miércoles, 19 de noviembre de 2008

Selección del Complexity Digest - Octubre y Noviembre

DNA Chunks, Chimps And Humans: Marks Of Differences Between Human And Chimp Genomes, Innovations-report

Excerpts: Researchers have carried out the largest study of differences between human and chimpanzee genomes, identifying regions that have been duplicated or lost during evolution of the two lineages. (...) "By looking at only one 'reference' sequence for human or chimpanzee, as has been done previously, it is not possible to tell which differences occur only among individual chimpanzees or humans and which are differences between the two species. (...) Rather than examining single-letter differences in the genomes (so-called SNPs), the researchers looked at copy number variation (CNV) - the gain or loss of regions of DNA. (...)

Human Genes Are Multitaskers - Up To 94% Of Human Genes Can Generate Different Products., Nature

Excerpts: Most genes are made from sections of DNA found at different locations along a strand. The data encoded in these fragments are joined together into a functional messenger RNA (mRNA) molecule that can be used as a template to generate proteins.

But researchers have found that the same gene can be assembled in different ways, sometimes leaving out a piece, for example, or including a bit of the intervening DNA sequence.


This process, called alternative splicing, can produce mRNA molecules and proteins with dramatically different functions, despite being formed from the same gene.

Being Human: Language: A Social History Of Words, Nature

Excerpts: The evolution of language probably occurred in concert with the evolution of many of the other traits we associate with being human, such as the ability to fashion tools or a strong propensity to learn. If this is true, it suggests that we shouldn't be trying to understand one characteristically human trait in isolation from the others. Moreover, instead of the brain being a collection of separate modules, each dedicated to a specific trait or capacity, humans are likely to have a complex cognitive architecture that is highly interconnected on multiple levels.

Being Human: Religion: Bound To Believe? Nature

Excerpts: Is religion a product of our evolution? The very question makes many people, religious or otherwise, cringe, although for different reasons. Some people of faith fear that an understanding of the processes underlying belief could undermine it. Others worry that what is shown to be part of our evolutionary heritage will be interpreted as good, true, necessary or inevitable. Still others, many scientists included, simply dismiss the whole issue, seeing religion as childish, dangerous nonsense.

How Evolution Learns From Past Environments To Adapt To New Environments, ScienceDaily

Excerpts: The evolution of novel characteristics within organisms can be enhanced when environments change in a systematic manner, according to a new study (...) suggest that in environments that vary over time in a non-random way, evolution can learn the rules of the environment and develop organisms that can readily generate novel useful traits with only a few mutations. (...) The ability to generate novelty is one of the main mysteries in evolutionary theory. (...) began with the observation that environments in nature seemingly vary according to common rules or regularities. They proposed that organisms can learn how previous environments changed, and then use this information (...).

Camouflage And Visual Perception, Phil. Tran. Biol. Sc.

Excerpts: How does an animal conceal itself from visual detection by other animals? This review paper seeks to identify general principles that may apply in this broad area. It considers mechanisms of visual encoding, of grouping and object encoding, and of search. In most cases, the evidence base comes from studies of humans or species whose vision approximates to that of humans. The effort is hampered by a relatively sparse literature on visual function in natural environments and with complex foraging tasks. (...) Finally, the paper considers how we may understand the processes of search for complex targets in complex scenes. (...)

  • Source: Review. Camouflage And Visual Perception, T. Troscianko, C. P. Benton, P. G. Lovell, D. J. Tolhurst, Z. Pizlo, DOI: 10.1098/rstb.2008.0218, Philosophical Transactions: Biological Sciences, 2008/11/06

Animal Behaviour: Idle Ants, Nature

Excerpts: Genetic tests showed that cheaters, although closely related to their nest-mates, are genetically distinct. They also revealed the same cheater lineage in more than one nest, suggesting that it can spread between colonies, and leading the researchers to describe the cheats as a transmissible 'social cancer' that has evolved to exploit the cooperative behaviour of the majority.

Visions Of Evolution: Self-Organization Proposes What Natural Selection Disposes, Biol. Theor.

Excerpts: This article reviews the seven "visions" of evolution (...) concluding that each posited relationship between natural selection and self-organization has suited different aims and approaches. (...) we show that these seven viewpoints may be collapsed into three fundamentally different ones: (1) natural selection drives evolution; (2) self-organization drives evolution; and (3) natural selection and self-organization are complementary aspects of the evolutionary process. We then argue that these three approaches are not mutually exclusive, since each may apply to different stages of development of different systems. What emerges from our discussion is a more encompassing view: that self-organization proposes what natural selection disposes.

Development Puts An End To Evolution Of Endless Forms, ScienceDaily

Excerpts: Researchers have put forward a simple model of development and gene regulation that is capable of explaining patterns observed in the distribution of morphologies and body plans (or, more generally, phenotypes). (...) Nature truly displays a bewildering variety of shapes and forms. Yet, with all its magnificence, this diversity still represents only a tiny fraction of the endless 'space' of possibilities, and observed phenotypes actually occupy only small, dense patches in the abstract phenotypic space. Borenstein and Krakauer demonstrate that the sparseness of variety in nature can be attributed to the interactions between multiple genes and genetic controls involved in the development of organisms (...).

The Relevance Of Brain Evolution For The Biomedical Sciences, Biol. Lett.

Excerpt: Most biomedical neuroscientists realize the importance of the study of brain evolution to help them understand the differences and similarities between their animal model of choice and the human brains in which they are ultimately interested. Many think of evolution as a linear process, going from simpler brains, as those of rats, to more complex ones, as those of humans. However, in reality, every extant species' brain has undergone as long a period of evolution as has the human brain, and each brain has its own species-specific adaptations. By understanding the variety of existing brain types, we can more accurately reconstruct the brains (...).

Mapping A Clan Of Mobile Selfish Genes, Innovations-report

Excerpt: Much of human DNA is the genetic equivalent of e-mail spam: short repeated sequences that have no obvious function other than making more of themselves. After starting out in our primate ancestors 65 million years ago, one type of repetitive DNA called an Alu retrotransposon now takes up 10 percent of our genome, with about one million copies. Roughly every 20th newborn baby has a new Alu retrotransposon somewhere in its DNA, scientists have estimated. As mutations gradually blur the features of older Alu elements, some become unable to make copies of themselves. (...)

Stone Age Innovation Out Of Africa, Science News

Excerpts: Technological revolutions rocked our world long before the information age. Between 80,000 and 60,000 years ago, it was spurts of innovative toolmaking, rather than extreme climate changes, in southern Africa's Stone Age cultures that heralded a human exodus out of Africa, a new investigation suggests.

Environmental changes in southern Africa, including those brought on by a massive volcanic eruption in Sumatra around 74,000 years ago, played a secondary role at best in instigating ancient cultural advances and intercontinental migrations, (...). Other researchers regard ancient climate fluctuations as key motivators of human movement out of Africa.

Ages For The Middle Stone Age Of Southern Africa: Implications For Human Behavior And Dispersal, Science

Excerpts: Dating of the first use of symbols and jewelry in South Africa shows that the emergence of modern human behavior was not influenced by just environmental factors.

The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa¡Xthe Still Bay and Howieson's Poort industries¡Xthat are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies.

The Iceman's Mysterious Genetic Past, Science News

Excerpts: Further genetic studies of modern Europeans might identify some who belong to what Rollo's group has dubbed "Oetzi's branch."

"Through the analysis of a complete mitochondrial genome in a particularly well-preserved body, we have obtained evidence of a significant genetic difference between present-day Europeans and a prehistoric human, despite the fact that the Iceman is only about 5,000 years old," Rollo says.

No Evidence For An Evolutionary Trade-Off Between Learning And Immunity In A Social Insect, Biol. Lett.

Excerpt: The immune response affects learning and memory in insects. Given this and the known fitness costs of both the immune system and learning, does an evolutionary trade-off exist between these two systems? We tested this by measuring the learning ability of 12 bumble-bee (...). We then tested their immune response using the zone of inhibition assay. We found a positive relationship between colony learning performance and immune response, that is, fast-learning colonies also show high levels of antimicrobial activity. We conclude that there is no a priori reason to demand an evolutionary relationship between two traits that are linked physiologically.

Evolutionary Biology: Small Regulatory RNAs Pitch In, Nature

Excerpts: How did organismal complexity evolve at a cellular level, and how does a genome encode it? The answer might lie in differences, not in the number of genes an organism has, but rather in the regulation of gene expression.

It is commonly believed that complex organisms arose from simple ones. Yet analyses of genomes and of their transcribed genes in various organisms reveal that, as far as protein-coding genes are concerned, the repertoire of a sea anemone - a rather simple, evolutionarily basal animal - is almost as complex as that of a human.

Experimental Evidence For Spatial Self-Organization And Its Emergent Effects In Mussel Bed Ecosystems, Science

Excerpts: Spatial self-organization is the main theoretical explanation for the global occurrence of regular or otherwise coherent spatial patterns in ecosystems. Using mussel beds as a model ecosystem, we provide an experimental demonstration of spatial self-organization. Under homogeneous laboratory conditions, mussels developed regular patterns, similar to those in the field. An individual-based model derived from our experiments showed that interactions between individuals explained the observed patterns.

No hay comentarios: