Re: Evolution increases the computational ability of organisms.

Tim Tyler wrote:

John Harshman wrote:

Tim Tyler wrote:

John Harshman wrote:

Tim Tyler wrote:


Most bushes seem to get more twigs on them as they grow -
ours probably has too.

I'm afraid that's nonsense. [...]

Well, I reckon my statement was literally true, under a
fairly reasonable interpretation. Your problem seems to
be with underlying analogy:

No, my problem is your attempt to use an analogy as support for your
position, when your choice of analogy is arbitrary.


Evolution as a bush is a pretty common analogy.

Yes, but you're pushing it beyond its limits of usefulness. It's a bush
in that it branches. But that doesn't mean it's a bush in that the bush
grows bigger. Now it's trivial that the bush as we see it today must
have grown, because it goes back to a single ancestor. But you need to
look up "coalescence". The bush of, say, chimpanzee mitochondria also
goes back to a single ancestor, but there's no reason to suppose that
the bush is growing. (I would have used humans, but of course the bush
has been growing for a while because the population is increasing.)

Using your analogy, what if the tree of life is a hedge, and
twigs are pruned back as fast as they grow?

That case isn't relevant, cos the tree of life is not like that.

And you know this how, exactly?

Well, I don't for sure.

Please bear in mind that not /all/ of my views are subject to having
their innards being publicly poked around in. Not even my analyst
understands how I arrive at some of them - and of course, my
explanatory time and energy budget has limits.

That doesn't necessarily stop me from giving out my views in an
authoritative manner - since I evidently think they have /some/
value, but asking after some of them may produce limited returns.

OK. So the tree of life may very well be like that.

There have been some suggestions that there is a species carrying

capacity that is rapidly achieved after any mass extinction, and
that species numbers expand to this level but not beyond it. Why
should that be a priori less reasonable than infinite expansion?

Whoah. I never said "infinite".

This is another "progress" issue. As evolution progresses, more
distinct niches open up - I claim. Or at least that is what I
reckon has happened so far.

You never seem to address this sort of question, but I'll try anyway: Do
you have any basis for what you reckon here?

Firstly there is the rather trivial observation that the number of
occupied niches was small at the origin of life, so the only way is up.

That's true.

Then there is the idea that speciation is positively selected.
Speciation is the species-level analog of individual reproduction.
Species selection favours species that reproduce (i.e. speciate)
This generates species that get stuck on islands, species with
mutable genitalia that verge on incompatability with the other
sex, and so on: speciation-friendly species.

The problem with this is that you consider only speciation, not
extinction. Many of the characteristics that promote speciation also
promote extinction, so it's not clear at all that tendency to speciate
is selected by species selection. And of course species selection is
much weaker than individual selection, so can't move the biota if there
is a conflict.

Speciation is often
followed by divergent selection to reduce sterile crosses - and
this can take the form of divergence into distinct niches.

This is an incorrect view of speciation. You are garbling the concept of
"reinforcement" here, and conflating it with "competitive displacement".

As with other adaptive traits, species may get better at
speciation over time.

Then there is this simple-but-important concept:

http://originoflife.net/complexity/

...and some related ideas. In some sense if you have
some composite technology you want to build, and a
single organism with which to build it, one way
is to mutate that organism to be able to perform
all the roles required in one body.

Another is to either derive multiple species from the organism,
each one specialising in part of the process involved, or use
phenotypic plasticity to produce a similar effect.

The latter way is usually a helluva lot easier and faster.

Your language is so tele
This fact tends to generate multiple niches whenever any
environmental problem needs solving - though there's a
parallel, confounding (but weaker) tendency for composite
organisms to form out of these societies, a-la jellyfish.

I assume you're talking about colonial jellyfish, like the Portuguese
man o' war. This too seems garbled. The roles of polyps presumably
differentiated after the species became colonial, not before.

Then there's a specialisation vs generalisation issue.
Evolution generates specialised creatures.
Specialisations then increase the scope for further specialisation.

For example, naturalists observe, a flea hath smaller fleas
that on him prey. Until these smaller fleas existed the
role of still lesser fleas on the smaller fleas was not
available. One specialised niche being occupied
opened up the doorway to another, even more specialised
one.

Enough for the moment ;-)


Even if there's a semi-fixed species-number saturation point
at any given point in time, it is probably approached
asymptotically from below from the last mass extinction -
which would mean that the increase in the number of species
slows down gradually as it is approached, but doesn't stop
for a very long time.

Such evidence as we have shows that it takes only a few million years
(on the order of 10) for species counts to recover.


Compared to some 62 million years between extinctions? Even if that
10 myr is not an underestimate, those figures are in the same ballpark.
The "asymptotic approach" idea does not seem unreasonable to me.
Part hedge, part bush.

But what it means is that the world would spend most of its time in a
sort of equilibrium in which species numbers do not increase over time.

If you are familar at all with Sepkoski's famous plot, it shows

> approximately constant numbers through most of the Paleozoic,
> punctuated by extinctions, and a rise after the Paleozoic
> that a lot of people attribute to that pull of the recent.
> Attempts to correct for this artifact (which I don't believe

are good enough) show a species peak in the Miocene, with a general
decline to the present.


One such plot:

"changes in marine biodiversity throughout the last 542 million years"

http://en.wikipedia.org/wiki/Image:Phanerozoic_Biodiversity.png

It looks like a challenging issue to get an empirical handle on to me.

It is indeed.

.

Relevant Pages

  • Re: Gould criticism and reviews
    ... > believing in "demand led" speciation. ... According to species selection, many of the species ... species selection for rapid speciation rates. ...
    (talk.origins)
  • Re: Species Selection Redux
    ... Species selection predicts that adaptations exist that benefit ... speciation often takes place in isolated ecosystems, ... species reproduction - allowing the offspring species to ...
    (sci.bio.evolution)
  • Re: Gould criticism and reviews
    ... > believing in "demand led" speciation. ... According to species selection, many of the species ... What you are doing here is the species selection equivalent of assuming that mutations arise because they are useful. ... nest, while another goes on quite successfully building the old sort. ...
    (talk.origins)
  • Re: Defining&testing "macroevolution" (was: Testing the Laws of Intelligence)
    ... evolution of populations below the level of speciation. ... It means that changes within a population or within one species is ... called "microevolution", as opposed to the origin of new species and ... Bacteria don't reproduce sexually, ...
    (talk.origins)
  • Re: Oregon: Teacher Fired Over Bible References
    ... This makes the speciation ... then according to the BSC they are the same species. ... On the other hand the paper does cite, skeptically, a report of a hybrid between the main group and a whistling duck. ... The three tetraploid species Brassica napus, Brassica juncea and Brassica carinata have been experimentally resynthesised ...
    (talk.origins)