Selección de "Noticias Complejas"

What Is Epigenetics?, Science

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
• VIDEO - What Is Epigenetics?

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. (...)

• Source: Is Life Impossible? Information, Sex, and the Origin of Complex Organisms, Joel R. Peck, David Waxman, DOI: 10.1111/j.1558-5646.2010.01074.x, Evolution Volume 64, Issue 11, pages 3300�"3309, 2010/11

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.

• Source: A map of human genome variation from population-scale sequencing, The 1000 Genomes Project Consortium, DOI: 10.1038/nature09534, Nature 467 , 1061"1073, 2010/10/27

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.

• Source: Diversity of Human Copy Number Variation and Multicopy Genes, Peter H. Sudmant, et al., DOI: 10.1126/science.1197005, Science Vol. 330. no. 6004, pp. 641 - 646, 2010/10/29

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.

• Source: Genome size, self-organization and DNA's dark matter, Ricard V. Solé, DOI: 10.1002/cplx.20326, Complexity Volume 16, Issue 1, pages 20"23, 2010/09-10

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

Gene Involved In Human Language Development Also Involved In Bat Echolocation

ScienceDaily (2007-09-19) -- When it comes to the FOXP2 gene, humans have had most to shout about. Discoveries that mutations in this gene lead to speech defects and that the gene underwent changes around the time language evolved both implicate FOXP2 in the evolution of human language. A new study has found that the FOXP2 gene shows unparalleled variation in echolocating bats. This gene's sequence differences among bat lineages correspond well to contrasting forms of echolocation. ... > read full article

'Toy Universe' Could Solve Life's Origins, Space.com

Excerpt:

The power of computer processing could one day solve the riddle of life's origin.
Scientists think life appeared about 4 billion years ago, and ancient rocks on Earth can give us some idea of what the environment was like. Life may have originated in an ocean rich in chemicals. This primordial soup may have been simmering, or it may have been zapped by lightning. Certainly energy of some sort must have helped drive a simple chemical system into a more complex state. But the clues are few, and the picture remains hazy.
Enter the Evogrid, a computer creation concept that would be a digital version of the primordial soup. (...)
See Also: http://www.evogrid.org/

• Source: 'Toy Universe' Could Solve Life's Origins, Leslie Mullen, Space.com, 2009/07/02

Freaks of Nature: What Anomalies Tell Us About Development and Evolution, Oxford University Press

Summary:

In this book, Blumberg turns a scientist's eye on the oddities of nature, showing how a subject once relegated to the sideshow can help explain some of the deepest complexities of biology. What we need to understand, Blumberg argues, is that anomalies are the natural products of development, and it is through developmental mechanisms that evolution works. Freaks of Nature induces a kind of intellectual vertigo as it upends our intuitive understanding of biology. What really is an anomaly? Why is a limbless human a "freak," but a limbless reptile-a snake-a successful variation?

• Source: Freaks of Nature: What Anomalies Tell Us About Development and Evolution, Mark S. Blumberg, Oxford University Press, 2008/11/10

In Retrospect: Lamarck's treatise at 200 - Nature

Excerpt:

But within the maddening, confusing and repetitive pages of Lamarck's exposition lurk concepts that are central to modern evolutionary thought. Stated in contemporary terminology, they include the ideas that species change through evolutionary time; that evolutionary change is slow and imperceptible; that evolution occurs through adaptation to the environment; that it generally progresses from the simple to the complex, although in a few cases it proceeds in reverse; and that species are related to one another by common descent. Furthermore, Lamarck incorporated into his theory the fact that the world is old, and proposed that the evolutionary process started with abiogenesis ?" the origin of life from inanimate matter.
So how and why has Lamarckism become shorthand for foolishness? (...)
In fact, the amount of scientific rubbish that Lamarck put on paper certainly exceeds the quantity of good science in his scientific oeuvre. In this respect, he is no different from Aristotle, Isaac Newton, Darwin, Albert Einstein, Fred Hoyle or Francis Crick.

• Source: In Retrospect: Lamarck's treatise at 200, Dan Graur, Manolo Gouy, David Wool, DOI: 10.1038/460688a, Nature 460, 688-689, 2009/08/06

Selección del Complexity Digest

Darwin Would Have Loved DNA: Celebrating Darwin 200, Biol. Lett.

Abstract: Analysis of DNA sequences now plays a key role in evolutionary biology research. If Darwin were to come back today, I think he would be absolutely delighted with molecular evolutionary genetics, for three reasons. First, it solved one of the greatest problems for his theory of evolution by natural selection. Second, it gives us a tool that can be used to investigate many of the questions he found the most fascinating. And third, DNA data confirm Darwin's grand view of evolution.

• Source: Darwin Would Have Loved DNA: Celebrating Darwin 200, L Bromham - lindell.bromhamanu.edu.au, DOI: 10.1098/rsbl.2009.0298, Biological Letters, 2009/08/23, online 2009/05/15

What can DNA tell us? Place your bets now, New Scientist

Excerpt: From Newton to Hawking, scientists love wagers. Now Lewis Wolpert has bet Rupert Sheldrake a case of fine port that: "By 1 May 2029, given the genome of a fertilised egg of an animal or plant, we will be able to predict in at least one case all the details of the organism that develops from it, including any abnormalities."

• Source: What can DNA tell us? Place your bets now, New Scientist, 2009/07/08

Evolutionary games on scale-free networks with a preferential selection mechanism, Physica A

Excerpt: Considering the heterogeneity of individuals' influence in the real world, we introduce a preferential selection mechanism to evolutionary games (the Prisoner's Dilemma Game and the Snowdrift Game) on scale-free networks and focus on the cooperative behavior of the system.

• Source: Evolutionary games on scale-free networks with a preferential selection mechanism, Wen-Bo D, Xian-Bin C, Lin Z, Mao-Bin H, DOI: 10.1016/j.physa.2009.07.012, Physica A: Statistical Mechanics and its Applications, 17 July 2009

Global patterns of speciation and diversity, Nature

Excerpts: In recent years, strikingly consistent patterns of biodiversity have been identified over space, time, organism type and geographical region. A neutral theory (assuming no environmental selection or organismal interactions) has been shown to predict many patterns of ecological biodiversity. This theory is based on a mechanism by which new species arise similarly to point mutations in a population without sexual reproduction. Here we report the simulation of populations with sexual reproduction, mutation and dispersal. We found simulated time dependence of speciation rates, species�"area relationships and species abundance distributions consistent with the behaviours found in nature. (...) Quantitative comparisons of specific cases are remarkably successful. Our biodiversity results provide additional evidence that species diversity arises without specific physical barriers. This is similar to heavy traffic flows, where traffic jams can form even without accidents or barriers.

• Source: Global patterns of speciation and diversity, M. A. M. de Aguiar, M. Baranger, E. M. Baptestini, L. Kaufman & Y. Bar-Yam, DOI: 10.1038/nature08168, Nature 460, 384-387, 2009/07/16

Disentangling the Web of Life, Science

Abstract: Biodiversity research typically focuses on species richness and has often neglected interactions, either by assuming that such interactions are homogeneously distributed or by addressing only the interactions between a pair of species or a few species at a time. In contrast, a network approach provides a powerful representation of the ecological interactions among species and highlights their global interdependence. Understanding how the responses of pairwise interactions scale to entire assemblages remains one of the great challenges that must be met as society faces global ecosystem change.

• Source: Disentangling the Web of Life, Jordi Bascompte, DOI: 10.1126/science.1170749, Science Vol. 325. no. 5939, pp. 416 - 419, 2009/07/24

Cultural Evolution Continues Throughout Life, Innovations-report

Excerpts: By successively acquiring culture in the form of values, ideas, and actions throughout their lives, humans influence future learning and the capacity for cultural evolution. (�) "Since there are many similarities between biological evolution and cultural changes, the research community has often suggested that the theory of biological evolution can also be applied in relatively unaltered form as a model for cultural evolution. Using these methods, genes are replaced by so-called memes, which are small cultural elements (�). The current article uses mathematical models to show that there is a crucial and often neglected difference between biological and cultural evolution. (�)

• Source: Cultural Evolution Continues Throughout Life Says New Research Theory, Innovations-report, 2009/08/11

Looking For Evidence Of Differentiation And Cooperation: Natural Measures For The Study Of Evolution Of Multicellularity, Advances in Complex Systems (ACS)

Abstract: The understanding of the evolutionary transitions is a major area of research in artificial life and in biology. We follow an artificial life approach to investigate these phenomena, in order to look for evidence of emerging differentiation and multicellular cooperation in colonies of individual cells. We introduce and apply new measures for assessing the impact of multicellular interaction on individual reproduction and on lifespan. The conclusion of these studies shows that the colony with the ability to communicate shows, with the help of our new measures, behaviors that hint at the emergence of early cooperation.

• Source: Looking For Evidence Of Differentiation And Cooperation: Natural Measures For The Study Of Evolution Of Multicellularity, M. Buck, C. L. Nehaniv, DOI: 10.1142/S0219525909002222, Advances in Complex Systems (ACS), vol. 12, issue 03, 2009/07/15

Design Complexity In Termite-Fishing Tools Of Chimpanzees, Biol. Lett.

Excerpts: Adopting the approach taken with New Caledonian crows (Corvus moneduloides), we present evidence of design complexity in one of the termite-fishing tools of chimpanzees (Pan troglodytes) in the Goualougo Triangle, Republic of Congo. Prior to termite fishing, chimpanzees applied a set of deliberate, distinguishable actions to modify herb stems to fashion a brush-tipped probe, which is different from the form of fishing tools used by chimpanzees in East and West Africa. This means that �brush-tipped fishing probes�, unlike �brush sticks�, are not a by-product of use but a deliberate design feature absent in other chimpanzee populations. (�) suggest that these wild chimpanzees are attentive to tool modifications. (�)

• Source: Design Complexity In Termite-Fishing Tools Of Chimpanzees (Pan Troglodytes), C. Sanz - sanzeva.mpg.de, J. Call, D. Morgan, DOI: 10.1098/rsbl.2008.0786, Biological Letters, 2009/06/23, online 2009/03/04

Capuchin Monkeys Display Affiliation Toward Humans Who Imitate Them, Science

Excerpts: During social interactions, humans often unconsciously and unintentionally imitate the behaviors of others, which increases rapport, liking, and empathy between interaction partners. This effect is thought to be an evolutionary adaptation that facilitates group living and may be shared with other primate species. Here, we show that capuchin monkeys, a highly social primate species, prefer human imitators over non-imitators in a variety of ways (...) These results demonstrate that imitation can promote affiliation in nonhuman primates. Behavior matching that leads to prosocial behaviors toward others may have been one of the mechanisms at the basis of altruistic behavioral tendencies in capuchins and in other primates, including humans.
Editor's Note: Imitation as a mechanism for cooperation may be present in many species other than primates. It has been speculated that the neural mechanism behind imitation is based on "mirror neurons". It still remains to be explored how widespread mirror neurons are in the animal kingdom.

• Source: Capuchin Monkeys Display Affiliation Toward Humans Who Imitate Them, Annika Paukner, Stephen J. Suomi, Elisabetta Visalberghi, Pier F. Ferrari, DOI: 10.1126/science.1176269, Science Vol. 325. no. 5942, pp. 880 - 883, 2009/08/14

Why Do Species Vary In Their Rate Of Molecular Evolution?, Biol. Lett.

Excerpts: Despite hopes that the processes of molecular evolution would be simple, clock-like and essentially universal, variation in the rate of molecular evolution is manifest at all levels of biological organization. Furthermore, it has become clear that rate variation has a systematic component: rate of molecular evolution can vary consistently with species body size, population dynamics, lifestyle and location. This suggests that the rate of molecular evolution should be considered part of life-history variation between species, which must be taken into account when interpreting DNA sequence differences between lineages. (�)

• Source: Why Do Species Vary In Their Rate Of Molecular Evolution?, L.Bromham - indell.bromhamanu.edu.au, DOI: 10.1098/rsbl.2009.0136, Biological Letters, 2009/06/23, online 2009/04/08

Lifetime of Anthropogenic Climate Change: Millennial Time Scales of Potential CO2 and Surface Temperature Perturbations, Journal of Climate

Abstract: Multimillennial simulations with a fully coupled climate�"carbon cycle model are examined to assess the persistence of the climatic impacts of anthropogenic CO2 emissions. It is found that the time required to absorb anthropogenic CO2 strongly depends on the total amount of emissions; for emissions similar to known fossil fuel reserves, the time to absorb 50% of the CO2 is more than 2000 yr. The long-term climate response appears to be independent of the rate at which CO2 is emitted over the next few centuries. Results further suggest that the lifetime of the surface air temperature anomaly might be as much as 60% longer than the lifetime of anthropogenic CO2 and that two-thirds of the maximum temperature anomaly will persist for longer than 10 000 yr. This suggests that the consequences of anthropogenic CO2 emissions will persist for many millennia.

• Source: Lifetime of Anthropogenic Climate Change: Millennial Time Scales of Potential CO2 and Surface Temperature Perturbations, Eby, M., K. Zickfeld, A. Montenegro, D. Archer, K.J. Meissner, and A.J. Weaver, DOI: 10.1175/2008JCLI2554.1, Journal of Climate Volume 22, Issue 10, pp. 2501�"2511, 2009/05

Jared Diamond on why societies collapse, TED.com

About this talk: Why do societies fail? With lessons from the Norse of Iron Age Greenland, deforested Easter Island and present-day Montana, Jared Diamond talks about the signs that collapse is near, and how -- if we see it in time -- we can prevent it.

• Source: Jared Diamond on why societies collapse, Jared Diamond, TED.com, 2008/10
• VIDEO - Watch this talk

Selección del Complexity Digest - Mayo

The reductionist blind spot, Complexity

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.

• Source: The reductionist blind spot, Russ Abbott, DOI: 10.1002/cplx.20274, Complexity Volume 14 Issue 5, Pages 10 - 22, 2009/02/09

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

ible theory of complex systems.

• Source: On irreducible description of complex systems, Victor Korotkikh, Galina Korotkikh, DOI: 10.1002/cplx.20256, Complexity Volume 14 Issue 5, Pages 40 - 46, 2008/09/29

Climate change: Too much of a bad thing, Nature

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.

• Source: Climate change: Too much of a ba d thing, Gavin Schmidt & David Archer, DOI: 10.1038/4581117a, Nature 458, 1117-1118, 2 009/04/30

  

The worst-case scenario, Nature

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.

• Source: The worst-case scenario, Stephen Schneider, DOI: 10.1038/4581104a, Nature 458, 1104-1105, 2009/04/30

What's Bugging Plants?, Science

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.

• Source: Alexander von Humboldt and the General Physics of the Earth, Stephen T. Jackson, DOI: 10.1126/science.1171659, Science Vol. 324. no. 5927, pp. 596 - 597, 2009/05/01