From: Robin Hanson (hanson@dosh.hum.caltech.edu)
Date: Thu Sep 05 1996 - 15:44:00 MDT
Eric Watt Forste writes:
>If yes, then the hard step (following the usual assumption that there's
>only one really hard step in the Great Filter) happened in the development
>of some common ancestor of birds and mammals.
I have been explicitly making a different assumption - the more
plausible hard steps candidates I can find, the less hard I need to
assume each step is, and the easier it is to fit my claim that a step
is hard with the usual understanding of the subject. (I currently
estimate about 11 hard steps.)
>I'm starting to feel like the opposite of the drunk who was looking for his
>lost wallet under the streetlamp on the corner because "That's where the
>light is best." We're looking for the Great Filter in our past, because we
>don't like the idea that it might lie in our future, and it seems that I
>keep wanting to locate it in the places where the light is poorest, to
>account for the fact that I can't find it. Ominous.
I really like this analogy!
Sean Morgan writes:
>John K Clark may refer to the controversial work of Russel Doolittle, UCSD
>(I'm getting this from _Discover_, June 1996, p.37, so add grains of salt to
>taste). He proposed a new clock based on the mutation rates of enzymes,
>using the same reasoning as RNA mutation rates. He extrapolated three times
>beyond the fossil record (so add more salt). Anyway, his timeline was:
> 2.0 GY ago -- prokarya
> 1.8 -- archaea
> 1.2 -- eukarya
Two of these dates are dates from the fossil record, so I guess the
extrapolation is to estimate two big events in the 1.8-2.0 bya region.
Mark Crosby quotes:
>This group of organisms could represent more than 50 percent of the
>earth's biomass,' says Venter"
I keep reading this figure, but haven't seen: just where are all these
big biomass buggers supposed to be?
Robin Hanson hanson@hss.caltech.edu http://hss.caltech.edu/~hanson/
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