>On Sat, 14 Dec 1996, Glenn Morton wrote:
>
>> Once one gets to multicellular organisms there is
>> very little "upward dynamic. In precisely what way is an amphibian higher
>> than a fish or a mammal more complex or higher than a reptile. What is the
>> criteria by which we place birds in this, ahem, pecking order? All have
>> stomachs, eyes, skin (of some sort) a heart, liver, an oxygen obtaining
organ,
>> ability to locomote in their respective habitats. This business of an
"upward
>> dynamic is a holdover from 19th century progressive philosophical systems
like
>> Hegel, Ficte, Marx etc. From a scientific and information theory point of
>> view, I see little reason to say that one organism is higher than another.
>
>Thanks Glenn for this. I've been thinking about this theme recently,
>as a correspondent presented me with various views about increasing
>complexity in the fossil record. It seems to me that this subject
>can be approached at different levels.
>
[...
>
>The conclusion: in the context of trilobites, claims of increasing
>complexity in the fossil record appear to lack a solid foundation.
>
One of the problems with determining whether complexity
increases during evolution is deciding exactly what one
means by "complexity". This brings to mind a little cartoon
I saw in a proceedings volume on complexity measures. Two
complexologists are talking:
C#1: "Complexity is what you don't understand"
C#2: "You don't understand complexity"
The main point of the little cartoon is to illustrate the
confusion, disagreements and controversies surrounding
the very fundamental issue of defining what complexity
is. The way I like to interpret the cartoon is that
C#1 is defining complexity in an intuitive sort of way
"gee this really looks complex". C#2 is saying that you
have to get beyond intuition to something objective if
you want to have any scientific theory of complexity.
I agree with #2, of course :-).
Anyway, many of us do have this intuitive feeling that
complexity is steadily increasing. As Paul Davies puts it:
Is the emergence of organized complexity just a
fluke or part of a lawlike trend?
-- Paul Davies [from the jacket of Johnson (1995)].
Elsewhere [Davies, 1988] Davies refers to this increasing complexity
as the "optimistic" arrow of time, as opposed to the "pessimistic"
arrow of the second law.
Finding the principles behind this increasing complexity is
the holy grail for complexology. But is complexity really
increasing? There is an interesting paper by McShea (1991)
which discusses these issues in the context of "morphological
complexity". The abstract follows:
ABSTRACT: The consensus among evolutionists seems to
be (and has been for at least a century) that the
morphological complexity of organisms increases in
evolution, although almost no empirical evidence for
such a trend exists. Most studies of complexity have
been theoretical, and the few empirical studies have
not, with the exception of certain recent ones, been
especially rigorous: reviews are presented of both the
theoretical and empirical literature. The paucity of
evidence raises the question of what sustains the
consensus, and a number of suggestions are offered,
including the possibility that certain cultural and/or
perceptual biases are at work. In addition, a shift in
emphasis from theoretical to empirical inquiry is
recommended for the study of complexity, and guidelines
for future empirical studies are proposed.
I also found in my archives a post to t.o from some time
ago which is more along the lines of Glenn's original
comment. Unfortunately, I do know who posted this so I
can't give appropriate credit:
=====from talk.origins==================================
This data is from Table 2 of a review article in Nature (v374,
16-Mar-95, pp. 227-232) by Eors Szathmary and John Maynard Smith
entitled: The major evolutionary transitions. On the basis of
coding genome (likely related to info content), vertebrates are
about the same. A lot of "macroevolution" happened in that
division with relatively little change in overall "information
content."
Genome size Coding Coding genome (1)
bp x 10E9 DNA % bp x 10E6
Bacteria (E. coli) 0.004 100 4
Yeast (Saccharomyces) 0.009 70 6
Nematode (Caenorhabditis) 0.09 25 23
Fruitfly (Drosophila) 0.18 33 59
Newt (Triturus) 19.0 1.5-4.5 285-855
Human 3.5 9-27 315-945
Newt Gingrich (human salamander) 3.5 1.5 53 (2)
Lungfish (Protopterus) 140.0 0.4-1.2 560-1680
Flowering plant (Arabidopsis) 0.2 31 62
Flowering plant (Fritillaria) 130.0 0.02 26
Notes: "Genome sizes" appear to be for haploid genomes.
Not in orignal paper:
1) "Coding genome" = Genome size * % Coding DNA.
2) A best guess.
=======end talk.origins excerpt====================================
I also intend to use this complexity discussion as an
illustration for the theory/fact controversy, but I'll
do that elsewhere to keep the two issues separate.
references:
Davies, P. (1988). <The Cosmic Blueprint>, Simon and Schuster.
Johnson, G. (1995). <Fire in the Mind>, Alfred A. Knopf.
McShea, Daniel W. (1991), "Complexity and Evolution: What
Everybody Knows", <Biology and Philosophy>, vol. 6, pp.
303-324.
========
Brian Harper | "If you don't understand
Associate Professor | something and want to
Applied Mechanics | sound profound, use the
The Ohio State University | word 'entropy'"
| -- Morrowitz
Bastion for the naturalistic |
rulers of science |