archiv~1.txt: Re: SETI Quote of the Day for March 9, 1999

Re: SETI Quote of the Day for March 9, 1999

John Bush ( )
Tue, 9 Mar 1999 12:14:40 -0800 (PST)

Dr. H. Paul Shuch wrote:
>At 07:35 AM 3/9/99 -0500, Larry Klaes wrote:
>>"Biologists, impressed by the inherent improbability of
>>every single step that led to the evolution of man,
>>consider...'the prevalance of humanoids' exceedingly
>> - Ernst Mayr
>Well yes, absolutely! The only reason we see so many erect humanoids in SF
>movies is that there are precious few green slime molds in the Screen
>Actor's Guild. But then Mayr goes on to generalize that statement to
>making 'the prevalence of life' exceedingly improbable. That's where he
>and I part company.
>H. Paul Shuch, Ph.D. Executive Director, The SETI League, Inc.

I suppose on this list we're all preaching to the choir; in fairness to
Mayr, he seems not to argue that the 'prevalence of life' is improbable (he
and Sagan in fact more-or-less agree on the first few terms of the Drake
equation). Rather he argues that the development of 'high' intelligence and
of technology is improbable to the point of impossibility. Mayr gets his
odds for high intelligence based on an enumeration of species; To quote:

"Once we have life (and almost surely it will be very different from life on
Earth), what is the probability of its developing a lineage with high
intelligence? On Earth, among millions of lineages of organisms and perhaps
50 billion speciation events, only one led to high intelligence; this makes
me believe in its utter improbability."

Well, I can't see the logic in counting the number of species to calculate
the odds; I'd think the time durations are more meaningful: ~1.5 million
years since homo erectus, ~500,000 yrs since controlling fire, 100,000 yrs
of completely modern homo sapiens sapiens, 10-20,000 yrs of 'modern
civilization', 500 yrs since industrial revolution, ~50-100 years for
'modern technology'. So assuming even a pessimistic 200 yrs of SETI
broadcast & search technology out of say 10 billion yrs for the lifetime of
an average sunlike star yields a time fraction (and odds, in my book) of one
in 50 million. This is 1000 times higher than Mayr's estimate based on
speciation events.

But even if we accept Mayr's one in 50 billion, and use Sagan's number of
500 billion planets in the MW, we might (arguably) expect about 10
technological species in our own galaxy at any particular epoch. Not 'utter
improbability', as Mayr claims.