Av, I didn't mean ultimate yardstick. Just, as you say, the best we have (because we're the most intelligent on this planet).
As with the other thread I linked in my first post here, I've been arguing for a long time that certain features will be recognizable as "intelligent" even across species, and in as much as we participate in those features, we are our current yardstick.
I don't think there is such a thing as species-dependent definitions of intelligence. I think intelligence is universal . . . though the ways we might
communicate our intelligence would depend upon our species-specific physiology. But if there isn't some truth to what I'm saying, then SETI is entirely pointless. At the bare minimum, we've got to expect aliens to recognize math and numbers, if we assume we'll be able to recognize signs of their intelligence. Math is universal. Though there will be different mathematical truths discovered by different cultures, those truths ought to be understandable by the others. This is what I mean about intelligence having a universal quality beyond individual species, because the kinds of things intelligence works upon (like math and logic) are themselves universal. They are in no way dependent upon psychology.
Here are some of the things I said in that other thread:
I don't think aliens would be as alien as we might think. Years ago, I saw something on the Disovery channel about "convergent evolution," I think they called it. Anyway, the basic point was that certain physical properties are so useful, that the likelihood of evolution heading down one of those pathways is much greater than available alternatives. That's not to say it's preordained, but rather that random mutations in these directions will get passed on more readily simply because they make sense in this universe.
For instance, physical symmetry would confer survival advantages in on nearly every world. Balance, coordination, speed, strength--all these benefit from symmetrical body shapes. Thus, I wouldn't be surprised to see beings with even-numbered appendages and linearly symmtrical bodies. And given the fact that light and sound exist on most worlds, I'd expect some kind of eyes and ears. Processing of sense data is more efficient when the transmission paths are shorter, so I'd expect sense organs to be grouped around the central-processing organ (brain). And I'd expect orifices for taking in nutrients and expelling waste.
So yeah, aliens might look weird, but there's good reasons to expect them to not look too weird.
I'd even expect sufficiently intelligent aliens to be fairly easy to communicate with. The logic of survival in a physical world necessitates recognition of universal patterns, i.e. being conscious of one's world in terms of physical objects which either help or hinder the organism's survival. This bare knowledge must be present if consciousness is to arise at all--after all, the whole reason why traits are passed on is because they affect the organism's survival. So consciousness of survival factors and of one's survival context would be a prerequisite for consciousness to be gradually developed over millennia. I think any sufficiently intelligent being would share this bare minimum common ground within their awareness: bodily existence among a collection of bodies.
From there, "concepts" such as life, death, hunger, energy, food--would all be common mental contexts we'd share. I think also more nebulous concepts would be universal, things like: need, harm, interpersonal relations. I think it follows directly from the nonrandom results of natural selection: if consciousness must arise in conjunction with consciousness of survival factors, these bare minimum concepts must be part of that consciousness.
Transmission methods for language might present a problem, but I think would could establish some kind of link. After all, humans communicate with each other in every sense. As long as these creatures are capable of detecting patterns within some form of energy, we could develop a form of communication with them.
I think physics and chemistry put constraints on the directions life will take. And I believe that consciousness arises within a survival context that necessitates universal features. (Indeed, I believe consciousness itself implies universal features.) Consider the fact that we train animals of all sorts. There is no reason why your dog should understand your commands. Sure, it's a mammel. But there is nothing about our biology that would lead one to expect this rudimentary communication. The consciousness of the dog is crude compared to ours, but we still manage to bridge this genetic gap and have a relationship.
If they [aliens] are intelligent, then I think we can make a couple safe assumptions about them. I think they'd recognize how rare life is. (You can hardly miss this fact, looking at the galaxy). It's a tricky matter to guess at their values, but the assumption of intelligence allows us to speculate that they'd recognize the value of rare, complex, and spontaneous presence of life on other planets. If they have the drive to explore the galaxy, and they are not imperialistic, and they have technology advanced enough for interstellar travel, then we can surmise that they're not simply looking for more resources for survival. They are traveling to the stars for another reason. It will be because they want to, not because they have to. (Again, if they are advanced enough for space travel, then they would have already solved environmental and resource issues on their own planet--ending the NEED to go anywhere else.)
[snip]
But this distance issue [interstellar distances] can't be ignored. It is a physical boundary across which only a select few can cross. It is a boundary not crossed by accidental, unintentional expansion, but rather a deliberate and intelligent expansion. It is itself a boundary of natural selection: nature will only select intelligent species to cross this threshold, becuase it is only possible for them. And it will necessarily be a level of intelligence I've outlined above.
This is the biggest mistake we can make: to fear anthropomorphism--a failure of prejudice--so much that we assume the opposite of what nature has shown us is the case. Here on earth, we have a 5 billion year history of how life works. We shouldn't eschew this evidence simply out of fear of being stereotypical or "racist" about life in general.
If there are general priniciples which govern all life--and especially all intelligent life--then obviously those general principles must be inherent on our planet, too. The trick is just figuring out which ones are general, and which ones are specific to our world. Natural selection, and the logic of survival through time, is a solid place to start.
A species that can produce technology sufficient for interstellar travel is extremely different from whales. Just the fact that the alien species must know about physics, astronomy, mathematics, etc. would be evidence of common conceptual territory we'd share--a common ground lightyears (literally) beyond any genetic or biological common ground we share with terrestrial animals. That's the crucial point: we'd share more conceptually with spacefaring aliens than we would with our own earthly "cousins."
There are certain conceptual prerequisites necessary for a species to acheive spaceflight. Their concepts of justice, morality, religion, etc. might be widely different from ours, but their concept of "planet," "distance," "escape velocity," "inertia," "gravity," etc., can't be very far off from ours, or they'd never get off the ground. Again, the nature of physical existence puts constraints on the consciousness of a species which can achieve spaceflight. We all live in the same universe, so our awareness of this universe must converge upon a common ground in order to achieve certain higher-order tasks. Indeed, the more specialized and advanced our knowledge of the world becomes, the more convergent our consciousness of the world becomes. Just look how the universal truths of astronomy has made a plethora of differing religious beliefs obsolete. A convergence of consciousness-of-the-world has occurred on our planet simply through learning the truth about the solar system--or the truth of evolution. Suddenly, all the differing religious beliefs about our origins and the large-scale structure of reality must either be discarded or updated. (And those who refuse this conceptual change aren't the ones getting rockets into space.)
Just in case anyone is interested. Or has some time to kill. Man, that was a good thread.
Anything that can do something as complex as locate food is demonstrating a degree of intelligence. 