In talk.origins John Harshman <jharshman.diespamdie@pacbell.net> wrote:

K_h wrote:

Fermi's paradox suggests that there are little or no other intelligent 
civilizations within the Milky Way galaxy.  On the other hand, intelligent 
life should exist on a substantial fraction of planets with life because 
natural selection broadly increases intelligence with time.

Does it? News to me. What evidence do you have that this is the case?

There is also the problem that there could easily be more than one
kind of intelligence.  Many living (and non-living) things respond 
to stimuli.  At what point does that become intelligence?

Does the definition of intelligence require that television be 
invented?

[snip]

That is, in the Drake equation, f_L should be far 
smaller than most people think it is.  Even on planets that are life 
friendly the formation of life should be extremely rare for the below 
reasons.

The Drake equation assumes that the ETs will be blasting out 
electromagnetic waves at a furious rate.  *We* started doing
that only in around 1920 or so and already we are doing less
and less of it.  By 2120 we could easily be using wired or
directed sources and no indiscriminate electromagnetic radiation
at all.

-- 
   --- Paul J. Gans