domingo, 31 de agosto de 2008

El fino arte de adivinar que terminarás opinando

Puede pasar que caminando por la calle, el dia menos pensado nos interceptan para preguntarnos que opinamos sobre tal o cual preocupación de los medios en ese dia particular y terminemos ilustrando unos segundos del noticiero de esa misma noche. Siempre con la sensación de que nos vemos horrendos o sin acostumbrarnos nunca a nuestro tono de voz cuando los escuchamos grabado y no desde los ecos de nuestra cabeza.
Científicos e investigadores son frecuentemente buscados por los mismos periodistas pero directamente en sus lugares de trabajo e interpelados sobre los mas variopintos temas. Lo distinto de esta situación es que se los consulta como autoridades y por lo tanto nuestra opinión tiene otro cariz. A veces de temas que manejas, y muy frecuentemente no. Sabiendo esto está en cada uno lo que dirá, opinará o rehusará contar en cada situación. Finalmente, y suponiendo que se obtuvo una información y opinión válida del tema, está la tiranía de la síntesis y búsqueda de impacto de las redacciones periodísticas que pueden terminar poniendo en boca de los consultados las ideas exactamente opuestas.
No digo que lo que muestro a continuación sea exactamente el caso pero seguro sirve para ver lo que se dice, lo que se pierde y lo que llega. Primero lo que escribí para el diario Perfil que me consultó sobre un movimiento sobre derechos de los simios que estaría cobrando fuerza en España ( las preguntas fueron enviadas por la redacción) y luego la nota tal cual fue publicada.

a) El correo electrónico

Primero quiero decirte que siempre son bienvenidas noticias que propongan reflexiones sobre la ética, la forma en que los humanos se relacionan con el resto de la naturaleza y los límites que debemos imponernos (o no).

¿Cuáles deberían ser los límites –si los hay– en la investigación biomédica con animales?

Esa es una pregunta realmente difícil de contestar. Por un lado, involucra determinar cual es la relación de uno con el animal objeto de manipulación y esa es una postura filosófica. Una postura donde los seres vivos “no humanos” son considerados mas como objetos que como seres sensibles va a afirmar que no hay límite teórico para experimentar con animales en pos del beneficio humano. Evidentemente se puede objetar contra este tipo de accionar, tal cual lo hacen los grupos de protección de los animales.
Por otro lado, el accionar científico no es algo independiente de la sociedad en donde se produce. Por lo tanto es la ética y la moral de nuestra cultura la que determinará los límites. Y si dudamos al respecto es porque no es un tema plenamente debatido. En la medida que esta pregunta se la hagan a biólogos (en la UBA, en ningún momento de nuestra formación se incluye Ética) y médicos exclusivamente y no se llame a gente formada en filosofía y ética no vamos a conseguir una respuesta acabada.

España estaría por aprobar una legislación que prohíbe cualquier tipo de investigación con homínidos, ¿qué contras tendría para la ciencia la imposición de esta limitación?

Así planteado los únicos afectados son los grupos españoles de investigaciones biomédicas con modelos homínidos y desconozco pero me atrevo a decir que no deben ser más que un par. Si esta medida termina siendo por toda la comunidad científica internacional entonces se deberá recurrir a métodos más indirectos, modelados teóricos o modelos biológicos más lejanamente emparentados de los humanos. Entiendo por ejemplo que el macaco Rhesus (Macaca mulatta) es un mono que queda afuera de esta discusión y es muy utilizado en los laboratorios.

Los movimientos que proponen que los simios deben gozar de los mismos derechos y garantías legales que los humanos, hablan de "especieísmo", en lugar de racismo, en tanto la investigación científica que experimenta con animales partiría del prejuicio de considerar como inferior a cualquier otra especie. ¿Tiene sentido el concepto? ¿Está de acuerdo?

Ambas posturas son falaces y antropocéntricas y solo discuten donde trazar la línea de “humanidad” y que queda excluido. No me parece que para proteger especies debamos “humanizarlas”. En vez de enumerar todos los aspectos que compartimos con los otros grandes simios deberíamos apreciar y proteger las diferencias. Y si las diferencias reside la riqueza de la biodiversidad entonces no debemos discutir sobre grandes simios sino sobre nuestro trato a todo el conjunto de seres vivos.
Una de las primeras lecciones del estudiante de Evolución es que no hay seres inferiores o superiores. Todos los organismos vivos en la actualidad descienden de un antepasado común y por lo tanto pertenecen a grupos que vienen evolucionando desde entonces, en ese sentido son igual de exitosos. Por otro lado, las adaptaciones no aseguran la perpetuación eterna y por eso la probabilidad de extinción siempre existe para todas las especies. En eso tampoco hay organismos superiores o inferiores. Y si bien hay seres más o menos complejos esto tampoco es una cualidad que se refleje en una superioridad intrínseca. Desde la biología evolutiva no hay un criterio para determinar en que sentido una gacela es “mejor” que su flora intestinal o el pasto que come.


b) La nota en el diario

http://www.diarioperfil.com.ar/edimp/0290/articulo.php?art=9404&ed=0290#sigue
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sábado, 23 de agosto de 2008

Selección del Complexity Digest - Agosto

Birds Are Tracking Climate Warming, But Not Fast Enough, Proc. Biol. Sc.

Excerpt: Range shifts of many species are now documented as a response to global warming. But whether these observed changes are occurring fast enough remains uncertain and hardly quantifiable. Here, we developed a simple framework to measure change in community composition in response to climate warming. This framework is based on a community temperature index (CTI) that directly reflects, for a given species assemblage, the balance between low- and high-temperature dwelling species. Using data from the French breeding bird survey, we first found a strong increase in CTI over the last two decades revealing that birds are rapidly tracking climate warming. (...)

Ecology: A Matter Of Timing, Science

Excerpts: Climate change is causing shifts in the distribution and phenology of many plants and animals. Birds have played a key role in detecting these changes, because long-term data are available on the distribution, migration, and breeding of many species. Studies of the timing of egg laying--a key trait with extensive records dating back half a century for some species--are providing crucial insights into the mechanisms that underlie the response to climate change.
  • Source: Ecology: A Matter Of Timing, Bruce E. Lyon, Alexis S. Chaine, David W. Winkler, DOI: 10.1126/science.1159822, Science : Vol. 321. no. 5892, pp. 1051 - 1052, 08/08/22

Self-Destructive Cooperation Mediated By Phenotypic Noise, Nature

Excerpts: In many biological examples of cooperation, individuals that cooperate cannot benefit from the resulting public good. This is especially clear in cases of self-destructive cooperation, where individuals die when helping others. If self-destructive cooperation is genetically encoded, these genes can only be maintained if they are expressed by just a fraction of their carriers, whereas the other fraction benefits from the public good. One mechanism that can mediate this differentiation into two phenotypically different sub-populations is phenotypic noise. Here we show that noisy expression of self-destructive cooperation can evolve if individuals that have a higher probability for self-destruction have, on average, access to larger public goods.

Exploding Chromosomes Fuel Research About Evolution, Innovations-report

Excerpt: Human cells somehow squeeze two meters of double-stranded DNA into the space of a typical chromosome, a package 10,000 times smaller than the volume of genetic material it contains. Now research into single-celled, aquatic algae called dinoflagellates is showing that these and related organisms may have evolved more than one way to achieve this feat of genetic packing. Even so, the evolution of chromosomes in dinoflagellates, humans and other mammals seem to share a common biochemical basis, (...). Packing the whole length of DNA into tiny chromosomes is problematic because DNA carries a negative charge that, unless neutralized, prevents any attempt at folding (...).

Genomics: 'Simple' Animal's Genome Proves Unexpectedly Complex, Science

Excerpts: Aptly named "sticky hairy plate," Trichoplax adhaerens barely qualifies as an animal. About 1 millimeter long and covered with cilia, this flat marine organism lacks a stomach, muscles, nerves, and gonads, even a head. It glides along like an amoeba, its lower layer of cells releasing enzymes that digest algae beneath its ever-changing body, and it reproduces by splitting or budding off progeny. Yet this animal's genome looks surprisingly like ours, says Daniel Rokhsar, an evolutionary biologist at the University of California, Berkeley (UCB) and the U.S. Department of Energy Joint Genome Institute in Walnut Creek, California. Its 98 million DNA base pairs include many of the genes responsible for guiding the development of other animals' complex shapes and organs, he and his colleagues report in the 21 August issue of Nature.


Animal Behaviour: Crowd Control, Nature

Excerpts: Many researchers would expect parasitic infection rates to increase as groups of animals get bigger and more hosts are available. Contrary to this, researchers reveal that as groups of red colobus monkeys (Procolobus rufomitratus) get larger, they have fewer parasites.

Tamaini Snaith at McGill University in Montreal, Canada, and her colleagues made the discovery while studying the monkeys in Uganda. They tested faeces for parasites and monitored group dynamics. The researchers noticed that large groups tended to spread out more than smaller ones, and suggest that this could lower infection rates.

Evolutionary Biology: Deciphering the Genetics of Evolution, Science

Excerpts: Powerful personalities in evolutionary biology have been tussling over how the genome changes to set the stage for evolution. (...)

Early suggestions that gene regulation could be important to evolution came in the 1970s from work by bacterial geneticists showing a link between gene expression and enzyme activity in bacteria. About the same time, Allan Wilson and Mary-Claire King of the University of California, Berkeley, concluded that genes and proteins of chimps and humans are so similar that our bipedal, hairless existence must be the product of changes in when, where, and to what degree those genes and proteins come into play. (...).


Evolution of Evolvability in Gene Regulatory Networks, PLoS Comput Biol

Excerpt: A cell receives signals both from its internal and external environment and responds by changing the expression of genes. In this manner the cell adjusts to heat, osmotic pressures and other circumstances during its lifetime. Over long timescales, the network of interacting genes and its regulatory actions also undergo evolutionary adaptation. Yet how do such networks evolve and become adapted?
In this paper we describe the study of a simple model of gene regulatory networks, focusing solely on evolutionary adaptation most fit.

Astronomy: Planetary System Formation, Science

Excerpts: To date, 307 extrasolar planets have been discovered and 29 multipleplanet systems have been identified (1, 2). The masses of the planets range from a few Earth masses up to several Jupiter masses, with orbital periods ranging from slightly over 1 day to several years. Unlike in our solar system, the orbital eccentricities of the extrasolar gas giant-sized planets may be large.

Do Subatomic Particles Have Free Will?, Science News

Excerpts: If we have free will, so do subatomic particles, mathematicians claim to prove. (...)

They used a pure mathematical argument to show that there is no way the particle can choose spins around every imaginable axis in a way that is consistent with the 1-0-1 rule. Indeed, there is a set of just 33 axes that are enough to force the particle into a paradox. It could choose spins around the first 32 axes that conform with the rule, but for the last, neither 0 nor non-zero would do.


Differential Selection According To The Degree Of Cheating In A Status Signal, Biol. Lett.

Excerpts: The maintenance of honesty in a badge-of-status system is not fully understood, despite numerous empirical and theoretical studies. Our experiment examined the relationship between a status signal and winter survival, and the long-term costs of cheating, by manipulating badge size in male house sparrows, Passer domesticus. The effect of badge-size manipulation on survival was complex owing to the significant interactions between the treatments and original (natural) badge size, and between the treatments and age classes (yearlings and older birds). (...) This indicates that differential selection can act on a trait according to the degree of cheating.

Brain Will Be Battlefield Of Future, Warns US Intelligence Report, Guardian

Excerpts:
On the battlefield, bullets may be replaced with "pharmacological land mines" that release drugs to incapacitate soldiers on contact, while scanners and other electronic devices could be developed to identify suspects from their brain activity and even disrupt their ability to tell lies when questioned, the report says. (...)

The report highlights one electronic technique, called transcranial direct current stimulation, which involves using electrical pulses to interfere with the firing of neurons in the brain and has been shown to delay a person's ability to tell a lie.

Survival Of The Fittest: Even Cancer Cells Follow The Laws Of Evolution, ScienceDaily

Excerpts: Scientists (...) discovered that the underlying process in tumor formation is the same as for life itself-evolution. After analyzing a half million gene mutations, the researchers found that although different gene mutations control different cancer pathways, each pathway was controlled by only one set of gene mutations. This suggests that a molecular "survival of the fittest" scenario plays out in every living creature as gene mutations strive for ultimate survival through cancerous tumors. This finding (...) improves our understanding of how evolution shapes life in all forms, while laying a foundation for new cancer drugs and treatments. (...)

A Blueprint to Regenerate Limbs, Technology review

Excerpts:
Growing limbs: The axolotl salamander is one of the only vertebrates that can regrow entire limbs as an adult. Scientists are now sequencing parts of its unusually large genome in order to understand the genetic basis for this capability.
Credit: Jeramiah Smith
Probing the salamander genome reveals clues to its remarkable ability to regrow damaged limbs and organs. (...)

In order to quickly identify sections of the salamander's genome involved in regeneration, the scientists sequenced genes that were most highly expressed during limb-bud formation and growth. They found that at least 10,000 genes were transcribed during regeneration. Approximately 9,000 of those seem to have related human versions, but there appear to be a few thousand more that don't resemble known genes. "We think many of them are genes that evolved uniquely in salamanders to help with this process," (...).


Slave Ants Rebel, Science News

Excerpts:
Members of a species of ants captured to work as slaves rebel against their captors by destroying the pupae they were enslaved to nurture.
Credit: Alexandra Achenbach/ Ludwig-Maximilians University
Killing sprees by slave nannies could be an overlooked form of resistance, Foitzik suggests. The baby-killing offers any kin in nearby colonies some protection from slave-makers, since the kidnapper queen's offspring make up the raiding parties. Paring back their number cuts back the raiding power. Foitzik proposes that this benefit to kin could drive the evolution of the trait.

"This is evolution to be a bad nanny," (...).

















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jueves, 7 de agosto de 2008

Selección del Complexity Digest - Junio- Julio

Why Do Mountains Support So Many Species Of Birds?, Ecography

Excerpt: Although topographic complexity is often associated with high bird diversity at broad geographic scales, little is known about the relative contributions of geomorphologic heterogeneity and altitudinal climatic gradients found in mountains. We analysed the birds in the western mountains of the New World to examine the two-fold effect of topography on species richness patterns, (...).We conclude that bird diversity gradients in mountains primarily reflect local climatic gradients. Widespread (lowland) species and narrow-ranged (montane) species respond similarly to changes in the environment, differing only in that the richness of lowland species correlates better with broad-scale climatic effects (...).

  1. Scientists Confirm That Parts Of Earliest Genetic Material May Have Come From The Stars, Innovations-report

    Excerpts: Scientists have confirmed for the first time that an important component of early genetic material which has been found in meteorite fragments is extraterrestrial in origin, in a paper (...). The finding suggests that parts of the raw materials to make the first molecules of DNA and RNA may have come from the stars. The scientists, (...) provides evidence that life's raw materials came from sources beyond the Earth. The materials they have found include the molecules uracil and xanthine, which are precursors to the molecules that make up DNA and RNA, and are known as nucleobases. (...)

    1. Genetic Building Blocks May Have Formed In Space, NewScientist.com

      Excerpts: Some fundamental building blocks of our genetic code might have come from outer space, according to a controversial new meteorite study.

      The study suggests that some organic compounds associated with genetic material might have formed in a meteorite called Murchison before it landed in Australia in 1969. The chemicals are two kinds of nucleobases, ring-like carbon molecules that are essential for the creation of nucleic acids like DNA and RNA.


  2. Scientists Close to Reconstructing First Living Cell, Scientific American

    Excerpts:
    THE FIRST CELL?: Scientists at Harvard Medical School have designed what they think is a reasonable model for the first cell on Earth, some 3.5 to four billion years ago.
    ? JANET IWASA
    Researchers get genetic material to copy itself in a recreation of a simple protocell that could have existed eons ago

    Harvard Medical School researchers report in Nature that they have built a model of what they believe the very first living cell may have looked like, which contains a strip of genetic material surrounded by a fatty membrane. The membranes of modern cells consist of a double layer of fatty acids known as phospholipids.


Bacteria Make Major Evolutionary Shift In The Lab, New Scientist

Excerpts:
But sometime around the 31,500th generation, something dramatic happened in just one of the populations - the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use.

Indeed, the inability to use citrate is one of the traits by which bacteriologists distinguish E. coli from other species. The citrate-using mutants increased in population size and diversity.

"It's the most profound change we have seen during the experiment.(...)".


Change Lifestyle, Change Genes - 3 Months On Ornish Diet Changes 500 Genes, Many With Anticancer Effects, WebMD Health News

Excerpts: WebMD Health News More than 500 genes changed the way they worked. Genes with beneficial effects, including some tumor-suppression genes, became more active. Genes with deleterious effects, including some cancer-promoting genes, were switched off.


Complex Food Webs Prevent Competitive Exclusion Among Producer Species, Proc. Biol. Sc.

Excerpts: Herbivorous top-down forces and bottom-up competition for nutrients determine the coexistence and relative biomass patterns of producer species. Combining models of predator-prey and producer-nutrient interactions with a structural model of complex food webs, I investigated these two aspects in a dynamic food-web model. While competitive exclusion leads to persistence of only one producer species in 99.7% of the simulated simple producer communities without consumers, embedding the same producer communities in complex food webs generally yields producer coexistence. (...) This negative feedback loop regulates the coexistence and biomass patterns of the producers by balancing biomass increases of producers and biomass fluxes to herbivores, (...).


How The Snake Got Its Fangs, Science News

Excerpts:
By observing gene activity in snake embryos, a team revealed that, on the evolutionary tree, fangs sprang from one source. Pictured is the 18-day-old embryo of an African night adder. (...)
Credit: F. Vonk and M. Richardson
It likely all started when the back of the mouth left the front. (...)

Dagger-sharp frontal fangs allow cobras and vipers to prey on feisty mammals such as the large desert rat. Garter snakes, corn snakes and others that hunt less volatile creatures do just fine with fangs in the back of their mouth. What confused biologists, however, was learning that the front-fanged snakes don't fall into a neat group. In the snake tree of life, rear-fanged snakes are scattered on evolutionary branches in between the cobras and the more recently evolved vipers, which indicates that fangs evolved at least a couple of times on separate branches leading to front-fanged snakes.

Genetics: Simple Sleepers, Science

Excerpts: Classic genetic model organisms--fruit flies, zebrafish, and roundworms--are popular newcomers in sleep research laboratories, although debate continues about how much their dozing relates to human slumber.(...)

When birds and mammals sleep, their brains generate characteristic electrical patterns that denote deep sleep and dreaming. Since discovering this phenomenon in 1953 using electroencephalogram recordings of human brains, scientists have incorporated EEG patterns into the definition of sleep. But the simpler brains of flies, worms, and even reptiles don't produce those patterns, and no one was certain these animals even sleep.


China: Where Have All The Flowers Gone?, Nature

Excerpts: At least 117 boys were being born for every 100 girls at the beginning of this century in China. (...)

In 1982 the average male-to-female ratio at birth in China was 1.07 (as opposed to the normal level of 1.03-1.06); by 2000, various estimates put it at 1.17-1.21. And according to even official figures, the female-to-male infant mortality ratio rose during this period from around 0.95 to 1.46. The timing seems to imply a direct link to the one-child policy, although Guilmoto points out that the sex ratio has also increased in recent times in countries where no such restrictions apply, such as India and South Korea.


Scientists Hope To Gain Insight Into Fossil Record By Studying Current Size Ranges, The New Mexican

Excerpts: That more recent fossil record, they think, can help scientists better understand the size differences between animals in a group - like mammals or lizards or dinosaurs - from times much further back than 50 million years, such as the time of the dinosaurs, which ended 65 million years ago, Clauset said.

"This model may give us a way of estimating what we're missing in the fossil record," Clauset said.

That could be useful because fossils from the time of the dinosaurs, for instance, can be very deceptive.


  1. The Evolution and Distribution of Species Body Size, Science

    Excerpts: The distribution of species body size within taxonomic groups exhibits a heavy right tail extending over many orders of magnitude, where most species are much larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for interspecific competition and other microevolutionary processes, yet fully explains the shape of this distribution. We estimate the model's parameters from fossil data and find that it robustly reproduces the distribution of 4002 mammal species from the late Quaternary.
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