quote:
Originally posted by Percipient:
mark24 writes:
Can you tell us why stabilising selection cannot act over 340 m.y.?
This isn't a critical factor in this discussion, since the main point is Karl's assertion that evolution prohibits stasis, but in the name of accuracy, and as Mister Pamboli has already stated in message 26, the coelacanth *has* evolved quite a bit over the past 340 million years. A few facts:
- To be technically accurate, the fish we're talking about is actually the Latimeria chalumnae. The complete classification:
Kingdom: Anamilia
Phylum: Chordata
Class: Osteichthyes (bony fishes)
Order: Coelacanthini
Family: Sarcopterygii
Genus: Latimeria
Species: chalumnae
- Latimeria chalumnae is the only known extant species representing an order, the Coelacanthini, that was once thought to have become extinct in the Cretaceous because no fossils from more recent periods have ever been found.
- The modern coelacanth's closest known relatives, species of the genus Macropoma such as Macropoma lewesiensis, went extinct about 70 million years ago in the Cretaceous. No fossil of Latimeria chalumnae has ever been found.
- It isn't the species coelacanth which has survived for 340 million years, but rather the order Coelacanthini, of which Latimeria chalumnae is the only known living representative. For this reason, use of the popular term "coelacanth" is both misleading and insufficiently accurate for this debate.
These facts indicate that Karl's assertion that the coelacanth is an example of a species surviving unchanged for hundreds of millions of years is simply wrong.
--Percy
[Edited to fix the link to the picture. --Percy]
[This message has been edited by Percipient, 05-11-2002]
Percy, you are being too modest, the point IS critical to Karl's argument. Karl seems to be claiming that the extant species of coelacanth has remained unchanged for 340 million years. Whereas the fact is that sufficient changes have accumulated over the last 70 million years that the extant species now resides within a different Genus!
How many other "living fossils" which Karl has cited are in the same situation? Where is the evidence that the extant SPECIES have remained unchanged over lengthy periods of time? If Karl cannot nominate such unchanged species then his original assertion becomes moot.
Karl, I believe the ball is your court to provide the evidence to support your assertion of unchange species over hundreds of millions of years.
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