Y con tanta ciencia una inútil ansia de tener lástima de algo, de que llueva aquí dentro, de que por fin empiece a llover, a oler a tierra, a cosas vivas, sí, por fin a cosas vivas.
Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve?, PLoS Biol
Excerpt: Throughout their evolutionary history, organisms have evolved numerous complex morphological, physiological, and behavioral adaptations to increase their chances of survival and reproduction. (...) The way that most of these and other adaptations first evolved, however, is still largely unknown. In the last two decades we have learned that novel traits appear to be built using old genes wired in novel ways [5], but it is still a mystery whether these novel traits evolve when genes are rewired de novo, one at a time, into new developmental networks, or whether clusters of pre-wired genes are co-opted into the development of the new trait. The speed of evolution of novel complex traits is likely to depend greatly on which of these two mechanisms underlies their origin. It is important, thus, to understand how novel complex traits evolve.
Neutrality and Robustness in Evo-devo: Emergence of Lateral Inhibition, SFI Working Papers
Abstract: Embryonic development is defined by the hierarchical dynamical process that translates genetic information (genotype) into a spatial gene expression pattern (phenotype) providing the positional information for the correct unfolding of the organism. The nature and evolutionary implications of genotype-phenotype mapping still remain key topics in evolutionary developmental biology (evo-devo). We have explored here issues of neutrality, robustness and diversity in evo-devo by means of a simple model of gene regulatory networks. The small size of the system allowed an exhaustive analysis of the entire fitness landscape and the extent of its neutrality. This analysis shows that evolution leads to a class of robust genetic networks with an expression pattern characteristic of lateral inhibition. This class is a repertoire of distinct implementations of this key developmental process, the diversity of whom provides valuable clues about its underlying causal principles.
Mutation Patterns in the Human Genome: More Variable Than Expected, PLoS Biol
Excerpt: The development, survival, and reproduction of an organism depend on the genetic information that is carried in its genome, yet the transmission of genetic information is not perfectly accurate: new mutations occur at each generation. These mutations are the primary cause of the genetic diversity on which natural selection can operate, and hence are the sine qua non of evolution. A better knowledge of mutation processes is crucial for investigating the causes of genetic diseases or cancer and for understanding evolutionary processes.
Excerpt: Traditionally evolution is seen as a process where from a pool of possible variations of a population (e.g. biological species or industrial goods) a few variations get selected which survive and proliferate, whereas the others vanish. Survival probability is typically associated with the fitness of a particular variation. In this paper we argue that the notion of fitness is an a posteriori concept, in the sense that one can assign higher fitness to species that survive but one can generally not derive or even measure fitness or fitness landscapes per se. For this reason we think that in a physical theory of evolution such notions should be avoided. In this spirit, here we propose a random matrix model of evolution where selection mechanisms are encoded in the interaction matrices of species. We are able to recover some key facts of evolution dynamics (...)
Excerpt: Consider two concepts of transcriptional regulation. In a "molecular autocracy," master genes respond to environmental or developmental stimuli by regulating thousands of genes, either directly or through other transcription factors. In a "molecular democracy," all genes exert a regulatory influence on all other genes, and phenotypic change (altered cell behavior) is brought about through the concerted action of thousands of genes. These scenarios are extreme and cells operate under a condition that is somewhere intermediate (see the figure) (1). But the choice of concept affects how regulation is studied.
Source:Attractors and Democratic Dynamics, Yaneer Bar-Yam, Dion Harmon, Benjamin de Bivort, DOI: 10.1126/science.1163225, Science Vol. 323. no. 5917, pp. 1016 - 1017, 2009/02/20
Excerpts: Since prehistoric times, left-handed individuals have been ubiquitous in human populations, exhibiting geographical frequency variations. Evolutionary explanations have been proposed for the persistence of the handedness polymorphism. (...) Data have suggested that left-handedness, as the rare hand preference, could represent an important strategic advantage in fighting interactions. However, the fact that left-handedness occurs at a low frequency indicates that some evolutionary costs could be associated with left-handedness. Overall, the evolutionary dynamics of this polymorphism are not fully understood. (...) We point out that hand preference is heritable, and report how hand preference is influenced by genetic, hormonal, developmental and cultural factors. (...)
...(no directamente por lo menos.) Un compilado del Complexity Digest:
How The Spider Spun Its Web: ‘Missing Link' In Spider Evolution Discovered, ScienceDaily
Excerpts: New interpretations of fossils have revealed an ancient missing link between today's spiders and their long-extinct ancestors. The research (...) may help explain how spiders came to weave webs. The research focuses on fossil animals called Attercopus fimbriunguis. While modern spiders make silk threads with modified appendages called spinnerets, the fossil animals wove broad sheets of silk from spigots on plates attached to the underside of their bodies. Unlike spiders, they had long tails. (...) caused the paleontologists to reinterpret their original findings. (...)
Historical and Philosophical Perspectives on Contemporary Biology, PLoS Biol
Excerpt: The work of historians and philosophers of science has long benefited from conversations with practicing scientists, but to many scientific researchers, perhaps especially to those engaged in laboratory work, the value that such dialogue might have for their own endeavor is not nearly so obvious. There are of course exceptions, evolutionary biology, for one. Over the last several decades, a tradition of active engagement between historians and philosophers on the one hand, and evolutionary biologists on the other, has become well established (...)
Excerpt: Two articles in this issue mark a substantial advance in our understanding of human population history in the Pacific area. On page 479, Gray et al. (1) report a computational linguistic analysis that offers a detailed and precise scenario for the dispersal and development of the Austronesian languages, and by implication of human populations among the Pacific islands. The authors come down decisively in favor of one of the two major models for the peopling of the Pacific. On page 527, Moodley et al. (2) come to the same conclusion as Gray et al. about the source and trajectory of spread of the human populations in question, based on results from a seemingly unrelated field: the archaeogenetics of human gastric bacterial parasites.
Abstract: Ever since the integration of Mendelian genetics into evolutionary biology in the early 20th century, evolutionary geneticists have for the most part treated genes and mutations as generic entities. However, recent observations indicate that all genes are not equal in the eyes of evolution. Evolutionarily relevant mutations tend to accumulate in hotspot genes and at specific positions within genes. Genetic evolution is constrained by gene function, the structure of genetic networks, and population biology. The genetic basis of evolution may be predictable to some extent, and further understanding of this predictability requires incorporation of the specific functions and characteristics of genes into evolutionary theory.
Source:Is Genetic Evolution Predictable?, David L. Stern and Virginie Orgogozo, DOI: 10.1126/science.1158997, Science Vol. 323. no. 5915, pp. 746 - 751, 2009/02/06
The evolution and distribution of species body size, arXiv
Abstract: The distribution of species body size within taxonomic groups exhibits a heavy right-tail extending over many orders of magnitude, where most species are significantly larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for inter-specific competition and other microevolutionary processes yet fully explains the shape of this distribution. We estimate the model's parameters from fossil data and find that it robustly reproduces the distribution of 4002 mammal species from the late Quaternary. The observed fit suggests that the asymmetric distribution arises from a fundamental tradeoff between the short-term selective advantages (Cope's rule) and long-term selective risks of increased species body size, in the presence of a taxon-specific lower limit on body size.
Excerpt: The rough draft of the Neandertal nuclear genome may usher in a brave new world of research on these extinct humans, but after 150 years of study, we already know a few things about them.
Source:A Neandertal Primer, Michael Balter, DOI: 10.1126/science.323.5916.870, Science Vol. 323. no. 5916, p. 870, 2009/02/13
Excerpt:Science is celebrating the 150th anniversary of the publication of Charles Darwin's On the Origin of Species and the 200th anniversary of the author's birth with a variety of news features, scientific reviews and other special content, all collected here.
Editor's Note: This article discusses cultural evolution, and how genes are not sufficient to understand how humanity evolved. Excerpt: Barely a decade after Charles Darwin published On the Origin of Species, he and his long-time correspondent Alfred Russel Wallace were engaged in a fierce debate. Darwin said that natural selection had shaped the human species just like any other. But Wallace disagreed, arguing that selection alone could not account for the exceptional capabilities of the human mind. "How could natural selection, or survival of the fittest in the struggle for existence, at all favour the development of mental powers so entirely removed from the material necessities of savage men?"
Excerpt: Although history is not made entirely, or even mostly, by prominent men and women, two great exceptions to that rule were born exactly 200 years ago today, on 12 February 1809: Charles Darwin and Abraham Lincoln. See Also:Darwin 200 online collection.
Source:Humanity and evolution, Editorial, DOI: 10.1038/457763a, Nature 457, 763-764, 2009/02/12
Big Year For Darwin, But What Would He Make Of The Climate Change Ahead?, ScienceDaily
Excerpts: Charles Darwin may have been born 200 years ago come Feb. 12, but his theory of evolution remains an everyday touchstone for modern biologists. And while the Origin of Species author might not have known the term "global warming," he wouldn't have been surprised that the environment is changing. He would, however, be astonished by the speed at which it's happening today, researchers believe. "Every species is under temporary permanence," says (...). Darwin would have predicted changes in species' habits and even changes in the environment, but the planet's facing changes that are both drastic and unpredictable. (...)
Excerpt: The 200th anniversary of the birth of Charles Robert Darwin falls on 12 February 2009. Darwin was arguably the most influential scientist of modern times. No single researcher has since matched his collective impact on the natural and social sciences; on politics, religions, and philosophy; on art and cultural relations, and in ways that the man himself would never have imagined.
Elysia chlorotica, the solar-powered sea slug, is about 3 cm long (Image: PNAS)
Solar-PoweredSea Slug Harnesses Stolen Plant Genes, New Scientist
Excerpts:
Young E. chlorotica fed with algae for two weeks, could survive for the rest of their year-long lives without eating, Rumpho found in earlier work.
But a mystery remained. Chloroplasts only contain enough DNA to encode about 10% of the proteins needed to keep themselves running. The other necessary genes are found in the algae's nuclear DNA. "So the question has always been, how do they continue to function in an animal cell missing all of these proteins," says Rumpho.
Excerpts: Yet group selection - the idea that evolution can choose between groups, not just the individuals that make them up - has a higher profile today than at any time since its apparent banishment from mainstream evolutionary theory. And it gets better press, too. This is in part owing to the efforts of David Sloan Wilson, of BinghamtonUniversity in New York, who argues that the dismissal of group selection was a major historical error that needs to be rectified. And it does not hurt that he has been joined by Edward O. Wilson, the great naturalist and authority on social insects.
Excerpts: You might think that once evolution has found one way to get something done, it will stick with it. But similar physical forms can hide radically different wiring, (...).
Tunicates - also known as sea squirts - are humans' closest invertebrate cousins. They have tadpole-like larvae that closely resemble miniature vertebrate embryos and so were expected to build their bodies in the same way. But they don't. (..) It's as if you had found a car in which components of the engine were scattered all over the back seat - but the car still worked.
Variation In Evolutionary Patterns Across The Geographic Range Of A Fossil Bivalve, Science
Excerpts: Within a fossil bivalve genus, evolution tended to occur as a random walk at the highest latitudes and to be in stasis mode in deep marine environments.
The fossil record is the only direct source of data for studying modes (patterns) and rates of morphological change over long periods of time. Determining modes and rates is important for understanding macroevolutionary processes, but just how modes and rates vary within a taxon, and why, remain largely unaddressed. We examined patterns of morphological change in the shell of the Mesozoic marine bivalve genus Buchia over its geographic and temporal range.
DNA Chunks, Chimps And Humans: Marks Of Differences Between Human And Chimp Genomes, Innovations-report
Excerpts: Researchers have carried out the largest study of differences between human and chimpanzee genomes, identifying regions that have been duplicated or lost during evolution of the two lineages. (...) "By looking at only one 'reference' sequence for human or chimpanzee, as has been done previously, it is not possible to tell which differences occur only among individual chimpanzees or humans and which are differences between the two species. (...) Rather than examining single-letter differences in the genomes (so-called SNPs), the researchers looked at copy number variation (CNV) - the gain or loss of regions of DNA. (...)
Human Genes Are Multitaskers - Up To 94% Of Human Genes Can Generate Different Products., Nature
Excerpts: Most genes are made from sections of DNA found at different locations along a strand. The data encoded in these fragments are joined together into a functional messenger RNA (mRNA) molecule that can be used as a template to generate proteins.
But researchers have found that the same gene can be assembled in different ways, sometimes leaving out a piece, for example, or including a bit of the intervening DNA sequence.
(...)
This process, called alternative splicing, can produce mRNA molecules and proteins with dramatically different functions, despite being formed from the same gene.
Being Human: Language: A Social History Of Words, Nature
Excerpts: The evolution of language probably occurred in concert with the evolution of many of the other traits we associate with being human, such as the ability to fashion tools or a strong propensity to learn. If this is true, it suggests that we shouldn't be trying to understand one characteristically human trait in isolation from the others. Moreover, instead of the brain being a collection of separate modules, each dedicated to a specific trait or capacity, humans are likely to have a complex cognitive architecture that is highly interconnected on multiple levels.
Excerpts: Is religion a product of our evolution? The very question makes many people, religious or otherwise, cringe, although for different reasons. Some people of faith fear that an understanding of the processes underlying belief could undermine it. Others worry that what is shown to be part of our evolutionary heritage will be interpreted as good, true, necessary or inevitable. Still others, many scientists included, simply dismiss the whole issue, seeing religion as childish, dangerous nonsense.
How Evolution Learns From Past Environments To Adapt To New Environments, ScienceDaily
Excerpts: The evolution of novel characteristics within organisms can be enhanced when environments change in a systematic manner, according to a new study (...) suggest that in environments that vary over time in a non-random way, evolution can learn the rules of the environment and develop organisms that can readily generate novel useful traits with only a few mutations. (...) The ability to generate novelty is one of the main mysteries in evolutionary theory. (...) began with the observation that environments in nature seemingly vary according to common rules or regularities. They proposed that organisms can learn how previous environments changed, and then use this information (...).
Excerpts: How does an animal conceal itself from visual detection by other animals? This review paper seeks to identify general principles that may apply in this broad area. It considers mechanisms of visual encoding, of grouping and object encoding, and of search. In most cases, the evidence base comes from studies of humans or species whose vision approximates to that of humans. The effort is hampered by a relatively sparse literature on visual function in natural environments and with complex foraging tasks. (...) Finally, the paper considers how we may understand the processes of search for complex targets in complex scenes. (...)
Source:Review. Camouflage And Visual Perception, T. Troscianko, C. P. Benton, P. G. Lovell, D. J. Tolhurst, Z. Pizlo, DOI: 10.1098/rstb.2008.0218, Philosophical Transactions: Biological Sciences, 2008/11/06
Excerpts: Genetic tests showed that cheaters, although closely related to their nest-mates, are genetically distinct. They also revealed the same cheater lineage in more than one nest, suggesting that it can spread between colonies, and leading the researchers to describe the cheats as a transmissible 'social cancer' that has evolved to exploit the cooperative behaviour of the majority.
Visions Of Evolution: Self-Organization Proposes What Natural Selection Disposes, Biol. Theor.
Excerpts: This article reviews the seven "visions" of evolution (...) concluding that each posited relationship between natural selection and self-organization has suited different aims and approaches. (...) we show that these seven viewpoints may be collapsed into three fundamentally different ones: (1) natural selection drives evolution; (2) self-organization drives evolution; and (3) natural selection and self-organization are complementary aspects of the evolutionary process. We then argue that these three approaches are not mutually exclusive, since each may apply to different stages of development of different systems. What emerges from our discussion is a more encompassing view: that self-organization proposes what natural selection disposes.
Development Puts An End To Evolution Of Endless Forms, ScienceDaily
Excerpts: Researchers have put forward a simple model of development and gene regulation that is capable of explaining patterns observed in the distribution of morphologies and body plans (or, more generally, phenotypes). (...) Nature truly displays a bewildering variety of shapes and forms. Yet, with all its magnificence, this diversity still represents only a tiny fraction of the endless 'space' of possibilities, and observed phenotypes actually occupy only small, dense patches in the abstract phenotypic space. Borenstein and Krakauer demonstrate that the sparseness of variety in nature can be attributed to the interactions between multiple genes and genetic controls involved in the development of organisms (...).
The Relevance Of Brain Evolution For The Biomedical Sciences, Biol. Lett.
Excerpt: Most biomedical neuroscientists realize the importance of the study of brain evolution to help them understand the differences and similarities between their animal model of choice and the human brains in which they are ultimately interested. Many think of evolution as a linear process, going from simpler brains, as those of rats, to more complex ones, as those of humans. However, in reality, every extant species' brain has undergone as long a period of evolution as has the human brain, and each brain has its own species-specific adaptations. By understanding the variety of existing brain types, we can more accurately reconstruct the brains (...).
Excerpt: Much of human DNA is the genetic equivalent of e-mail spam: short repeated sequences that have no obvious function other than making more of themselves. After starting out in our primate ancestors 65 million years ago, one type of repetitive DNA called an Alu retrotransposon now takes up 10 percent of our genome, with about one million copies. Roughly every 20th newborn baby has a new Alu retrotransposon somewhere in its DNA, scientists have estimated. As mutations gradually blur the features of older Alu elements, some become unable to make copies of themselves. (...)
Excerpts: Technological revolutions rocked our world long before the information age. Between 80,000 and 60,000 years ago, it was spurts of innovative toolmaking, rather than extreme climate changes, in southern Africa's Stone Age cultures that heralded a human exodus out of Africa, a new investigation suggests.
Environmental changes in southern Africa, including those brought on by a massive volcanic eruption in Sumatra around 74,000 years ago, played a secondary role at best in instigating ancient cultural advances and intercontinental migrations, (...). Other researchers regard ancient climate fluctuations as key motivators of human movement out of Africa.
Ages For The Middle Stone Age Of Southern Africa: Implications For Human Behavior And Dispersal, Science
Excerpts: Dating of the first use of symbols and jewelry in South Africa shows that the emergence of modern human behavior was not influenced by just environmental factors.
The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa¡Xthe Still Bay and Howieson's Poort industries¡Xthat are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies.
The Iceman's Mysterious Genetic Past, Science News
Excerpts: Further genetic studies of modern Europeans might identify some who belong to what Rollo's group has dubbed "Oetzi's branch."
"Through the analysis of a complete mitochondrial genome in a particularly well-preserved body, we have obtained evidence of a significant genetic difference between present-day Europeans and a prehistoric human, despite the fact that the Iceman is only about 5,000 years old," Rollo says.
No Evidence For An Evolutionary Trade-Off Between Learning And Immunity In A Social Insect, Biol. Lett.
Excerpt: The immune response affects learning and memory in insects. Given this and the known fitness costs of both the immune system and learning, does an evolutionary trade-off exist between these two systems? We tested this by measuring the learning ability of 12 bumble-bee (...). We then tested their immune response using the zone of inhibition assay. We found a positive relationship between colony learning performance and immune response, that is, fast-learning colonies also show high levels of antimicrobial activity. We conclude that there is no a priori reason to demand an evolutionary relationship between two traits that are linked physiologically.
Evolutionary Biology: Small Regulatory RNAs Pitch In, Nature
Excerpts: How did organismal complexity evolve at a cellular level, and how does a genome encode it? The answer might lie in differences, not in the number of genes an organism has, but rather in the regulation of gene expression.
It is commonly believed that complex organisms arose from simple ones. Yet analyses of genomes and of their transcribed genes in various organisms reveal that, as far as protein-coding genes are concerned, the repertoire of a sea anemone - a rather simple, evolutionarily basal animal - is almost as complex as that of a human.
Experimental Evidence For Spatial Self-Organization And Its Emergent Effects In Mussel Bed Ecosystems, Science
Excerpts: Spatial self-organization is the main theoretical explanation for the global occurrence of regular or otherwise coherent spatial patterns in ecosystems. Using mussel beds as a model ecosystem, we provide an experimental demonstration of spatial self-organization. Under homogeneous laboratory conditions, mussels developed regular patterns, similar to those in the field. An individual-based model derived from our experiments showed that interactions between individuals explained the observed patterns.
