Monday, December 06, 2004

The fish, that really was just a fish.

"A particularly interesting case which illustrates both the problem
of convergence and the danger of judging overall biology on
skeletal grounds is that of the rhipidistian fishes. For nearly
a century these ancient lobe finned fishes, as they are often
known, have been generally considered to be ideal amphibian
ancestors and have been classed as intermediate between
fish and the terrestrial vertebrates. This judgment was based
on a number of skeletal features including the pattern of their
skull bones, the structure of their teeth and vertebral columns and e
ven the pattern of bones in their fins, in all of which they closely
resembled the earliest known amphibians. It was assumed that their
soft biology would be also transitional between that of typical fish
and amphibia. But in 1938 fishermen in the Indian Ocean, off Cape
Province in South Africa, hauled to the surface a living relative of
the ancient Rhipidistia - the coelacanth. It was an astonishing discovery,
as the coelacanth had been thought to be extinct for a hundred million
years. Because the coelacanth is a close relative of the Rhipidistia,
here at last was the opportunity to examine first hand the biology
of one of the classic evolutionary links. Its discovery provoked
considerable excitement. Peter Forey comments:

'We had to wait nearly one hundred years before discovery of the
Recent coelacanth. During that time many fossil coelacanths were
described and, on the basis of osteological features, their systematic
position as near relatives of the extinct rhipidistians and as tetrapod
cousins had become part of "evolutionary fact", perpetuated today
in textbooks. Great things were therefore expected from the study
of the soft anatomy and physiology of Latimeria. With due allowance
for the fact that Latimeria is a truly marine fish, it was expected
that some insight might be gained into the soft anatomy and physiology
of that most cherished group, the rhipidistians. Here, at last, was
a chance to glimpse the workings of a tetrapod ancestor. These
expectations were founded on two premises. First, that rhipidistians
are the nearest relatives of tetrapods and secondly, that
Latimeria is a rhipidistian derivative.'

But examination of the living coelacanth proved very disappointing.
Much of its soft anatomy, particularly that of the heart, intestine
and brain, was not what was expected of a tetrapod ancestor.
[....]
If the case of the coelacanth illustrates anything, it shows
how difficult it is to draw conclusions about the overall biology
of organisms from their skeletal remains alone. Because the
soft biology of extinct groups can never be known with any
certainty then obviously the status of even the most convincing
intermediates is bound to be insecure. The coelacanth represents
yet another instance where a newly discovered species, which
might have provided the elusive evidence of intermediacy so
long sought by evolutionary biology, ultimately proved to
be only another peripheral twig on the pre sumed tree of life."
(Evolution: A Theory In Crisis
By Michael Denton :179, 180)

3 comments:

mynym said...

Notice how geeks talk,
"...it was expected that some insight might be gained into the soft anatomy and physiology of that most cherished group, the rhipidistians. Here, at last, was a chance to glimpse the workings of a tetrapod ancestor."

These issues are sexy to them. That most cherished group. One says, "You found a rhipidistian? Oh, goodie, goodie!"

It is rather funny. The people now called geeks, the scribes of old, the observant obersvers and the studious studiers are amusing. I know, because I get excited about good writing or philosophy that probably leave others scratching their heads and wondering what the big deal is.

A lot of the time, it really is not a big deal. However, on the issue of Good and Evil it is a big deal, worth looking at. That is to a fair degree what this blog is about and to a lesser degree the esoteric things that fellow geeks may be interested in.

Later.

Anonymous said...

"...fellow geeks..."

I fail to see how someone who windsurfs--I think it is--could consider themselves to be a 'geek.'

Carl

mynym said...

Yes, one does have to drop that in once in a while to mess with things.

I tend to avoid identity altogether so that people can look to writing and concepts as such. It's for their own good. It can be tiresome trying to get mental retards to think conceptually rather than taking things personally, feeling personal, etc.

I'm reminded of writers like George Orwell using a pseudonym, etc., it's just a way of saying, "Would you just look at what I am writing and quit staring at me?"

But personally, you're right in a way. I never fit in so well with geeks because of my vanity about facial symetry or what not. Yet I never fit in so well with the Beautiful People of facial symetry because they often are mental retards relying on it to get by.

But yes, if geeks windsurf they do not tend to windsurf the ocean or in 40-50mph winds either. Yet I have seen geek windsurfers, glasses, helmet and all. I have nothing against people, you know. It is what it is. They're usually charming, actually.

The extreme conditions and the ocean is fun. But you'd best windsurf for some years before trying it. You have to jump from wave to wave a bit when it goes to 40mph. Man....I hope spring gets here fast and there are more windy days.

Anyway, I have been and was fine with not fitting in with various groupies so well. I hate groups anyway. I talk to people as individuals. That may just be a series of excuses which mean, "I will live as I please. For the freedom of it all!"

That probably is closer to the truth, come to think of it.