scholarly journals Evolutionary Dynamics Do Not Motivate a Single-Mutant Theory of Human Language

2019 ◽  
Author(s):  
Bart de Boer ◽  
Bill Thompson ◽  
Andrea Ravignani ◽  
Cedric Boeckx
Keyword(s):  
Evolutionary Dynamics ◽  
A Priori ◽  
Value Theory ◽  
Language Faculty ◽  
Single Mutant ◽  
Fitness Advantage ◽  
Diffusion Analysis ◽  
Frequency Independent ◽  
First Time ◽  
Minimalist Theory

AbstractOne of the most controversial hypotheses in cognitive science is the Chomskyan evolutionary conjecture that language arose instantaneously in our species as the result of a single staggeringly fortuitous mutation. Here we analyze the evolutionary dynamics implied by this hypothesis, which has never been formalized. The theory supposes the emergence and fixation of a single mutant (capable of the syntactic operation Merge) during a narrow historical window as a result of frequency-independent selection under a huge fitness advantage in a population of an effective size that is standardly assumed to have been no larger than ~15 000 early humans. We examine this proposal by combining diffusion analysis and extreme value theory to derive a probabilistic formulation of its dynamics. Perhaps counter-intuitively, a macro-mutation is much more unlikely a priori than multiple mutations with smaller fitness effects, yet both hypotheses predict fixation with high conditional probability. The consequences of this asymmetry have not been accounted for previously. Our results diffuse any suggestion that evolutionary reasoning provides an independent rationale for the controversial single-mutant theory of language.Significance statementIn recent years, Chomsky and colleagues have sought support for their minimalist theory of the language faculty from evolutionary considerations. They have argued for a spontaneous emergence of a mutation conferring an advantage for thought independent of communication. Here for the first time a formalization of this view is offered, and contrasted with a more gradual evolutionary scenario. The outcome of our analysis argues against the Chomskyan view.

scholarly journals Connecting signals and benefits through partner choice in plant–microbe interactions

2019 ◽  
Vol 366 (18) ◽  
Author(s):  
Brett S Younginger ◽  
Maren L Friesen
Keyword(s):  
Nitrogen Fixation ◽  
Evolutionary Dynamics ◽  
Empirical Studies ◽  
A Priori ◽  
Partner Choice ◽  
Host Fitness ◽  
Fitness Advantage ◽  
Signaling Mechanisms ◽  
Microbe Interactions ◽  
Mutualism Stability

ABSTRACT Stabilizing mechanisms in plant–microbe symbioses are critical to maintaining beneficial functions, with two main classes: host sanctions and partner choice. Sanctions are currently presumed to be more effective and widespread, based on the idea that microbes rapidly evolve cheating while retaining signals matching cooperative strains. However, hosts that effectively discriminate among a pool of compatible symbionts would gain a significant fitness advantage. Using the well-characterized legume–rhizobium symbiosis as a model, we evaluate the evidence for partner choice in the context of the growing field of genomics. Empirical studies that rely upon bacteria varying only in nitrogen-fixation ability ignore host–symbiont signaling and frequently conclude that partner choice is not a robust stabilizing mechanism. Here, we argue that partner choice is an overlooked mechanism of mutualism stability and emphasize that plants need not use the microbial services provided a priori to discriminate among suitable partners. Additionally, we present a model that shows that partner choice signaling increases symbiont and host fitness in the absence of sanctions. Finally, we call for a renewed focus on elucidating the signaling mechanisms that are critical to partner choice while further aiming to understand their evolutionary dynamics in nature.

scholarly journals Dinosaurs in decline tens of millions of years before their final extinction

2016 ◽  
Vol 113 (18) ◽  
pp. 5036-5040 ◽  
Author(s):  
Manabu Sakamoto ◽  
Michael J. Benton ◽  
Chris Venditti
Keyword(s):  
Mass Extinction ◽  
Marked Reduction ◽  
Evolutionary Dynamics ◽  
General Pattern ◽  
Extinction Rate ◽  
Catastrophic Event ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
First Time

Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous–Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.

scholarly journals Evolutionary Dynamics Do Not Motivate a Single-Mutant Theory of Human Language

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bart de Boer ◽  
Bill Thompson ◽  
Andrea Ravignani ◽  
Cedric Boeckx
Keyword(s):  
Evolutionary Dynamics ◽  
Human Language ◽  
Single Mutant

scholarly journals LQAC-5: The fifth release of the Large Quasar Astrometric Catalogue

2019 ◽  
Vol 624 ◽  
pp. A145 ◽  
Author(s):  
J. Souchay ◽  
C. Gattano ◽  
A. H. Andrei ◽  
D. Souami ◽  
B. Coelho ◽  
...  
Keyword(s):  
A Priori ◽  
Proper Motions ◽  
Positional Accuracy ◽  
Mid Infrared ◽  
Additional Information ◽  
Complete Catalogue ◽  
Absolute Magnitudes ◽  
Celestial Sphere ◽  
First Time ◽  
Cross Match

Context. In addition to their great astrophysical interest, quasars represent quasi-ideal reference objects in the celestial sphere with, a priori, a lack of significant proper motion. Since the fourth release of the Large Quasar Astrometric Catalogue (LQAC-4), a large number of quasars have been discovered, in particular those coming from the DR14Q release of the SDSS. With the advent of the Gaia Data Release 2 (DR2), it is now also possible to fold in extremely accurate quasar positions. Aims. Following the same procedure as in the previous releases of the LQAC, our aim is to compile the large majority of the recorded quasars, with their best estimated coordinates and substantial information about their physical properties such as the redshift, multi-bands apparent, and absolute magnitudes. Emphasis is given to the results of the cross-matches with the Gaia DR2 catalogue, which considerably increases the positional accuracy. Methods. New quasars from the SDSS DR14Q release were cross-matched with the precedent LQAC-4 compilation with a 1″ search radius, which leads to 149 084 objects not present in the previous LQAC-4 release. Another cross-match was done with the Gaia DR2 catalogue, which enables us to considerably improve the positioning of these objects. For the first time, parallaxes and proper motions from the DR2, when available, are added to our compilation. Furthermore, a cross-identification of the LQAC-5 with the AllWISE survey gives additional mid-infrared information for an important percentage of objects. Results. Our final catalogue, namely the LQAC-5, contains 592 809 quasars. This represents roughly a 34% increase with respect to the number of objects recorded in the LQAC-4. Among them, 398 697 objects were found in common with the Gaia DR2, within a 1″ search radius. That corresponds to 67.26% of the whole population of the compilation. Conclusion. The LQAC-5 delivers a nearly complete catalogue of spectroscopically confirmed quasars (including a small proportion of 14 126 compact AGN’s) to the astronomical community, with the aim of giving their best equatorial coordinates with respect to the ICRF2 and with exhaustive additional information. For more than 50% of the sample, these coordinates are extracted from the very recent Gaia DR2.

Variability of transit light curves of Kepler objects of interest

2020 ◽  
Vol 638 ◽  
pp. A143
Author(s):  
O. V. Arkhypov ◽  
M. L. Khodachenko ◽  
A. Hanslmeier
Keyword(s):  
Large Scale ◽  
Time Windows ◽  
A Priori ◽  
Spherical Shape ◽  
Light Curves ◽  
Aerosol Generation ◽  
Timing Variability ◽  
Cross Correlation Analysis ◽  
Medium Time ◽  
First Time

Context. Hitherto, the study of exoplanetary transit timing and duration variability has supposed transit light curves (TLCs) to be symmetric, suggesting a priori a spherical shape for the transiting object, for example, an exoplanet. As a result, the independent positions of transit borders are unknown. However, the borders of TLCs are most sensitive to the presence of exo-rings and/or dust formations of great interest. Aims. For the first time we check for a timing variability of independently treated borders of transits of different types of exoplanets. Methods. Using quadratic approximation for the start-, end-, and minimum parts of the long-cadence TLCs from the Kepler mission archive after their whitening and phase folding, we find the corresponding transit border timings: Δts, Δte, respectively, and the TLC minimum time Δtm. These parameters were found separately for each folded TLC constructed in the consequent non-overlapping time-windows with the respective medium time tw. Temporal and cross-correlation analysis of the obtained series of Δts(tw), Δte(tw), and Δtm(tw) were applied for the detection and diagnostics of variability of transit borders and TLC asymmetry. Results. Among the considered TLCs of 98 Kepler objects of interest (KOIs), 15 confirmed giant exoplanets and 5 objects with still debatable status (probably non-planets) show variations in their transit timing parameters at timescales from ≈400 to ≳1500 days. These variations are especially well manifested as an anti-correlation between Δts and Δte, indicating variability in the dimensions of transiting shadows, especially along their trajectories. There are also objects with well pronounced oscillations of transit border timing and asymmetry. Conclusions. The discovered variability of transit timing is important as an indicator of large-scale non-stationary processes in the atmospheres of KOIs, as well as dust and aerosol generation in their upper layers and in their close vicinity. These findings highlight the need for a dedicated and detailed study.

Adaptive value within natural language discourse

2006 ◽  
Vol 7 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Michael L. Best
Keyword(s):  
Natural Language ◽  
Evolutionary Dynamics ◽  
Selective Advantage ◽  
Online Environment ◽  
Word Usage ◽  
Fitness Advantage ◽  
Language Discourse ◽  
Adaptive Value

A trait is of adaptive value if it confers a fitness advantage to its possessor. Thus adaptiveness is an ahistorical identification of a trait affording some selective advantage to an agent within some particular environment. In results reported here we identify a trait within natural language discourse as having adaptive value by computing a trait/fitness covariance; the possession of the trait correlates with the replication success of the trait’s possessor. We show that the trait covaries with fitness across multiple unrelated discursive groups. In our analysis the trait in question is a particular statistically derived word-in-context, that is, a word set. Variation of the word-usage is measured as the relative presence of the word set within a particular text, that is, the percentage of the text devoted to this set of words. Fitness is measured as the rate in which the text is responded to, or replicates, within an online environment. Thus we are studying the micro-evolutionary dynamics of natural language discourse.

scholarly journals Frequency-dependent attenuation analysis of ground-penetrating radar data

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. J7-J16 ◽  
Author(s):  
John H. Bradford
Keyword(s):  
Attenuation Coefficient ◽  
Ground Penetrating Radar ◽  
A Priori ◽  
Radar Data ◽  
Frequency Dependent ◽  
First Order ◽  
Reflection Data ◽  
Frequency Independent ◽  
Band Limited ◽  
Ground Penetrating

In the early 1990s, it was established empirically that, in many materials, ground-penetrating radar (GPR) attenuation is approximately linear with frequency over the bandwidth of a typical pulse. Further, a frequency-independent [Formula: see text] parameter characterizes the slope of the band-limited attenuation versus frequency curve. Here, I derive the band-limited [Formula: see text] function from a first-order Taylor expansion of the attenuation coefficient. This approach provides a basis for computing [Formula: see text] from any arbitrary dielectric permittivity model. For Cole-Cole relaxation, I find good correlation between the first-order [Formula: see text] approximation and [Formula: see text] computed from linear fits to the attenuation coefficient curve over two-octave bands. The correlation holds over the primary relaxation frequency. For some materials, this relaxation occurs between 10 and [Formula: see text], a typical frequency range for many GPR applications. Frequency-dependent losses caused by scattering and by the commonly overlooked problem of frequency-dependent reflection make it difficult or impossible to measure [Formula: see text] from reflection data without a priori understanding of the materials. Despite these complications, frequency-dependent attenuation analysis of reflection data can provide valuable subsurface information. At two field sites, I find well-defined frequency-dependent attenuation anomalies associated with nonaqueous-phase liquid contaminants.

Optimization of Elastic Supports for Laminated Composite Plates

2012 ◽  
Vol 249-250 ◽  
pp. 881-886
Author(s):  
Jackson Kong
Keyword(s):  
A Priori ◽  
Laminated Composite ◽  
Composite Plates ◽  
Optimization Method ◽  
Vibration Modes ◽  
Laminated Composite Plates ◽  
Nodal Lines ◽  
Search Optimization ◽  
Rigid Supports ◽  
First Time

The fundamental frequency of a plate can be raised by placing appropriate number of rigid supports at various optimal locations along the nodal lines of vibration modes, as previously shown by other researchers. Unlike previous works, however, the present study aims to determine the optimal locations and the corresponding minimum stiffness of elastic spring supports using a direct search optimization method, presuming that the nodal lines of vibration modes can be identified a priori. As examples of applications, the optimal locations and stiffness are determined for isotropic plates and laminated composite plates with various lamination schemes, results of the latter are presented for the first time in open literature. Although only plates with regular geometry are treated in this preliminary study, further extension to plates with irregular geometry and other boundary conditions is being carried out.

scholarly journals Variability of contemporary vegetation around Petuniabukta, central Spitsbergen

2012 ◽  
Vol 33 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Karel Prach ◽  
Jitka Klimešová ◽  
Jiří Košnar ◽  
Olexii Redčenko ◽  
Martin Hais
Keyword(s):  
High Latitude ◽  
Vascular Plants ◽  
Native Species ◽  
Spatial Scales ◽  
A Priori ◽  
Vegetation Pattern ◽  
Svalbard Archipelago ◽  
Species Lists ◽  
Phytosociological Relevés ◽  
First Time

Abstract Vegetation was described in various spatial scales in the area of 37.8 km2 including distinguishing vegetation units, vegetation mapping, recording phytosociological relevés (53), and completing species lists of vascular plants (86), mosses (124) and lichens (40). Phytosociological relevés were elaborated using ordination methods DCA and CCA. The relevés formed clusters corresponding well to a priori assigned vegetation units. Slope and stoniness significantly influenced the vegetation pattern. Despite the high latitude (nearly 80° N), the vegetation is rather rich in species. Non-native species do not expand. The moss Bryum dichotomum is reported for the first time from Svalbard archipelago.

scholarly journals Fitness estimation for viral variants in the context of cellular coinfection

2021 ◽  
Author(s):  
Huisheng Zhu ◽  
Brent E Allman ◽  
Katia Koelle
Keyword(s):  
Evolutionary Dynamics ◽  
Sequence Data ◽  
Population Level ◽  
Viral Fitness ◽  
Fitness Effects ◽  
Fitness Advantage ◽  
Viral Adaptation ◽  
Zoonotic Viruses ◽  
Frequency Changes

AbstractAnimal models are frequently used to characterize the within-host dynamics of emerging zoonotic viruses. More recent studies have also deep-sequenced longitudinal viral samples originating from experimental challenges to gain a better understanding of how these viruses may evolve in vivo and between transmission events. These studies have often identified nucleotide variants that can replicate more efficiently within hosts and also transmit more effectively between hosts. Quantifying the degree to which a mutation impacts viral fitness within a host can improve identification of variants that are of particular epidemiological concern and our ability to anticipate viral adaptation at the population level. While methods have been developed to quantify the fitness effects of mutations using observed changes in allele frequencies over the course of a host’s infection, none of the existing methods account for the possibility of cellular coinfection. Here, we develop mathematical models to project variant allele frequency changes in the context of cellular coinfection and, further, integrate these models with statistical inference approaches to demonstrate how variant fitness can be estimated alongside cellular multiplicity of infection. We apply our approaches to empirical longitudinally-sampled H5N1 sequence data from ferrets. Our results indicate that previous studies may have significantly underestimated the within-host fitness advantage of viral variants. These findings underscore the importance of considering the process of cellular coinfection when studying within-host viral evolutionary dynamics.

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