Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population, it is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules. The scientific theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book On the Origin of Species. Evolution by natural selection was first demonstrated by the observation that more offspring are produced than can survive.
This is followed by three observable facts about living organisms: 1) traits vary among individuals with respect to their morphology and behaviour, 2) different traits confer different rates of survival and reproduction and 3) traits can be passed from generation to generation. Thus, in successive generations members of a population are more to be replaced by the progenies of parents with favourable characteristics that have enabled them to survive and reproduce in their respective environments. In the early 20th century, other competing ideas of evolution such as mutationism and orthogenesis were refuted as the modern synthesis reconciled Darwinian evolution with classical genetics, which established adaptive evolution as being caused by natural selection acting on Mendelian genetic variation. All life on Earth shares a last universal common ancestor that lived 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, to fossilised multicellular organisms.
Existing patterns of biodiversity have been shaped by repeated formations of new species, changes within species and loss of species throughout the evolutionary history of life on Earth. Morphological and biochemical traits are more similar among species that share a more recent common ancestor, can be used to reconstruct phylogenetic trees. Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology, their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture and computer science. The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles; such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura.
In contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms. This was part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and gave examples of how new types of living things could come to be. In the 17th century, the new method of modern science rejected the Aristotelian approach, it sought explanations of natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types.
John Ray applied one of the more general terms for fixed natural types, "species," to plant and animal types, but he identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan. Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species. Georges-Louis Leclerc, Comte de Buffon suggested that species could degenerate into different organisms, Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism; the first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809, which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents.
These ideas were cond
Research comprises "creative and systematic work undertaken to increase the stock of knowledge, including knowledge of humans and society, the use of this stock of knowledge to devise new applications." It is used to establish or confirm facts, reaffirm the results of previous work, solve new or existing problems, support theorems, or develop new theories. A research project may be an expansion on past work in the field. Research projects can be used to develop further knowledge on a topic, or in the example of a school research project, they can be used to further a student's research prowess to prepare them for future jobs or reports. To test the validity of instruments, procedures, or experiments, research may replicate elements of prior projects or the project as a whole; the primary purposes of basic research are documentation, interpretation, or the research and development of methods and systems for the advancement of human knowledge. Approaches to research depend on epistemologies, which vary both within and between humanities and sciences.
There are several forms of research: scientific, artistic, social, marketing, practitioner research, technological, etc. The word research is derived from the Middle French "recherche", which means "to go about seeking", the term itself being derived from the Old French term "recerchier" a compound word from "re-" + "cerchier", or "sercher", meaning'search'; the earliest recorded use of the term was in 1577. Research has been defined in a number of different ways, while there are similarities, there does not appear to be a single, all-encompassing definition, embraced by all who engage in it. One definition of research is used by the OECD, "Any creative systematic activity undertaken in order to increase the stock of knowledge, including knowledge of man and society, the use of this knowledge to devise new applications."Another definition of research is given by John W. Creswell, who states that "research is a process of steps used to collect and analyze information to increase our understanding of a topic or issue".
It consists of three steps: pose a question, collect data to answer the question, present an answer to the question. The Merriam-Webster Online Dictionary defines research in more detail as "studious inquiry or examination; this material is of a primary source character. The purpose of the original research is to produce new knowledge, rather than to present the existing knowledge in a new form. Original research can take a number of forms, depending on the discipline. In experimental work, it involves direct or indirect observation of the researched subject, e.g. in the laboratory or in the field, documents the methodology and conclusions of an experiment or set of experiments, or offers a novel interpretation of previous results. In analytical work, there are some new mathematical results produced, or a new way of approaching an existing problem. In some subjects which do not carry out experimentation or analysis of this kind, the originality is in the particular way existing understanding is changed or re-interpreted based on the outcome of the work of the researcher.
The degree of originality of the research is among major criteria for articles to be published in academic journals and established by means of peer review. Graduate students are required to perform original research as part of a dissertation. Scientific research is a systematic way of harnessing curiosity; this research provides scientific information and theories for the explanation of the nature and the properties of the world. It makes practical applications possible. Scientific research is funded by public authorities, by charitable organizations and by private groups, including many companies. Scientific research can be subdivided into different classifications according to their academic and application disciplines. Scientific research is a used criterion for judging the standing of an academic institution, but some argue that such is an inaccurate assessment of the institution, because the quality of research does not tell about the quality of teaching. Research in the humanities involves different methods such as for example hermeneutics and semiotics.
Humanities scholars do not search for the ultimate correct answer to a question, but instead, explore the issues and details that surround it. Context is always important, context can be social, political, cultural, or ethnic. An example of research in the humanities is historical research, embodied in historical method. Historians use primary sources and other evidence to systematically investigate a topic, to write histories in the form of accounts of the past. Other studies aim to examine the occurrence of behaviours in societies and communities, without looking for reasons or motivations to explain these; these studies may be qualitative or quantitative, can use a variety of approaches, such as queer theory or feminist theory. Artistic research seen as'practice-based research', can take form when creative works are considered both the research and the object of research itself, it is the debatable body of thought which offers an alternative t
Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms and evolution. Despite the complexity of the science, there are certain unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, evolution as the engine that propels the creation and extinction of species. Living organisms are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis. Sub-disciplines of biology are defined by the research methods employed and the kind of system studied: theoretical biology uses mathematical methods to formulate quantitative models while experimental biology performs empirical experiments to test the validity of proposed theories and understand the mechanisms underlying life and how it appeared and evolved from non-living matter about 4 billion years ago through a gradual increase in the complexity of the system.
See branches of biology. The term biology is derived from the Greek word βίος, bios, "life" and the suffix -λογία, -logia, "study of." The Latin-language form of the term first appeared in 1736 when Swedish scientist Carl Linnaeus used biologi in his Bibliotheca botanica. It was used again in 1766 in a work entitled Philosophiae naturalis sive physicae: tomus III, continens geologian, phytologian generalis, by Michael Christoph Hanov, a disciple of Christian Wolff; the first German use, was in a 1771 translation of Linnaeus' work. In 1797, Theodor Georg August Roose used the term in the preface of a book, Grundzüge der Lehre van der Lebenskraft. Karl Friedrich Burdach used the term in 1800 in a more restricted sense of the study of human beings from a morphological and psychological perspective; the term came into its modern usage with the six-volume treatise Biologie, oder Philosophie der lebenden Natur by Gottfried Reinhold Treviranus, who announced: The objects of our research will be the different forms and manifestations of life, the conditions and laws under which these phenomena occur, the causes through which they have been effected.
The science that concerns itself with these objects we will indicate by the name biology or the doctrine of life. Although modern biology is a recent development, sciences related to and included within it have been studied since ancient times. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, the Indian subcontinent, China. However, the origins of modern biology and its approach to the study of nature are most traced back to ancient Greece. While the formal study of medicine dates back to Hippocrates, it was Aristotle who contributed most extensively to the development of biology. Important are his History of Animals and other works where he showed naturalist leanings, more empirical works that focused on biological causation and the diversity of life. Aristotle's successor at the Lyceum, wrote a series of books on botany that survived as the most important contribution of antiquity to the plant sciences into the Middle Ages. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz, Al-Dīnawarī, who wrote on botany, Rhazes who wrote on anatomy and physiology.
Medicine was well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew on Aristotelian thought in upholding a fixed hierarchy of life. Biology began to develop and grow with Anton van Leeuwenhoek's dramatic improvement of the microscope, it was that scholars discovered spermatozoa, bacteria and the diversity of microscopic life. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop the basic techniques of microscopic dissection and staining. Advances in microscopy had a profound impact on biological thinking. In the early 19th century, a number of biologists pointed to the central importance of the cell. In 1838, Schleiden and Schwann began promoting the now universal ideas that the basic unit of organisms is the cell and that individual cells have all the characteristics of life, although they opposed the idea that all cells come from the division of other cells. Thanks to the work of Robert Remak and Rudolf Virchow, however, by the 1860s most biologists accepted all three tenets of what came to be known as cell theory.
Meanwhile and classification became the focus of natural historians. Carl Linnaeus published a basic taxonomy for the natural world in 1735, in the 1750s introduced scientific names for all his species. Georges-Louis Leclerc, Comte de Buffon, treated species as artificial categories and living forms as malleable—even suggesting the possibility of common descent. Although he was opposed to evolution, Buffon is a key figure in the history of evolutionary thought. Serious evolutionary thinking originated with the works of Jean-Baptiste Lamarck, the first to present a coherent theory of evolution, he posited that evolution was the result of environmental stress on properties of animals, meaning that the more and rigorously an organ was used, the more complex and efficient it would become, thus adapting the animal to its environment. Lamarck believed that these acquired traits could be passed on to the animal's offspring, who would
Gerd B. Müller
Gerd B. Müller is an Austrian biologist, professor at the University of Vienna where he heads the Department of Theoretical Biology in the Center for Organismal Systems Biology, his research interests focus on vertebrate limb development, evolutionary novelties, evo-devo theory, the Extended Evolutionary Synthesis. He is concerned with the development of 3D based imaging tools in developmental biology. Müller received an M. D. in 1979 and a Ph. D. in zoology in 1985, both from the University of Vienna. He has been a sabbatical fellow at the Department of Developmental Biology, Dalhousie University, a visiting scholar at the Museum of Comparative Zoology, Harvard University, received his Habilitation in Anatomy and Embryology in 1989, he is a founding member of the Konrad Lorenz Institute for Evolution and Cognition Research, Austria, of which he has been President since 1997. Müller is on the editorial boards of several scientific journals, including Biological Theory where he serves as an Associate Editor.
He is editor-in-chief of the Vienna Series in Theoretical Biology, a book series devoted to theoretical developments in the biosciences, published by MIT Press. Müller has published on developmental imaging, vertebrate limb development, the origins of phenotypic novelty, EvoDevo theory, evolutionary theory. With the cell and developmental biologist Stuart Newman, Müller co-edited the book Origination of Organismal Form; this book on evolutionary developmental biology is a collection of papers on generative mechanisms that were plausibly involved in the origination of disparate body forms during early periods of organismal life. Particular attention is given to epigenetic factors, such as physical determinants and environmental parameters, that may have led to the spontaneous emergence of bodyplans and organ forms during a period when multicellular organisms had plastic morphologies. Natural selection acting on variant genotypes is suggested to have "locked in" these bodyplans. Together with Eva Jablonka, Kevin Laland, Alex Mesoudi, Stuart Newman, Massimo Pigliucci, Kim Sterelny, John Odling-Smee, Tobias Uller, as well as Denis Noble and others, Gerd Müller is an advocate of an alternative evolutionary framework, one version of, termed the Extended Evolutionary Synthesis.
In contrast to the Modern Synthesis, the population dynamical model of evolution established in the early twentieth century that had concentrated on the processes of variation and adaptation, the focus of the EES is on the generative properties of evolution, integrating conceptual developments from evolutionary developmental biology, genomics and other fields. It differs from the standard theory in its inclusion of the constructive processes in development, the consideration of reciprocal dynamics of causation, the relinquishment of a predominantly genetic explanation. A range of novel predictions and testable empirical projects result from the EES. Scientific papers ResearchGateEdited books Evolution – The Extended Synthesis Modeling Biology Environment and Evolution: Towards a Synthesis Origination of Organismal Form Selected articles Axel Lange and Gerd B. Müller. Polydactyly in Development and Evolution. Q. Rev. Biol. Vol. 92, No. 1, Mar. 2017, pp. 1–38. Doi: 10.1086/690841. Favé M-J, Johnson RA, Cover S, Handschuh S, Metscher BD, Müller GB, Gopalan S, Abouheif E. 2015.
Past climate change on Sky Islands drives novelty in a core developmental gene network and its phenotype. BMC Evolutionary Biology:1–21. Doi: 10.1186/s12862-015-0448-4. Laland KN, Uller T, Feldman MW, Sterelny K, Müller GB, Moczek A, Jablonka E, Odling-Smee J. 2015. The Extended Evolutionary Synthesis: Its structure and predictions. Proc Biol Sci 282. Doi: 10.1098/rspb.2015.1019. Noble D, Jablonka E, Joyner MJ, Müller GB, Omholt SW. 2014. Evolution evolves: Physiology returns to centre stage. J Physiol 592:2237–2244. #REDIRECT doi: 10.1113/jphysiol.2014.273151. Mayer C, Metscher BD, Müller GB, Mitteroecker P. 2014. Studying developmental variation with geometric morphometric image analysis. PLoS ONE 9:e115076. Doi: 10.1371/journal.pone.0115076. Lange A, Nemeschkal HL, Müller GB. 2014. Biased polyphenism in polydactylous cats carrying a single point mutation: The Hemingway model for digit novelty. Evol Biol 41:262–275. Doi:10.1007/s11692-013-9267-y. Čapek D, Metscher BD, Müller GB. 2013. Thumbs down: A molecular-morphogenetic approach to avian digit homology.
J Exp Zool B Mol Dev Evol 322:1–12. Doi: 10.1002/jez.b.22545. Peterson T, Müller GB. 2013. What is evolutionary novelty? Process versus character based definitions. J Exp Zool B Mol Dev Evol 320:345–350. Doi: 10.1002/jez.b.22508. Epub 2013 Jun 21. Metscher BD, Müller GB. 2011. MicroCT for molecular imaging: Quantitative visualization of complete three-dimensional distributions of gene products in embryonic limbs. Dev Dyn 240:2301–2308. Doi: 10.1002/dvdy.22733. Müller GB. 2008. Evo-devo as a discipline. In: Minelli A, Fusco G, editors. Evolving Pathways: Key Themes in Evolutionary Developmental Biology. Cambridge: Cambridge University Press. Müller GB. 2007. Evo-devo: Extending the evolutionary synthesis. Nat Rev Genet 8:943–949. Doi:10.1038/nrg2219. Müller GB, Newman SA. 2005. The innovation triad: An EvoDevo agenda. J Exp Zool B Mol Dev Evol 304:487–503. Doi: 10.1002/jez.b.21081. Personal homepage Gerd B. Müller Department of Theoretical Biology, University of Vienna Konrad Lorenz Institute for Evolution and Cognition Research Does evolutionary theory need a rethink?
Modernizing the Evolutionary Synthesis. Science 321 Postmodern Ev
In the fields of molecular biology and genetics, a genome is the genetic material of an organism. It consists of DNA; the genome includes both the genes and the noncoding DNA, as well as mitochondrial DNA and chloroplast DNA. The study of the genome is called genomics; the term genome was created in 1920 by Hans Winkler, professor of botany at the University of Hamburg, Germany. The Oxford Dictionary suggests the name is a blend of the words chromosome. However, see omics for a more thorough discussion. A few related -ome words existed, such as biome and rhizome, forming a vocabulary into which genome fits systematically. A genome sequence is the complete list of the nucleotides that make up all the chromosomes of an individual or a species. Within a species, the vast majority of nucleotides are identical between individuals, but sequencing multiple individuals is necessary to understand the genetic diversity. In 1976, Walter Fiers at the University of Ghent was the first to establish the complete nucleotide sequence of a viral RNA-genome.
The next year, Fred Sanger completed the first DNA-genome sequence: Phage Φ-X174, of 5386 base pairs. The first complete genome sequences among all three domains of life were released within a short period during the mid-1990s: The first bacterial genome to be sequenced was that of Haemophilus influenzae, completed by a team at The Institute for Genomic Research in 1995. A few months the first eukaryotic genome was completed, with sequences of the 16 chromosomes of budding yeast Saccharomyces cerevisiae published as the result of a European-led effort begun in the mid-1980s; the first genome sequence for an archaeon, Methanococcus jannaschii, was completed in 1996, again by The Institute for Genomic Research. The development of new technologies has made genome sequencing cheaper and easier, the number of complete genome sequences is growing rapidly; the US National Institutes of Health maintains one of several comprehensive databases of genomic information. Among the thousands of completed genome sequencing projects include those for rice, a mouse, the plant Arabidopsis thaliana, the puffer fish, the bacteria E. coli.
In December 2013, scientists first sequenced the entire genome of a Neanderthal, an extinct species of humans. The genome was extracted from the toe bone of a 130,000-year-old Neanderthal found in a Siberian cave. New sequencing technologies, such as massive parallel sequencing have opened up the prospect of personal genome sequencing as a diagnostic tool, as pioneered by Manteia Predictive Medicine. A major step toward that goal was the completion in 2007 of the full genome of James D. Watson, one of the co-discoverers of the structure of DNA. Whereas a genome sequence lists the order of every DNA base in a genome, a genome map identifies the landmarks. A genome map is less detailed than aids in navigating around the genome; the Human Genome Project was organized to sequence the human genome. A fundamental step in the project was the release of a detailed genomic map by Jean Weissenbach and his team at the Genoscope in Paris. Reference genome sequences and maps continue to be updated, removing errors and clarifying regions of high allelic complexity.
The decreasing cost of genomic mapping has permitted genealogical sites to offer it as a service, to the extent that one may submit one's genome to crowdsourced scientific endeavours such as DNA. LAND at the New York Genome Center, an example both of the economies of scale and of citizen science. Viral genomes can be composed of either RNA or DNA; the genomes of RNA viruses can be either single-stranded or double-stranded RNA, may contain one or more separate RNA molecules. DNA viruses can have either double-stranded genomes. Most DNA virus genomes are composed of a single, linear molecule of DNA, but some are made up of a circular DNA molecule. Prokaryotes and eukaryotes have DNA genomes. Archaea have a single circular chromosome. Most bacteria have a single circular chromosome. If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and partially replicated chromosomes.
Most prokaryotes have little repetitive DNA in their genomes. However, some symbiotic bacteria have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins; some bacteria have auxiliary genetic material part of their genome, carried in plasmids. For this, the word genome should not be used as a synonym of chromosome. Eukaryotic genomes are composed of one or more linear DNA chromosomes; the number of chromosomes varies from Jack jumper ants and an asexual nemotode, which each have only one pair, to a fern species that has 720 pairs. A typical human cell has two copies of each of 22 autosomes, one inherited from each parent, plus two sex chromosomes, making it diploid. Gametes, such as ova, sperm and pollen, are haploid, meaning they carry only one copy of each chromosome. In addition to the chromosomes in the nucleus, organelles such as the chloroplasts and mitochondria have their own DNA. Mitochondria are sometimes said to have their own genome referred to as the "mitochondrial genome".
The DNA found within the chloroplast may be referred to as the "plastome". Like the bacteria they originated from and chloroplasts have a circular chromosome
The Cambrian explosion or Cambrian radiation was an event 541 million years ago in the Cambrian period when most major animal phyla appeared in the fossil record. It lasted for about 20–25 million years and resulted in the divergence of most modern metazoan phyla; the event was accompanied by major diversification of other organisms. Before the Cambrian explosion, most organisms were simple, composed of individual cells organized into colonies; as the rate of diversification subsequently accelerated, the variety of life began to resemble that of today. All present animal phyla appeared during this period; the rapid appearance of fossils in the "Primordial Strata" was noted by William Buckland in the 1840s, in his 1859 book On the Origin of Species, Charles Darwin discussed the inexplicable lack of earlier fossils as one of the main difficulties for his theory of descent with slow modification through natural selection. The long-running puzzlement about the appearance of the Cambrian fauna abruptly, without precursor, centers on three key points: whether there was a mass diversification of complex organisms over a short period of time during the early Cambrian.
Interpretation is difficult due to a limited supply of evidence, based on an incomplete fossil record and chemical signatures remaining in Cambrian rocks. The first discovered Cambrian fossils were trilobites, described by Edward Lhuyd, the curator of Oxford Museum, in 1698. Although their evolutionary importance was not known, on the basis of their old age, William Buckland realised that a dramatic step-change in the fossil record had occurred around the base of what we now call the Cambrian. Nineteenth-century geologists such as Adam Sedgwick and Roderick Murchison used the fossils for dating rock strata for establishing the Cambrian and Silurian periods. By 1859, leading geologists including Roderick Murchison, were convinced that what was called the lowest Silurian stratum showed the origin of life on Earth, though others, including Charles Lyell, differed. In On the Origin of Species, Charles Darwin considered this sudden appearance of a solitary group of trilobites, with no apparent antecedents, absence of other fossils, to be "undoubtedly of the gravest nature" among the difficulties in his theory of natural selection.
He reasoned that earlier seas had swarmed with living creatures, but that their fossils had not been found due to the imperfections of the fossil record. In the sixth edition of his book, he stressed his problem further as: To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the Cambrian system, I can give no satisfactory answer. American paleontologist Charles Walcott, who studied the Burgess Shale fauna, proposed that an interval of time, the "Lipalian", was not represented in the fossil record or did not preserve fossils, that the ancestors of the Cambrian animals evolved during this time. Earlier fossil evidence has since been found; the earliest claim is that the history of life on earth goes back 3,850 million years: Rocks of that age at Warrawoona, were claimed to contain fossil stromatolites, stubby pillars formed by colonies of microorganisms. Fossils of more complex eukaryotic cells, from which all animals and fungi are built, have been found in rocks from 1,400 million years ago, in China and Montana.
Rocks dating from 580 to 543 million years ago contain fossils of the Ediacara biota, organisms so large that they are multicelled, but unlike any modern organism. In 1948, Preston Cloud argued that a period of "eruptive" evolution occurred in the Early Cambrian, but as as the 1970s, no sign was seen of how the'relatively' modern-looking organisms of the Middle and Late Cambrian arose; the intense modern interest in this "Cambrian explosion" was sparked by the work of Harry B. Whittington and colleagues, who, in the 1970s, reanalysed many fossils from the Burgess Shale and concluded that several were as complex as, but different from, any living animals; the most common organism, was an arthropod, but not a member of any known arthropod class. Organisms such as the five-eyed Opabinia and spiny slug-like Wiwaxia were so different from anything else known that Whittington's team assumed they must represent different phyla unrelated to anything known today. Stephen Jay Gould's popular 1989 account of this work, Wonderful Life, brought the matter into the public eye and raised questions about what the explosion represented.
While differing in details, both Whittington and Gould proposed that all modern animal phyla had appeared simultaneously in a rather short span of geological period. This view led to the modernization of Darwin's tree of life and the theory of punctuated equilibrium, which Eldredge and Gould developed in the early 1970s and which views evolution as long intervals of near-stasis "punctuated" by short periods of rapid change. Other analyses, some more recent and some dating back to the 1970s, argue that complex animals similar to modern types evolved well before the start of the Cambrian. Radiometric dates for much of the Cambrian, obtained by analysis of radioactive elements contained within rocks, have only become available, for only a few regions. Relative dating is assumed sufficient for studying processes of evolution, but this, has been difficult, because of the problems involved in matching up rocks of the same age across different continents. Therefore, dates or descriptions of sequences of events should be regarded with some caution until better data become
Günter P. Wagner
Günter P. Wagner is Alison Richard Professor of Ecology and Evolutionary biology at Yale University, head of the Wagner Lab. After undergraduate education in chemical engineering, Wagner studied zoology and mathematical logic at the University of Vienna, Austria. During his graduate study, Wagner worked with the Viennese zoologist Rupert Riedl and the theoretical chemist Peter Schuster, finished his PhD in theoretical population genetics in 1979. Wagner conducted postdoctoral research at Max Planck Institutes in Göttingen and Tübingen, as well as at the University of Göttingen. Wagner began his academic career as assistant professor in the Theoretical Biology Department of the University of Vienna in 1985. In 1991, he moved to Yale University as a full professor of biology and has served as the first chair of Yale's Department of Ecology and Evolution 1997-2002 and 2005-2008; the focus of Wagner's work is on the evolution of complex characters. His research utilizes both the theoretical tools of population genetics as well as experimental approaches in evolutionary developmental biology.
Wagner has contributed to the current understanding of evolvability of complex organisms, the origin of novel characters, modularity. Wagner's early work was focused on mathematical population genetics. Together with the mathematician Reinhard Bürger at the University of Vienna, he contributed to the theory of mutation-selection balance and the evolution of dominance modifiers. Wagner shifted his focus on issues of the evolution of variational properties like canalization and modularity, he introduced the seminal distinction between variation and variability, the former describing the existing differences among individuals while the latter measures the tendency to vary, as measured in mutation rate and mutational variance. He published the first mathematical model for the evolution of genetic canalization, thus contributed to the renaissance of studies of canalization in the mid 1990s, his more recent work is on the measurement of gene interaction, the evolution of evolvability and how it relates to the evolution of genetic architecture.
With the advent of comparative developmental genetics in the early 1991 Wagner's research program shifted towards the molecular evolution of developmental genes Hox genes and Hox gene clusters. The Wagner lab was the first to identify major blocks of ultraconserved non-coding sequences in the intergenic regions between Hox genes, dated the “fish-specific” Hox cluster duplication to nearly coincide with the most recent common ancestor of Teleostei fish; this work led to the theory that Hox cluster and genome duplications create a window of opportunity which, if coincidental with ecological changes, can lead to the fixation of these genes and novel gene functions. In recent years the Wagner lab has focussed on the evolution of gene regulatory networks, in particular the role of transcription factor protein evolution in evolutionary innovation. In August 2016, an article by Wagner and Mihaela Pavlicev, gained attention for proposing a possible evolutionary connection between the female orgasm in humans and ovulation induced by copulation in other mammals.
A key conceptual and mechanistic problem in evolutionary biology is the nature of character identity, aka homology. Wagner was an early proponent of a mechanistic understanding of homology, together with Louise Roth at Duke University and Gerd Müller at the University of Vienna. A test case for this approach arose when Wagner and his colleague Jacques Gauthier proposed a solution of the century old problem of the identity of avian digits; the core of the problem is that the three digits in the bird wing have the morphology of digits 1, 2, 3, but develop from the digit condensations 2, 3, 4, which according to some shows that they should be digits 2, 3, 4. Wagner and Gauthier proposed that during the evolution of theropod dinosaurs, the closest relatives of birds, digits have "changed place" so that in the bird wing digit 1 develops from position 2 and digit 2 from position 3 and digit 3 from position 4 in the wing bud; this view is now supported by molecular and experimental evidence and shows how mechanistic insights can solve intractable conceptual problems.
According to Wagner the homology concept has that of innovation. While homology refers to the historical continuity of character identity, the term innovation refers to the origin of novel characters, i.e. the origin of novel homologues. Therefore, Wagner and Müller argue that the origin and maintenance of character identity is a central goal of evolutionary developmental biology. Günter Wagner is recipient of numerous awards, among them the prestigious MacArthur Prize in 1992, the Bobby Murcer Prize in 2001, the Humboldt Prize in 2007, he received nominations as Gomperz Lecturer, University of California, Berkeley 1993. He is a corresponding Member of Austrian Academy of Sciences, a Fellow of the American Association for the Advancement of Science, a Fellow of the American Academy of Arts and Sciences, he was elected to the National Academy of Sciences in 2018. Wagner has published numerous book chapters and more than 270 scientific articles. Books The Character Concept in Evolutionary Biology, Academic Press.
2000 Modularity in Development and Evolution, University of Chicago Press, 2004 Morphology and the Evolution of Development, Yale University Press. 2007 Homology and Evolutionary Innovation. Princeton University Press. 2014Articles ResearchGate Publication list Yale University Department of Ecology & Evolutionary Biology