[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Theories on the extinction of dinosaurs



At 04:57 PM 11/21/99 -0500, Dinogeorge@aol.com wrote:
>
>For that matter, we still have no proof of causes of >local< extinctions, 
>just a bunch of speculation, except in the case of direct human intervention. 
>Whole subject of extinction needs to be carefully rethought and redefined, 
>including such concepts as cause and effect as inferred from coincidences in 
>fossil record. Bad things happen all the time to animals, so you can expect 
>lots of coincidences among such bad things everywhere in the fossil record. 
>Most of the time these yield no mass extinctions; why not? On the other hand, 
>when a mass extinction occurs at the same time as a documented asteroid 
>impact that scatters itself all around the globe, why should we infer no 
>connection?

Um, who's saying NO connection?  I am certainly not saying any such thing.

Actually, I know of no large scale flood basalt deposits that are *not*
associated with a mass extinction, at least a minor one.  So, flood basalt
deposition is *not* happening all the time, and when it does happen it
appears to be linked with elevated net extinction rates.  A similar
staement can be made concerning ocean anoxic events.  (We may find out:
global warming is likely to trigger oceanic anoxia).

Similarly, extreme low sea levels are quite rare. And only the Pleistocene
and Holocene have lower sea levels that the terminal Cretaceous during the
Panerozoic. And we appear to be in the middle of a mass extinction right
now.  Now, admittedly many people tend to give Homo sapiens the *entire*
blame for this, but I have my doubts.  It is certainly worth noting that
many of the earliest victims of it were the largest land animals, which
matches the large animal bias seen in other mass extinctions.  [Mind,
people certainly have *contributed to the current extinctions, but I
suspect that in some cases, such as the condors, we have actually
*prevented* an extinction that would ordinarily have happened].


So we are not talking about the sorts of "bad things" that happen all the
time.  We are talking about extraordinary bad things that almost never happen.

--------------
May the peace of God be with you.         sarima@ix.netcom.com