Re: Fossil Records Show Biodiversity Comes and Goes

From: John Harshman (jharshman.diespamdie_at_pacbell.net)
Date: 03/19/05 

Date: Sat, 19 Mar 2005 14:33:50 GMT

Carsten Troelsgaard wrote:

> "John Harshman" <jharshman.diespamdie@pacbell.net> skrev i en meddelelse
> news:IBE_d.20027$Pz7.8401@newssvr13.news.prodigy.com...
>
>>George wrote:
>
>
> snip
>
>
>>>My purpose in pointing it out was that it has been accepted for quite
>>>some time,
>>>so I don't understand your objection to it.
>>>
>>
>>Well, "thought about" and "accepted" are two quite different things.
>>Accepted on what basis? We just know it's true? It sounds nice? Or was
>>this established on the basis of rigorous tests? If so, do you have
>>citations? The Paleobiology paper you cited was one such test, which
>>seems to show an effect in crinoids -- though again, greater speciation
>>rates among the specialists compensated for the greater extinction
>>rates. What else you got?
>
>
> Whatever the specific details the two of you disagree upon, George has a
> point in his example of the selection pressure a drowned reef could be. The
> author of the below link estimates 1/4'th of the marine diversity to inhabit
> the reefs. I figure that the Permo/Triassic event would count heavily in the
> statistics of some cyclicity in diversity - the author does not find an
> impact event very likely compared to the alternatives.
>
> http://www.killerinourmidst.com/index.html#anchorContents

Doesn't that argue against cyclicity, then? If the various mass
extinctions have different causes, some astronomical, some terrestrial,
then any regular period must be due to highly unlikely chance or some
joke of the creator. Unless you can think of a unitary cause behind all
the proximate causes.

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