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Re: mass extinctions and technology



----- Original Message -----
From: "Mark Harvey" <mharvey@scu.edu.au>
Sent: Monday, September 30, 2002 4:56 AM

> To my knowledge, the organic
> environmental geochemistry of  extinction boundary sediments has never
been
> examined.

There are those extraterrestrial amino acids in the K-T layer, not to
mention fullerenes.

> You are forgetting the dimension of time.  We may be abundant and
> widespread, but for how long?

Should that matter?
BTW, we've been widespread, though not abundant, for almost the last 2 Ma.

> One of the explanations given for SETI [...] NOT receiving any alien
> broadcasts is that civilizations capable of radio technology don't last
long.

A much more parsimonious one is the Rare Earth hypothesis.

> Shopping malls and airports are relics of the last 100 years.   This gives
> them a very short window of opportunity for preservation.

Erosion has a hard job destroying them completely, I think.

> How much of the
> pyramids will remain in even another 10,000 years?

Quite a lot. Why "another"?

> >We have been responsible for [...] large scale homogenization
> >of the [...] biota [...]
>
> This homogenization could be obscured by an associated mass extinction /
> climate change = sea level instability.

Blackbirds and foxes in NZ won't come there from Europe by themselves in the
foreseeable geological future.

> > > 2. Given two isolated civilizations, be they isolated by time OR
space,
> > > technology will evolve along similar lines.
> >
> >Actually, a VERY questionable assumption,

Yeah. It's already a questionable assumption that "technology will evolve"
_at all_ -- in huge areas of the world it used to stay constant for
millennia, if not tens thereof.

> > For example, there are good arguments to be made that the idea
> >of writing may have only been developed twice independantly (Sumeria &
> >Mesoamerica),

Of course arguments have been made repeatedly that even these are not
independent, but that Old World folks crossed the Atlantic in ancient times.
The evidence is pretty good meanwhile that the Chachapoya in Peru had
something to do with Carthaginians and their mercenaries...

> > > Let us assume the PHC would cause a gradual mass extinction, as does
our
> > > existing civilization.
> >
> >WHOA there!!  Check your time scales!  What appears to be a "gradual mass
> >extinction" at the scales of human societies would look like an
> >instantaneous event from the point of view of a couple of million years
from
> >now or more.  In fact, it would BE what a geologist would refer to as an
> >instantaneous event.

If we count all the Pleistocene megafaunal extinctions, including the dwarf
*Stegodon* species on Flores that is suggested to have died out when *Homo
erectus* reached the island over the sea IIRC 850.000 years ago, we might
reach the concept of "gradual", though, given improbably good resolution
(such as that around the Tr-J boundary in the Newark Supergroup) globally.
(Here! Dinosaurs! Dinosaurs!!! :-) )

> Try to tell someone that the earth is warming by .5 celcius every
> 10 years and they will yawn and turn up the sport on the television.

Try to tell them that this slow warming could bring dry spells to the
tropical rainforests, which then could go up in flames, releasing lots of
CO2 and accelerating the warming, which then could trigger some methane
clathrate deposits to go off, producing Eocene climate within this century.
:-)
        (OK, then they'll say this is by far the worst-case scenario... and
of course that's right. No need to calm down, though.)

> 2.  We think we are pretty special (see the dark ages when we literally
> thought the univers revolved around us)

Now that we've learnt that we aren't special, we should maybe learn that we
aren't even normal, that a blue planet is something exceedingly improbable
(if we ignore those like Neptune that are colored by their methane...).
Looks like we aren't to be expected more than the average, but much less
than it. And the same holds for dinosaurs. :-)