Reply #31: Or maybe...

[frogmarch]

http://www.space.com/6978-aliens.html

snip:

But is there reason to think that actual aliens, from a star system a thousand light-years away, would be similar in appearance to the evolved apes that we now call Homo sapiens? Some scientists, such as Cambridge University paleontologist Simon Conway Morris, think there is. After all, there’s a phenomenon in nature known as convergent evolution. It’s the tendency of evolutionary processes to find similar solutions to any given environmental challenge. For instance, if you’re a predator whose existence depends on catching lunch day after day, you probably have two eyes with overlapping fields of view. Stereo vision is a real plus for pouncing on prey.

Similarly, for marine creatures that have a need for speed, the laws of hydrodynamics favor being long, thin, and oh-so-streamlined. Convergent evolution has ensured that barracudas are shaped like dolphins, even though the former are fish and the latter are mammals. Being built like a torpedo just works better.

This mechanism is often invoked by sci-fi writers as a convenient explanation for why so many of their alien protagonists resemble earthlings brushed with battery acid. (Even the language – “convergent evolution” - which is so ponderously Latinate, bespeaks academic merit and scientific plausibility.)

As a consequence, it’s possible that a hominid shape is the best body plan for sentient beings on any world, and no doubt Tinseltown would be pleased to learn that its rubber-suit aliens are good approximations to the real thing.

The other night I heard a scientist (I don't recall his name, Maybe it was Simon Conway Morris ) on TV say that not only are appendages great for locomotion, but having a nervous system culminating in some kind of brain is a good idea too, even if the brain is just a bulblike swelling - and having a head to house the brain is a pretty good plan as well. Many unrelated (well, okay, distantly related, since we may have all evolved from the same strain of bacteria) animals on Earth have all of these characteristics. I don't think it's implausible to think that some aliens might have these characteristics too. That's not to say they'd look like any animal on Earth, but they could still be recognizable as living beings.