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Placental takeover: nowhere-near-final comment



> On Tue, 29 May 2001, David Marjanovic wrote:
>
> > > They later make a plea: "the most pressing need today is for new and
> > > better paleontological _data_, derived from as yet unknown parts of
the
> > > fossil record..."
> >
> > Of course. I'm not going to, say, publish anything on this. But I think
the
> > decimation of NA metatherians at the K-T does not contradict the impact
> > theory (I think theory rather than hypothesis has become suitable), and
I
> > think it is not total dilletantism to post this here.
>
> No, it doesn't contradict the hypothesis.  But the word "theory" is
> inappropriate.  The fact of a bolide doesn't generate a theory of species
> survival.

But a theory of mass extinctions. Plural here because there's (less)
evidence for impacts as the cause for several other mass extinction (P-Tr,
Tr-J...)

> A theory explains phenomena.  The bolide isn't a theory
> because it does not do a good job of explaining.

Spend an hour or two in the archives and you'll find megabytes of phenomena
that the bolide explains.

> Natural selection is a
> good theory because it has broad explanatory power.  Plate tectonics,
> ditto.

Sure.

> Indeed, there are no surviving alternate hypotheses for how
> continents came to be where they are.  This is _not_ true for speciation
> across the K/T!

This is not the criterion for differentiating hypotheses from theories --
according to http://www.dinosauria.com/jdp/law/evolfact.htm, which I use
here.

The phlogiston theory also was a theory. It explained all phenomena of
burning that were known at the time. And it turned out to be rubbish
nonetheless. Theories are not necessarily facts.

> But saying the case is closed

I don't

> gives people, funders, etc., the
> impression that nothing more needs to be known.  I mean, if you come to me
> for money to dig up more fossils at the K/T, I say: "Why bother if you
> already know what happened."
> [...]
> Let's do some more research to find out.
> I know you agree with the research part.  But what's the point in asking a
> question if you already have your answer?

I'd say "I want to know more _exactly_ what happened, I only have a rather
vague idea at the time [understatement], I don't know lots of important
details about the extinction [no understatement]".

> A better way of approaching it is to say the speciation _may_ be explained
> by the bolide.

You mean the failure of speciation = the extinction?

>  > > But when you
> > > say you already know what caused species distribution

BTW, what do you mean here by species distribution?

> > > at this time, you
> > > are ineffect saying we don't need more data.
> >
> > Mmm... no. Never in science are more data useless.
>
> But there are always choices about which research is funded.

It doesn't have any official consequences if I call an idea a theory and you
call it a hypothesis. So why should this affect funding?

> No one is
> going to fund an inquiry into whether the Earth is spherical.

Because that's a fact, no longer a theory or a hypothesis.

> > > would have...blah, blah, and firestorms would have...blah, blah.  I
mean,
> > > it was just yesterday that everyone was warning everyone else not to
make
> > > up stories without having direct evidence.
> >
> > I haven't read the book :.-( ; however, there is evidence for global
> > firestorms -- the boundary layer contains lots of soot. Tsunami deposits
> > from the K-T are also known,
>
> As far as I know, none of these things appear in the sediment of this
> study.

Which study?

The soot has been known since the 1980s, and I gave a URL for an "impact
breccia" ?= tsunami deposit.

In a related post, HP "Graydon" wrote:

> > > and on the other side of the world from the
> > > regions affected by flood vulcanism -- and that it hit at a bad *time*
> > > for at least North America -- seaways down, diversity down, so fewer
> > > species present.
> >
> > So why attribute the prime cause to the bolide?
>
> Because the information available indicates that the magnitude of the
> disaster was such that the thing to explain is not differential success,
> but survivial.

BTW, the effects of flood volcanism are still much more poorly understood
than those of impacts, and whether the diversity was down in NA at the time
is still in debate -- newer evidence regularly disputes this, and the
3-m-gap has shrunk to 37 cm long ago. A regression is probably way not such
stress, especially a regression that began 2 Ma before the K-T boundary (and
ended 2 Ma after it)!