Re: Bet Hedging, Risk Aversion, Sex, and the Unit of Selection


"g" <gillawton@xxxxxxxxxxxxx> wrote in message news:dr3g4g$vr6$1@xxxxxxxxxxxxxxxxxxxxxx
>
> "Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx> wrote in message
> news:dr1gik$80f$1@xxxxxxxxxxxxxxxxxxxxxx
>
> Jim,
>
> Please let me first say that this is one of the most well-expressed
> contributions to sbe I ever have read. ...

Thanks.

> And now let me say, merely, that the following statement suggests (quite
> likely to me, only) something that bothers me -- namely, just a hint of
> suggesting that species are proactive in their evolution.
>
> The idea is that an organism can and
> > should 'hedge its bets' by having some offspring adapted to one
> > environment and other offspring adapted to different environments.
>
> You need not explain to me that proactive participation by species in the
> fates of their progeny is in the slightest intended, nor that it is
> conventional among those who clearly know and understand this to use
> analogs that are not perfect.

In the interests of full disclosure, I should admit I am a bit out of
the mainstream in my tolerance for and use of teleological language
for natural entities which quite clearly DO NOT think conscious thoughts.

But not all THAT far from the mainstream. I didn't invent the biological
use of the term 'bet hedging', for example.

[snip]

> > 1. Sex exists because it provides a mechanism for bet hedging.

> But please allow me to submit that other mechanisms may work, too. Consider
> for example some of the mechanisms utilized by pathogens for spreading
> "advantageous traits" which currently are tormenting medical researchers
> with respect to the increasing resistance of pathogens to antibiotics and,
> concomitant increase of those same pathogens for resistance even to the
> innate immune systems of humans. One of those mechanisms is "conjugation,"
> I think, and another "transformation."

Yes indeed. In fact, if you have looked at the Bergstrom/Lachmann paper,
you will notice that they are talking about asexual bacteria as the
hedgers of bets.

> > 2. But this only makes sense if the unit of selection is seen
> > as the gene-clone, as in a gene's eye view justification
> > of Hamilton's rule. A gene clone can spread its bets
> > evenly among the alternatives - it has a 'stake' that is
> > divisible. Organisms, for the most part, do not.
>
> Sorry, but every time someone makes this leap, I end up jumping my hardest
> and ending up at the bottom of a canyon of confusion. For me, something is
> assumed in arriving at a gene's eye view that leaves me (not having assumed
> it) unable to take it and run with it to anywhere. Every gene's-eye-view
> seems to me to suggest that genes are proactive in assessing what the
> ecology of a given evolutionary moment is doing, and what vectors of change
> are occurring within that moment which can predict in advance what is going
> to neutral now, but advantageous later on, and such... but I am unable to
> presume that genes are psychic, that genes are able to assess by some
> physiological means what is going around them, and that genes are capable of
> strategizing what to do -- or try to do -- about what is in the road
> immediately ahead or at some distance ahead.

Quite frankly, I don't see your problem. Under random mutation and
natural selection, those entities which do leave progeny can be said
to have behaved AS IF they had directed their own mutations so as to
achieve some end. That is true of rabbits, which evolve as if 'trying'
to increase their fitness; it is true of bacteria, which evolve as if
trying to maximize the count of offspring; and it is true of genes.

The same metaphor is being used in all cases; it is a standard metaphor;
and those who refuse to 'get used to it' are going to be perpetually
condemned to having their complaints fall on deaf ears.

> > 3. As suggested in the paper by Bergstrom and Lachmann
> > The Fitness Value of Information
> > Carl Bergstrom and Michael Lachmann
> > http://arxiv.org/PS_cache/q-bio/pdf/0510/0510007.pdf
> > the process of natural selection can be given an information
> > theoretic interpretation in which there is an identity between
> > fitness (Fisher's r) and information acquired about the actual
> > distribution of environments.
>
> Bergstrom and Lachmann may have something there... something which can be
> put to actual testing in lab. If so, I look forward to being told how, and
> what the results are. In absence of that, I hold in reserve any conclusion
> pro or con on the issue.

Bergstrom and Lachmann have constructed a model, not a theory about how
nature works. You don't test this kind of thing in the lab or in the field.
You and Edser both seem confused on this issue.

What Bergstrom and Lachmann have discovered is an unexpected property
of models of evolution. They haven't discovered something about
evolution itself - about physical reality.

> ... I get the impression some
> might make a single assumption as to what might be, and then launch into a
> long, intricate chain of assumptions which -- unless the first is valid --
> the rest are leaving empirical things farther and farther behind...
> advancing,
> as it were, into more and more complex suppositions based upon suppositions.

Yes. And what is wrong with that?


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