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Old June 23rd, 2005, 07:18 AM
James Brody James Brody is offline
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Default Two Papers on Emergent Networks

Two Papers on Networks
6/22/05 posted bol
Network research grows in several cultures. Nature, 435, 2005, visits two of them.
1) Achioloptas, Naor, & Peres (Rigorous location of phase transitions in hard optimization problems, pp. 759-764) attack the prediction of phase transitions within computational problems. That is, if you have a number of participants with a number of constraints between them, problems that include all participants while satisfying all constraints are easy to solve or, suddenly, very difficult to impossible to solve. Solvability varies as the ratio of participants to constraints: few participants in comparison to the numbers of rules means unsolvable problems. (Think about it!)
Relevance to evolution? Satisfiability problems are a part of human history (Brody, 2001, 2002). That is, being able to match your team of hunters with their weapons and the liabilities of wild game is a challenge for logic or trial and error. Likewise, for matching resources with children and the individuals able to supply those resources. Individuals who can solve these problems should be recognized for their "political skill" and therefore, per Buss, more attractive as mates and more powerful in assuring the survival of their offspring.
There is a second relevance: phase transitions usually occur whenever you have an emergent network. Brains to termite colonies organize according to power laws and exhibit phase transitions between chaotic and static arrangements. The survivable and reproductive option is that of being a bit rigid and a bit flexible when you track environments. Exploratory systems (immune reactions, calluses, blood vessels, muscularity, and CNS specializations) follow exactly this strategy of two steps forward and one backward. Niches and occupants match...
Conclusion: once more, the math of emergent networks is a more persuasive part of our EEA than cat's teeth or human jealousy. (Incidentally, the two lead authors work for Microsoft rather than for a university and engage in problems of chip design.)
2) Palla, Derenyi, Farkas, & Vicsek (pp.814-818) propose a set of labels for organizations that consist of overlapping neighborhoods. A protein community, a semantic community, and a coauthorship community display similar power law curves for the local neighborhood but also hint of exponential relationships for the number of nodes that are shared when several communities overlap. Palla and team want to retain information about the relationships that exist between several communities when they share a set of nodes, as when one protein participates in several metabolic processes. This sort of analysis is perhaps the next step in analyses started by Barabasi, Albert, Watts, & Strogatz.
It also promises to enrich our understanding of evolution and, perhaps, to resolve some of the conflicts between the saltationists and channel theorists such as Rudy Raff, Steven Gould, or Sean Carroll, on the one hand, and the neodarwinian progressivists, a very small camp outside of HBES, on the other.
James Brody
References:
Brody, J. (2001) Evolutionary recasting: ADHD, mania and its variants. Journal of Affective Disorders. 65: 197-215.
Barabasi, A-L (2002) Linked: The New Science of Networks. NY: Perseus.
Brody, J. (2002) From Physics and Evolutionary Neuroscience to Psychotherapy: Phase Transitions and Adaptations, Diagnosis and Treatment. In G. Cory & R. Gardner (Eds.) The Evolutionary Neuroethology of Paul MacLean: Convergences & Frontiers, Praeger-Greenwood, pp. 231-259.
Carroll, S. (2004) Endless Forms Most Beautiful: The New Science of Evo Devo. NY: Norton.
Carroll, Sean, Grenier, J., & Weatherbee, S. (2001) From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design. Malden, MA: Blackwell.
Gould, S. (1977) Ontogeny and Phylogeny. Cambridge, MA: Harvard Belknap.
Gould, S. (2002) The Structure of Evolutionary Theory. Cambridge, MA: Harvard Belknap.
Raff, Rudolf (1996) The Shape of Life. Chicago, IL: University of Chicago Press.
Strogatz, S. (2003) Sync: The Emerging Science of Spontaneous Order. NY: Hyperion.
Watts, D. (2000/2004) Small Worlds: The Dynamics of Networks between Order and Randomness. Princeton, NJ: Princeton University Press.
Watts, D. (2003) Six Degrees: The Science of a Connected Age. NY: Norton.
Watts, D. & Strogatz, S. (1998) Collective dynamics of 'small-world' networks. Nature. 393: 440-442.
Copyright, James Brody, all rights reserved, 2005
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