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Scott Badger <firstname.lastname@example.org> Wrote:
>If the clock is currently reset every few 100 million years
>[from Gamma ray bursters] how could we still be here? Hasn't
> life been evolving here for more than a couple billion years now?
If the average galaxy generates a Gamma ray burst every few hundred million years then by chance a few lucky galaxies will not get one even after 4 billion years. Perhaps we live in such a galaxy. Anyway, such a burst could only directly effect half of a planet so we're not talking about global sterilization of all life.
>Besides, Jay Gould once stated that the contingency based character of
>natural selection was such that if evolution were replayed millions of
>times, intelligence would not appear on the planet.
If evolution were replayed it's very clear that nothing like human beings would appear, perhaps intelligence would not appear either but that's much less clear. Gould likes to emphasize that evolution has no direction. He says the only exception is the very simplest forms of life because if they were any simpler they wouldn't be alive at all so any change can only be toward more complexity. After this minimum requirement has been met the number of species that become more complex is no greater than the number that become simpler. Gould has written entire books on this subject and I think his observation is correct but less profound than he seems to think. Even Gould admits (reluctantly) that the most complex organism of an era tends to be more complex than the most complex organism of a previous era. That's good enough for me because I'm only interested in the best, I don't care what most species are doing. He does make one good point however, complexity does not necessarily breed more complexity. The most complex organism of an era is very often not related to the complexity champion of the past but evolved from a much simpler creature. Some get simpler, some get more complex, most stay the same.
John K Clark email@example.com
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