On Saturday, May 12, 2001 4:17 PM Spike Jones spike66@attglobal.net wrote:
> > I admit, I have some problems with it. What!?! The usual way the
scenario
> > is put, it's hard to believe anything above bugs and bacteria would
survive.
> > There has to be a reason why crocodiles, mammals, lizards, toads, and
birds
> > made it, but T. rex didn't. A big asteroid hit would seem to be more
> > egalitarian in its affects, taking out all major groups -- not
specifically
> > targeting nonavian dinosaurs.
>
> Some species are more robust and more capable of
> adapting to changing environments than others.
I agree, but this assumes that only those survived the impact. Are you sure
this fits the data?
> We
> have plenty of examples of species living today that
> are on the ragged edge, such as the taxifornia condor.
> It survives today only because of extraordinary efforts
> on the part of the environmentalists to keep them
> soaring. Apparently this movement does not accept
> extinctions as a natural part of evolution, and so attempt
> to prevent all extinctions.
I'm not sure.
> On the flip side, we have plenty of examples of super
> robust, super-adaptable species, such as rats, mosquitos
> and humans. spike
Did only "super-adaptable" organisms survive? What is the evidence?
Archibald does not completely disagree here, though he does look over which
species survived, when the extinctions seem to take place, and alternatives
to explain its disappearance. On the first, it's important to know to
narrow down the causes. Marine regression would kill certain organisms and
benefit others. Specifically, freshwater species would do better under
marine regression, while large land vertebrates and marine species would
not.
On the second, timing is important; if the last example of a certain species
occurs five million years before the impact, cannot be sure that an impact
did them in. There seems to be plenty of evidence of a decline in nonavian
dinosaurs before the Creataceous-Tertiary Boundary.
On the third, it's just good science to have alternative explanations. May
the best one win. Again, Archibald does think a bolide impact played a
role. He also thinks the evidence is strong for marine regression. Imagine
this: small impact combined with an ongoing process of marine regression.
If this was the case, it would have a huge impact -- no pun intended -- on
the biosphere. The ongoing marine regression would've upset many local
biomes, putting them on edge. An impact might have pushed them over the
edge.
Cheers!
Daniel Ust
See more of my blatantly mistaken ideas at:
http://uweb.superlink.net/neptune/
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