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From: cramer@optilink.UUCP (Clayton Cramer)
Newsgroups: sci.astro,sci.space,sci.space.shuttle
Subject: Re: Asteroids and Dinosaurs (was Re: asteroid almost hits earth)
Message-ID: <1493@optilink.UUCP>
Date: 19 May 89 16:11:10 GMT
References: <256@ringwood.Morgan.COM> <3200009@hpindda.HP.COM> <1212@irisa.UUCP> <40171@bbn.COM>
Organization: Optilink Corporation, Petaluma, CA
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In article <40171@bbn.COM>, ncramer@bbn.com (Nichael Cramer) writes:
> In article <1216@irisa.UUCP> saouter@irisa.UUCP (saouter yannick) writes:
> >In article <13111@ut-emx.UUCP>, ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:
# ## It is also true that this is not the most dramatic mass extinction in the
# ## fossil record. 
# #
# #Such collisions occurs about every 50 000 000 years and I've heard that others
# #species have disappeared as suddenly as the dinosaurs did, so earlier
# #collisions might be the cause for that, too.
# #
# #Does anyone knows others example of strange disappearance ?
# 
# I don't remember the numbers (in species/yr) offhand, but I've read
# arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
# the one of greatest (if not in fact _the_ greatest) of mass extinctions of
# all time.
# 
# If I recall right, the numbers work out to ~1 species/100,000 increase in
# human population.

I've read that the current rate of extinction is about 15 species/century --
which is clearly far lower than ~1 species/100,000 increase in human
population.

Of course, we still don't know all the species on the planet, and I 
very much doubt that we notice many that come and go anyway.

One of the Paleozoic extinctions involved 99% of all species then alive
being killed off.  But over what time scale?

-- 
Clayton E. Cramer                   {pyramid,pixar,tekbspa}!optilink!cramer
Assault rifle possession is a victimless crime.
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