Complexity Digest 2001.18

30-Apr-2001

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Content

  1. Archaeological Site in Peru Is Called Oldest City in Americas, NYTimes
    1. The First Urban Center in the Americas, Science
    2. Dating Caral, a Preceramic Site in the Supe Valley on the Central Coast of Peru, Science
  2. Cultural Responses to Climate Change During the Late Holocene, Science
    1. The Shadow of Droughts' Deaths, Science
  3. Nonlinear Effects Of Large-Scale Climatic Variability On Wild And Domestic Herbivores, Nature
    1. Increased Abundance Of Juvenile Corals On A Caribbean Reef, PNAS
  4. Entanglement Purification For Quantum Communication
  5. Selective Bond Breaking with Strong Laser Fields, Science
    1. Keeping Reactions Under Quantum Control, Science
    2. Selective Bond Dissociation and Rearrangement with Optimally Tailored, Strong-Field Laser Pulses, Science
  6. How the Brain Understands Music, Science
    1. How Our Brains Tell The Difference Between Music And Noise, New Scientist
    2. Pitch Perception: A Dynamical-Systems Perspective, PNAS
  7. A Wholly Empirical Explanation Of Perceived Motion, PNAS
  8. A Default Mode of Brain Function, Proc. Natl. Acad. Sci.
  9. A Neural Model Of Perceptual Grouping And Learning, Cerebral Cortex
  10. Russia Hails Breakthrough In Building Artificial Brain, The Christian Science Monitor
  11. Rhesus Monkeys Know When They Remember, PNAS
    1. Animals Know More Than We Used To Think, PNAS
    2. What Do Those Barks Mean?, NYTimes
  12. Tracking Memory's Trace, PNAS
  13. Covert Attention Accelerates The Rate Of Visual Information Processing, PNAS
  14. Blindsided by the Future, Vitamin B
  15. Adding Art to the Rigor of Statistical Science, NYTimes
  16. Life's Little Mysteries, NYTimes
    1. Universality And Diversity Of Protein Folding And Molecular Recognition Mechanisms, Chem.Phys.Let.
  17. Democracy at Risk, Tikkun Magazine
    1. Little Change Forecast For Election Process, NYTimes
    2. Playing At Life, Christian Science Monitor
  18. Why Wait for That Money? Download It Instead, NYTimes
  19. Links & Snippets
    1. Other Articles
    2. Announcements

  1. Archaeological Site in Peru Is Called Oldest City in Americas, NYTimes Next Article Bookmark and Share

    Excerpt: Researchers investigating a long-ignored Peruvian archaeological site say they have determined that it is the oldest city in the Americas, with a complex, highly structured society The finding is forcing a re-evaluation of ideas about the rise of the earliest civilizations in the New World, particularly how and when ancient peoples moved from the coasts, with reliable ocean food sources, to inland settlements with less stable supplies of food.


    1. The First Urban Center in the Americas, Science Next Article Bookmark and Share

      Summary: New dates from an archaeological team working at the sprawling inland site of Caral, some 200 kilometers north of Lima, push back the emergence of urban life and monumental architecture in the Americas by nearly 800 years--to 2627 B.C.--and cast serious doubt on one commonly held view of the relationships between inland and coastal centers in early Peru. But the research, reported on page 723, suggests an answer to the puzzle of why the desert sites became so prominent early on: Some were relatively easy to irrigate.

    2. Dating Caral, a Preceramic Site in the Supe Valley on the Central Coast of Peru, Science Next Article Bookmark and Share

      Excerpt: Radiocarbon dates from the site of Caral in the Supe Valley of Peru indicate that monumental corporate architecture, urban settlement, and irrigation agriculture began in the Americas by 4090 years before the present (…) to 3640 years before the present (…). Caral is located 23 kilometers inland from the Pacific coast and contains a central zone of monumental, residential, and nonresidential architecture covering an area of 65 hectares. Caral is one of 18 large preceramic sites in the Supe Valley.

  2. Cultural Responses to Climate Change During the Late Holocene, Science Next Article Bookmark and Share

    Excerpt: Modern complex societies exhibit marked resilience to interannual-to- decadal droughts, but cultural responses to multidecadal-to-multicentury droughts can only be addressed by integrating detailed archaeological and paleoclimatic records. Four case studies drawn from New and Old World civilizations document societal responses to prolonged drought, including population dislocations, urban abandonment, and state collapse. Further study of past cultural adaptations to persistent climate change may provide valuable perspective on possible responses of modern societies to future climate change.

    1. The Shadow of Droughts' Deaths, Science Next Article Bookmark and Share

      Summary: In this passionate discussion of interactions among climate, economics, and politics, Davis argues that the widespread catastrophic crop failures of the late 19th-century led not only to tens of millions of deaths but also to the deepened division of humanity into haves and have-nots.

      • The Shadow of Droughts' Deaths, Vaclav Smil, Science 2001 April 27; 292(5517): P. 644 , Science
      • Book review of: Late Victorian Holocausts El Niño Famines and the Making of the Third World, Mike Davis, Verso, London, 2001. 474 pp.

  3. Nonlinear Effects Of Large-Scale Climatic Variability On Wild And Domestic Herbivores, Nature Next Article Bookmark and Share

    Excerpts: Large-scale climatic fluctuations, such as the North Atlantic Oscillation (NAO), have been shown to affect many ecological processes. Such effects have been typically assumed to be linear. (…) Here we show that there is a strong nonlinear and non-monotonic (that is, reversed) effect of the NAO on body weight during the subsequent autumn for 23,838 individual wild red deer (Cervus elaphus) and 139,485 individual domestic sheep (Ovis aries) sampled over several decades on the west coast of Norway.

    1. Increased Abundance Of Juvenile Corals On A Caribbean Reef, PNAS Next Article Bookmark and Share

      Excerpts: Many coral reefs throughout the Western Atlantic region have undergone dramatic changes (…). where reefs that were formerly dominated by scleractinian corals and diminutive algal turfs have become overgrown by macroalgae. This transition is referred to often as a phase shift to an alternate state.(…)

      If the patterns documented here result in a reversal of the phase shift from macroalgae to corals (…), it would indicate that macroalgal dominance of Caribbean reefs is not an inevitable and terminal consequence of natural and anthropogenic disturbances.


  4. Entanglement Purification For Quantum Communication Next Article Bookmark and Share

    Excerpts: The distribution of entangled states between distant locations will be essential for the future large-scale realization of quantum communication schemes such as quantum cryptography and quantum teleportation. (…) Entanglement purification is thus essential to distil highly entangled states from less entangled ones. (…) Here we present a scheme for the entanglement purification of general mixed entangled states, which achieves 50 per cent of the success probability of schemes based on the CNOT operation, but requires only simple linear optical elements.

  5. Selective Bond Breaking with Strong Laser Fields, Science Next Article Bookmark and Share

    Abstract: Bond-selective photochemistry has been a long-sought but elusive goal. One difficulty is that photoexcited states can rapidly redistribute energy in ways that can be difficult to predict. Levis et al. (p. 709; see the Perspective by Hurley and Castleman) now report that different reaction outcomes can be selected through a closed-loop feedback algorithm that tailors the phase and amplitude of "strong-field" pulses. For very intense laser pulses (1013 watts per square centimeter), the various eigenstates of the molecule can be resonance-ionized by multiphoton adsorption; the states come into resonance through the Stark shifting that occurs in the strong electric fields generated by the laser pulse. By "training" the pulse shape, they can control, for example, whether acetophenone dissociates to form C6H5CO and CH3 or rearrange to form toluene and CO.

    1. Keeping Reactions Under Quantum Control, Science Next Article Bookmark and Share

      Summary: It has long been proposed that reactions can be controlled with lasers, but success with complex systems had to wait until ultrafast lasers heralded the field of femtosecond chemistry. In their Perspective, Hurley and Castleman highlight the report of Levis et al., who show that strong-field laser pulses can be used to control a dissociative rearrangement reaction. Bonds are not only selectively broken but also selectively formed.


    2. Selective Bond Dissociation and Rearrangement with Optimally Tailored, Strong-Field Laser Pulses, Science Next Article Bookmark and Share

      Excerpt: We used strong-field laser pulses that were tailored with closed-loop optimal control to govern specified chemical dissociation and reactivity channels in a series of organic molecules. (…) Strong-field control appears to have generic applicability for manipulating molecular reactivity because the tailored intense laser fields (about 1013 watts per square centimeter) can dynamically Stark shift many excited states into resonance, and consequently, the method is not confined by resonant spectral restrictions found in the perturbative (weak-field) regime.

  6. How the Brain Understands Music, Science Next Article Bookmark and Share

    Excerpt: A brain imaging study in the May issue of Nature Neuroscience confirms that people's brains are finely tuned to recognizing "musical syntax," just as they are for verbal grammar. What's more, they have found that some of this musical processing goes on in Broca's area, which is chiefly associated with language.

    1. How Our Brains Tell The Difference Between Music And Noise, New Scientist Next Article Bookmark and Share

      Excerpt: It's not just personal taste that distinguishes music from noise. German researchers say our brains are pre-programmed to tell the difference, and the ability is hard-wired into the same circuits that let us tell a meaningful sentence from nonsense.

    2. Pitch Perception: A Dynamical-Systems Perspective, PNAS Next Article Bookmark and Share

      Excerpt: Two and a half millennia ago Pythagoras initiated the scientific study of the pitch of sounds; yet our understanding of the mechanisms of pitch perception remains incomplete. (…) A proposal of nonlinear and complex systems research is that dynamical attractors may form the basis of neural information processing. Because the auditory system is a complex and highly nonlinear dynamical system, it is natural to suppose that dynamical attractors may carry perceptual and functional meaning. (…) this idea, (…) can be successfully applied to pitch perception.

  7. A Wholly Empirical Explanation Of Perceived Motion, PNAS Next Article Bookmark and Share

    Excerpts: Because the retinal activity generated by a moving object cannot specify which of an infinite number of possible physical displacements underlies the stimulus, its real-world cause is necessarily uncertain. (…) Here we explore the hypothesis that the visual system solves this problem by a probabilistic strategy in which perceived motion is generated entirely according to the relative frequency of occurrence of the physical sources of the stimulus. (…) The velocities reported by observers in a variety of stimulus contexts can be accounted for in this way.

  8. A Default Mode of Brain Function, Proc. Natl. Acad. Sci. Next Article Bookmark and Share

    In PET ( Positron Emission Technology) of fMRI (functional Magnetic Resonance) task induced increase in regional brain activity during specific goal-orientated behavior are commonly observed by comparing between a specific experimental task and a control task. The difference between the two is considered to represent the brain activity that is associated with the process of interest. Task induced decreases in regional activity has also been observed even when the control task consists of lying quietly. But what does the resting brain activity represent? In the following paper a theory on 'baseline' state of the brain is proposed.

    The authors have used PET to measure a variety of metabolic and circulation relationship between blood flow and oxygen consumption in the brain. They have formulated 'oxygen extraction factor' [OEF] that is the fraction of oxygen available to the brain to that used by the brain and cerebral blood flow [CBF] . Through measuring OEF, the authors propose to define the baseline state of the brain activity. OEF should indicate which area is deactivated during resting state. The deflection from the baseline state may be interpreted stimulus processing in the brain. In support of their claim, experimental data and images from subjects are given by the authors as 1) Maps of the fraction of oxygen extracted by the brain from arterial blood 2) Regions of the brain regularly observed to decrease their activity.

    Excerpts: A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge. (…) All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. (…) These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.

    • A Default Mode of Brain Function, Marcus E. Raichle, Ann Mary MacLeod, Abraham Z. Snyder, William J. Powers, Debra A. Gusnard, and Gordon L. Shulman, Proc. Natl. Acad. Sci., USA, 98, 676-682 (2001), Contributed by Atin Das

  9. A Neural Model Of Perceptual Grouping And Learning, Cerebral Cortex Next Article Bookmark and Share

    Excerpts: A neural model suggests how horizontal and interlaminar connections in visual cortical areas V1 and V2 develop within a laminar cortical architecture and give rise to adult visual percepts. The model suggests how mechanisms that control cortical development in the infant lead to properties of adult cortical anatomy, neurophysiology and visual perception. The model clarifies how excitatory and inhibitory connections can develop stably by maintaining a balance between excitation and inhibition. (…) These balanced connections interact via intracortical and intercortical feedback to realize properties of perceptual grouping, attention and perceptual learning in the adult, and help to explain the observed variability in the number and temporal distribution of spikes emitted by cortical neurons.

  10. Russia Hails Breakthrough In Building Artificial Brain, The Christian Science Monitor Next Article Bookmark and Share

    Excerpt: Russian scientists claim to have developed the first artificial brain, a "neuro-computer" with the same intellectual potential as its human counterpart, the Interfax news agency reported last weekend.The new Russian computer is based on the human brain cell, or neuron, and outstrips previous brain models by using state-of-the-art findings in neurophysiology and neuromorphology to produce a truly thinking machine, scientist Vitaly Valtsev said. But he warned of the potential hazards of the scientific breakthrough, saying the brand new brain could turn into a Frankenstein monster if mistreated. (...)

    "Having correct models of neurons might be a necessary condition for simulating "the intellectual potential of human" but it is by far not sufficient. In fact, most mammals have the same general classes of neocortex neurons (ie. pyramidal, granule, chandelier, large/small basket, double bouquet, neurogliagorm cells, etc...) that we do. Thus, I hope he has made a great structural breakthrough in the design of his AI rather than simply replaced the neuron model."

    Ben Houston, posting on Global Brain discussion list, 01/04/25

    Editor's note: The background of this story is an example of rapid emergence of global information networks, triggered by a news story: Mason and picked up the story, Anton could verify independent links (besides the ones that all repeated the Interfax message), and Ben provided critical background information.

    Other relevant URLs:


  11. Rhesus Monkeys Know When They Remember, PNAS Next Article Bookmark and Share

    Excerpts: Humans are consciously aware of some memories and can make verbal reports about these memories. Other memories cannot be brought to consciousness, even though they influence behavior. This conspicuous difference in access to memories is central in taxonomies of human memory systems but has been difficult to document in animal studies, suggesting that some forms of memory may be unique to humans. Here I show that rhesus macaque monkeys can report the presence or absence of memory. (…) Animals able to discern the presence and absence of memory should improve accuracy if allowed to decline memory tests when they have forgotten, and should decline tests most frequently when memory is attenuated experimentally. (…) leaving detection of the absence of memory per se as the most likely mechanism underlying the monkeys' abilities to selectively decline memory tests when they had forgotten.

    1. Animals Know More Than We Used To Think, PNAS Next Article Bookmark and Share

      Excerpt: There is no need for a double standard by which evidence of animal consciousness is accepted only if it provides perfect proof, whereas in other areas of science we are accustomed to weighing and evaluating imperfect or ambiguous data. This consideration is especially relevant when dealing with areas where we know very little, as is clearly the case with nonhuman consciousness. Hampton's experiments, along with the other recent discoveries listed above, have increased the probability of simple subjective, conscious experience in at least some animals to the level where the burden of proof rests on those who are inclined to deny its presence.


    2. What Do Those Barks Mean?, NYTimes Next Article Bookmark and Share

      Excerpts: The results, (…) graphically portray how different barks express different emotions, including loneliness, fear, distress, stress and pleasure, as well as a need for care among puppies - and serve to alert other dogs, people or animals to changing external circumstances.

      "This work on barking is extremely careful and extremely important because it calls attention to the complex social life of dogs that we have barely begun to comprehend," said Dr. Marc Bekoff, an ethologist at the University of Colorado (...)


  12. Tracking Memory's Trace, PNAS Next Article Bookmark and Share

    Excerpts: (…)during sleep, the memory of newly learned information is stabilized (…) mediated by fluctuations in the activity of different neuromodulatory systems (e.g., noradrenergic, serotonergic, cholinergic) and in the levels of plasma glucocorticoids.

    We have tracked the changes in neuronal responses that occur with learning in a real memory system (…). These changes are surprisingly nonlinear. Our findings present a challenge to current ideas concerning cellular mechanisms of memory, in particular those that assume that, through learning, the strength of synapses (…) increase monotonically to a stable asymptote.


  13. Covert Attention Accelerates The Rate Of Visual Information Processing, PNAS Next Article Bookmark and Share

    Abstract: Whenever we open our eyes, we are confronted with an overwhelming amount of visual information. Covert attention allows us to select visual information at a cued location, without eye movements, and to grant such information priority in processing. Covert attention can be voluntarily allocated, to a given location according to goals, or involuntarily allocated, in a reflexive manner, to a cue that appears suddenly in the visual field. Covert attention improves discriminability in a wide variety of visual tasks. An important unresolved issue is whether covert attention can also speed the rate at which information is processed. To address this issue, it is necessary to obtain conjoint measures of the effects of covert attention on discriminability and rate of information processing. We used the response-signal speed-accuracy tradeoff (SAT) procedure to derive measures of how cueing a target location affects speed and accuracy in a visual search task. Here, we show that covert attention not only improves discriminability but also accelerates the rate of information processing.

  14. Blindsided by the Future, Vitamin B Next Article Bookmark and Share

    Abstract: "May you live in interesting times" is an ancient Chinese curse that is taking on special meaning in the third millennium. Over the past decade we have seen the equivalent of the Cambrian explosion in the global economy. New technologies and organizational forms are evolving at an accelerating rate. Joseph Schumpeter's process of creative destruction is alive and well in the econosphere. In the 21st century, it will be crucial for analysts to devote an increasing portion of their research to understanding complex adaptive systems and non-conventional models. Those analysts that embrace what legendary investor Charlie Munger calls a "latticework of models" approach--that is, one that draws on the body of knowledge found in fields of study ranging from quantum physics, biology, computer science, economics, sociology, psychology--and other disciplines and abandon an intuitive linear/rational expectations view of the world are likely to prosper in the third millennium. Analysts who refuse to upgrade their wetware and internal models of the economy and markets may well end up getting blindsided by the future.


  15. Adding Art to the Rigor of Statistical Science, NYTimes Next Article Bookmark and Share

    Abstract: (…) a small British company called Autonomy, whose founder wrote his doctoral thesis on Bayesian methods, sells software that helps computers intelligently sort through the vast amounts of information that large organizations now produce on any given day. (…)But once both data and beliefs enter the picture, the math can become stupefyingly complex. (…)The software, now being tested, combines facts about who has sent an e-mail message and the words it contains with information about a user's habits.


  16. Life's Little Mysteries, NYTimes Next Article Bookmark and Share

    Abstract:Thermodynamic and kinetic aspects of ligand-protein binding are studied for the methotrexate-dihydrofolate reductase system from the binding free energy profile constructed as a function of the order parameter. Thermodynamic stability of the native complex and a cooperative transition to the unique native structure suggest the nucleation kinetic mechanism at the equilibrium transition temperature. Structural properties of the transition state ensemble and the ensemble of nucleation conformations are determined by kinetic simulations of the transmission coefficient and ligand-protein association pathways. Structural analysis of the transition states and the nucleation conformations reconciles different views on the nucleation mechanism in protein folding.

    1. Universality And Diversity Of Protein Folding And Molecular Recognition Mechanisms, Chem.Phys.Let. Next Article Bookmark and Share

      Abstract: Thermodynamic and kinetic aspects of ligand-protein binding are studied for the methotrexate-dihydrofolate reductase system from the binding free energy profile constructed as a function of the order parameter. Thermodynamic stability of the native complex and a cooperative transition to the unique native structure suggest the nucleation kinetic mechanism at the equilibrium transition temperature. Structural properties of the transition state ensemble and the ensemble of nucleation conformations are determined by kinetic simulations of the transmission coefficient and ligand-protein association pathways. Structural analysis of the transition states and the nucleation conformations reconciles different views on the nucleation mechanism in protein folding.


  17. Democracy at Risk, Tikkun Magazine Next Article Bookmark and Share

    Besides pointing out problems with the political system or Wall Street, Gates could also comment on our educational standards and schools that we have witnessed over the past several decades. It's no coincidence that the political problems Gates discusses coincide with a decline in educational standards, particularly at the grade school level. A strong democracy requires an educated public. Raising America's educational standards is probably the safest way to strengthen a democracy. To be sure, there are many steps that Gates discusses in his book that could be taken to help shore up some of the problems in our political system today. Complexity theory tells us that there is much wisdom in the collective thinking of large groups. Given this, it's not difficult to imagine a more robust body politic emerging from a highly educated public. Therefore promoting education and better schooling appears to be a valuable goal. This would undoubtedly go a long way toward creating the type of robust democracy that Gates and others so badly seek.

    Excerpts: Revolutions are born of adversity. Systemic change often proves impossible until a system proves itself unquestionably dysfunctional. Today, the system is broke. Our goal now is to chronicle the dangers to democracy that accompany today's de facto merger of political parties, particularly when both have geared their economic policies not to democratic principles and to the needs of future generations but to the peculiar appetites of Wall Street. What democracy most needs is a process that dignifies elections. A valid election must provide essential time for reflection, for voter education, and for media-induced consciousness raising and information sharing. The predictable result of the current rules is today's staged and restricted debates, with their minimal discussion and superficial analysis. Elections thereby become impressionistic and simplistic, as both policies and politicians come prepackaged, predictable, even typecast. In the case of the three overproduced 2000 presidential "debates," even the stage set was designed to suggest electoral legitimacy, right down to studios adorned with the trappings of high office (eagles, bunting, banners, etc.).


    1. Little Change Forecast For Election Process, NYTimes Next Article Bookmark and Share

      Excerpt: (...) the next national election will probably occur under virtually the same circumstances as the last, with the same unreliable voting systems and under the same dizzying hodgepodge of rules that vary from county to county across the nation.

      The reasons vary, from a lack of cash to partisan positioning and difficulties in interpreting the United States Supreme Court decision that finally ended the presidential contest. Those studying how to overhaul the system have found that it is exceedingly complex.

      Editor's question: What would it cost to modernize all voting machines, the dollar amount expressed in minutes of TV-campaign advertizing?


    2. Playing At Life, Christian Science Monitor Next Article Bookmark and Share

      Excerpts: (…) complex questions computer games raise for players "can sometimes lead to profound forms of interaction. Even if two players are interacting through a crude medium and manipulating simple characters, sometimes that can serve to spark conversations about life as it's actually lived." (…)"Creating more complex and believable social interactions is one of our main focus areas," (…), the basic irony of the game - that players win points for virtual social prowess, while glued to their computer screens(…).

  18. Why Wait for That Money? Download It Instead, NYTimes Next Article Bookmark and Share

    Excerpts: About a dozen person-to-person online payment services - from systems offered by Citibank and Western Union to a Web- based venture called PayPal - have emerged over the last year or so. They allow consumers to transfer money quickly online through their bank accounts or credit cards, (…)

    "It's one of the fastest-growing Internet services out there," said Paul Jamieson, director of financial services at Gomez Advisors, a research firm based in Lincoln, Mass., that ranks e-commerce sites.

    Editor's note: Money has emerged thousands of years ago as convenient "fitnes function" in human societies around the world. It is only natural that the reduced time-scales of global information exchange need to impact the time-scales of the corresponding incentives for transferring valued information. As soon as secure credit card transactions were available, the commercial use of the Internet has blossomed. The original idea of CyberCash was to facilitate rapid, small payments for information services over the web. But even today, it still is a major hassle to send, say, $25 to a place in India without the transaction cost being a major fraction of the transaction amount.


  19. Links & Snippets Next Article Bookmark and Share

    1. Other Articles Next Article Bookmark and Share

      1. Publishing On The Semantic Web, T Berners-Lee , J Hendler, Nature 410, 1023 - 1024 (2001)
      2. Nonlinear-Dynamical Arrhythmia Control In Humans, David J. Christini, Kenneth M. Stein, Steven M. Markowitz, Suneet, Mittal, David J. Slotwiner, Marc A. Scheiner, Sei Iwai, Bruce B. Lerman, Proc. Natl. Acad. Sci. USA published 24 April 2001, 10.1073/pnas.091553398
      3. A Phenomenological Description Of Space-Time Noise In Quantum Gravity, G Amelino-Camelia, Nature 410, 1065 - 1067 (2001)
      4. Nonlinear-Dynamical Arrhythmia Control In Humans, David J. Christini, Kenneth M. Stein, Steven M. Markowitz, Suneet, Mittal, David J. Slotwiner, Marc A. Scheiner, Sei Iwai, Bruce B. Lerman, Proc. Natl. Acad. Sci. USA published 24 April 2001, 10.1073/pnas.091553398
      5. Genetic Documentation Of Filial Cannibalism In Nature, J. Andrew DeWoody, Dean E. Fletcher, S. David Wilkins, and John C. Avise, PNAS 2001;98 5090-5092


    2. Announcements Bookmark and Share


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