And of course, the biggest and least supported assumption of all is that intelligence has a survival value. For all we know, it may be a fatal form of overspecialization that soon leads to the extinction of the species and the biosphere that achieves it.

My intuition (I have no objective or scientific reason to believe this, but I have thought about it a lot :=) ) is that there are at most only a handful of technical civilizations capable of interstellar communication in the Galaxy at any one time.

If civilizations are extremely long lived, older than the normal life spans of species, planets or stars, they can only do so if they are capable of developing interstellar travel, genetic prostheses, machine proxies and descendants, and lots of other things that if they were possible, we probably wouldn’t even recognize as artifacts if we ran into them.

I don’t see any good reason why aliens would visit us just yet (Besides studying “zoo” specimens, that is), and I’ve gotta admit – one of my favorite parts about playing games like Spore is using your might as an interstellar species to terrorist the less-advanced ones and stealing their resources from them. I figure if any aliens DO make their existence known to us, they’d be quite the sadistic bastards.

“Hey, look at that planet over there, they haven’t even colonised another world! Let’s fly around and scare the crap out of them!”

“LOLZ, yeah!”

-Two drunk alien frosh on their way to the Interstellar University of the Virgo Cluster-

Even so, industrial robots don’t look like the mechanical men of science fiction. It can be argued that an Asimov-style humanoid robot has to be humanoid so it can operate human machinery and tools. But our industrial robots have their own built-in tools. They don’t need to grab and twist a screwdriver, for example, or swing a hammer. They have a spinning shaft for driving fasteners and a reciprocating pounder for hammering.

Human muscular/skeletal design is very clever, but it has to come up with awkward work-arounds for things like axles, full rotation, etc. There is nothing in nature like a wheel, or a spinning shaft, but our robots can take advantage of those simple machines easily.

Yes, speculating about alien biology and culture is very enjoyable. Science fiction writers have come up with some very believable and ingenious ideas in this area, and are worth reading. Real aliens may not actually look or act like that, but speculations grounded in real science are good preparation for the day we actually meet ET.

For example, I believe aliens will have an organic/water-based chemistry similar to ours. The reason is that carbon is common, and the element most capable of easily forming complex molecules and water is a common and very effective solvent at the temperatures where carbon chemistry is easily facilitated. There may be other alternatives, but I’m not familiar with them, and we’ve never found them in nature so far.

Aliens will also be composed of proteins similar to ours because the building blocks of proteins, amino acids, easily form in many environments, even deep space, far from any planet. However, I also believe alien tissue may be sufficiently different from ours that neither of us could eat the other. We might even be allergic, or even poisonous to each other; not because of some specific toxin, but because our biochemistries are incompatible.

As for body plans and anatomy, any structure that has evolved independently here on earth will probably be found on other worlds, such as lensed eyes, tentacles, exoskeletons, nature has created millions of designs here, and many have been successful for eons, so we will probably find analogues elsewhere. What works here will work there.

But some things, like intelligence, and communication, have only evolved once, (maybe twice if you count dolphins). And it took evolution a long time to come up with them, and they haven’t been tested for long. Intelligence may be very rare in the cosmos. And even high intelligence does not necessarily lead to technology.

My guess (based on earth history and our own timeline of 4.6 billion years) is single-celled life is extremely common (3-4 billion years ago). Photosynthesis much less common (2-3 billion years ago), so not all living worlds will have oxygen atmospheres. Multi-cellular organisms only arose in the last half billion years,they are probably relatively rare, but after they arose evolution really took off. Intelligence, and especially technical intelligence, may be extremely rare. Dolphins, after all, don’t need flint tools, and they’re not likely to learn about fire without some outside help.

It used to be thought life was a lucky accident, but once you had it a technical civilization would quickly arise. The best guess now is that life is abundant, but civilizations are the lucky accident.

I hope I’m wrong, but we may be the only space-faring race in the galaxy today.

Limbs.

Imagining what they’d be like is fun stuff isn’t it.

The reason why I picked humanoid is because of our arms/hands. Heavy industry modeled manufacturing robots on human movement because it was the most efficient way to do fine object manipulation. Maybe because it was just the simplest system to model, unlike tentacles.

Some kind of grasping and manipulative organ capable of delicate work would probably be predictable for a technological species, but it could be a tentacle, lip, trunk, tongue, who knows? Look at all the little labial parts insects have to manipulate their food, shape mud balls for nesting, build honeycombs, etc. Our own hands (and feet) originally evolved for grasping branches and picking fruit, not working flint or building spacecraft.

We can even speculate on more bizarre configurations. Maybe they parasitize, or domesticate and train other creatures and have them do all the manual work, while they ride along. After all, we use horses, camels, oxen, elephants and dogs in similar ways. Maybe they are sexually differentiated this way, one sex does the lifting and drawing, the other is in the driver’s seat. (No snide comments, Jody!). There appear to be very good reasons for sexes, and also very good reasons for only two of them, but after that, anything goes.

One of Larry Niven’s races is tri-sexual, with the third sex being of a different species altogether, like the digger wasp’s prey, where the female lays her egg IN it so the hatched larva will have plenty of live meat to eat. The third sex has coevolved with the Puppeteers and they have further modified it for breeding purposes. It survives because they nurture and protect it. It is thoroughly domesticated and could not survive at all without their protection.

We can visualize hive species, with multiple castes, larva and pupal and adult (or even more) stages, or even alternating generations of totally different body plans. All these variations exist on earth, they could very well exist out there. And who knows what prosthetic appliances or genetic or surgical engineering could be employed by a truly advanced species.

Chances are they will be totally disgusting, and they’ll probably feel the same way about us.

The real question is…will they be Communist or Capitalist? Or will they (shudder) have come up with some other alternative.

If they get off their planet, they’re not going to have claws or spiked fingers.

There going to be humanoid with shoulders, elbows, wrists and hands with at least 2 opposable digits. They’ll need to be physically proportionate to their planets gravity in order to manipulate natural resources.

The show I mentioned was called “Mice” and it was on the “Outer Limits”, not the “Twilight Zone”.

I love the old series. I wasn’t allowed to watch a lot of that stuff as a kid.