There are 4 fundimental reasons why the “powers that be” take the position they do:

1. They are deathly afraid of a national panic.

2. They cannot admit that they have been lying to the public for over 60 years.

3. They cannot admit that compartmental elements of both the military and intelligence communities have and are cooperating with Aliens.

4. They cannot admit that human body parts have been found stored aboard downed alien space craft and that humans are abducted and kept alive in special storage vats underground for “scientific use” .

Note: All of the above is true for all nations to greater or lesser degrees.

Unfortunately the dolphin has one fatal flaw…it has no hands, or at least no way to manipulate the environment in any meaningful way. So for an alien species to become a civilisation, and eventually space-faring, I believe that hands, or at least some form of highly dexterous manipulator are an absolute must. As for being bi-pedal, I feel that although its not absolutely necessary, it would be advantageous from an evolutionary standpoint to be bi-pedal, since it would free the hands to preform other tasks. As far as intelligence goes, its hard to say. There are many forms of intelligence, even here on earth. Human intelligence is basically measured by the average of all individual human beings. A single human being can be highly intelligent, while another can be incredibly inept. Other species such as ants are intelligent in a different way. An individual ant is surprisingly incapable. But when you have a hive of ants, they can accomplish some amazing feats. This isn’t because ants are telepathic, or can magically become smarter the more of them there are. Its because each ant plays an individual role within the hive, and the hive follows strict protocols which are sometimes dictated on demand by sensory organs. So while human intelligence can be measured individually, the ant’s intelligence can only be fully realised when viewed as a whole.

Taking all of this into account, I think that if we were to ever encounter extraterrestrials, they would likely (and I stress LIKELY, and not ABSOLUTELY) be bipedal, with hands or some other structure that serves the same purpose, and may or may not be particularly intelligent (at least not individually).

In any case, if I ever do see one of these extraterrestrials, I will rush back to this post to tell you exactly what it looked like, and surely enough, I will promptly be labelled a loon.

I personally believe an advanced civilization could have seeded life throughout the galaxy, maybe even the universe by a means not yet known to us. They have may piggybacked on an asteroid, directing the object as they pleased – crashing into planets throughout the universe with knowledge of how to start the process of life. However, they may not have been in control of how that life evolved. They would have given the seeds a program of adaptation with the main goal of SURVIVAL.

Any highly advanced civilization will bypass the need for any one body. They would be able to switch bodies like we switch clothes. That is difficult to grasp, but we are already working on mapping the brain and pulling the data. If a person’s every thought, every memory were pulled and placed into a computer ‘database’ of sorts with a fully functional program to manipulate those thoughts and memories, they would become immortal. A living consciousness without the need for a body. How would they manipulate their environment? They would control their robots or biological creations with their technology, thus eliminating any danger to them.

I kind of think of it as an unlimited redundancy against death. Type III civ is immortal, right?

The most I would hazard is that [1] bilateral symmetry would probably be fairly common because it’s an efficient, effective attribute for a body plan, and [2] anything with at least four limbs would probably have two of them freed up from locomotion in order to grasp and carry stuff.

Beyond that, there are simply too many implicit assumptions about speciation & physiology to be an interesting question.

Life on Earth is life as we know it. Life on other worlds could be radically different – for example, using different sorts of energy pathways, a different element for respiration, etc. And the sorts of planets upon which this life resides may also be radically different, with a whole bunch of abiotic factors that must be taken into account (like the strength of gravity, the planet’s proximity to any satellites and other planets, the pressure in the atmosphere, the temperature, etc). If this is so, then all these factors – to do with the organisms themselves and the environments in which they live – could impose important constraints on the sorts of design solutions open to evolution. If, nevertheless, intelligent life is possible on worlds that are very dissimilar to ours (and that’s a big “if”), then the form that intelligent beings are likely to take will probably be vastly different to us, simply because the sorts of challenges posed by these factors may favour very different solutions, and to the extent that intelligence is favoured, it will likely be arrived at through a very dissimilar route to what took place on Earth. However, if planetary conditions and biological constitutions are more like those on Earth, then it is not at all unlikely – and is perhaps even inevitable – that that these beings will resemble us in many key respects (though I would be very surprised if they had, for example, five fingers on each hand and shared most of our mammalian characteristics. In broad outline, though, they would likely resemble us, and I imagine that they would be equipped with at least, say, the capacity for speech and some sort of symbolic representational system like language. They would also have sub-optimalities associated with being bipedal, some surely reminiscent to ours).

As another complication, we need to take into account the pathways that might have been actualised if evolution on this planet could be rewound and started up again, how likely they are to prevail on planets with similar conditions to those on ours, and how likely they are to yield intelligent life if they are actualised (perhaps we could run a simulation some day of a million births of life). If Stephen Gould was right, then there is nothing particularly inevitable about the sorts of life that have as a matter of fact evolved. So on each planet, we need to have an idea of the tree of possibilities that is open from the inception of life on that planet.

Although a bit tongue in cheek, this isn’t off the facts. There were two studies, (I’ll have to see if I can find them again), that showed the “evolution” of proposed aliens ~ with the current socially accepted model being that of the “Grey’s”.

Hollywood has more to do with humanoid alien shapes than evolution, under current known evidence.