martes, 20 de marzo de 2012

Compilado AZyNE 20/3

No entailing laws, but enablement in the evolution of the biosphere, arXiv

Excerpt: Biological evolution is a complex blend of ever changing structural stability, variability and emergence of new phenotypes, niches, ecosystems. We wish to argue that the evolution of life marks the end of a physics world view of law entailed dynamics. Our considerations depend upon discussing the variability of the very "contexts of life": the interactions between organisms, biological niches and ecosystems. These are ever changing, intrinsically indeterminate and even unprestatable: we do not know ahead of time the "niches" which constitute the boundary conditions on selection. More generally, by the mathematical unprestatability of the "phase space" (space of possibilities), no laws of motion can be formulated for evolution. We call this radical emergence, from life to life. (…)

What is your favorite deep, elegant, or beautiful explanation?, edge.org

Excerpt: Since this question is about explanation, answers may embrace scientific thinking in the broadest sense: as the most reliable way of gaining knowledge about anything, including other fields of inquiry such as philosophy, mathematics, economics, history, political theory, literary theory, or the human spirit. The only requirement is that some simple and non-obvious idea explain some diverse and complicated set of phenomena. [192 contributors]


Drew Berry: Animations of unseeable biology, TED.com

About this talk: We have no ways to directly observe molecules and what they do -- Drew Berry wants to change that. At TEDxSydney he shows his scientifically accurate (and entertaining!) animations that help researchers see unseeable processes within our own cells.


Natural selection: A concept in need of some evolution?, Complexity

Abstract: In some respects natural selection is a quite simple theory, arrived at through the logical integration of three propositions (the presence of variation within natural populations, an absolutely limited resources base, and procreation capacities exceeding mere replacement numbers) whose individual truths can hardly be denied. Its relation to the larger subject of evolution, however, remains problematic. It is suggested here thata scaling-down of the meaning of natural selection to “the elimination of the unfit,” as originally intended by Alfred Russel Wallace (1823��"1913), might ultimately prove a more effective means of relating it to larger-scale, longer-term, evolutionary processes.

Evolution of increased complexity in a molecular machine, Nature

Excerpt: Many cellular processes are carried out by molecular ‘machines’��"assemblies of multiple differentiated proteins that physically interact to execute biological functions. Despite much speculation, strong evidence of the mechanisms by which these assemblies evolved is lacking. Here we use ancestral gene resurrectionand manipulative genetic experiments to determine how the complexity of an essential molecular machine (…) increased hundreds of millions of years ago. (…) Our experiments show that increased complexity in an essential molecular machine evolved because of simple, high-probability evolutionary processes, without the apparent evolution of novel functions. They point to a plausible mechanism for the evolution of complexity in other multi-paralogue protein complexes.


Schelling, Hegel, and Evolutionary Progress, Perspectives on Science

Abstract: This article presents Schelling's claim that nature has an evolutionary process and Hegel's response that nature is the development of the concept. It then examines whether evolution is progressive. This article argues that, insofar as a notion of progress is conceptually ineliminatable from evolutionary biology or required to articulate the shape of life's history, progress should be viewed as constitutive.


Predictability of Evolutionary Trajectories in Fitness Landscapes, PLoS Comput Biol

Excerpt: Is evolution deterministic, hence predictable, or stochastic, that is unpredictable? What would happen if one could “replay the tape of evolution”: will the outcomes of evolution be completely different or is evolution so constrained that history will be repeated? Arguably, these questions are among the most intriguing and most difficult in evolutionary biology. In other words, the predictability of evolution depends on the fraction of the trajectories on fitness landscapes that are accessible for evolutionary exploration.

Antonio Damasio: The quest to understand consciousness, TED.com

About this talk: Every morning we wake up and regain consciousness -- that is a marvelous fact -- but what exactly is it that we regain? Neuroscientist Antonio Damasio uses this simple question to give us a glimpse into how our brains create our sense of self.


The Diversity Paradox: How Nature Resolves an Evolutionary Dilemma, arXiv

Excerpt: Adaptation to changing environments is a hallmark of biological systems. Diversity in traits is necessary for adaptation and can influence the survival of a population faced with novelty. In habitats that remain stable over many generations, stabilizing selection reduces trait differences within populations, thereby appearing to remove the diversity needed for heritable adaptive responses in new environments. Paradoxically, field studies have documented numerous populations under long periods of stabilizing selection and evolutionary stasis that have rapidly evolved under changed environmental conditions. In this article, we review how cryptic genetic variation (CGV) resolves this diversity paradox by allowing populations in a stable environment to gradually accumulate hidden genetic diversity that is revealed as trait differences when environments change. (…)


Impact of epistasis and pleiotropy on evolutionary adaptation, Proc. R. Soc. B

Excerpt: Evolutionary adaptation is often likened to climbing a hill or peak. While this process is simple for fitness landscapes where mutations are independent, the interaction between mutations (epistasis) as well as mutations at loci that affect more than one trait (pleiotropy) are crucial in complex and realistic fitness landscapes.


Energetics and the evolution of human brain size, Nature

Excerpt: The human brain stands out among mammals by being unusually large. The expensive-tissue hypothesis1 explains its evolution by proposing a trade-off between the size of the brain and that of the digestive tract, which is smaller than expected for a primate of our body size. Although this hypothesis is widely accepted, empirical support so far has been equivocal. Here we test it in a sample of 100 mammalian species, including 23 primates, by analysing brain size and organ mass data. We found that, controlling for fat-free body mass, brain size is not negatively correlated with the mass of the digestive tract or any other expensive organ, thus refuting the expensive-tissue hypothesis.

miércoles, 28 de diciembre de 2011

Compilado AZyNE 28-12

To Group or Not to Group?, Science

Summary: The phenomenon of cooperation between potentially competing individuals raises an interesting question related to evolution: Why should a competitor favor someone else's fitness at the expense of its own? One way to approach this question is through insights on how cooperation and population structure coevolve.

  • Source: To Group or Not to Group?, Eörs Szathmáry, DOI: 10.1126/science.1209548, Science Vol. 334 no. 6063 pp. 1648-1649, 2011/12/23


Antonio Damasio: The quest to understand consciousness, TED.com

About this talk: Every morning we wake up and regain consciousness -- that is a marvelous fact -- but what exactly is it that we regain? Neuroscientist Antonio Damasio uses this simple question to give us a glimpse into how our brains create our sense of self.


Evolution and development of Brain Networks: From Caenorhabditis elegans to Homo sapiens, arXiv

Abstract: Neural networks show a progressive increase in complexity during the time course of evolution. From diffuse nerve nets in Cnidaria to modular, hierarchical systems in macaque and humans, there is a gradual shift from simple processes involving a limited amount of tasks and modalities to complex functional and behavioral processing integrating different kinds of information from highly specialized tissue. However, studies in a range of species suggest that fundamental similarities, in spatial and topological features as well as in developmental mechanisms for network formation, are retained across evolution. 'Small-world' topology and highly connected regions (hubs) are prevalent across the evolutionary scale, ensuring efficient processing and resilience to internal (e.g. lesions) and external (e.g. environment) changes. Furthermore, in most species, even the establishment of hubs, long-range connections linking distant components, and a modular organization, relies on similar mechanisms. In conclusion, evolutionary divergence leads to greater complexity while following essential developmental constraints.


The Diversity Paradox: How Nature Resolves an Evolutionary Dilemma, arXiv

Excerpt: Adaptation to changing environments is a hallmark of biological systems. Diversity in traits is necessary for adaptation and can influence the survival of a population faced with novelty. In habitats that remain stable over many generations, stabilizing selection reduces trait differences within populations, thereby appearing to remove the diversity needed for heritable adaptive responses in new environments. Paradoxically, field studies have documented numerous populations under long periods of stabilizing selection and evolutionary stasis that have rapidly evolved under changed environmental conditions. In this article, we review how cryptic genetic variation (CGV) resolves this diversity paradox by allowing populations in a stable environment to gradually accumulate hidden genetic diversity that is revealed as trait differences when environments change. (…)


Facing Complexity: Prediction vs. Adaptation, arXiv

Abstract: One of the presuppositions of science since the times of Galileo, Newton, Laplace, and Descartes has been the predictability of the world. This idea has strongly influenced scientific and technological models. However, in recent decades, chaos and complexity have shown that not every phenomenon is predictable, even if it is deterministic. If a problem space is predictable, in theory we can find a solution via optimization. Nevertheless, if a problem space is not predictable, or it changes too fast, very probably optimization will offer obsolete solutions. This occurs often when the immediate solution affects the problem itself. An alternative is found in adaptation. An adaptive system will be able to find by itself new solutions for unforeseen situations.

lunes, 12 de diciembre de 2011

Compilado AZyNE 12-12

Cheryl Hayashi: The magnificence of spider silk, TED.com

About this talk: Cheryl Hayashi studies spider silk, one of nature's most high-performance materials. Each species of spider can make up to 7 very different kinds of silk. How do they do it? Hayashi explains at the DNA level -- then shows us how this super-strong, super-flexible material can inspire.

Impact of epistasis and pleiotropy on evolutionary adaptation, Proc. R. Soc. B

Excerpt: Evolutionary adaptation is often likened to climbing a hill or peak. While this process is simple for fitness landscapes where mutations are independent, the interaction between mutations (epistasis) as well as mutations at loci that affect more than one trait (pleiotropy) are crucial in complex and realistic fitness landscapes.

Energetics and the evolution of human brain size, Nature

Excerpt: The human brain stands out among mammals by being unusually large. The expensive-tissue hypothesis1 explains its evolution by proposing a trade-off between the size of the brain and that of the digestive tract, which is smaller than expected for a primate of our body size. Although this hypothesis is widely accepted, empirical support so far has been equivocal. Here we test it in a sample of 100 mammalian species, including 23 primates, by analysing brain size and organ mass data. We found that, controlling for fat-free body mass, brain size is not negatively correlated with the mass of the digestive tract or any other expensive organ, thus refuting the expensive-tissue hypothesis.

viernes, 25 de noviembre de 2011

Compilado AZyNE 25-11

Lynn Margulis 1938-2011 "Gaia Is A Tough Bitch", Edge.org

Excerpt: Biologist Lynn Margulis died on November 22nd. She stood out from her colleagues in that she would have extended evolutionary studies nearly four billion years back in time. Her major work was in cell evolution, in which the great event was the appearance of the eukaryotic, or nucleated, cell " the cell upon which all larger life-forms are based. Nearly forty-five years ago, she argued for its symbiotic origin: that it arose by associations of different kinds of bacteria. Her ideas were generally either ignored or ridiculed when she first proposed them; symbiosis in cell evolution is now considered one of the great scientific breakthroughs.

The role of sex separation in neutral speciation, arXiv

Abstract: Neutral speciation mechanisms based on isolation by distance and sexual selection, termed topopatric, have recently been shown to describe the observed patterns of abundance distributions and species-area relationships. Previous works have considered this type of process only in the context of hermaphrodic populations. In this work we extend a hermaphroditic model of topopatric speciation to populations where individuals are explicitly separated into males and females. We show that for a particular carrying capacity speciation occurs under similar conditions, but the number of species generated decreases as compared to the hermaphroditic case. Evolution results in fewer species having more abundant populations.

Evolutionary Time Travel, Science

Summary: With clever and challenging lab experiments, researchers are forcing species to become multicellular, develop new energy sources, and start having sex.

  • Source: Evolutionary Time Travel, Elizabeth Pennisi, DOI: 10.1126/science.334.6058.893, Science Vol. 334 no. 6058 pp. 893-895, 2011/11/18

sábado, 12 de noviembre de 2011

Compilado AZyNE 12-11

Social Network Size Affects Neural Circuits in Macaques, Science

Abstract: It has been suggested that variation in brain structure correlates with the sizes of individuals’ social networks. Whether variation in social network size causes variation in brain structure, however, is unknown. To address this question, we neuroimaged 23 monkeys that had been living in social groups set to different sizes. Subject comparison revealed that living in larger groups caused increases in gray matter in mid-superior temporal sulcus and rostral prefrontal cortex and increased coupling of activity in frontal and temporal cortex. Social network size, therefore, contributes to changes both in brain structure and function. The changes have potential implications for an animal’s success in a social context; gray matter differences in similar areas were also correlated with each animal’s dominance within its social network.


Evolutionary biology: The path to sociality, Nature

Excerpt: (…) some hints about the sequence of events that led to the evolution of human social systems are emerging. The latest evidence comes from Shultz et al.1, who (…) trace the evolution of complex sociality within the order Primates. Their data provide a strong foundation for modelling the origins of hominid mating systems by constraining the range of likely trajectories of social change.


Stepwise evolution of stable sociality in primates, Nature

Excerpt: (…) This supports suggestions that social living may arise because of increased predation risk associated with diurnal activity. Sociality based on loose aggregation is followed by a second shift to stable or bonded groups. This structuring facilitates the evolution of cooperative behaviours5 and may provide the scaffold for other distinctive anthropoid traits including coalition formation, cooperative resource defence and large brains.


Martin Hanczyc: The line between life and not-life, TED.com

About this talk: In his lab, Martin Hanczyc makes "protocells," experimental blobs of chemicals that behave like living cells. His work demonstrates how life might have first occurred on Earth ... and perhaps elsewhere too.


Daniel Wolpert: The real reason for brains, TED.com

About this talk: Neuroscientist Daniel Wolpert starts from a surprising premise: the brain evolved, not to think or feel, but to control movement. In this entertaining, data-rich talk he gives us a glimpse into how the brain creates the grace and agility of human motion.


Mathematics: Alice in time, Nature

Excerpt: Time haunts both Alice books. Lewis Carroll, author of Alice's Adventures in Wonderland (1865) and Through the Looking-Glass (1871), was also Charles Dodgson, mathematician and logician, and so was aware of the disturbing arguments, new in the mid-nineteenth century, that suggested our view of the geometry of space and time was not universal.
As Dodgson, he was a devout Euclidean, believing that planes are flat and parallel lines never meet.
As Lewis Carroll, he stepped across those boundaries.

lunes, 31 de octubre de 2011

Compilado AZyNE 31-10

Dynamical modeling of collective behavior from pigeon flight data: flock cohesion and dispersion, arXiv

Excerpt: Several models of flocking have been promoted based on simulations with qualitatively naturalistic behavior. In this paper we provide the first direct application of computational modeling methods to infer flocking behavior from experimental field data. We show that this approach is able to infer general rules for interaction, or lack of interaction, among members of a flock or, more generally, any community. Using experimental field measurements of homing pigeons in flight we demonstrate the existence of a basic distance dependent attraction/repulsion relationship and show that this rule is sufficient to explain collective behavior observed in nature.
See Also: Hierarchical group dynamics in pigeon flocks



Stuart Kauffman - The End Of A Physics Worldview: Heraclitus and the Watershed of Life, NECSI

Excerpt: At the dawn of Western philosophy and science, some 2,700 years ago, Heraclitus, declared that, "the world bubbles forth." There is, in this fragment of thought, a natural magic, a creativity beyond the entailing laws of modern physics. I believe Heraclitus was right about the evolution of the biosphere and human life. We live beyond entailing law in a natural magic we co-create.


Bombings, beheadings? Stats show a peaceful world, Physorg.com

Excerpt: Yes, thousands of people have died in bloody unrest from Africa to Pakistan, while terrorists plot bombings and kidnappings. Wars drag on in Iraq and Afghanistan. In peaceful Norway, a man massacred 69 youths in July. In Mexico, headless bodies turn up, victims of drug cartels. This month eight people died in a shooting in a California hair salon.
Yet, historically, we've never had it this peaceful.
That's the thesis of three new books, including one by prominent Harvard psychologist Steven Pinker. Statistics reveal dramatic reductions in war deaths, family violence, racism, rape, murder and all sorts of mayhem.


Evolution of Networks for Body Plan Patterning; Interplay of Modularity, Robustness and Evolvability, PLoS Comput Biol

Excerpt: An important question in evolutionary developmental biology is how the complex organisms we see around us have evolved, and how this complexity is encoded in their DNA. An often heard statement is that the gene regulatory networks underlying developmental processes are modular; that is, different functions are carried out by largely independent network parts. It is argued that this network modularity allows both for robust functioning and evolutionary tinkering, and that selection thus produces modular networks. Here we use a simulation model for the evolution of animal body plan patterning to investigate these ideas. (…)


10 Unsolved Mysteries, Scientific American

Excerpt: 1. How Did Life Begin?
2. How Do Molecules Form?
3. How Does the Environment Influence Our Genes?
4. How Does the Brain Think and Form Memories?
5. How Many Elements Exist?
6. Can Computers Be Made Out of Carbon?
7. How Do We Tap More Solar Energy?
8. What Is the Best Way to Make Biofuels?
9. Can We Devise New Ways to Create Drugs?
10. Can We Continuously Monitor Our Own Chemistry?


What we learned from 5 million books, TED.com

About this talk: Have you played with Google Labs' Ngram Viewer? It's an addicting tool that lets you search for words and ideas in a database of 5 million books from across centuries. Erez Lieberman Aiden and Jean-Baptiste Michel show us how it works, and a few of the surprising things we can learn from 500 billion words.


Change and Aging Senescence as an Adaptation, PLoS ONE

Excerpt: Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual, and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory.


Diurnal and Seasonal Mood Vary with Work, Sleep, and Daylength Across Diverse Cultures, Science

Abstract: We identified individual-level diurnal and seasonal mood rhythms in cultures across the globe, using data from millions of public Twitter messages. We found that individuals awaken in a good mood that deteriorates as the day progresses"which is consistent with the effects of sleep and circadian rhythm"and that seasonal change in baseline positive affect varies with change in daylength. People are happier on weekends, but the morning peak in positive affect is delayed by 2 hours, which suggests that people awaken later on weekends.


Neutrality in evolutionary algorithms… What do we know?, Evolving Systems

Abstract: Over the last years, the effects of neutrality have attracted the attention of many researchers in the Evolutionary Algorithms (EAs) community. A mutation from one gene to another is considered as neutral if this modification does not affect the phenotype. This article provides a general overview on the work carried out on neutrality in EAs. Using as a framework the origin of neutrality and its study in different paradigms of EAs (e.g., Genetic Algorithms, Genetic Programming), we discuss the most significant works and findings on this topic. This work points towards open issues, which we belive the community needs to address.


A Geometric Approach to Complexity, SFI Working Papers

Abstract: We develop a geometric approach to complexity based on the principle that complexity requires interactions at different scales of description. Complex systems are more than the sum of their parts of any size, and not just more than the sum of their elements. Using information geometry, we therefore analyze the decomposition of a system in terms of an interaction hierarchy. In mathematical terms, we present a theory of complexity measures for finite random fields using the geometric framework of hierarchies of exponential families. Within our framework, previously proposed complexity measures find their natural place and gain a new interpretation.


Lee Cronin: Making matter come alive, TED.com

About this talk: Before life existed on Earth, there was just matter, inorganic dead "stuff." How improbable is it that life arose? And -- could it use a different type of chemistry? Using an elegant definition of life (anything that can evolve), chemist Lee Cronin is exploring this question by attempting to create a fully inorganic cell using a "Lego kit" of inorganic molecules -- no carbon -- that can assemble, replicate and compete.

Edward Tenner: Unintended consequences, TED.com

About this talk: Every new invention changes the world -- in ways both intentional and unexpected. Historian Edward Tenner tells stories that illustrate the under-appreciated gap between our ability to innovate and our ability to foresee the consequences.