Re: Sergey Gavrilets and the adaptive landscape


"William Morse" <wdmorse@xxxxxxxxxxxx> wrote in message news:dkepms$2m6i$1@xxxxxxxxxxxxxxxxxxxxxx
> dkomo <dkomo871@xxxxxxxxxxx> wrote in
> news:dkb125$107d$1@xxxxxxxxxxxxxxxxxxx:
>
> > Wirt Atmar wrote:
> >> The nearly complete decoupling between the range of mutations
> >> expressed and the shape of the adaptive topography intrinsically
> >> makes evolutionary optimatization algorithms surprisingly resistant
> >> to entrapment in local optima. Perhaps completely counter-intuitive,
> >> it is not the height of the intervening barrier that represents the
> >> problem to continuing evolution but its width.
> >>
> >> With this introduction, to continue the discussion, please see:
> >>
> >> http://aics-research.com/research/notes.html#IID
> >>
> > dkomo:-
> > As far as I can tell, everything you wrote here and on the above web
> > page assumes a static fitness topology. Is that right? Yet, in the
> > real world the environment is constantly changing, which will affect
> > the topology of the fitness landscape. This can also happen if a
> > population of animals migrates to a new location or encounters a new
> > type of predator or prey. So a particular population can rather
> > quickly shift from being on the slopes of a local peak to being at the
> > bottom of a valley due to these kind of environmental changes.
> >
> > I don't see how a static fitness landscape can realistically model
> > biological evolution. You must take into account that the landscape
> > is itself dynamic.
> >
> Morse:-
> There is an interesting article that discusses this in the 9/25/2005
> Science, p. 2075 "Phenotypic Diversity, Population Growth, and
> Information in Fluctuating Environments" by Kussell and Leibler. I have
> not yet read the article itself, but the Perspective piece (p. 2005) on
> it makes several points: that the reproductive success in fluctuating
> environments can be calculated using the Lyapunov exponent (whatever that
> is). That in a fluctuating environment organisms respond by randomizing
> their phenotype, known as bet-hedging. That selection may favor
> "stochastic switching" - producing variable offspring by chance - over
> "responsive switching" - producing variable offspring only after sensing
> a change in the environment. This last would support Larry Moran's
> contention that organisms are often not well adapted - but it might be
> considered an "adaptationist" explanation for observed stochasticism :-)
>
Thanks, Bill. I was unsuccessful finding much about this paper online
without a subscription, but in my searching, I came across this online
paper which seems to be related. I strongly recommend it:

The Fitness Value of Information
Carl Bergstrom and Michael Lachmann
http://arxiv.org/PS_cache/q-bio/pdf/0510/0510007.pdf

Abstract
Biologists measure information in different ways. Neurobiologists and
researchers in bioinformatics often measure information using information-
theoretic measures such as Shannon?s entropy or mutual information. Be-
havioral biologists and evolutionary ecologists more commonly use decision-
theoretic measures, such the value of information, which assess the worth
of information to a decision maker. Here we show that these two kinds
of measures are intimately related in the context of biological evolution.
We present a simple model of evolution in an uncertain environment, and
calculate the increase in Darwinian fitness that is made possible by infor-
mation about the environmental state. This fitness increase ? the fitness
value of information ? is a composite of both Shannon?s mutual infor-
mation and the decision-theoretic value of information. Furthermore, we
show that in certain cases the fitness value of responding to a cue is exactly
equal to the mutual information between the cue and the environment. In
general the Shannon entropy of the environment, which seemingly fails to
take anything about organismal fitness into account, nonetheless imposes
an upper bound on the fitness value of information.


.

Relevant Pages

  • Re: The wirehead problem
    ... rather they attempt to maximise their *expected* fitness, ... long search process of evolution, in a particular environment. ... It seems like the ordinary sense of the word "expectations" to me. ...
    (comp.ai.philosophy)
  • Re: pre-tuning to baldwin effect
    ... mean that the fitness level of an organism is hardly determined by the ... You seem to want 'fitness' to mean 'ability to evolve progressively'. ... the ability to cope with different types of environment ... the environment doesn't change and there isn't much evolution, ...
    (sci.bio.evolution)
  • Re: Absolute or just relative fitness?
    ... >> would argue that there is a general overall increase in absolute fitness. ... > is, in some sense, a fitness that would result if the environment ... > of evolution, such a concept is purely theoretical. ... The argument that fitness is increasing suggests that organisms are ...
    (sci.bio.evolution)
  • Re: Felsenstein and reproductive excess
    ... >conspecifics constitutes a deterioration in the environment for you. ... >model which would allow fitness to "increase" over time without population ... we have to distinguish between mutations that make an individual ...
    (sci.bio.evolution)
  • Re: DNA carries information
    ... The Fitness Value of Information ... on a detail (DNA), it took me some time to develop a coherent ... the germ of a distinction between significant ... tasting, making any measurement on the environment, nothing at all ...
    (talk.origins)