In article <qgr8a4l8avo36tvb8g46c7a18j3vviij79@4ax.com>,
 Chris L Peterson <clp@alumni.caltech.edu> wrote:

On Thu, 14 Aug 2008 09:01:04 -0700 (PDT), Ben Standeven
<berry@pop.networkusa.net> wrote:

You can lose the "except for humans"; we don't actually know that
some of those fossil animals weren't more intelligent than we are,
after all. They just didn't leave any signs of civilization, a hundred
million years later.

In a sense that is true. Defining "intelligence" seems extraordinarily
difficult. But in the context of this discussion, I think it can be
taken as the ability to create sophisticated technology (a likely
requirement for traveling between the stars). I think that if a
technological species had inhabited the Earth at some earlier time, we'd
probably have evidence of it.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

If it was among the denizens of the pre chlorophyll world, I doubt 
anything would have survived.