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?,

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,

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,

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.

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