In answer to your question above, I would say no, it is not
obvious, not to me.
As indicated earlier, I believe the stage we're at now is that
of determining what the facts are, which will no doubt involve
overcoming some prejudices that we may have.
There is an excellent article by Dan McShea which attempts to
answer this question for what he refers to as "morphological
complexity". Here's the abstract:
========================================================
McShea, Daniel W., "Complexity and Evolution: What
Everybody Knows," Biology and Philosophy, vol. 6,
pp. 303-324, 1991.
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.
=======================================================
McShea's conclusion is that there is insufficient evidence
at present to say one way or another.
There is also an article about McShea available on the
WWW:
========================================================
Frank Zoretich (1996). "Dan McShea and the Great Chain of
Being: Does Evolution Lead to More Complexity?," The Bulletin of
the Santa Fe Institute, summer 1996, volume 11, number 2.
http://www.santafe.edu/sfi/publications/Bulletins/bulletin-fall96/mcshea.html
========================================================
The article above mentions another paper by McShea published in
the journal <Evolution>. I haven't seen this article, nor do I
know the volume etc., but I do have the abstract:
==========================================================
"Metazoan Complexity and Evolution: Is There a Trend?"
Daniel W. McShea
Abstract: The notion that complexity increases in evolution
is widely accepted, but the best-known evidence is highly
impressionistic. In this paper, I propose a scheme for
understanding complexity which provides a conceptual basis
for objective measurement. The Scheme also shows complexity
to be a composite term covering four independent types. For
each type, I describe some of the measures that have been
devised and review the evidence for trends in the maximum
and mean. In metazoans as a whole, there is good evidence
only for an early-Phanerozoic trend, and only in one type of
complexity. For each of the other types, some trends have been
documented but only in a small number of metasoan subgroups.
==============================================================
BH:===
>> As Terry pointed out, Gould gives a convincing argument that a
>> move towards increasing complexity is almost guaranteed during
>> the early stages of evolution. Whether this trend continues
>> after that is still open.
>
Cliff:===
>This seems only trivially true; for surely one must concede that
>abiogenesis and its first ramifications must involve an increase
>in complexity. And surely subsequent events may go either way.
>
I'm not sure why this is considered trivial. Its an example of
how a constraint can result in a preferential direction toward
increasing complexity and may offer a clue that there may be
other types of constraints which also give a direction to
evolution.
Cliff:==
>One might argue that well-developed ecosystems freeze out evolutionary
>novelty, as competition is too fierce, and niches are too well-filled,
>to allow truly novel mutants to survive their first awkward stages
>and gain a foothold.
>
One might argue many things. For example, one might argue that
evolution can only work with whatever is available at the
moment, it cannot plan ahead, it cannot back up. So the easiest
thing to do is to adapt some structure already present (making
it more complex) rather than starting from scratch to achieve
the simplest solution.
But, from my point of view, what is needed is not more arguments
but more data.
Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University
"He who establishes his arguments
by noise and command shows that
reason is weak" -- Montaigne