perspectives are distinctly evolutionary syntheses. Importantly, we observe the same body of evidence and it prompts us to question whether interpretive assumptions derived from the NDT, or the EES, are valid for anything more than trivial cases. For instance, which tests in the scientific literature enable us to confidently identify the sources of genetic or epigenetic changes underlying adaptive phenotypes that originate from copying mistakes? Additionally, what studies have demonstrated that genetic changes are random or undirected, or that altered genetic sequences should be classified as “broken” or as “loss-of-function” rather than being precisely modified to produce purposeful changes in function? Is it observational data or NDT that constrains researchers to expect that phenotypic changes will be very slight in extent, and sorted out through “hit and miss” or “trial and error” processes that only advance through very gradual rates of change? Is the Weisman Barrier physically identifiable or is it a necessary interpretive assumption of NDT? The lack of details in the literature to support these assumptions makes them more conspicuous as dogmatic declarations rather than experimental demonstrations. E.The cavefish Astyanax mexicanus is a suitable research model to test theoretical assumptions Organisms that live in caves for their entire life are known as troglobites. Cave animals share an astonishingly consistent set of sensory, morphological, physiological and behavioral traits. Though not expressed identically in all organisms, or even between cavefish, shared troglomorphic traits are highly similar across insects, crustaceans, centipedes, millipedes, spiders and salamanders, all animals that are permanent cave inhabitants (Borowski 2018). Borowski adds, “in fact, as far as we know, whenever a surface species comes to live in a cave, given enough time, it changes in the same way. Thus, cave animals are a natural model for the study of convergent and adaptive evolution…” Importantly, even different types of cavefish with shared traits are known to be unrelated and geographically widespread. Cavefish are not uncommon and their range is remarkably diverse. Over a nine-year period from 2011 to 2020 an average of eight new species per year were documented (Maldonado 2020). The number of fish species characterized as full-time cave dwellers likely exceeds 230, and worldwide they have been found on all continents except Antarctica (Borowski 2018). Borowski suggests that, “all of them have evolved independently from surface ancestors.” Independent lines are important for studying differences in genetic expression, physiologic pathways or mechanisms that produce very similar phenotypic outcomes. The Mexican cavefish Astyanax mexicanus is the most studied vertebrate model for troglomorphic traits. Other genera of cavefish that significantly add to the body of knowledge are the Chinese cavefish Sinocyclocheilus (Yang 2016), the Somali cavefish Phreatichthys andruzzii (Cavallari 2011) and the Northern cavefish Amblyopsis spelaea (Hart 2020). In Southeast Asia and southern China, even though there are many cavefish, most are in the loach and cyprinid (carp) families, yet in South America, most cavefish are in the catfish family. Our model, A. mexicanus (Characid Mexican tetra), is abundant, robust and easily maintained in the laboratory. Mexican tetras are freshwater fish with well-differentiated, interfertile morphotypes: eyed surface-dwelling fish (surface fish) with a distinct pigmentation pattern, and eyeless cave-dwelling fish (cavefish) with minimal pigmentation (Fig. 1). Surface fish and cavefish reach sexual maturity in only 4-6 months and produce hundreds of relatively large translucent internal mechanisms that integrate molecular, biochemical, physiological and behavioral functionality of the whole organism. These mechanisms are predicted to operate by the same integrative principles that govern human-engineered tracking systems, suggesting that fish and other animals make highly-regulated responses in order to compensate for changes in external conditions that may exceed their routine efforts to maintain homeostasis. Moreover, the theory also predicts that organisms can modify the course of their development; that adaptive larval and adult traits are sometimes reversible; that many epigenetic modifications are heritable across multiple generations; and that phenotypic traits will trend toward convergence among a diversity of organisms living within similar environments. Collectively, there are multiple major points of departure in assumptions and predictions between the CET model of adaptation and the (essentially synonymous) conventional evolutionary and non-evolutionary interpretations for the origin of blind cavefish. First, in terms of how adaptation is characterized (descriptors of how the mechanism of adaptation operates) CET expects adaptive outcomes to be tightly regulated, rapid, repeatable, sometimes reversible, and highly targeted – even predictable – responses. Second, in terms of the extent of resulting adaptations, CET expects that “adaptation” should be viewed as a temporal continuum where an organism’s adaptations can range from very rapid physiological self-adjustments, to intra-lifetime, to multi-generational. Third, the environment is viewed as a range of conditions to which organisms are variably exposed, and to which organisms themselves control their variable responses. It is the traits of organisms that specify which environmental conditions are “stimuli” and the extent to which each individual organism can relate to its environment and solve environmental challenges. Environments are not personified with intelligent agent-like powers to “select,” “favor,” or “act on” creatures. Fourth, in terms of the organisms themselves, CET would view organisms as active, problem-solving entities that successfully navigate environmental challenges and fill new niches. Thus, creatures are not viewed as passive modeling clay that is constantly being shaped by their environment; they are actively in control of adapting to their environment. D. Biological observations are inconsistent with the assumptions of neo-Darwinian theory Before the Linnean Society on July 1st 1858, Sir Charles Lyell and J. D. Hooker read papers by Charles Darwin and Alfred Wallace highlighting their respective deductions on the “Perpetuation of Varieties and Species by Natural Means of Selection”. Their philosophical ‘convergence’ on similar proposals reflected an emphasis on nature as the ultimate creative agency behind the diversity of all life forms on earth. This perspective has changed little over the ensuing years, and remains as the standard academic view today. However, evolutionists are struggling to reconcile a surging number of observable mechanisms for adaptive change that are not compatible with NDT, which has led to heated discussions over the future of evolutionary theory (Lewontin 1983; Gould 2002; Koonin 2009; Laland et al. 2014; Laland et al. 2015; Bateson et al. 2017; Muller 2017; West-Eberhard 2019; Jablonka and Lamb 2020; Sultan 2021). And on top of such discussion comes a remarkable new emphasis, from a review of research on the extended evolutionary synthesis (EES), which proposes, “more sources of biological innovation and adaptations” in order to update the “structure of evolutionary theory” (Chiu 2022). With the EES, there is an apparent interest to move past a “gene-centric” view, toward recognizing “more agency for organisms to affect their own evolution”, or in other words, a growing interest toward an “organism-centered perspective” (Chiu 2022). Yet, both NDT and EES BOYLE, ARLEDGE, THOMAS, TOMKINS, AND GULIUZZA Testing the cavefish model 2023 ICC 123
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