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.
Excerpt: The cells in a multicellular organism have nominally identical DNA sequences (and therefore the same genetic instruction sets), yet maintain different terminal phenotypes. This nongenetic cellular memory, which records developmental and environmental cues (and alternative cell states in unicellular organisms), is the basis of epi-(above)"genetics.
Source:What Is Epigenetics?, Guy Riddihough and Laura M. Zahn, DOI: 10.1126/science.330.6004.611, Science Vol. 330. no. 6004, p. 611, 2010/10/29
Is Life Impossible? Information, Sex, and the Origin of Complex Organisms, Evolution
Excerpt: The earliest organisms are thought to have had high mutation rates. It has been asserted that these high mutation rates would have severely limited the information content of early genomes. This has led to a well-known “paradox” because, in contemporary organisms, the mechanisms that suppress mutations are quite complex and a substantial amount of information is required to construct these mechanisms. The paradox arises because it is not clear how efficient error-suppressing mechanisms could have evolved, and thus allowed the evolution of complex organisms, at a time when mutation rates were too high to permit the maintenance of very substantial amounts of information within genomes. Here, we use concepts from the formal theory of information to calculate the amount of genomic information that can be maintained. (...)
A map of human genome variation from population-scale sequencing, Nature
Excerpt: The 1000 Genomes Project aims to provide a deep characterization of human genome sequence variation as a foundation for investigating the relationship between genotype and phenotype. Here we present results of the pilot phase of the project, designed to develop and compare different strategies for genome-wide sequencing with high-throughput platforms.
Diversity of Human Copy Number Variation and Multicopy Genes, Science
Excerpt: Copy number variants affect both disease and normal phenotypic variation, but those lying within heavily duplicated, highly identical sequence have been difficult to assay. By analyzing short-read mapping depth for 159 human genomes, we demonstrated accurate estimation of absolute copy number for duplications as small as 1.9 kilobase pairs, ranging from 0 to 48 copies. (...) These data identify human-specific expansions in genes associated with brain development, reveal extensive population genetic diversity, and detect signatures consistent with gene conversion in the human species. Our approach makes ~1000 genes accessible to genetic studies of disease association.
Genome size, self-organization and DNA's dark matter, Complexity
Abstract: Chromosomes exhibit several features indicating that its spatiotemporal dynamics is self-organized. It has been recently suggested that a negative correlation between genome size and mean chromosome number would also be a fingerprint of selforganization, related to how human language is organized at the level of words and syllables. However, the vast dominance of non-coding DNA in eukaryotic genomes should prevent an interpretation of genome/chromosome size based on functional trade-offs related to information storage and transmission. Moreover, the reported negative correlation is shown to be an inevitable consequence of the definitions of chromosome and genome length and it is thus unrelated to any type of special generative process.
The Origins Of Modern Biodiversity On Land, Phil. Trans. B
Excerpt: Comparative studies of large phylogenies of living and extinct groups have shown that most biodiversity arises from a small number of highly species-rich clades. To understand biodiversity, it is important to examine the history of these clades on geological time scales. This is part of a distinct phylogenetic expansion view of macroevolution, and contrasts with the alternative, non-phylogenetic equilibrium approach to the history of biodiversity. The latter viewpoint focuses on density-dependent models in which all life is described by a single global-scale model, and a case is made here that this approach may be less successful at representing the shape of the evolution of life.
Source:The Origins Of Modern Biodiversity On Land, M. J. Benton - mike.bentonbristol.ac.uk, DOI: 10.1098/rstb.2010.0269, Phil. Trans. R. Soc. B, 2010/11/27:558, 3667-3679
Abstract: Can there be higher level laws of nature even though everything is reducible to the fundamental laws of physics? The computer science notion of level of abstraction explains how there can be. The key relationship between elements on different levels of abstraction is not the is-composed-of relationship but the implements relationship. I take a scientific realist position with respect to (material) levels of abstraction and their instantiation as (material) entities. They exist as objective elements of nature. Reducing them away to lower order phenomena produces a reductionist blind spot and is bad science.
On irreducible description of complex systems, Complexity
Abstract: The aim of the article is to present the description of complex systems in terms of self-organization processes of prime integer relations and illustrate its main properties. Based on the integers and controlled by arithmetic only, the processes can characterize complex systems by information not requiring further simplification. This raises the possibility to develop an irreduc
Excerpt: There are various and confusing targets to limit
global warming due to emissions of greenhouse gases. Estimates based on the total slug of carbon emitted are possibly the most robust, and are worrisome.
See Also:The Climate Crunch online collection.
Excerpt: In a 1,000 p.p.m. scenario, many unique or rare systems would probably be lost, including Arctic sea ice, mountain-top glaciers, most threatened and endangered species, coral-reef communities, and many high-latitude and high-altitude indigenous human cultures. People would be vulnerable in other ways too: Asian mega-delta cities would face rising sea levels and rapidly intensifying tropical cyclones, creating hundreds of millions of refugees; valuable infrastructure such as the London or New York underground systems could be damaged or lost; the elderly would be at risk from unprecedented heat waves; and children, who are especially vulnerable to malnutrition in poor areas, would face food shortages.
Excerpt: Plants, like other organisms, including animals, live immersed in a thriving community of microbes. The diversity of fungi, oomycetes, and bacteria with which plants interact brings both plague and benefit. The more we understand how plants tame, thwart, and succumb to their bugs, the more likely we will be able to extract new resources for antimicrobial treatments and manage agricultural challenges
Source:What's Bugging Plants?, Pamela J. Hines and Laura M. Zahn, DOI: 10.1126/science.324_741, Science Vol. 324. no. 5928, p. 741, 2009/05/08
Alexander von Humboldt and the General Physics of the Earth, Science
Excerpt: As scientists are celebrating the 200th anniversary of Charles Darwin's birth and the 150th anniversary of the publication of his On the Origin of Species, Darwin's ideas continue to shape and enrich the sciences. 6 May 2009 marks the 150th anniversary of the death of another 19th-century figure�"Alexander von Humboldt�"whose scientific legacy also flourishes in the 21st century. Humboldt helped create the intellectual world Darwin inhabited, and his writings inspired Darwin to embark on H.M.S. Beagle. More pertinent to our time, Humboldt established the foundation for the Earth system sciences: the integrated system of knowledge on which human society may depend in the face of global climate change.
Human societies have long used the capability of argumentation and dialogue to overcome and resolve conflicts that may arise within their communities. Today, there is an increasing level of interest in the application of such dialogue games within artificial agent societies. In particular, within the field of multi-agent systems, this theory of argumentation and dialogue games has become instrumental in designing rich interaction protocols and in providing agents with a means to manage and resolve conflicts.
The architecture of mutualistic networks minimizes competition and increases biodiversity, Nature
Excerpt: These networks have been found to be highly nested5, with the more specialist species interacting only with proper subsets of the species that interact with the more generalist. We show that nestedness reduces effective interspecific competition and enhances the number of coexisting species. Furthermore, we show that a nested network will naturally emerge if new species are more likely to enter the community where they have minimal competitive load. Nested networks seem to occur in many biological and social contexts, suggesting that our results are relevant in a wide range of fields.
Excerpt: In The Vanishing Face Of Gaia, Lovelock argues that model projections of the climate a century ahead are of little use. The models of the Intergovernmental Panel on Climate Change (IPCC) extrapolate from a smooth trend of warming, yet the real climate system, complex and fully coupled to the biology of land and ocean, is unlikely to change in this simple way. It is more likely to flip from one state to another, with non-linear tipping points that the IPCC models are too simplistic to capture. Lovelock fears that the climate will shift to a new and considerably hotter regime, and that once underway, this shift will be irreversible.
Excerpt: The [paradoxical] result, like a dog chasing its tail, should be familiar to anyone who has thought about a gene network or biological process. Common descriptions of biological interactions, such as 'This gene represses itself' or 'gene A activates gene B. Gene B inhibits gene A', are similarly self-referential, potentially causing endless cycles.
Source:This title is false, Mark Isalan & Matthew Morrison, DOI: 10.1038/458969a, Nature 458, 969, 2009/04/22
Excerpt: This is not the first time that these villagers have sacrificed their body fluids for science. Mohammad Pur Umri has become somewhat famous, not for the milk or mustard that provides the villagers with their livelihood, but for its prolific production of identical monozygotic twins. Globally, only 1 in every 250 to 300 births are identical twins. In Umri, roughly one in ten is of this type, births that the villagers â€" including the twin village leaders call "gifts from God".
Time to sequence the 'red and the dead', Nature News
Excerpt: "Now it is possible to entertain sequencing the genomes of other extinct and endangered species, and the benefits could be huge." Referring to the 'Red List' of highly endangered species drawn up by the International Union for Conservation of Nature (IUCN), Schuster suggests that researchers should plan for sequencing "the red and the dead: a suite of carefully chosen endangered and extinct species."
The Human Brain Is On The Edge Of Chaos, ScienceDaily
Excerpts: Cambridge-based researchers provide new evidence that the human brain lives "on the edge of chaos", at a critical transition point between randomness and order. The study provides experimental data on an idea previously fraught with theoretical speculation. Self-organized criticality (where systems spontaneously organize themselves to operate at a critical point between order and randomness), can emerge from complex interactions in many different physical systems, including avalanches, forest fires, earthquakes, and heartbeat rhythms. According to this study, (...) the dynamics of human brain networks have something important in common with some superficially very different systems in nature. (...)
Excerpt: As the water temperatures plunged by about 5 °C to below zero over the next few million years, most fish became extinct or moved on to warmer climes. But one group, the Notothenioidei, remained. Thanks to some extraordinary evolutionary innovations, these bottom-dwellers radiated, speciated and ultimately dominated. Crucial proteins shifted shape so they could work at cold temperatures, and a digestive enzyme fragment took on a new role as antifreeze.
Excerpt: How did flowering plants diversify and spread so rapidly across the globe? From rice paddies to orange groves, alpine meadows to formal gardens, prairies to oak-hickory forests, the 300,000 species of angiosperms alive today shape most terrestrial landscapes and much of human life and culture. Their blooms color and scent our world; their fruits, roots, and seeds feed us; and their biomass provides clothing, building materials, and fuel. And yet this takeover, which took place about 100 million years ago, apparently happened in a blink of geological time, just a few tens of millions of years.
Source:On the Origin of Flowering Plants, Elizabeth Pennisi, DOI: 10.1126/science.324.5923.28, Science Vol. 324. no. 5923, pp. 28 - 31, 2009/04/03
Mutated Gene In Zebrafish Sheds Light On Blindness In Humans, Innovations-report
Excerpts: Among zebrafish, the eyes have it. Inside them is a mosaic of light-sensitive cells whose structure and functions are nearly identical to those of humans. There, biologists at The Florida State University discovered a gene mutation that determines if the cells develop as rods (the photoreceptors responsible for dim-light vision) or as cones (the photoreceptors needed for color vision). (...) are the first scientists to identify the crucial function of a previously known gene called "tbx2b." The researchers have named the newfound allele (a different form of a gene) "lor" -- for "lots-of-rods" -- because the mutation results in too many rods (...).
Darwin's ‘One Special Difficulty': Celebrating Darwin 200, Biol. Lett.
Abstract:Darwin identified eusocial evolution, especially of complex insect societies, as a particular challenge to his theory of natural selection. A century later, Hamilton provided a framework for selection on inclusive fitness. Hamilton's rule is robust and fertile, having generated multiple subdisciplines over the past 45 years. His suggestion that eusociality can be explained via kin selection, however, remains contentious. I review the continuing debate on the role of kin selection in eusocial evolution and suggest some lines of research that should resolve that debate.
Abstract: All cancers arise as a result of changes that have occurred in the DNA sequence of the genomes of cancer cells. Over the past quarter of a century much has been learnt about these mutations and the abnormal genes that operate in human cancers. We are now, however, moving into an era in which it will be possible to obtain the complete DNA sequence of large numbers of cancer genomes. These studies will provide us with a detailed and comprehensive perspective on how individual cancers have developed.
Source:The cancer genome, Michael R. Stratton, Peter J. Campbell & P. Andrew Futreal, DOI: 10.1038/nature07943, Nature 458, 719-724, 2009/04/09
Parental Effects In Ecology And Evolution: Mechanisms, Processes And Implications, Phil. Tran. Biol. Sc.
Excerpt: As is the case with any metaphor, parental effects mean different things to different biologists-from developmental induction of novel phenotypic variation to an evolved adaptation, and from epigenetic transference of essential developmental resources to a stage of inheritance and ecological succession. (...) Here, we suggest that by emphasizing the complexity of causes and influences in developmental systems and by making explicit the links between development, natural selection and inheritance, the study of parental effects enables deeper understanding of developmental dynamics of life cycles and provides a unique opportunity to explicitly integrate development and evolution. (...)
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
...(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
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.
bristol.ac.uk, DOI: 10.1098/rstb.2010.0269, Phil. Trans. R. Soc. B, 2010/11/27:558, 3667-3679
