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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 marine iguanas as a model system where body size differs by more than one order of magnitude between island ...
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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 evolutionary responses, in which a population of genomes continually updates its e...
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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 genomic imprinting has played over the course of mammalian evolution, but at present it is not clear if a single hypothesis can fully account for the diversity of roles that imprinted genes play. In this review, we discuss effo...
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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 with bird jaw tissue, the bird tissue is able to follow the instructions given by the mouse tissue and partici...
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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 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 mouse affects the health of not only her pups, but also their pups - her grandchildren.The study will be published in the November issue of the Proceedin...
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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 - varies considerably among vertebrates (homology of form does not require homology of development) and was possibly co-opted from a preexisting asy...
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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 developmental biology that is revitalizing and providing answers to old and important questions involving the formation of b...
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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). I want in this essay to revisit Behe's concept of irreducible complexity and indicate wh...
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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 development, environment and genetics by articulating the concept of "developmental reaction norms"......Jablonka and La...
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