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Mirror-image flowers (enantiostyly) involve a form of sexual asymmetry in which a flower's style is deflected either to the left or right side, with a pollinating anther orientated in the opposite direction. This curious floral polymorphism, which was known but not studied by Charles Darwin, occurs in at least 11 unrelated angiosperm families and represents a striking example of adaptive convergence in form and function associated with cross-pollination by insects. In several lineages, dimorphic enantiostyly (one stylar orientation per plant, both forms occurring within populations) has evolved from monomorphic enantiostyly, in which all plants can produce both style orientations. We use a modelling approach to investigate the emergence of dimorphic enantiostyly from monomorphic enantiostyly under gradual evolution. We show using adaptive dynamics that depending on the balance between inbreeding depression following geitonogamy, pollination efficiency, and plant density, dimorphism can evolve from an ancestral monomorphic population. In general, the newly emergent dimorphic population is stable against invasion of a monomorphic mutant. However, our model predicts that under certain ecological conditions, for example, a decline of pollinators, dimorphic enantiostyly may revert to a monomorphic state. We demonstrate using population genetics simulations that the observed evolutionary transitions are possible, assuming a plausible genetic architecture. [ABSTRACT FROM AUTHOR]

Abstract Background Habitat transitions have considerable consequences in organism homeostasis, as they require the adjustment of several concurrent physiological compartments to maintain stability and adapt to a changing environment. Within the range of molecules with a crucial role in the regulation of different physiological processes, neuropeptides are key agents. Here, we examined the coding status of several neuropeptides and their receptors with pleiotropic activity in Cetacea. Results Analysis of 202 mammalian genomes, including 41 species of Cetacea, exposed an intricate mutational landscape compatible with gene sequence modification and loss. Specifically for Cetacea, in the 12 genes analysed we have determined patterns of loss ranging from species-specific disruptive mutations (e.g. neuropeptide FF-amide peptide precursor; NPFF) to complete erosion of the gene across the cetacean stem lineage (e.g. somatostatin receptor 4; SSTR4). Conclusions Impairment of some of these neuromodulators may have contributed to the unique energetic metabolism, circadian rhythmicity and diving response displayed by this group of iconic mammals.

Background: Habitat transitions have considerable consequences in organism homeostasis, as they require the adjustment of several concurrent physiological compartments to maintain stability and adapt to a changing environment. Within the range of molecules with a crucial role in the regulation of different physiological processes, neuropeptides are key agents. Here, we examined the coding status of several neuropeptides and their receptors with pleiotropic activity in Cetacea. Results: Analysis of 202 mammalian genomes, including 41 species of Cetacea, exposed an intricate mutational landscape compatible with gene sequence modification and loss. Specifically for Cetacea, in the 12 genes analysed we have determined patterns of loss ranging from species-specific disruptive mutations (e.g. neuropeptide FF-amide peptide precursor; NPFF) to complete erosion of the gene across the cetacean stem lineage (e.g. somatostatin receptor 4; SSTR4). Conclusions: Impairment of some of these neuromodulators may have contributed to the unique energetic metabolism, circadian rhythmicity and diving response displayed by this group of iconic mammals. [ABSTRACT FROM AUTHOR]

Conspicuous colours have fascinated biologists for centuries, leading to research on the evolution and functional significance of colour traits. In many cases, research suggests that conspicuous colours are adaptive and serve a function in sexual or aposematic signalling. In other cases, a lack of evidence for the adaptive value of conspicuous colours garners interest from biologists, such as when organisms that live underground and are rarely exposed to the surface are nevertheless colourful. Here, we use phylogenetic comparative methods to investigate colour evolution throughout freshwater crayfishes that vary in burrowing ability. Within the taxa we analysed, conspicuous colours have evolved independently over 50 times, and these colours are more common in semi-terrestrial crayfishes that construct extensive burrows. The intuitive but not evolutionarily justified assumption when presented with these results is to assume that these colours are adaptive. But contrary to this intuition, we discuss the hypothesis that colouration in crayfish is neutral. Supporting these ideas, the small population sizes and reduced gene flow within semi-terrestrial burrowing crayfishes may lead to the fixation of colour-phenotype mutations. Overall, our work brings into question the traditional view of animal colouration as a perfectly adapted phenotype. [ABSTRACT FROM AUTHOR]

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use.

Summary: Poales are one of the most species‐rich, ecologically and economically important orders of plants and often characterise open habitats, enabled by unique suites of traits. We test six hypotheses regarding the evolution and assembly of Poales in open and closed habitats throughout the world, and examine whether diversification patterns demonstrate parallel evolution.We sampled 42% of Poales species and obtained taxonomic and biogeographic data from the World Checklist of Vascular Plants database, which was combined with open/closed habitat data scored by taxonomic experts. A dated supertree of Poales was constructed. We integrated spatial phylogenetics with regionalisation analyses, historical biogeography and ancestral state estimations.Diversification in Poales and assembly of open and closed habitats result from dynamic evolutionary processes that vary across lineages, time and space, most prominently in tropical and southern latitudes. Our results reveal parallel and recurrent patterns of habitat and trait transitions in the species‐rich families Poaceae and Cyperaceae. Smaller families display unique and often divergent evolutionary trajectories.The Poales have achieved global dominance via parallel evolution in open habitats, with notable, spatially and phylogenetically restricted divergences into strictly closed habitats. [ABSTRACT FROM AUTHOR]

In comparison to biodiversity on Earth's surface, subterranean biodiversity has largely remained concealed. The olm (Proteus anguinus) is one of the most enigmatic extant cave inhabitants, and until now little was known regarding its genetic structure and evolutionary history. Olms inhabit subterranean waters throughout the Dinaric Karst of the western Balkans, with a seemingly uniform phenotypic appearance of cave‐specialized traits: an elongate body, snout and limbs, degenerated eyes and loss of pigmentation ("white olm"). Only a single small region in southeastern Slovenia harbours olms with a phenotype typical of surface animals: pigmented skin, eyes, a blunt snout and short limbs ("black olm"). We used a combination of mitochondrial DNA and genome‐wide single nucleotide polymorphism data to investigate the molecular diversity, evolutionary history and biogeography of olms along the Dinaric Karst. We found nine deeply divergent species‐level lineages that separated between 17 and 4 million years ago, while molecular diversity within lineages was low. We detected no signal of recent admixture between lineages and only limited historical gene flow. Biogeographically, the contemporaneous distribution of lineages mostly mirrors hydrologically separated subterranean environments, while the historical separation of olm lineages follows microtectonic and climatic changes in the area. The reconstructed phylogeny suggests at least four independent transitions to the cave phenotype. Two of the species‐level lineages have miniscule ranges and may represent Europe's rarest amphibians. Their rarity and the decline in other lineages call for protection of their subterranean habitats. [ABSTRACT FROM AUTHOR]

Summary: Heterogeneity in gene trees, morphological characters, and composition has been associated with several major plant clades. Here, we examine heterogeneity in composition across a large transcriptomic dataset of plants to better understand whether locations of shifts in composition are shared across gene regions and whether directions of shifts within clades are shared across gene regions.We estimate mixed models of composition for both nucleotide and amino acids across a recent large‐scale transcriptomic dataset for plants.We find shifts in composition across both nucleotide and amino acid datasets, with more shifts detected in nucleotides. We find that Chlorophytes and lineages within experience the most shifts. However, many shifts occur at the origins of land, vascular, and seed plants. While genes in these clades do not typically share the same composition, they tend to shift in the same direction. We discuss potential causes of these patterns.Compositional heterogeneity has been highlighted as a potential problem for phylogenetic analysis, but the variation presented here highlights the need to further investigate these patterns for the signal of biological processes. [ABSTRACT FROM AUTHOR]

In this commentary, as philosophers of evolutionary biology, we will consider the evolutionary framework used in the Target Article by: (i) emphasising the fruitfulness of the interdisciplinary approach employed; (ii) highlighting some potentially controversial aspects of the proposal; and finally (iii) outlining some ideas for further integration within the UAL framework. The critical analysis will focus on the relationship between learning and consciousness, on the assumed need for a function for consciousness, and on the type of phylogenetic demarcation introduced by UAL. [ABSTRACT FROM AUTHOR]

Animal behavior, physiology, and fitness are influenced by materials transferred between conspecifics (e.g., milk or ejaculate), even in solitary taxa. Such socially transferred materials are currently studied separately, without acknowledgment that they are instigators of evolutionary change and potent mechanisms for indirect genetic effects. Recent methodological advances allow the linkage of socially transferred gene products to their physiological, behavioral, and fitness impacts, yet such integrative approaches are rarely used. This conceptual framing and classification of socially transferred materials bridges proximate and ultimate scales and connects molecular biology to evolution. The concept of socially transferred materials has the potential to bring about transformative innovation in fundamental research and also in applied fields, such as medicine and agriculture. When biological material is transferred from one individual's body to another, as in ejaculate, eggs, and milk, secondary donor-produced molecules are often transferred along with the main cargo, and influence the physiology and fitness of the receiver. Both social and solitary animals exhibit such social transfers at certain life stages. The secondary, bioactive, and transfer-supporting components in socially transferred materials have evolved convergently to the point where they are used in applications across taxa and type of transfer. The composition of these materials is typically highly dynamic and context dependent, and their components drive the physiological and behavioral evolution of many taxa. Our establishment of the concept of socially transferred materials unifies this multidisciplinary topic and will benefit both theory and applications. [ABSTRACT FROM AUTHOR]

The transition to grain agriculture restructured human societies, creating a new whole, an economic superorganism. Homo sapiens became expansionary, structurally interdependent in material life, and a duality between them and Earth was created that had not previously existed. Yet H. sapiens are not the only species to make the transition to agriculture. Cross-species comparisons create an opening for a movement toward a focus on the universal and powerful agricultural system as a unique expression of the evolution of species cooperation. This shifts the focus around human social evolution away from culture and toward the formation and power of the economic system that took hold with the cultivation of annual grains. The basic structure and dynamic to economic life that began with grain agriculture has endured for 10 000 years and the duality between humans and Earth established therein is now reaching an apogee with the spectre of climate change and the mass extinction of other species on Earth. In this light, the questions emerge: Is the agricultural revolution an evolutionary transition adequately captured in existing frameworks of human social evolution? Is the human capacity for culture sufficient to override the power and dynamic of the economic superorganism? [ABSTRACT FROM AUTHOR]

Did human culture arise through an evolutionary transition in individuality (ETI)? To address this question, we examine the steps of biological ETIs to see how they could apply to the evolution of human culture. For concreteness, we illustrate the ETI stages using a well-studied example, the evolution of multicellularity in the volvocine algae. We then consider how those stages could apply to a cultural transition involving integrated groups of cultural traditions and the hominins that create and transmit traditions. We focus primarily on the early Pleistocene and examine hominin carnivory and the cultural change from Oldowan to Acheulean technology. We use Pan behaviour as an outgroup comparison. We summarize the important similarities and differences we find between ETI stages in the biological and cultural realms. As we are not cultural anthropologists, we may overlook or be mistaken in the processes we associate with each step. We hope that by clearly describing these steps to individuality and illustrating them with cultural principles and processes, other researchers may build upon our initial exercise. Our analysis supports the hypothesis that human culture has undergone an ETI beginning with a Pan-like ancestor, continuing during the Pleistocene, and culminating in modern human culture. [ABSTRACT FROM AUTHOR]

Great transitions are thought to embody major shifts in locus of selection, labour diversification and communication systems. Such expectations are relevant for biological and cultural systems as decades of research has demonstrated similar dynamics within the evolution of culture. The evolution of the Neo-Inuit cultural tradition in the Bering Strait provides an ideal context for examination of cultural transitions. The Okvik/Old Bering Sea (Okvik/OBS) culture of Bering Strait is the first representative of the Neo-Inuit tradition. Archaeological evidence drawn for settlement and subsistence data, technological traditions and mortuary contexts suggests that Okvik/OBS fits the definition of a major transition given change in the nature of group membership (from families to political groups with social ranking), task organization (emergent labour specialization) and communication (advent of complex art forms conveying social and ideological information). This permits us to develop a number of implications about the evolutionary process recognizing that transitions may occur on three scales: (1) ephemeral variants, as for example, simple technological entities; (2) integrated systems, spanning modular technology to socio-economic strategies; and (3) simultaneous change across all scales with emergent properties. [ABSTRACT FROM AUTHOR]

Eörs Szathmáry and John Maynard Smith famously argued that the evolution of life on earth has been marked by a series of transitions to greater complexity, the last being from primate to human societies. I argue that this last transition, covering all of human evolutionary history, in turn comprises two phases: the first defined by increases in the capacity of the human brain/mind to structurally integrate causal inferences and selectively apply them to construct increasingly sophisticated sociocultural niches; the second defined by manipulation of the universal Darwinian mechanisms driving sociocultural evolution. During the first phase, hominin cognitive structure passed through three key transitions to produce the brain/mind of archaic Homo sapiens. The fourth transition, to fully modern Homo sapiens sapiens equipped with symbolic cognition and language, marks the fulcrum that leveraged the second phase in which changes in the scope and rate of niche construction were primarily driven by manipulation of sociocultural evolutionary mechanisms. The fifth transition to sedentary living enabled new selection pressures to be exerted through the concentration and application of social power, while the sixth transition multiplied the cognitive variation available to construct more elaborate sociocultural niches. Finally I note that decreasing intervals between transitions creates a pattern of accelerating sociocultural change. [ABSTRACT FROM AUTHOR]

Mirror-image flowers (enantiostyly) involve a form of sexual asymmetry in which a flower's style is deflected either to the left or right side, with a pollinating anther orientated in the opposite direction. This curious floral polymorphism, which was known but not studied by Charles Darwin, occurs in at least 11 unrelated angiosperm families and represents a striking example of adaptive convergence in form and function associated with cross-pollination by insects. In several lineages, dimorphic enantiostyly (one stylar orientation per plant, both forms occurring within populations) has evolved from monomorphic enantiostyly, in which all plants can produce both style orientations. We use a modelling approach to investigate the emergence of dimorphic enantiostyly from monomorphic enantiostyly under gradual evolution. We show using adaptive dynamics that depending on the balance between inbreeding depression following geitonogamy, pollination efficiency, and plant density, dimorphism can evolve from an ancestral monomorphic population. In general, the newly emergent dimorphic population is stable against invasion of a monomorphic mutant. However, our model predicts that under certain ecological conditions, for example, a decline of pollinators, dimorphic enantiostyly may revert to a monomorphic state. We demonstrate using population genetics simulations that the observed evolutionary transitions are possible, assuming a plausible genetic architecture., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE).)

The length of the deepest branches of the tree of life would tend to support the hypothesis that the distance of the branch that separates the sequences of archaea from those of bacteria, i.e. the interdomain one, is longer than the intradomain ones, i.e. those that separate the sequences of archaea and those of bacteria within them. Why should interdomain distance be larger than intradomain distances? The fact that the rate of amino acid substitutions was slowed as the domains of life appeared would seem to imply an evolutionary transition. The slowdown in the speed of evolution that occurred during the formation of the two domains of life would be the consequence of the progenote- > cell evolutionary transition. Indeed, the evolutionary stage of the progenote being characterized by an accelerated tempo and mode of evolution might explain the considerable interdomain distance because the accumulation of many amino acid substitutions on this branch would indicate the progenote stage that is also characterized by a high rate of amino acid substitutions. Furthermore, the fact that intradomain distances are smaller than interdomain distances would corroborate the hypothesis of the achievement of cellularity at the appearance of the main phyletic lineages. Indeed, the cell stage, unlike the progenotic one, definitively establishes the relationship between the genotype and phenotype, lowering the rate of evolution. Therefore, the arguments presented lead to the conclusion that LUCA was a progenote., Competing Interests: Declaration of competing interest Author declares no conflict of interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Nested hierarchical structure is one of life's most familiar properties and a major component of biological diversity and complexity. However, there is little effort to teach the evolution of the hierarchy of life, as there is little effort to teach biological complexity per se. We propose a framework for teaching biological complexity based on research on evolutionary transitions in individuality (ETI theory). Translating ETI theory into the classroom allows students to see the connections between natural selection, social behavior in groups, and the major landmarks of biodiversity in the hierarchy of life. The translation of ETI theory into pedagogic content and practices involves (i) the new content that must be taught, (ii) the development of general teaching tools to teach this new content, and (iii) connecting the new content and teaching tools to the specific educational context including integrating with learning standards and benchmarks. We show how teaching ETIs aids in the teaching of science practices and in teaching the process of evolutionary change. Evolutionary transitions research provides a way to teach biological complexity that is familiar and engaging to students, leveraging their inherent understanding of social dynamics and group behavior. [ABSTRACT FROM AUTHOR]

To understand why avian eggs are so variable in colour and patterning, we investigated the characteristics of extant bird species that provide insight into the evolutionary transitions that occurred during the early radiation of the songbirds. We quantified egg colour and patterning from museum collections of 269 species of Australian passerine and collated it to nest type data (cup‐ or dome‐nesting species). Using phylogenetically reconstructed trait data, we showed that the ancestral passerine egg was likely to be white, and to have been laid inside a domed nest. Egg colouration and nest type were both phylogenetically clustered, and there was evidence of correlated evolution between the two traits. As nests transitioned from domes to cups, there was an increase in the range of egg colours observed, presumably as a response to additional stressors. Finally, we found that egg colour changes occurred more than twice as frequently in cup‐nesting species than in dome‐nesting species. This suggests that colour may be an adaptive trait that compensates for the loss of the protective nest roof in cup‐nesting species. [ABSTRACT FROM AUTHOR]

This is a response to the nine commentaries on our target article “Unlimited Associative Learning: A primer and some predictions”. Our responses are organized by theme rather than by author. We present a minimal functional architecture for Unlimited Associative Learning (UAL) that aims to tie to together the list of capacities presented in the target article. We explain why we discount higher-order thought (HOT) theories of consciousness. We respond to the criticism that we have overplayed the importance of learning and underplayed the importance of spatial modelling. We decline the invitation to add a negative marker to our proposed positive marker so as to rule out consciousness in plants, but we nonetheless maintain that there is no positive evidence of consciousness in plants. We close by discussing how UAL relates to development and to its material substrate. [ABSTRACT FROM AUTHOR]

Since the emergence of the first fungi some 700 million years ago, unicellular yeast-like forms have emerged multiple times in independent lineages via convergent evolution. While tens to hundreds of millions of years separate the independent evolution of these unicellular organisms, they share remarkable phenotypic and metabolic similarities, and all have streamlined genomes. Yeasts occur in every aquatic environment yet examined. Many species are aquatic; perhaps most are amphibious. How these species have evolved to thrive in aquatic habitats is fundamental to understanding functions and evolutionary mechanisms in this unique group of fungi. Here we review the state of knowledge of the physiological and ecological diversity of amphibious yeasts and their key evolutionary adaptations enabling survival in aquatic habitats. We emphasize some genera previously thought to be exclusively terrestrial. Finally, we discuss the ability of many yeasts to survive in extreme habitats and how this might lend insight into ecological plasticity, including amphibious lifestyles. [ABSTRACT FROM AUTHOR]

Evolutionary transitions from animal to wind pollination have occurred repeatedly during the history of the angiosperms, but the selective mechanisms remain elusive. Here, we propose that knowledge of pollen release biomechanics is critical for understanding the ecological and evolutionary processes underpinning this shift in pollination mode. Pollen release is the critical first stage of wind pollination (anemophily) and stamen properties are therefore likely to be under strong selection early in the transition. We describe current understanding of pollen release biomechanics to provide insights on the phenotypic and ecological drivers of wind pollination. Pollen release occurs when detachment forces dominate resistive forces retaining pollen within anthers. Detachment forces can be active or passive depending on whether they require energy input from the environment. Passive release is more widespread in anemophilous species and involves processes driven by steady or unsteady aerodynamic forces or turbulence‐induced vibrations that shake pollen from anthers. We review empirical and theoretical studies suggesting that stamen vibration is likely to be a key mechanism of pollen release. The vibration response is governed by morphological and biomechanical properties of stamens, which may undergo divergent selection in the presence or absence of pollinators. Resistive forces have rarely been investigated for pollen within anthers, but are probably sensitive to environmental conditions and depend on flower age, varying systematically between animal‐ and wind‐pollinated species. Animal and wind pollination are traditionally viewed as dichotomous alternatives because they are usually associated with strikingly different pollination syndromes. But this perspective has diverted attention from subtler, continuously varying traits which mediate the fluid dynamic process of pollen release. Reinterpreting the flower as a biomechanical entity that responds to fluctuating environmental forces may provide a promising way forward. We conclude by identifying several profitable areas for future research to obtain deeper insight into the evolution of wind pollination. [ABSTRACT FROM AUTHOR]

The article discusses successive stages in the evolution of life up to the establishment of the prokaryotic cell emphasizing the transitions from pre-biotic environment to organic precursors, pre-RNA-RNA, RNA-proteins-DNA, DNA-LUCA. They are paired with the development of pre-biotic structural progenitors of a cell - micelles, vesicles, protocells, prokaryotic ancestor, two prokaryotic branches – Eubacteria and Archaebacteria. The driving force is the natural selection (chemical, biochemical and biological), maintaining the correspondence between the emerging structures and their environment [ABSTRACT FROM AUTHOR]

It is of fundamental importance for the field of evolutionary biology to understand when and why major evolutionary transitions occur. Live‐bearing young (viviparity) is a major evolutionary change and has evolved from egg‐laying (oviparity) independently in many vertebrate lineages and most abundantly in lizards and snakes. Although contemporary viviparous squamate species generally occupy cold climatic regions across the globe, it is not known whether viviparity evolved as a response to cold climate in the first place. Here, we used available published time‐calibrated squamate phylogenies and parity data on 3,498 taxa. We compared the accumulation of transitions from oviparity to viviparity relative to background diversification and a simulated binary trait. Extracting the date of each transition in the phylogenies and informed by 65 my of global palaeoclimatic data, we tested the nonexclusive hypotheses that viviparity evolved under the following: (a) cold, (b) long‐term stable climatic conditions and (c) with background diversification rate. We show that stable and long‐lasting cold climatic conditions are correlated with transitions to viviparity across squamates. This correlation of parity mode and palaeoclimate is mirrored by background diversification in squamates, and simulations of a binary trait also showed a similar association with palaeoclimate, meaning that trait evolution cannot be separated from squamate lineage diversification. We suggest that parity mode transitions depend on environmental and intrinsic effects and that background diversification rate may be a factor in trait diversification more generally. [ABSTRACT FROM AUTHOR]

How animals evolved from a single-celled ancestor, transitioning from a unicellular lifestyle to a coordinated multicellular entity, remains a fascinating question. Key events in this transition involved the emergence of processes related to cell adhesion, cell–cell communication and gene regulation. To understand how these capacities evolved, we need to reconstruct the features of both the last common multicellular ancestor of animals and the last unicellular ancestor of animals. In this review, we summarize recent advances in the characterization of these ancestors, inferred by comparative genomic analyses between the earliest branching animals and those radiating later, and between animals and their closest unicellular relatives. We also provide an updated hypothesis regarding the transition to animal multicellularity, which was likely gradual and involved the use of gene regulatory mechanisms in the emergence of early developmental and morphogenetic plans. Finally, we discuss some new avenues of research that will complement these studies in the coming years.

It is unknown how abundant extraterrestrial life is, or whether such life might be complex or intelligent. On Earth, the emergence of complex intelligent life required a preceding series of evolutionary transitions such as abiogenesis, eukaryogenesis, and the evolution of sexual reproduction, multicellularity, and intelligence itself. Some of these transitions could have been extraordinarily improbable, even in conducive environments. The emergence of intelligent life late in Earth's lifetime is thought to be evidence for a handful of rare evolutionary transitions, but the timing of other evolutionary transitions in the fossil record is yet to be analyzed in a similar framework. Using a simplified Bayesian model that combines uninformative priors and the timing of evolutionary transitions, we demonstrate that expected evolutionary transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude. Our results corroborate the original argument suggested by Brandon Carter that intelligent life in the Universe is exceptionally rare, assuming that intelligent life elsewhere requires analogous evolutionary transitions. Arriving at the opposite conclusion would require exceptionally conservative priors, evidence for much earlier transitions, multiple instances of transitions, or an alternative model that can explain why evolutionary transitions took hundreds of millions of years without appealing to rare chance events. Although the model is simple, it provides an initial basis for evaluating how varying biological assumptions and fossil record data impact the probability of evolving intelligent life, and also provides a number of testable predictions, such as that some biological paradoxes will remain unresolved and that planets orbiting M dwarf stars are uninhabitable. [ABSTRACT FROM AUTHOR]

Organisms are subject to the laws of physics, so the process of evolution by genetic variation and natural selection is constrained by these fundamental laws. Classic and recent studies of the biophysical limits facing organisms have shown how fundamental physical constraints can be used to predict broad-scale relationships between body size and organismal biomechanics and physiology. These relationships often take the form of power laws across a wide range of body sizes for organisms sharing a common body plan. However, such biophysical perspectives have not been fully connected with the detailed dynamics of evolution by natural selection, nor with the variation between species around the central scaling relationships. Here we first discuss what a general biophysical theory of evolution would require and provide a mathematical framework for constructing such a theory. We discuss how the theory can predict not only scaling relationships, but also of identifying the types of tradeoffs made by different species living in particular niches. In addition, we discuss how a key higher-order requirement of a biophysical theory of evolution is its ability to predict asymptotic behavior and the limits of a particular body plan. We use several examples to illustrate how dominant physical constraints can be used to predict the minimum and maximum body sizes for a particular body plan, and we argue that prediction of these limits is essential for identifying the dominant physical constraints for a given category of organisms. Our general framework proposes that a major portion of fitness should be the overlay of how all traits of a particular body plan interact with fundamental physical constraints. To illustrate this concept, we investigate multiple physical limits on particular traits, such as insect legs, and show how the interaction of a number of traits determines the size limits on entire body plans, such as those of vascular plants. We use bacteria as an example of the shifts in which physiological traits and physical constraints are most limiting at various organism sizes. Finally, we address the effects of environmental conditions and ecological interactions in determining which of the physical constraints faced by organisms are most likely to affect their growth, survival, and reproduction, and hence their fitness. We consider such ecological effects on our examples of bacteria, insects, mammals and trees, and we nest the constraints-perspective in the broader picture of evolutionary processes.

Bipedal locomotion is a defining characteristic of humans and birds and has a profound effect on how these groups interact with their environment. Results from extensive hominin research indicate that there exists an intermediate stage in hominin evolution—facultative bipedality—between obligate quadrupedality and obligate bipedality that uses both forms of locomotion. It is assumed that archosaur locomotor evolution followed this sequence of functional and hence character-state evolution. However, this assumption has never been tested in a broad phylogenetic context. We test whether facultative bipedality is a transitionary state of locomotor mode evolution in the most recent early archosaur phylogenies using maximum-likelihood ancestral state reconstructions for the first time. Across a total of seven independent transitions from quadrupedality to a state of obligate bipedality, we find that facultative bipedality exists as an intermediary mode only once, despite being acquired a total of 14 times. We also report more independent acquisitions of obligate bipedality in archosaurs than previously hypothesized, suggesting that locomotor mode is more evolutionarily fluid than expected and more readily experimented with in these reptiles.

Learning is a widespread ability among animals and, like physical traits, is subject to evolution. But how did learning first arise? What selection pressures and phenotypic preconditions fostered its evolution? Neither the fossil record nor phylogenetic comparative studies provide answers to these questions. Here, we take a novel approach by studying digital organisms in environments that promote the evolution of navigation and associative learning. Starting with a nonlearning sessile ancestor, we evolve multiple populations in four different environments, each consisting of nutrient trails with various layouts. Trail nutrients cue organisms on which direction to follow, provided they evolve to acquire and use those cues. Thus, each organism is tested on how well it navigates a randomly selected trail before reproducing. We find that behavior evolves modularly and in a predictable sequence, where simpler behaviors are necessary precursors for more complex ones. Associative learning is only one of many successful behaviors to evolve, and its origin depends on the environment possessing certain information patterns that organisms can exploit. Environmental patterns that are stable across generations foster the evolution of reflexive behavior, while environmental patterns that vary across generations but remain consistent for periods within an organism's lifetime foster the evolution of learning behavior. Both types of environmental patterns are necessary, since the prior evolution of simple reflexive behaviors provides the building blocks for learning to arise. Finally, we observe that an intrinsic value system evolves alongside behavior and supports associative learning by providing reinforcement for behavior conditioning. [ABSTRACT FROM AUTHOR]

Summary: Heterostylous genetic polymorphisms provide paradigmatic systems for investigating adaptation and natural selection. Populations are usually comprised of two (distyly) or three (tristyly) mating types, maintained by negative frequency‐dependent selection resulting from disassortative mating. Theory predicts this mating system should result in equal style‐morph ratios (isoplethy) at equilibrium. Here, I review recent advances on heterostyly, focusing on examples challenging stereotypical depictions of the polymorphism and unresolved questions. Comparative analyses indicate multiple origins of heterostyly, often within lineages. Ecological studies demonstrate that structural components of heterostyly are adaptations improving the proficiency of animal‐mediated cross‐pollination and reducing pollen wastage. Both neutral and selective processes cause deviations from isoplethy in heterostylous populations, and, under some ecological and demographic conditions, cause breakdown of the polymorphism, resulting in either the evolution of autogamy and mixed mating, or transitions to alternative outcrossing systems, including dioecy. Earlier ideas on the genetic architecture of the S‐locus supergene governing distyly have recently been overturned by discovery that the dominant S‐haplotype is a hemizygous region absent from the s‐haplotype. Ecological, phylogenetic and molecular genetic data have validated some features of theoretical models on the selection of the polymorphism. Although heterostyly is the best‐understood floral polymorphism in angiosperms, many unanswered questions remain. [ABSTRACT FROM AUTHOR]

Summary: Transitions from animal to wind pollination have occurred repeatedly in flowering plants, driven by structural and biomechanical modifications to flowers. But the initial changes promoting wind pollination are poorly understood, especially those required to release pollen into airflows – the critical first stage of wind pollination.Using a wind tunnel, we performed a comparative study of pollen release biomechanics in 36 species of animal‐ and wind‐pollinated Thalictrum. We quantified pollination syndromes and stamen natural frequency (fn), a key vibration parameter, to determine if floral traits reliably predicted pollen release probability. We then investigated if pollen release was caused by wind‐induced resonance vibration of stamens.We detected wind‐induced stamen resonance in 91% of species and a strong effect of stamen acceleration on pollen release, inversely driven by fn. However, unlike fn, pollination syndromes did not reliably predict the probability of pollen release among species.Our results directly link fn to the capacity of stamens to release pollen by wind and suggest that structural mechanisms reducing fn are likely to be important for initiating transitions from animal to wind pollination. Our inability to predict the probability of pollen release based on pollination syndromes suggests diverse phenotypic trajectories from animal to wind pollination. [ABSTRACT FROM AUTHOR]

Fungi are a highly diverse group of heterotrophic eukaryotes characterized by the absence of phagotrophy and the presence of a chitinous cell wall. While unicellular fungi are far from rare, part of the evolutionary success of the group resides in their ability to grow indefinitely as a cylindrical multinucleated cell (hypha). Armed with these morphological traits and with an extremely high metabolical diversity, fungi have conquered numerous ecological niches and have shaped a whole world of interactions with other living organisms. Herein we survey the main evolutionary and ecological processes that have guided fungal diversity. We will first review the ecology and evolution of the zoosporic lineages and the process of terrestrialization, as one of the major evolutionary transitions in this kingdom. Several plausible scenarios have been proposed for fungal terrestralization and we here propose a new scenario, which considers icy environments as a transitory niche between water and emerged land. We then focus on exploring the main ecological relationships of Fungi with other organisms (other fungi, protozoans, animals and plants), as well as the origin of adaptations to certain specialized ecological niches within the group (lichens, black fungi and yeasts). Throughout this review we use an evolutionary and comparative‐genomics perspective to understand fungal ecological diversity. Finally, we highlight the importance of genome‐enabled inferences to envision plausible narratives and scenarios for important transitions. [ABSTRACT FROM AUTHOR]

Abstract: The 'managed-metabolism' hypothesis suggests that a 'cooperation barrier' must be overcome if self-producing chemical organizations are to undergo the transition from non-life to life. This dynamical barrier prevents un-managed autocatalytic networks of molecular species from individuating into complex, cooperative organizations. The barrier arises because molecular species that could otherwise make significant cooperative contributions to the success of an organization will often not be supported within the organization, and because side reactions and other 'free-riding' processes will undermine cooperation. As a result, the barrier seriously impedes the emergence of individuality, complex functionality and the transition to life. This barrier is analogous to the cooperation barrier that also impedes the emergence of complex cooperation at all levels of living organization. As has been shown at other levels of organization, the barrier can be overcome comprehensively by appropriate 'management'. Management implements a system of evolvable constraints that can overcome the cooperation barrier by ensuring that beneficial co-operators are supported within the organization and by suppressing free-riders. In this way, management can control and manipulate the chemical processes of a collectively autocatalytic organization, producing novel processes that serve the interests of the organization as a whole and that could not arise and persist in an un-managed chemical organization. Management self-organizes because it is able to capture some of the benefits that are produced when its interventions promote cooperation, thereby enhancing productivity. Selection will therefore favour the emergence of managers that take over and manage chemical organizations so as to overcome the cooperation barrier. The managed-metabolism hypothesis demonstrates that if management is to overcome the cooperation barrier comprehensively, its interventions must be digitally coded. In this way, the hypothesis accounts for the two-tiered structure of all living cells in which a digitally-coded genetic apparatus manages an analogically-informed metabolism.Graphical Abstract: [ABSTRACT FROM AUTHOR]

ABSTRACT: Evolutionary theory is formulated in terms of individuals that carry heritable information and are subject to selective pressures. However, individuality itself is a trait that had to evolve – an individual is not an indivisible entity, but a result of evolutionary processes that necessarily begin at the lower level of hierarchical organisation. Traditional approaches to biological individuality focus on cooperation and relatedness within a group, division of labour, policing mechanisms and strong selection at the higher level. Nevertheless, despite considerable theoretical progress in these areas, a full dynamical first‐principles account of how new types of individuals arise is missing. To the extent that individuality is an emergent trait, the problem can be approached by recognising the importance of individuating mechanisms that are present from the very beginning of the transition, when only lower‐level selection is acting. Here we review some of the most influential theoretical work on the role of individuating mechanisms in these transitions, and demonstrate how a lower‐level, bottom‐up evolutionary framework can be used to understand biological complexity involved in the origin of cellular life, early eukaryotic evolution, sexual life cycles and multicellular development. Some of these mechanisms inevitably stem from environmental constraints, population structure and ancestral life cycles. Others are unique to specific transitions – features of the natural history and biochemistry that are co‐opted into conflict mediation. Identifying mechanisms of individuation that provide a coarse‐grained description of the system's evolutionary dynamics is an important step towards understanding how biological complexity and hierarchical organisation evolves. In this way, individuality can be reconceptualised as an approximate model that with varying degrees of precision applies to a wide range of biological systems. [ABSTRACT FROM AUTHOR]