Re: Remine & Haldane on sci.bio.evolution


Friar Broccoli wrote:
David Wilson wrote:
In article <e7rkoj$2qgt$1@xxxxxxxxxxxxxxxxxxx> on June 27th in
sci.bio.evolution "Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxx> wrote:

Felsenstein recently mentioned a 1968 paper by Sved. Quoting from
the introduction of that paper:

Haldane (1957) was apparently the first to approach concisely
the problem of estimating evolutionary rates and to put forward
the view that the intensity of selection observed for most species
implied that there must be an upper limit to the possible rate
of their evolution. In discussing this point, he introduced the
notion of "the cost of natural selection". Assuming selection
to occur through the death in each generation of a constant
proportion of individuals carrying a particular gene, he calculated
that the total number of "selective deaths" occurring in the
replacement of that gene is of the order of 30 times the population
size, independent of the strength of selection involved. From
this he concluded that there could not be much more than one
substitution per genome per 300 generations on the average, based
on the view that most species could not tolerate a depression in
fitness of more than 10% per generation due to this cause. A
similar figure was accepted by Kimura ...


I reread the following:

http://www.talkorigins.org/indexcc/CB/CB121.html


so I just want to make sure I understand.

Am I correct in believing that the reference to "sexual recombination"
just means that you can break the population into small groups (say
little tribes spread all over one or more continents) and apply
Haldane's limit to each group.

I'm not sure what that reference means, but I suspect it means
something
different. In fact, I suspect it is wrong.

I interpret it as implying that since recombination can place two good
alleles
or two bad alleles into a single individual, you can get two units
worth of
evolution for the cost of one. It also seems to suggest that Haldane
and
ReMine failed to consider this possibility.

The suggestion that they failed to consider it is ridiculous and the
implication,
as I (mis?)understand it, is wrong. Recombination also means that half
of the population will have one good and one bad gene. And that means
that while one selective death does two units of work, the other
selective
death does nothing. Every analysis of the issue, including Haldane's
and
ReMine's, has taken recombination into account. It is not the magic
bullet
refuting Haldane.

Thus two separate groups could each evolve (and fix) a different
beneficial enhancement and then at a later time individuals from each
group could combine the characteristics.

Thus if there were 100 groups Haldane's limit could be multiplied by
100, from 1,667 to 166,700.

Do I have this right?

I'm pretty sure this doesn't work either. For one thing, the Haldane
limit
doesn't even apply to small populations. In a small population, there
is
a more severe limit on adaptive substitution - a small population is
probably
limited by the fact that it doesn't even get beneficial mutations all
that often.

And even if you start with a huge population, such that each of your
100
demes is large enough that it faces the Haldane limit rather than the
mutation limit, it still probably doesn't work. It is still going to
take a long
time for the eventual merged population to sort out which good genes to

keep and which to discard. Deme #23 may have come up with a better
version of the XYZZY gene than did deme #73, though both were better
than what you started with. All your barriers accomplish is to defer
the
merge. My intuition tells me that you get better throughput using a
merge-as-you-go strategy. But then, my intuitions have been wrong
before.

There is a link from the CB121 page to a web site by Williams that is
pretty
good. And it references and describes research by Ewens which suggests
that a limit does exist, but it is closer to something like 10
generations
per substitution than to the 300 generations estimated by Haldane.

ReMine's argument is weak. Silly statements like "Recombination solves
the problem" don't make his argument weaker. Instead they stregthen
his
secondary argument that evolutionists are conducting a campaign of
falsehood
and confusion.

.

Relevant Pages

  • Re: Remine & Haldane on sci.bio.evolution
    ... Haldane was apparently the first to approach concisely ... notion of "the cost of natural selection". ... proportion of individuals carrying a particular gene, ... you can get two units worth of evolution for the cost of one. ...
    (talk.origins)
  • Remine & Haldane on sci.bio.evolution
    ... The limit comes from Haldane, ... notion of "the cost of natural selection". ... applicable to the general course of evolution. ... of beneficial substitution that he thought might have occurred during ...
    (talk.origins)
  • Re: attempt of illustration of the role of sexual recombination in (partly, at least) solving Haldan
    ... evolution of a few specific traits, ... Very subtle or nearly "absent" selection, in the other hand, would be ... mutations that would have already achieved higher frequencies. ... The other, Haldane, limit arises from the finite power of ...
    (talk.origins)
  • Re: Remine & Haldane on sci.bio.evolution
    ... The limit comes from Haldane, ... notion of "the cost of natural selection". ... applicable to the general course of evolution. ... of beneficial substitution that he thought might have occurred during ...
    (talk.origins)
  • Re: Remine & Haldane on sci.bio.evolution
    ... The limit comes from Haldane, ... notion of "the cost of natural selection". ... applicable to the general course of evolution. ... of beneficial substitution that he thought might have occurred during ...
    (talk.origins)