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Author Topic:   Stasis and Evolution
Modulous
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Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


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Message 36 of 61 (532907)
10-27-2009 7:11 AM
Reply to: Message 34 by Arphy
10-27-2009 6:46 AM


Darwin on punctuated equilibrium
Trying to hunt this down. Can you give a quote, or reference?
Chapter 10, On the Origin of Species (first ed):
quote:
Species of different genera and classes have not changed at the same rate, or in the same degree. In the oldest tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms. Falconer has given a striking instance of a similar fact, in an existing crocodile associated with many strange and lost mammals and reptiles in the sub-Himalayan deposits. The Silurian Lingula differs but little from the living species of this genus; whereas most of the other Silurian Molluscs and all the Crustaceans have changed greatly. The productions of the land seem to change at a quicker rate than those of the sea, of which a striking instance has lately been observed in Switzerland.
and
Chapter 15, same (though I think this particular quote was added in a later edition):
quote:
Only a small portion of the world has been geologically explored. Only organic beings of certain classes can be preserved in a fossil condition, at least in any great number. Many species when once formed never undergo any further change but become extinct without leaving modified descendants; and the periods during which species have undergone modification, though long as measured by years, have probably been short in comparison with the periods during which they retained the same form. It is the dominant and widely ranging species which vary most frequently and vary most, and varieties are often at first local--both causes rendering the discovery of intermediate links in any one formation less likely. Local varieties will not spread into other and distant regions until they are considerably modified and improved; and when they have spread, and are discovered in a geological formation, they appear as if suddenly created there, and will be simply classed as new species
Edited by Modulous, : added note about the later edition

This message is a reply to:
 Message 34 by Arphy, posted 10-27-2009 6:46 AM Arphy has not replied

  
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