>>Clearly from this, there has been an increase in complexity throughout
>>geologic time.
I replied:
>That depends entirely on the chosen perspective. For example, *among*
>porifera, has there been an increase in complexity in the last 570 million
>years? Among arthropods, has there been an increase in complexity in
>the last 530 million years? Etc. [Also, don't forget to change the date of
>agnatha in light of the recent fossil finds].
Glenn replies:
>Let me ask you something Mike. What perspective do you want to present?
>The number of different cellular types is certainly a measure of
>complexity. But if the perspective is as you seem to desire, one that says
>"no evidence whatsoever for evolution will be allowed into my
>consciousness", then your perspective will certainly never see any evidence.
But I agree there is plenty of evidence for evolution. I'm simply interested
in the pattern of data involved with evolution. And in this case, your
claim that there "has been an increase in complexity throughout
geologic time" only seems to be true with a very restricted perspective.
As I mentioned before, it's like trying to argue the exception proves
the rule.
Me:
>So why haven't sponges and arthropods increased their number of cell types?
>Are we to think they stopped evolving since they appeared half a billion
>years ago?
Glenn:
>Let me describe the computer models the authors created. They had 2000
>different 'beings' each of which could go up or down in the number of cell
>types with every iteration of the computer. While the maximum number of
>cellular types continued to go up, the average species didn't go up in
>cellular types very rapidly.
I'm not easily impressed by virtual reality.
>Secondly, if the arthropods and sponges had
>increased their cell nubmers then they would not be arthropods or sponges.
Really? What makes them so special? Consider again the list you
posted:
>Porifera 10 cell types 570 myr
>Cnidaria 14 cell types 560 myr
>Haemocoelic Bilaterian 30 cell types 560 myr
>Arthropoda 51 cell types 530 myr
>Echinodermata, Annelids 39 cell types 525 myr
>Agnatha 64 cell types 510 myr
>Cephalopoda 75 cell types 500 myr
>Actinopterygii 132 cell types 400 myr
>Amphibia 150 cell types 330 myr
>Diapsida 154 cell types 300 myr
>Aves 187 cell types 150 myr
>Hominidae 210 cell types 5 myr
Notice anything? Porifera, Arthropoda, Echinodermata, Annelida,
and Cnidaria are all *phyla.* And your list shows that
much change *can* happen within a phylum, as
the Chordates go from 64 cell types to 210.
So why think the other phyla could not tolerate
such increases in cell types? Either there is
something unique (perhaps special) about chordates
and/or verterbrates, or the authors of this article didn't
do their homework by representing phyla with
species data.
>Populations of fish that did evolve are now called amphibians,
>reptiles, birds, mammals etc.
Yes, 5 data points against a backdrop of thousands where no
significant increase is seen. And you call this a trend?
Mike