explain changes over time in hominid morphology, behavior and life history. THs are produced in a distinctly pulsatile manner and appear to generate species-specific TH rhythms with distinct ontogenic shifts. Individual variations in genetically controlled TH rhythms (TR phenotypes) must generate coordinated individual variation in morphology, reproduction and behavior within populations. Selection for any manifestation of a particular TR phenotype in an ancestral population selects all traits under thyroid control, resulting in rapid and well-coordinated changes in descendants. The concept provides the first really plausible explanation for a number of phenomena, including the convergent evolution of bipedalism in early hominids, species-specific sexual dimorphism, coordinated changes in morphology, brain function and gut length over time in hominids, cold adaptation in Homo neanderthalensis, the possible independent evolution of H. sapiens in Asia, and regional adaptation of hominid populations. This new paradigm provides a unique theoretical framework for explaining human origins that has important implications for human health.     

Shape variability in tridactyl dinosaur footprints: the significance of size and function

The functional anatomy of the hindlimb of bipedal dinosaurs has been intensively studied. Yet, surprisingly little work has been done concerning functional adaptation of digits for terrestrial locomotion. While complete and articulated pes skeletons are scarce, pes shape is abundantly recorded by fossil footprints. We elucidate the significance of footprint shape and size for locomotion using a large sample (n = 303) of tridactyl dinosaur footprints from a broad range of geographical localities and time slots. Size and shape variation are characterized separately for theropods and ornithischians, the two principal trackmaker taxa. At smaller sizes, theropod footprints are best discriminated from ornithischian footprints by their smaller interdigital angle and larger projection of digit III; at larger sizes digital widths are effective discriminants. Ornithischian footprints increase in size from the Early Jurassic to the Late Cretaceous, a trend not observed in theropod footprints. Size and function are argued to be important determinants of footprint shape, and an attempt made to infer function from shape. Digit III projection and length-to-width ratio of the footprints are negatively correlated with size in both groups; digit impression width is positively correlated with size only in ornithischians. Digit III projection appears to be positively correlated with cursorial ability. Increased interdigital angles are associated with a decrease in digital width, possibly an adaptation for stability. Weak digit III projection and increased digital width are interpreted as adaptations for graviportality. Footprints yield great potential for the understanding of the functional morphology of dinosaur feet.     

A systems-analytical approach to macro-evolutionary phenomena.

Two sets of evolutionary phenomena find no explanation through current theory. For the static phenomena (such as homology, homonomy, systematic weight, and "Type") there is no causal base, although these principles are responsible for all phenomena of predictable order in the living world. The dynamic phenomena (such as homodynamy, coadaptation, parallel evolution, orthogenesis, Cartesian transformation, typostrophy, hetermorphosis, systemic mutation, and spontaneous atavism) have no causal explanation, although they are responsible for all directed phenomena in macroevolution. These phenomena share one unifying principle which can be explained by a system theory of evolution based on, but extending, the current synthetic theory. This system theory envisages feedback conditions between genotype and phenotype by which the chances of successful adaptation increase if the genetic units, by insertion of superimposed genes, copy the functional dependencies of those phene structures for which they code. This positive feedback of the adaptive speed (or probability) within a single adaptive direction is compensated by negative feedback in most of the alternative directions. The negative feedback operates as selection not be environmental but by systemic conditions developed by the organization of the organism. The consequences are an imitatively organized system of gene interractions, the rehabilitation of classical systematics, the reality of the "natural system," and, in general, the resolution of the contradiction between neodarwinists and their critics, between reductionists and holists, between "a priori" and "a posteriori" views, between idealism and materialism, and between the notions of freedom and of purpose in evolution.     

Optimierung und ökonomisierung im kontext von evolutionstheorie und phylogenetischer rekonstruktion

The meaning of optimality and economy in phylogenetics and evolutionary biology is discussed. It can be shown that the prevailing concepts of optimality and economy are equivocal as they are not based on strict theoretical positions and as they have a variable meaning in different theoretical contexts. The ideas of optimality and economy can be considered to be identical with the expectation of a relatively simple order in a particular field of study. Although there exists no way of inferring one or several methods of solving scientific problems from the presupposed idea of economy and optimality, a lack of motivation for scientific investigations would result if the concepts of economy and optimality in nature were dropped. By reference to several examples, it is shown that the concepts of optimality and economy are only useful against the background of indispensable theories. If there is a shift from one theory to another, a restriction on the use of these concepts is necessary. Optimality and economy in the sense of operations research in engineering or economical sciences depend on the principle of minimum costs. Both theoretical concepts: technical efficiency in relation to the energy required to run a machine and profit maximation in an economical framework must be shown to be realistic assumptions. In the field of biology processes of optimization and economization are normally discussed under two different views:

1. The concept of economy is used in cases of functional adaptation when the organism makes good use of the building material which is available to fulfill one (or more) functions. The theoretical background must be seen in the energy-consuming aspect of the organism.
2. In evolutionary change and phylogeny ‘economization’ and ‘optimization’ are deduced from the evolutionary theory, and evolution is shown to produce a special kind of biological economy in biological systems (Bock & von Wahlert, 1965). The ‘Okonomie-Prinzip’ or ‘Lesrichtungskriterium’ points out the arguments needed to state a phylogenetic theory and to construct a dendrogram (Peters & Gutmann, 1971).

In every phylogenetic theory concerning the adaptational change in the evolving biological system an explanation for the function of all stages is required. Only those statements should be accepted as phylogenetic theories which are characterized by the demonstration of the process of economization in the functional relations of the evolving organism. The process of adaptation can be determined by the improved chance of some mutants to propagate their genetical information. In this process all functional systems in their interrelations — i.a. mutual dependence — and their relation with the environment add their functional efficiency to the information to be delivered to their progeny, because the more economical biological system in a certain environment will have a better chance to produce offspring. This outcome is affirmed by natural selection which works on all levels of the evolving biological systems (Gutmann & Peters 1973). Nevertheless a judgment about adaptation cannot be taken as a scale of measurement in the phylogenetic process. The conditions in the organism itself and in the environment or in the organic system alone can change in so profound a manner that the marginal conditions of the earlier stages of the process of adaptation are not the same as in the derived ones. During phylogenetic change of the evolving organism the selective strains are also continuously changing. As a consequence no state or invariant concept of economy can cover the different stages of the phylogenetic process. The pragmatical meaning of the theoretical consideration is substantiated by the example of the hydrostatic skeleton theory in which the chordates are derived from metameric worms with a fluid skeleton. Herrn Professor Dr. P. Dullemeijer sind die Verfasser für kritische Lektüre und wertovolle Hinweise zu Dank verpflichtet.