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| Evolution Research - Main Blog |
| Research into the possible existence of an Internal Evolutionary Mechanism based on an extension to homeostasis (see 'Links'). Also included are those areas where the investigation of natural reality conflicts with cultural conditioning: "The only thing that interferes with my learning is my education" (Einstein). |
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| Body Size, Performance and Fitness in Galapagos Marine Iguanas |
| 2007-01-16 06:12:48 |
| Integrative and Comparative Biology 2003 43(3):376-386; doi:10.1093/icb/43.3.376Martin Wikelski and L. Michael RomeroComplex organismal traits such as body size are influenced by innumerable selective pressures, making the prediction of evolutionary trajectories for those traits difficult. A potentially powerful way to predict fitness in natural systems is to study the composite response of individuals in terms of performance measures, such as foraging or reproductive performance. Once key performance measures are identified in this top-down approach, we can determine the underlying physiological mechanisms and gain predictive power over long-term evolutionary processes. Here we use
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| Balancing Robustness and Evolvability |
| 2007-01-14 12:56:56 |
From PloS Biology:Balancing Robustness and EvolvabilityRichard E. Lenski et al.One of the most important features of biology is the ability of organisms to persist in the face of changing conditions. Consider the remarkable fact that every organism alive today is the product of billions of generations in which its progenitors, without fail, managed to produce progeny that survived to reproduce. To achieve this consistency, organisms must have a balance between robustness and evolvability, that is, between resisting and allowing change in their own internal states [1 - 3]. Moreover, they must achieve this balance on multiple time scales, including physiological responses to changes over an individual life and evol...
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| Genomic Imprinting in Mammals: Emerging Themes and Established Theories |
| 2006-12-04 08:36:38 |
| [This post also appears in the General Evolution News category]An open access/free review paper from PLoS Genetics:Genomic Imprinting in Mammals: Emerging Themes and Established TheoriesAndrew J. Wood, Rebecca J. OakeyThe epigenetic events that occur during the development of the mammalian embryo are essential for correct gene expression and cell-lineage determination. Imprinted genes are expressed from only one parental allele due to differential epigenetic marks that are established during gametogenesis. Several theories have been proposed to explain the role that
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| Birds that make teeth (Press Release + Summary) |
| 2006-11-18 20:21:03 |
Contents:1) Birds that make teeth (Press Release)Gone does not necessarily mean forgotten, especially in biology. A recent finding by researchers at the University of Wisconsin, Madison, and colleagues from the University of Manchester have found new evidence that the ability to form previously lost organs--in this case, teeth--can be maintained millions of years after the last known ancestor possessed them. Birds do not have teeth. However, their ancestors did--about 70 - 80 million years ago. The evolutionary loss of teeth corresponded to the formation of the beak that is present in all living birds. Nonetheless, it has been known that if mouse tooth-forming tissue is in contact wit...
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| Epigenetics: Mother's Diet during Pregnancy can affect Grandchildren |
| 2006-11-14 14:38:10 |
[This post also appears in the General Evolution News category]Oakland, California: A new study by scientists at Children's Hospital Oakland Research Institute (CHORI) is the first to show that a mother's diet Pregnancy">during pregnancy influences the health of her grandchildren by changing the behavior of a specific gene. The study was conducted using mice of an unique strain called 'viable yellow agouti' also known as A-vy in scientific terms. These mice possesss a gene that influences the color of their coats as well as their tendency to become obese and develop diabetes and cancer. The new research shows that the diet consumed by a pregnant Avy...
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| Symmetry Breaking and the Evolution of Development |
| 2006-10-25 17:29:02 |
Symmetry Breaking and the Evolution of Development[Palmer, Science, Oct '04]Because of its simplicity, the binary-switch nature of left-right asymmetry permits meaningful comparisons among many different organisms. Phylogenetic analyses of asymmetry variation, inheritance, and molecular mechanisms reveal unexpected insights into how development evolves. First, directional asymmetry, an evolutionary novelty, arose from nonheritable origins almost as often as from mutations, implying that genetic assimilation ('phenotype precedes genotype') is a common mode of evolution. Second, the molecular pathway directing hearts leftward - the nodal cascade ...
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| From symmetry to asymmetry: Phylogenetic patterns of asymmetry variation |
| 2006-10-25 10:27:38 |
[A. Richard Palmer, PNAS, Dec '96]From symmetry to asymmetry: Phylogenetic patterns of asymmetry variation in animals and their evolutionary significanceAbstract:Phylogenetic analyses of asymmetry variation offer a powerful tool for exploring the interplay between ontogeny and evolution because (i) conspicuous asymmetries exist in many higher metazoans with widely varying modes of development, (ii) patterns of bilateral variation within species may identify genetically and environmentally triggered asymmetries, and (iii) asymmetries arising at different times during development may be more sensitive to internal cytoplasmic inhomogeneities compared to external environmental stimuli. Using four broadly comparable asymmetry states (symmetry, antisymmetry, dextral, and sinistral), and two stages at which asymmetry appears developmentally (larval and postlarval), I evaluated relations between ontogenetic and phylogenetic patterns of asymmetry variation. Among 140 inferred phylogenetic transitions between asymmetry states, recorded from 11 classes in five phyla, directional asymmetry (dextral or sinistral) evolved directly from symmetrical ancestors proportionally more frequently among larval asymmetries. In contrast, antisymmetry, either as an end state or as a transitional stage preceding directional asymmetry, was confined primarily to postlarval asymmetries. The ontogenetic origin of asymmetry thus significantly influences its subsequent evolution. Furthermore, because antisymmetry typically signals an environmentally triggered asymmetry, the phylogenetic transition from antisymmetry to directional asymmetry suggests that many cases of laterally fixed asymmetries evolved via genetic assimilation.------- Books on Symmetry from the Science and Evolution Bookshop: UK | US technorati tags: asymmetry, variation, ontogeny, evolution, development, symmetry, antisymmetry, phyla, directional, origin, genetic+assimilation
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| The morphogenesis of evolutionary developmental biology (Int. J, Dev. Biol.) |
| 2006-09-30 23:35:38 |
[Gilbert, Int. J. Dev. Biol. 47: 467-477 (2003)]Abstract:The early studies of evolutionary developmental biology (Evo-Devo) come from several sources. Tributaries flowing into Evo-Devo came from such disciplines as embryology, developmental genetics, evolutionary biology, ecology, paleontology, systematics, medical embryology and mathematical modeling. This essay will trace one of the major pathways, that from evolutionary embryology to Evo-Devo and it will show the interactions of this pathway with two other sources of Evo-Devo: ecological developmental biology and medical developmental biology. Together, these three fields are forming a more inclusive evolutionary developm...
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| Irreducible Complexity Revisited (PCID) |
| 2006-09-26 14:02:18 |
[Dembski, PCID, '04]Abstract:"Michael Behe's concept of irreducible complexity, and in particular his use of this concept to critique Darwinism, continues to come under heavy fire from the biological community. The problem with Behe, so Darwinists inform us, is that he has created a problem where there is no problem. Far from constituting an obstacle to the Darwinian mechanism of random variation and natural selection, irreducible complexity is thus supposed to be eminently explainable by this same mechanism. But is it really? It's been eight years since Behe introduced irreducible complexity in Darwin's Black Box - a book that continues to sell 15,000 copies per year in English alone (Amazon UK | US)....
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| Expanding evolution: A broader view of inheritance puts pressure on the neo-darwinian synthesis |
| 2006-09-26 13:45:45 |
Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life by Eva Jablonka & Marion J. Lamb Bradford Books: 2005. 462 pp (Amazon UK | US).Book Review by Massimo Pigliucci (Nature Magazine)Extracts:There have been rumblings for some time to the effect that the neo-darwinian synthesis of the early twentieth century is incomplete and due for a major revision. In the past decade, several authors have written books to articulate this feeling and to begin the move towards a second synthesis. In the past decade, several authors have written books to articulate this feeling......I framed the debate in terms of the integration of developme...
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| Cardiovascular and diabetes mortality determined by nutrition |
| 2006-09-18 16:57:04 |
A non-pdf version can be found hereAbstract:Overfeeding and overeating in families are traditions that are often transferred from generation to generation. Irrespective of these family traditions, food availability might lead to overfeeding, in its turn leading to metabolic adaptations. Apart from selection, could these adaptations to the social environment have transgenerational effects? This study will attempt to answer the following question: Can overeating during a child's slow growth period (SGP), before their prepubertal peak in growth velocity influence descendants' risk of death from cardiovascular disease and diabetes? Data were collected by following three cohorts born in 1890, 1905 and 1920 in Overkalix parish in northern Sweden up until death or 1995. The parents' or grandparents' access to food during their SGP was determined by referring to historical data on harvests and food prices, records of local community meetings and general historical facts. If food was not readily available during the father's slow growth period, then cardiovascular disease mortality of the proband was low. Diabetes mortality increased if the paternal grandfather was exposed to a surfeit of food during his slow growth period. (Odds Ratio 4.1, 95% confidence interval 1.33-12.93, P=0.01). Selection bias seemed to be unlikely. A nutrition-linked mechanism through the male line seems to have influenced the risk for cardiovascular and diabetes mellitus mortality. [evolution]See New theory of environmental inheritance ('05 Press Release)technorati tags: overfeeding, overeating, generation, family, food, selection, metabolic, adaptations, child, death, descendants, cardiovascular, disease, diabetes, sweden, parents, grandparents, mortality, mechanism, evolution
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| Response to Comment on 'Gene Regulatory Networks and the Evolution of Animal Body Plans' (Science) |
| 2006-09-18 11:17:12 |
The journal Science 11 August 2006:Vol. 313. no. 5788, p. 761DOI: 10.1126/science.1126765Douglas H. Erwin and Eric H. DavidsonContrary to Coyne's assertions, our paper did not advocate a macromutational innovation of phyla but considered the consequences of the introduction of developmental constraints for the evolution of gene regulatory networks based on recent empirical studies of gene regulatory networks.Most of Coyne's concerns (1) are restatements of long-standing debates over the nature of evolutionary change (2). The comment offers no new data or interpretations but rather comments on issues, such as the nature of phyla, that have a lengthy and disputed history in evolutionary biology and which were not the subject of our paper. Specifically, Coyne seems to reject the role of regulatory genes in evolution. This is refuted by experimental studies of Drosophila, butterflies, echinoderms, fish, amniotes, and other organisms. Therefore, Coyne's conflict is not with our review as much as with developmental biology and its implications for evolutionary process. [Response]--See Comment on "Gene Regulatory Networks and the Evolution of Animal Body Plans"and the originalGene Regulatory Networks and the Evolution of Animal Body Planstechnorati tags: journal, science, innovation, phyla, developmental, constraints, evolution, gene, regulatory, networks, nature, evolutionary, change, new, data, history, biology, genes, experimental, drosophila, butterflies, fish, organisms, process, response, comment
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| Proximodistal patterning of the limb: insights from evolutionary morphology (ED) |
| 2006-09-09 19:35:42 |
[Richardson et al., Evolution and Development, Jan '04]Summary:There is an active debate about how skeletal elements are encoded along the proximodistal (PD) axis of the developing limb. Our aim here is to see whether consideration of the evolutionary morphology of the limb can contribute to our understanding of patterning mechanisms. Of special interest in this context are animals showing reiterated skeletal elements along the PD axis (e.g., dolphins and plesiosaurs with hyperphalangy). We build on previous hypotheses to propose a two-step model of PD patterning in which specification of broad domains in the early limb bud is distinct from subsequent processes that divides a...
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| On Making the Right Choice: The Deliberation-Without-Attention Effect |
| 2006-08-27 11:46:16 |
Journal: Science 17 February 2006:Vol. 311. no. 5763, pp. 1005 - 1007DOI: 10.1126/science.1121629ReportsOn Making the Right Choice: The Deliberation-Without-Attention EffectAp Dijksterhuis,* Maarten W. Bos, Loran F. Nordgren, Rick B. van BaarenContrary to conventional wisdom, it is not always advantageous to engage in thorough conscious deliberation before choosing. On the basis of recent insights into the characteristics of conscious and unconscious thought, we tested the hypothesis that simple choices (such as between different towels or different sets of oven mitts) indeed produce better results after conscious thought, but that choices in complex matters (such as between different houses or different cars) should be left to unconscious thought. Named the "deliberation-without-attention" hypothesis, it was confirmed in four studies on consumer choice, both in the laboratory as well as among actual shoppers, that purchases of complex products were viewed more favorably when decisions had been made in the absence of attentive deliberation.Department of Psychology, University of Amsterdam, Roetersstraat 15, 1018 WB, Amsterdam, the Netherlands.--The General Evo News category carries an entry from the Guardian (UK) about the above paper - "Trust your instincts: The conscious mind isn't much use in making hard decisions"technorati tags: journal, science, deliberation, doi, attention, effect, wisdom, conventional, conscious, unconscious, thought, hypothesis, choices, laboratory, complex, department, psychology, university, amsterdam, instints, trust, mind, decisions
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| Evolution: Where Darwin meets Lamarck? Discussion Forum |
| 2006-08-24 19:22:25 |
'Evolution - Where Darwin meets Lamarck?' places an emphasis on concepts and discoveries consistent with the possible existence of testable internal evolutionary mechanisms and alternative (non-creationist) explanations for 'problem areas' of conventional evolutionary theory.In their paper "The Spandrels of San Marco and the Panglossian Paradigm" Gould and Lewontin briefly described the European concept of Bauplan ('bodyplan') which, in its 'strong' form, speculates:"But the important steps of evolution, the construction of the Bauplan itself and the transition between Baupläne, must involve some other unknown, and perhaps 'internal,' mechanism."An internal mechanism cannot be 'mystical' simply because, if one exists, ...
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| Common objections to 'Internal Evolutionary Mechanisms' (1) |
| 2006-08-24 19:18:04 |
Brief notes on four common objections to current or historical proposals of internal evolutionary mechanisms (if you can think of any more then please leave a comment or email me): 1) Internal Evolutionary Mechanisms are 'Mystical' 2) Internal Evolutionary Mechanisms are 'Lamarckian' 3) "Populations Evolve, Individuals Do Not" 4) Weismann's experiment with Rodents 1) Internal Evolutionary Mechanisms are 'Mystical' [Return to Top] In their paper "The Spandrels of San Marco and the Panglossian Paradigm" Gould and Lewontin briefly described the European concept of Bauplan ('bodyplan') which, in its 'strong' form, speculates: "But the important steps of evolution, the construction of the Bauplan itself and...
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| Inherited epigenetic variation - revisiting soft inheritance |
| 2006-08-23 02:36:48 |
Perspective: Nature Reviews Genetics 7, 395-401 (May 2006) | doi:10.1038/nrg1834Opinion: Inherited epigenetic variation - revisiting soft inheritanceEric J. RichardsPhenotypic variation is traditionally parsed into components that are directed by genetic and environmental variation. The line between these two components is blurred by inherited epigenetic variation, which is potentially sensitive to environmental inputs. Chromatin and DNA methylation-based mechanisms mediate a semi-independent epigenetic inheritance system at the interface between genetic control and the environment. Should the existence of inherited epigenetic variation alter our thinking about evolutionary change?[Associated Washington University of St. Louis news release]technorati tags: nature, reviews, genetics, inherited, epigenetic, variation, inheritance, soft, phenotypic, chromatin, dna, environment, evolutionary, washington, st.+louis
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| Color blindness and contrast perception in cuttlefish (Sepia officinalis) determined by a visual sensorimotor assay |
| 2006-08-15 15:52:16 |
Full paper at above linkAbstract:We tested color perception based upon a robust behavioral response in which cuttlefish (Sepia officinalis) respond to visual stimuli (a black and white checkerboard) with a quantifiable, neurally controlled motor response (a body pattern).In the first experiment, we created 16 checkerboard substrates in which 16 grey shades (from white to black) were paired with one green shade (matched to the maximum absorption wavelength of S. officinalis' sole visual pigment, 492 nm), assuming that one of the grey shades would give a similar achromatic signal to the tested green.In the second experiment, we created a checkerboard using one blue and one yellow shade whose intensities were matched to the cuttlefish's visual system.In both assays it was tested whether cuttlefish would show disruptive coloration on these checkerboards, indicating their ability to distinguish checkers based solely on wavelength (i.e., color).Here, we show clearly that cuttlefish must be color blind, as they showed non-disruptive coloration on the checkerboards whose color intensities were matched to the Sepia visual system, suggesting that the substrates appeared to their eyes as uniform backgrounds.Furthermore, we show that cuttlefish are able to perceive objects in their background that differ in contrast by approximately 15%. This study adds support to previous reports that S. officinalis is color blind, yet the question of how cuttlefish achieve "color-blind camouflage" in chromatically rich environments still remains. [colour]technorati tags: cuttlefish, color, colour, experiment, checkerboard, blind, camouflage, visual
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| Comment on "Gene Regulatory Networks and the Evolution of Animal Body Plans" |
| 2006-08-11 01:28:05 |
Davidson and Erwin (Science Reviews, 10 February 2006, p. 796) argued that known microevolutionary processes cannot explain the evolution of large differences in development that characterize phyla. Instead, they proposed that phyla arise from novel evolutionary processes involving large mutations acting on conserved core pathways of development. I question some of their assumptions and show that natural selection adequately explains the origin of new phyla.(Jerry A. Coyne, Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA)See: Gene Regulatory Networks and the Evolution of Animal Body Planstechnorati tags: science, evolution, phyla, novel, evolutionary, processes, mutations, development, natural+selection, origin, ecology, chicago, university
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| New theory of environmental inheritance ('05 Press Release) |
| 2006-07-28 02:32:46 |
New research has provided evidence for 'environmental inheritance', a radical theory of transgenerational genetic adaptation proposed by Professor Marcus Pembrey of the Institute of Child Health, UCL in the mid 1990'sThe latest evidence challenges accepted thinking on genetic inheritance, suggesting that historic events can contribute to some common modern illnesses.The research, published by the Children of the 90s study based at the University of Bristol in collaboration with Umea University, Sweden, could have far-reaching implications for our understanding of modern health epidemics - such as obesity or cardiovascular disease.Conventionally scientists believe that how we develop as adults depends on two factors - the genes (DNA) we inherit from our parents, and the environmental influences, such as diet, lifestyle, exposure to pollution from conception onwards.Professor Marcus Pembrey, who is also head of Genetics at Children of the 90s, says that over the long term, the process of Darwinian evolution by random errors in DNA followed by natural selection ensures that the human race adapts to changes in our environment. But it takes very many generations.Now there is evidence for another mechanism which no-one had considered... some of the father's own experiences in his childhood are captured in some way by his sperm, so affecting the genes that he bequeaths to his descendants.[NB Although this is only a press release I've got at least one relevant technical paper which I'll be posting soon - when I find it!]14th December 2005technorati tags: research, theory, adaptation, marcus+pembrey, obesity, cardiovascular, disease, genes, dna, parents, diet, lifestyle, pollution, genetics, darwinian, evolution, natural+selection, environment, mechanism, sperm
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| Evolution: Bacterial Mutation in Stationary Phase |
| 2006-07-25 12:30:14 |
[After clicking on the above link, click on "Full Text"]Evolution: Bacterial Mutation in Stationary PhasePaul Sniegowski, Current Biology, March '04Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USAAbstract:A recent study indicates that the genomic mutation rate of the gut bacterium Escherichia coli is substantially higher in nongrowing than growing cultures. These findings are important in the light of the ongoing controversy over the generality and robustness of stationary phase mutagenesis and its evolutionary implications.Article Outline begins:The genomic mutation rate is a fundamental evolutionary parameter of any population, determining the rate of influx of new deleterious and beneficial alleles. Because most mutations are likely to be harmful to fitness, DNA repair and proofreading systems have probably evolved so as to minimize rates of mutation. Even the microbial extremophiles that normally inhabit harsh and potentially mutagenic environments seem to have low genomic mutation rates, suggesting that selection almost always puts a premium on the faithful maintenance and transmission of genetic information. Nonetheless, geneticists have long known that some environmental extremes can elevate mutation rates; indeed, this is the basis for the use of DNA damaging agents to induce mutations for study.[email if the link stops working]technorati tags: e.+coli, controversy, stationary, phase, mutagenesis, evolutionary, population, bacterium, alleles, dna, extremophiles, selection, mutations
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| The Changing Concept of Epigenetics (New York Academy of Sciences) |
| 2006-07-23 04:42:40 |
The Changing Concept of EpigeneticsAnnals of the New York Academy of Sciences, 981: 82-96. (2002)Eva Jablonka and Marion J. LambCohn Institute for the History and Philosophy of Science and Ideas, Tel Aviv University, Tel Aviv 69978, IsraelABSTRACT: We discuss the changing use of epigenetics, a term coined by Conrad Waddington in the 1940s, and how the epigenetic approach to development differs from the genetic approach. Originally, epigenetics referred to the study of the way genes and their products bring the phenotype into being. Today, it is primarily concerned with the mechanisms through which cells become committed to a particular form or function and through which that functional or structural state is then transmitted in cell lineages. We argue that modern epigenetics is important not only because it has practical significance for medicine, agriculture, and species conservation, but also because it has implications for the way in which we should view heredity and evolution. In particular, recognizing that there are epigenetic inheritance systems through which non-DNA variations can be transmitted in cell and organismal lineages broadens the concept of heredity and challenges the widely accepted gene-centered neo-Darwinian version of Darwinism.technorati tags: epigenetics, new+york, academy, jablonka, lamb, cohn, institute, genetic, genes, phenotype, cells, medicine, agriculture, heredity, evolution, inheritance, dna, darwinian, darwinism, tel+aviv
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| The Imaginary Lamarck (The Textbook Letter) |
| 2006-07-23 02:48:50 |
A Look at Bogus "History" in SchoolbooksMichael T. GhiselinJean-Baptiste de Lamarck (1744-1829) takes a prominent place in many biology textbooks and life-science textbooks, which depict him as the author of a "theory" of evolution based upon the inheritance of acquired characteristics. Lamarck's views, these books say, should be rejected in favor of the theory of evolution by natural selection, propounded by Charles Darwin (1809-1882), because only Darwin's theory is compatible with the findings of 20th-century genetics. The Lamarck presented in schoolbooks, however, is a fiction -- an imaginary figure who has been fashioned from hearsay and wrong guesses, and who has been replicated in countless books by successive teams of plagiarists. This figure ...
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| Darwinism's Rules of Reasoning: Phillip Johnson on Pierre Grasse |
| 2006-07-22 17:14:41 |
From "Darwinism's Rules of Reasoning" (Chapter 1 of "Darwinism: Science or Philosophy") by Phillip Johnson:"MY STARTING POINT is a book review that Theodosius Dobzhansky published in 1975, critiquing Pierre Grasse's The Evolution of Life.{1} Grasse, an eminent French zoologist, believed in something that he called "evolution." So did Dobzhansky, but when Dobzhansky used that term he meant neo-Darwinism, evolution propelled by random mutation and guided by natural selection. Grasse used the same term to refer to something very different, a poorly understood process of transformation in which one general category (like reptiles) gave rise to anot...
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| Epigenetic germline inheritance |
| 2006-07-20 03:23:09 |
Our increased knowledge of epigenetic reprogramming supports the idea that epigenetic marks are not always completely cleared between generations. Incomplete erasure at genes associated with a measurable phenotype can result in unusual patterns of inheritance from one generation to the next. It is also becoming clear that the establishment of epigenetic marks during development can be influenced by environmental factors. In combination, these two processes could provide a mechanism for a rapid form of adaptive evolution.Current Opinion in Genetics and DevelopmentChong S, Whitelaw ESchool of Molecular and Microbial Biosciences, Biochemistry Building-G08, University of Sydney, New South Wales 2006, Australia.technorati tags: epigenetic, genes, phenotype, inheritance, genetics, development, evolution, university, sydney, australia
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| The Killer Rat-Kangaroo's Tooth |
| 2006-03-23 03:53:11 |
"Natural selection didn't come up with the best design; it just made the best of what was available.The 'hand' of the Giant Panda (Ailuropoda melanoleuca) has six 'digits'. In processing its staple diet of bamboo, the Giant Panda drags the stalks between its sixth 'digit' and its paw to strip off the leaves. This sixth 'digit' or 'thumb' is a curious device. It is not, as one might expect, simply an additional finger of the type sometimes produced through congenital defect. In fact, the Panda's 'thumb' is not a real digit at all, but a greatly enlarged and specialised wrist bone called the radial sesamoid that lacks much of the flexibility of true digits. Why, one might wonder, did the Panda evolve a 'thumb' out of a wrist bone when it already had a 'real' thumb?Evolution can be a fickle and opportunistic process. Often the end result can appear surprisingly imperfect, even 'sloppy'. The bottom line is that, at any juncture in its evolution, a species is constrained by accidents of history. When 'fashioning' new adaptations, natural selection can only work with what it's got. Because the real thumb (the first digit) of the Giant Panda was already modified and in use for another task (for walking on), evolution could only work with what was available, in this case, a radial sesamoid bone. It is this very fact of imperfection that underpins the reality of natural selection."A pdf version is available heretechnorati tags: natural+selection, giant+panda, panda, evolution, thumb
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| The Genetics of Hearing and Balance in Zebrafish |
| 2006-03-19 11:44:13 |
Annual Review of GeneticsVol. 39: 9-22 (Volume publication date December 2005)The Genetics of Hearing and Balance in ZebrafishTeresa NicolsonOregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239Abstract:The zebrafish is an excellent model system for studying the molecular basis of inner ear development and function. The eggs develop ex utero and the ear is transparent for the first few weeks of life. Forward genetic screens and antisense technology have helped to elucidate the signaling pathways and molecules required for inner ear development and function. This review addresses the most recent advances in our understanding of how the ear forms and discusses the molecules in hair cells that are essential for sensing sound and movement in the zebrafish.[This item has been included because a post on the lateral line and the proposed internal evolutionary mechanism will eventually appear in the Personal Posts category of this weblog]technorati tags: lateral+line, zebrafish, genetics, ear, weblog
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| Re: The evolution of adaptations (Waddington) (MB) |
| 2006-03-18 08:26:26 |
On tuesday Waddington's "The Evolution of adaptations" (link goes to the paper itself) appeared on the Main Blog and since then 3 commentaries have been added to the Personal Posts category:Re: The evolution of adaptations (Waddington) (1)The reigning modern view is that, in nature, the direction of mutational change is entirely at random, and that adaptation results solely from the natural selection of mutations which happen to give rise to individuals with suitable characteristics. I want to argue that this theory is an extremist oneBrief comments on the intellectual strategy used to reduce an initially 'incredible' possibility (derived from the above quote) to a far more 'credible' one.Re: The evolution of adaptations (Waddington) (2)Describes how ostrich callosities could have become hereditary from the perspective of the proposed internal evolutionary mechanism.Re: The evolution of adaptations (Waddington) (3)Waddington only refers to the callosities found "fore and aft" on the underside of the body.The ostrich also has callosities on the ankle and the proposed mechanism shows why these have 'persisted' even though they "are of no use" (further indicating the proposed mechanism has no connection with such outmoded concepts as "The Law of Use and Disuse).John Lattertechnorati tags: internal+evolutionary+mechanism, waddington, ostrich, nature, random, theory, strategy
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| Darwinism Design and Purpose: A European Perspective |
| 2006-03-16 02:23:46 |
Paper Title: Darwinism Design and Purpose: A European PerspectiveAuthor: Jean StauneInstitutional Affiliation: General Secretary, Université Interdiciplinare de Paris(This paper was prepared for "Science and Religion: Global Perspectives" June 4-8,2005, in Philedelphia, PA, USA , a program of the Metanexus InstituteAbstract:In the USA 'Issues in Biology and Religion' usually implies a debate between neo- Darwinians and Creationists or, more recently, the Intelligent Design movement. In Europe, however, the situation is somewhat different since no one really believes in creationism anymore and Intelligent Design is unheard of. Consequently the debate is completely different. It is a...
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| Evolution Of Morphological Integration: Developmental Accommodation Of Stress-induced Variation |
| 2006-03-15 06:18:29 |
Contents:1) Press ReleaseStress is a major factor in evolution, but for stress-induced modifications to have evolutionary importance they have to be inherited and persist in a sufficient number of individuals within a population. This requires an organism to survive stress and reproduce at least once; thus stress-induced variation has to be accommodated by an organism without much reduction in its functionality. How is such accommodation accomplished?In an article in the September issue of The American Naturalist, Alexander V. Badyaev (University of Arizona) and colleagues show that complexity and cohesiveness of foraging structures of shrews enables accommodation of stress-induc...
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| The evolution of adaptations (Waddington) |
| 2006-03-14 08:55:50 |
Endeavour 134-139 (July 1953)The evolution of adaptationsC. H. WADDINGTONCurrent biological belief regards evolution as being primarily the result of the natural selection of random mutations, useful adaptations gradually spreading throughout a race. Professor Waddington regards this as an 'extreme view, and in this article puts forward a hypothesis to explain how acquired characteristics may become hereditarily fixed by a process of genetic assimilation not invoking the generally discredited theory of direct inheritance.It is abundantly found in the living world that the structure of an animal or plant is very precisely adapted to the functions which it has to perform. The nature of the processes by which this situation has been brought about during ev...
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| Common objections to 'Internal Evolutionary Mechanisms' (2) |
| 2006-03-14 08:49:57 |
5) Internal Mechanisms are 'directional' (objections 1 to 4 are here)The mathematical model currently used is very basic so an explanation of why the proposed homeostatic internal evolutionary mechanism isn't 'directional' has initially been posted to the Personal Posts category:"An Internal Evolutionary Mechanism and 'Direction in Evolution': Preliminary Notes"John Lattertechnorati tags: internal, evolutionary, mechanism
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| The fall and rise of Dr. Pangloss: Adaptationism and the Spandrels Paper 20 years later |
| 2006-03-13 04:31:31 |
[Pigliucci & Kaplan, Trends in Ecology and Evolution, '00]"Twenty years have passed since Gould and Lewontin published their critique of 'the adaptationist program' - the tendency of some evolutionary biologists to assume, rather than demonstrate, the operation of natural selection. After the 'Spandrels paper', evolutionists were more careful about producing just-so stories based on selection, and paid more attention to a panoply of other processes. Then came reactions against the excesses of the anti-adaptationist movement, which ranged from a complete dismissal of Gould and Lewontin's contribution to a positive call to overcome the problems. We now have an excellent opportunity for finally affirming a more balanced and pluralistic approach to the study of evolutionary biology."See:""The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme"STEPHEN JAY GOULD AND RICHARD C. LEWONTINAn adaptationist programme has dominated evolutionary thought in england and the united states during the past forty years. It is based on faith in the power of natural selection as an optimizing agent. It proceeds by breaking an organism into unitary 'traits' and proposing an adaptive story for each considered separately... technorati tags: spandrels, biology, natural+selection, evolution, traits, ecology
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| Mutation and adaptation: the directed mutation controversy in evolutionary perspective |
| 2006-03-12 13:02:26 |
[Lenski & Sniegowski, Annual Review of Systematics, Nov '95]Abstract:A central tenet of evolutionary theory is that mutation is random with respect to its adaptive consequences for individual organisms; that is, the production of variation precedes and does not cause adaptation. Several recent experimental reports have challenged this tenet by suggesting that bacteria (and yeast) ''may have mechanisms for choosing which mutations will occur'' (6, p. 142). The phenomenon of nonrandom mutation claimed in these experiments was initially called ''directed mutation'' but has undergone several name changes during its brief and controversial history. The directed mutation hypothesis has not fared well; many examples of ap...
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