Surprising finding: Tree's
leaves genetically different from its roots
Black cottonwood trees
(Populus trichocarpa) can clone themselves to produce offspring that are
connected to their parents by the same root system. Now, after the first
genome-wide analysis of a tree, it turns out that the connected clones have
many genetic differences, even between tissues from the top and bottom of a
single tree. The variation within a tree is as great as the variation across
unrelated trees. Such somatic mutations — those that occur in cells other than sperm
or eggs — are familiar to horticulturalists, who have long bred new plant
varieties by grafting mutant branches onto ‘normal’ stocks. But until now, no
one has catalogued the total number of somatic mutations in an individual
plant.
In one tree, the top buds
of the parent and offspring were genetically closer to each other than to their
respective roots or lower branches. In another tree, the top bud was closer to
the reference cottonwood genome than to any of the other tissues from the same
individual.The tissue-specific mutations affected mainly genes involved in cell
death, immune responses, metabolism, DNA binding and cell communication. Olds
think that this may be because many of the mutations are harmful, and the tree
reacts by destroying the mutated tissues or altering its metabolic pathways and
the way it controls its genes, which leads to further mutations.
The findings have parallels
to cancer studies, which have recently shown that separate parts of the same
tumor can evolve independently and build up distinct genetic mutations, meaning
that single biopsies give only a narrow view of the tumor’s diversity.
Human cycles: History as
science
For the past 15 years,
Turchin has been taking the mathematical techniques that once allowed him to
track predator–prey cycles in forest ecosystems, and applying them to human
history. He has analysed historical records on economic activity, demographic
trends and outbursts of violence in the United States, and has come to the
conclusion that a new wave of internal strife is already on its way1. The peak
should occur in about 2020, he says, and will probably be at least as high as
the one in around 1970. “I hope it won't be as bad as 1870,” he adds.
Human cycles: History as
science
Laura Spinney
Inescapable Pull
Black holes, once the
preserve of theory and science fiction, are well-established inhabitants of the
universe. Observations of the motions of stars orbiting the center of the Milky
Way have proved beyond doubt that a black hole 4 million times as massive as
the Sun resides there. Many other galaxies are thought to host similarly heavy
or even heavier black holes at their centers. Scattered out beyond the center,
there are thought to be millions of lighter, stellar-mass black holes, produced
when the most massive stars collapse in on themselves at the end of their
lives. This week, Science explores the current state of understanding of black
holes with a series of Perspectives and Reviews.
Inescapable Pull
Maria Cruz
Maria Cruz
Science 3 August 2012:
Vol. 337 no. 6094 p. 535
http://dx.doi.org/10.1126/science.337.6094.535
Vol. 337 no. 6094 p. 535
http://dx.doi.org/10.1126/science.337.6094.535
Measuring the Complexity of
Ultra-Large-Scale Evolutionary Systems
Ultra-large scale (ULS)
systems are becoming pervasive. They are inherently complex, which makes their
design and control a challenge for traditional methods. Here we propose the
design and analysis of ULS systems using measures of complexity, emergence,
self-organization, and homeostasis based on information theory. We evaluate the
proposal with a ULS computing system provided with genetic adaptation
mechanisms. We show the evolution of the system with stable and also changing
workload, using different fitness functions. When the adaptive plan forces the
system to converge to a predefined performance level, the nodes may result in
highly unstable configurations, that correspond to a high variance in time of
the measured complexity. Conversely, if the adaptive plan is less
"aggressive", the system may be more stable, but the optimal performance
may not be achieved.
Measuring the Complexity of
Ultra-Large-Scale Evolutionary Systems
Michele Amoretti, Carlos Gershenson
Some Computational Aspects
of Essential Properties of Evolution and Life
While evolution has
inspired algorithmic methods of heuristic optimisation, little has been done in
the way of using concepts of computation to advance our understanding of
salient aspects of biological phenomena. We argue that under reasonable
assumptions, interesting conclusions can be drawn that are of relevance to
behavioural evolution. We will focus on two important features of
life--robustness and fitness--which, we will argue, are related to algorithmic
probability and to the thermodynamics of computation, disciplines that may be
capable of modelling key features of living organisms, and which can be used in
formulating new algorithms of evolutionary computation.
Some Computational Aspects
of Essential Properties of Evolution and Life
Hector Zenil, James A.R.
Marshall
Why We Lie
Over the past decade or so,
my colleagues and I have taken a close look at why people cheat, using a
variety of experiments and looking at a panoply of unique data sets—from
insurance claims to employment histories to the treatment records of doctors
and dentists. What we have found, in a nutshell: Everybody has the capacity to
be dishonest, and almost everybody cheats—just by a little. Except for a few
outliers at the top and bottom, the behavior of almost everyone is driven by
two opposing motivations. On the one hand, we want to benefit from cheating and
get as much money and glory as possible; on the other hand, we want to view
ourselves as honest, honorable people. Sadly, it is this kind of small-scale
mass cheating, not the high-profile cases, that is most corrosive to society.
Introducing the Computable
Universe
Some contemporary views of
the universe assume information and computation to be key in understanding and
explaining the basic structure underpinning physical reality. We introduce the
Computable Universe exploring some of the basic arguments giving foundation to
these visions. We will focus on the algorithmic and quantum aspects, and how
these may fit and support the computable universe hypothesis.
Introducing the Computable Universe
Hector Zenil
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