"But such things as bilateral symmetry, four limbs, binocular vision, and binaural hearing have immense survival advantages."

That's tetrapod-centric bunkum I'm afraid. The vast majority of living beings on the planet have no limbs at all and many of the rest far more than four, any number of eyes that have developed into several variations on the theme and vision suited to their particular lifestyle - binocular vision is no use to a mantis shrimp or a fly.

"And we haven't been able actually communicate with them, nor figure out a way in which we can!"

That's down to us, not them. We can communicate with captive cetaceans and do so readily (they even use iPads for the task) but are still no nearer to identifying a language apart from identification whistles (itself a contentious issue, see following link), and as the authors of this paper observe, "Human observers do not represent an unbiased filter through which one can classify the vocalizations of nonhuman animal species."

That quote could equally apply to the whole 'what is alien life like?' debate, as we are so fond of creating aliens in our image as humanoid beings - it's difficult to bypass our "unbiased filter". In fact, to fully understand the remoteness of aliens being like us you have to look back at the development of life on earth, and the dominating role that chance plays in that process; our own evolution is massively unlikely, if you could rewind time to before the Cambrian explosion and press play again the outcome would be vastly different. Do it a thousand times and you'll have a thousand different outcomes, a million and you'll have a million etc etc. Apply that to the millions of planets that could support life and . . . phew! Almost unimaginable diversity.

Apply that to the myriad of ways that life as we know it and life as we don't could evolve and the Drake equation begins to look a tad shaky; the variables are impossible to guess. In truth, the value of the Drake equation is in the questions it forces the observer to ask, rather than the number it generates.


Loved the link VT!