Noticias sobre Complejidad

A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus, Science

Abstract: Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, which substitutes arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bioelements may have profound evolutionary and geochemical significance.

o Source: A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus, Felisa Wolfe-Simon, et al., DOI: 10.1126/science.1197258, Science Published Online, 2010/12/02

Swarm Intelligence in Animal Groups: When Can a Collective Out-Perform an Expert?, PLoS ONE

Excerpt: Using a set of simple models, we present theoretical conditions (involving group size, and diversity of individual information) under which groups should aggregate information, or follow an expert, when faced with a binary choice. We found that, in single-shot decisions, experts are almost always more accurate than the collective across a range of conditions. However, for repeated decisions - where individuals are able to consider the success of previous decision outcomes - the collective's aggregated information is almost always superior.

o Source: Swarm Intelligence in Animal Groups: When Can a Collective Out-Perform an Expert?, Katsikopoulos KV, King AJ, DOI: 10.1371/journal.pone.0015505, PLoS ONE 5(11): e15505, October 2010

Infectious Disease Modeling of Social Contagion in Networks, PLoS Comput Biol

Excerpt: Information, trends, behaviors and even health states may spread between contacts in a social network, similar to disease transmission. However, a major difference is that as well as being spread infectiously, it is possible to acquire this state spontaneously. For example, you can gain knowledge of a particular piece of information either by being told about it, or by discovering it yourself. In this paper we introduce a mathematical modeling framework that allows us to compare the dynamics of these social contagions to traditional infectious diseases. (...) As an example, we study the spread of obesity (...)

§ Source: Infectious Disease Modeling of Social Contagion in Networks, Alison L. Hill, David G. Rand, Martin A. Nowak, Nicholas A. Christakis, DOI: 10.1371/journal.pcbi.1000968, PLoS Comput Biol 6(11): e1000968, 2010/11/04

Cycling in the Complexity of Early Societies, Cliodynamics

Abstract Excerpt: Warfare is commonly viewed as a driving force of the process of aggregation of initially independent villages into larger and more complex political units that started several thousand years ago and quickly lead to the appearance of chiefdoms, states, and empires. Here we build on extensions and generalizations of Carneiro’s (1970) argument to develop a spatially explicit agent-based model of the emergence of early complex societies via warfare. (...) A general prediction of our model is continuous stochastic cycling in which the growth of individual polities in size, wealth/power, and complexity is interrupted by their quick collapse. (...)

o Source: Cycling in the Complexity of Early Societies, Gavrilets, Sergey, Anderson, David G, Turchin, Peter, Cliodynamics: The Journal of Theoretical and Mathematical History 1(1), 2010

New Clues About What Makes the Human Brain Special, Science

Excerpt: (...) researchers who've examined preserved samples of cerebral cortex from humans and several species of ape say they've found some intriguing clues about what makes the human brain unique. They report that in a particular region of the prefrontal cortex, an area that contributes to abstract thinking and other sophisticated cognition, neurons have more space between them in the human brain than in the brains of apes. This extra space allows more room for connections between neurons (...)

o Source: New Clues About What Makes the Human Brain Special, Greg Miller, DOI: 10.1126/science.330.6008.1167, Science Vol. 330 no. 6008 p. 1167, 2010/11/26

Sixteen common misconceptions about the evolution of cooperation in humans, Evolution and Human Behavior

Abstract: The occurrence of cooperation poses a problem for the biological and social sciences. However, many aspects of the biological and social science literatures on this subject have developed relatively independently, with a lack of interaction. This has led to a number of misunderstandings with regard to how natural selection operates and the conditions under which cooperation can be favoured. Our aim here is to provide an accessible overview of social evolution theory and the evolutionary work on cooperation, emphasising common misconceptions.

o Source: Sixteen common misconceptions about the evolution of cooperation in humans, West SA, Mouden CE, Gardner A, DOI: 10.1016/j.evolhumbehav.2010.08.001, Evolution and Human Behavior, in Press, November 2010