> Sure. But a dictionary is not going to tell me what the scientific
> definition of evolution is. I don't think that increase in complexity
> is 1) easily measurable 2) part of the definition of evolution.
>
> Evolution: "Change through time" A view of Life, Gould.
>
> "p. 647: Darwinism is not a theory of intrinsic progress"
[...]
I agree that increases in complexity are not easily measured, or at least
readily
quantified wrt biological systems. However, I do think that the biological
complexity of many lineages has increased over the course of evolution. John
Maynard Smith's short article was an attempt to begin thinking about the major
changes in life (regulatory systems, genetic flexibility, & etc.) that have
lead
to increasingly complex systems. Is there a "natural" inclination of life
to produce certain forms of complexity or isn't there one? How does one begin
thinking about this? These are some of the questions John poses in his paper.
Now, he proposed some possible answers, but the main goal was to start
research
moving in that direction (...which it has to some degree).
Now, John and most other biologists think that life did develop "naturally"
via evolution. They also think that the complexity of some lineages of
organisms
have increased. Thus it is legitimate to say that evolutionary thought does
embrace changes in biological complexity. How this occurs or whether is in an
intrinsic "drive" of life remains an open question. This is also complicated
by the fact that one can't look at a newt, a human or a lungfish and make any
sort of a case for which is the most "complex". Much of evolution does not
seem
to have involved sustained increases in complexity.
I do agree with you that it is wrong to say "evolution predicts all species
_must
therefore_ display individual increases in complexity over time." That
would be
a bogus statement.
Ah, here's the article reference: Eors Szathmary & John Maynard Smith - "The
major evolutionary transitions" 16-Mar-1995 Nature (374):227-232
Responding to Andrew
> Andrew: <<Sick-cell anemia is caused by a loss of genetic information that
> instruct blood cells how to form.>>
>
> Please explain what genetic information was lost? Perhaps you are trying
> to say that "information was changed"? [...]
Well, now that's three times in the last month I've heard sickle-cell anemia
associated with complexity loss -- But it doesn't really count because someone
said it twice... Unfortunately the biochemical details still aren't there,
are they?
This is for Andrew:
The HbS mutation produces a change in the way hemoglobin molecules associate
in the red blood cell. It sometimes "stacks" or "crystallizes", leading to
the sickled shape of the RBCs. Given that this is a "new" or novel thing for
hemoglobin to do, couldn't we likewise make a case that this is a positive
increase in complexity? How do we quantitate the change in overall complexity
here?
Let's try this from another angle: In malaria-prone environments, there
is actually positive selection for maintaining the HbS allele in human
populations. In fact, the selection balances in such a way that both the
"wild-type" and HbS alleles are maintained in the population. Thus _two_
distinct alleles are retained whereas in normal populations there would
mostly be the one wild-type. Which is more complex; an organism with the
same copies of a gene or an organism with two different alleles?
If you can answer any of these questions, please respond with some details
-- Because I certainly don't have a clue.
Regards,
Tim Ikeda
(tikeda@sprintmail.com)