[Basic principles of evolutionary histology].
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Adaptation, Biological↗
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Beyond Arabidopsis. Translational biology meets evolutionary developmental biology.
Developmental processes shape plant morphologies, which constitute important adaptive traits selected for during evolution. Identifying the genes that act in developmental pathways and determining how they are modified during evolution is the focus of the field of evolutionary developmental biology, or evo-devo. Knowledge of genetic pathways in the plant model Arabidopsis serves as the starting point for investigating how the toolkit of developmental pathways has been used and reused to form different plant body plans. One productive approach is to identify genes in other species that are orthologous to genes known to control developmental pathways in Arabidopsis and then determine what changes have occurred in the protein coding sequence or in the gene's expression to produce an altered morphology. A second approach relies on natural variation among wild populations or crop plants. Natural variation can be exploited to identify quantitative trait loci that underlie important developmental traits and, thus, define those genes that are responsible for adaptive changes. The possibility of applying comparative genomics approaches to Arabidopsis and related species promises profound new insights into the interplay of evolution and development.
Arabidopsis↗
The adaptive nature of the human neurocognitive architecture: an alternative model.
The model of the human neurocognitive architecture proposed by evolutionary psychologists is based on the presumption that the demands of hunter-gatherer life generated a vast array of cognitive adaptations. Here we present an alternative model. We argue that the problems inherent in the biological markets of ancestral hominids and their mammalian predecessors would have required an adaptively flexible, on-line information-processing system, and would have driven the evolution of a functionally plastic neural substrate, the neocortex, rather than a confederation of evolutionarily prespecified social cognitive adaptations. In alignment with recent neuroscientific evidence, we suggest that human cognitive processes result from the activation of constructed cortical representational networks, which reflect probabilistic relationships between sensory inputs, behavioral responses, and adaptive outcomes. The developmental construction and experiential modification of these networks are mediated by subcortical circuitries that are responsive to the life history regulatory system. As a consequence, these networks are intrinsically adaptively constrained. The theoretical and research implications of this alternative evolutionary model are discussed.
Adaptation, Biological↗
A genetic algorithm with adaptive mutations and family competition for training neural networks.
In this paper, we present a new evolutionary technique to train three general neural networks. Based on family competition principles and adaptive rules, the proposed approach integrates decreasing-based mutations and self-adaptive mutations to collaborate with each other. Different mutations act as global and local strategies respectively to balance the trade-off between solution quality and convergence speed. Our algorithm is then applied to three different task domains: Boolean functions, regular language recognition, and artificial ant problems. Experimental results indicate that the proposed algorithm is very competitive with comparable evolutionary algorithms. We also discuss the search power of our proposed approach.
Algorithms↗
Ecological and evolutionary opportunities of apomixis: insights from Taraxacum and Chondrilla.
The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short-term ecological success of apomixis. Allozymes and DNA markers indicate that apomictic populations are highly polyclonal. In Taraxacum, clonal diversity can be generated by rare hybridization between sexuals and apomicts, the latter acting as pollen donors. Less extensive clonal diversity is generated by mutations within clonal lineages. Clonal diversity may be maintained by frequency-dependent selection, caused by biological interactions (e.g. competitors and pathogens). Some clones are geographically widespread and probably represent phenotypically plastic 'general-purpose genotypes'. The long-term evolutionary success of apomictic clones may be limited by lack of adaptive potential and the accumulation of deleterious mutations. Although apomictic clones may be considered as 'evolutionary dead ends', the genes controlling apomixis can escape from degeneration and extinction via pollen in crosses between sexuals and apomicts. In this way, apomixis genes are transferred to a new genetic background, potentially adaptive and cleansed from linked deleterious mutations. Consequently, apomixis genes can be much older than the clones they are currently contained in. The close phylogenetic relationship between Taraxacum and Chondrilla and the similarity of their apomixis mechanisms suggest that apomixis in these two genera could be of common ancestry.
Asteraceae↗
The effects of exercise on human articular cartilage.
The effects of exercise on articular hyaline articular cartilage have traditionally been examined in animal models, but until recently little information has been available on human cartilage. Magnetic resonance imaging now permits cartilage morphology and composition to be analysed quantitatively in vivo. This review briefly describes the methodological background of quantitative cartilage imaging and summarizes work on short-term (deformational behaviour) and long-term (functional adaptation) effects of exercise on human articular cartilage. Current findings suggest that human cartilage deforms very little in vivo during physiological activities and recovers from deformation within 90 min after loading. Whereas cartilage deformation appears to become less with increasing age, sex and physical training status do not seem to affect in vivo deformational behaviour. There is now good evidence that cartilage undergoes some type of atrophy (thinning) under reduced loading conditions, such as with postoperative immobilization and paraplegia. However, increased loading (as encountered by elite athletes) does not appear to be associated with increased average cartilage thickness. Findings in twins, however, suggest a strong genetic contribution to cartilage morphology. Potential reasons for the inability of cartilage to adapt to mechanical stimuli include a lack of evolutionary pressure and a decoupling of mechanical competence and tissue mass.
Adaptation, Physiological↗
Environmental stress and evolution: a theoretical study.
A haploid population subject to recurrent deleterious mutations and two environments that provide two different profiles of selection coefficients over loci are modeled. The population is supposed to inhabit one "home" environment where it evolves the corresponding genetic constitution. One generation of the population is then exposed to the second, "foreign" environment. The decline in the mean population fitness is considered as a measure of stress in the population caused by the foreign environment. I define the relative strength of stress as 1 minus the ratio of the mean fitnesses in the foreign and home environments, and give the corresponding analytical expression. The stress strength is composed of three different contributors: the environmental component of stress, which is determined by purely external, non-genetic factors of the foreign environment (its carrying capacity), and two genetic components. The latter consists of the environment x genetic component, caused by the direct influence of the foreign environment on selection coefficients, and of the evolutionary component that is due to the adaptation of the population to the home environment. Among others, it is shown that even if the home and foreign environments were equivalent, so that both the environmental and environmental x genetic components of stress were absent, stress would still occur in the foreign environment due to the evolutionary component. The model also predicts that stressful foreign environments cause an increase in the genotypic variance of fitness. Some other features of population variability in stressful environments are discussed. A general conclusion that can be drawn from this model is that a certain environment may be claimed as stressful only if considered with respect to both a given population and the environment in which the population has evolved.
Animals↗
Why g is not an adaptation: a comment on Kanazawa (2004).
In S. Kanazawa's evolutionary theory of general intelligence (g), g is presented as a species-typical information-processing mechanism. This conceptualization of g departs radically from the accepted conceptualization of g as a source of individual differences that is manifest in the positive manifold. Kanazawa's theory is thus problematic in the sense that it concerns a purely hypothetical, and empirically unsupported, conceptualization of g. The authors argue that an evolutionary account of g should address it as a source of individual differences--that is, in a manner that is consistent with the empirical support for g.
Adaptation, Psychological↗
Topology of resultant networks shaped by evolutionary pressure.
Understanding the topology of complex systems abstracted to networks is important for unraveling their functional capabilities. Many such networks follow the small-world and scale-free regimes. Several models of artificially growing networks lead to this observed network topology. Most previously proposed models for growing networks, such as rich-get-richer and duplication-divergence, produce realistic network topologies but do not consider the effects of exogenous forces such as optimization for adaptation in shaping network topology. It is likely that such forces have shaped complex systems throughout their evolution. To develop further insights into possible mechanisms that shape networks, a model that uses several previously proposed network growth algorithms was developed to grow networks that adapt under exogenous stress. A decision tree problem was used to generate a complex Boolean function. Growing networks were required to adapt to correctly decode this function using an evolutionary selection process. Under this growth regimen all growing network models are similarly adaptable. The newly added nodes tend to cluster into pathways emanating from few inputs, regardless of the growth algorithm. Distribution of redundant pathways from inputs to the output follow a power-law function with a scaling exponent (approximately 1.3). Similar distribution of redundant pathways was observed from inputs in a cell signaling network and an air traffic control network. A flat distribution of redundant pathways from inputs was observed in growing networks that do not attempt to adapt. This analysis provides initial insights into distribution of pathways in naturally evolving complex systems that have defined input-output relationships.
Algorithms↗
Comparative evolutionary psychology of sperm competition.
A comparative evolutionary psychological perspective predicts that species that recurrently faced similar adaptive problems may have evolved similar psychological mechanisms to solve these problems. Sperm competition provides an arena in which to assess the heuristic value of such a comparative evolutionary perspective. The sperm competition that results from female infidelity and polyandry presents a similar class of adaptive problems for individuals across many species. The authors first describe mechanisms of sperm competition in insects and in birds. They suggest that the adaptive problems and evolved solutions in these species provide insight into human anatomy, physiology, psychology, and behavior. The authors then review recent theoretical and empirical arguments for the existence of sperm competition in humans and discuss proposed adaptations in humans that have analogs in insects or birds. The authors conclude by highlighting the heuristic value of a comparative evolutionary psychological approach in this field.
Animals↗
Community assembly through adaptive radiation in Hawaiian spiders.
Communities arising through adaptive radiation are generally regarded as unique, with speciation and adaptation being quite different from immigration and ecological assortment. Here, I use the chronological arrangement of the Hawaiian Islands to visualize snapshots of evolutionary history and stages of community assembly. Analysis of an adaptive radiation of habitat-associated, polychromatic spiders shows that (i) species assembly is not random; (ii) within any community, similar sets of ecomorphs arise through both dispersal and evolution; and (iii) species assembly is dynamic with maximum species numbers in communities of intermediate age. The similar patterns of species accumulation through evolutionary and ecological processes suggest universal principles underlie community assembly.
Adaptation, Physiological↗
Constraint to adaptive evolution in response to global warming.
We characterized the genetic architecture of three populations of a native North American prairie plant in field conditions that simulate the warmer and more arid climates predicted by global climate models. Despite genetic variance for traits under selection, among-trait genetic correlations that are antagonistic to the direction of selection limit adaptive evolution within these populations. Predicted rates of evolutionary response are much slower than the predicted rate of climate change.
Adaptation, Physiological↗
Physiological adaptations and the concepts of optimal reproductive strategy and physiological constraint in marine invertebrates.
The dominant 'demographic' theory of life history evolution supposes that different lifetime patterns of reproduction are the result of selection of alternative optimal solutions for the allocation of limited resources between somatic and reproductive functions. A number of trade-off possibilities have been recognized--those between current reproductive output and residual reproductive value and between fecundity and initial offspring size being considered especially important. Many theoretical studies assume that natural selection will favour the adoption of optimal solutions, but it has been pointed out that such solutions may not be obtainable due to design constraints and the development of physiological adaptations to specific reproductive traits which limit subsequent evolutionary potential. The validity of this idea is examined in this paper through a review of the major reproductive strategies available to marine invertebrates and the physiological adaptations associated with them. The ecologically important distinction between planktotrophic and lecithotrophic development is not necessarily associated with major physiological adaptations in the adults, but the distinction between strictly semelparous and iteroparous life histories is. This is demonstrated in a survey of the endocrinological and environmental control of reproductive processes in related organisms with contrasting modes or reproduction. Particular reference is made to the Polychaeta, in which the contrast between semelparous and iteroparous life histories is particularly marked. A similar contrast is found between cephalopoda and other mollusca, and the discussion of physiological adaptations is extended to include these groups and the Echinodermata.
Adaptation, Physiological↗
On the coevolution of cognition and consciousness.
In this article it is argued that an evolutionary perspective leads to the view that adaptation and learning is a widespread and old property of living organisms, even as old as life itself. Cognition, defined as knowledge processing mediated by a centralised nervous system, is suggested mainly to be based on the same principles as non-neural adaptive processes. The emergence of conscious cognition, however, is seen as a major transition in the evolution of life, although it appears in different degrees and at various stages in evolution. Both cognition and consciousness depend on the organisation and complexity of the organism, primarily with regard to the nervous system. Computational and neurophysiological approaches are discussed, in particular some experimental attempts to determine anatomical, physiological and physical correlates to consciousness. It is argued that an evolutionary perspective suggests an interactionistic solution to the mind-brain problem, i.e. the question of subjective experience. In an interactionistic perspective consciousness can be understandable as a biological phenomenon. It can be regarded as a driving force in evolution, amplifying and improving the adaptive and cognitive processes of an organism.
Biological Evolution↗
Relationship-specific social psychological adaptations.
Mainstream social psychology has sought parsimonious explanations of broad general applicability, and has in practice focused on stranger interactions. An evolutionary perspective; however, justifies predicting a rich diversity of relationship-specific social psychological adaptations. The demands of motherhood, fatherhood, mateship, sibship and other relationships are qualitatively distinct, and so, it appears, are the psychophysiological mechanisms that have evolved to deal with them. One window on what distinguishes social relationships is provided by the substance and epidemiology of interpersonal conflicts. Homicides exhibit victim-killer relationship-specific patterns in context, motive and demography, which we discovered only because we adopted an evolutionary psychological perspective. We offer a number of specific hypotheses about possible human psychological adaptations that have yet to be assessed, but are readily derived from consideration of the particular qualities of specific relationship types.
Adaptation, Psychological↗
Cold adaptation of a mesophilic subtilisin-like protease by laboratory evolution.
Enzymes isolated from organisms native to cold environments generally exhibit higher catalytic efficiency at low temperatures and greater thermosensitivity than their mesophilic counterparts. In an effort to understand the evolutionary process and the molecular basis of cold adaptation, we have used directed evolution to convert a mesophilic subtilisin-like protease from Bacillus sphaericus, SSII, into its psychrophilic counterpart. A single round of random mutagenesis followed by recombination of improved variants yielded a mutant, P3C9, with a catalytic rate constant (k(cat)) at 10 degrees C 6.6 times and a catalytic efficiency (k(cat)/K(M)) 9.6 times that of wild type. Its half-life at 70 degrees C is 3.3 times less than wild type. Although there is a trend toward decreasing stability during the progression from mesophile to psychrophile, there is not a strict correlation between decreasing stability and increasing low temperature activity. A first generation mutant with a >2-fold increase in k(cat) is actually more stable than wild type. This suggests that the ultimate decrease in stability may be due to random drift rather than a physical incompatibility between low temperature activity and high temperature stability. SSII shares 77. 4% identity with the naturally psychrophilic protease subtilisin S41. Although SSII and S41 differ at 85 positions, four amino acid substitutions were sufficient to generate an SSII whose low temperature activity is greater than that of S41. That none of the four are found in S41 indicates that there are multiple routes to cold adaptation.
Adaptation, Physiological↗
Evolutionary and functional significance of hominoid tooth enamel.
The purpose of this investigation is to evaluate enamel thickness in extant and extinct hominoids. The material used in this study spans the evolutionary history of this group, from 20 million years ago to the present. The objectives of this investigation are to test three hypotheses: (1) the Loading Hypothesis: loading areas of the crown have thicker enamel than non-loading areas; (2) the Phyletic Hypothesis: differences in enamel thickness provide a basis for determining evolutionary relationships; and (3) the Functional Hypothesis: differences among hominoids result from adaptations to differing dietary and ecological habitats, that is from folivory to frugivory to hard object feeding and from tropical to forest to savanna habitats. Thin sections were prepared and polished to approximately 100 microm in thickness. Each section was then enlarged and digitally captured to the computer. Image processing and analysis software, SigmaImage (was used to measure the sections. Subsequent statistical analysis was conducted with SigmaStat and SPSS statistical software programs. The data provides statistical support for all hypotheses. In particular, the data support the proposal that "thick" enamel is the ancestral condition for the great apes and human clade. Therefore, Pongo would have retained its enamel thickness from the common ancestor of the great apes and Gorilla and Pan would have secondarily reduced enamel thickness to "thin." The common ancestor of the hominids, the australopithecines, would have "thick" enamel. The "hyper-thick" enamel of the australopithecines would be a derived character for this clade due to increased crushing and grinding and adaptation to savanna habitat. Homo would have secondarily reduced enamel thickness to "thick." Evolutionary biology of enamel differs markedly in hominids from that found in other hominoids and primates. Increased enamel thickness involved both increases in absolute thickness of enamel and crown size in response to increase masticatory loading.
Animals↗
Stress-driven strategic games in cancer.
Tumor cells face chronic genotoxic, metabolic, hypoxic, and immune stress that shapes their evolution. While stress-response molecular pathways are well characterized, cancer biology lacks a predictive framework for how cells select among alternative adaptive strategies and how these selections interact to produce tumor-level behavior. We propose that evolutionary game theory, previously applied to cooperation in cancer, should be extended to position stress adaptation itself as the organizing principle of tumor evolution. In this framework, stress-adaptive strategies constitute frequency-dependent games whose payoffs depend on population composition. We introduce a three-level distinction between cell states (transcriptional snapshots), game states (local configurations of stress and neighbor composition that define the active payoff structure), and cell strategies (conditional behavioral policies mapping game states to fitness-relevant outputs). This perspective explains the maintenance of intratumor heterogeneity through frequency-dependent selection, the reversibility of resistance through bet-hedging dynamics, and therapy resistance as an equilibrium outcome rather than genetic inevitability. Integrating insights from single-cell genomics, spatial profiling, and lineage tracing, we outline testable predictions and experimental approaches for measuring payoff structures. Therapeutically, the framework suggests exploiting adaptive trade-offs, restricting phenotypic plasticity, and reshaping competitive landscapes. Re-framing cancer as an evolving game of stress adaptation provides a unifying structure for predictive oncology.
Animals↗