It looks like this thread has died down, but I had a few thoughts:
As for the title of this thread, personally, I don't think it is possible to define intelligence in a simplistic way at this point in time. Intelligent beings may not be qualified to define their own intelligence objectively (a conflict of interest, as someone said earlier... current understanding of intelligence already assumes that we are the most intelligent beings encountered, and bases measurements of animal intelligence on that) while at the same time, we require intelligent beings to define what an intelligent being is ... which again, they may not be able to do objectively ... it's a paradox.
A biological explanation for intelligence might solve the paradox, but that will require more insight into the way that brains function than we currently have. For now, we rely on observation of patterns to identify intelligence. With that ... some patterns in nature are familiar to our way of thinking and might seem like applications of intelligence when they actually are not (for example, a process like evolution seems to progress intelligently until you really understand what's going on) Similarly, you could conclude that some applications of intelligence may be so alien to us, that we wouldn't consider it as such (for instance, if a theoretical animal on earth was to possess a greater intelligence than us but not apply it to tool-making and talking, as humans do, or if it is not at all self-aware, we would never define it as intelligence until we explained intelligence biologically, and it was shown to biologically exist in their brains)
To assume our way of using intelligent reasoning is flawless and 100% objective would be a rather large assumption, seeing as we can't step outside our brain structure to know for sure. We intuitively believe ourselves to be the most intelligent creature on earth, and so we intuitively define intelligence as being human-like ... and that other creatures must behave like us in some way or have brain/body measurements like us to have any measurable intelligence. So a short definition of intelligence might be 'human-like behavior' and any use of intelligence in a non-human way would require a new word all together, with it's own, separate definition.
