jueves, 27 de agosto de 2009

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.

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."

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.

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.

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.

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. (�)

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.

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. (�)

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.

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. (�)

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.

Jared Diamond on why societies collapse,

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.

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