Now as we've yet to encounter life from or on another planet, this is a huge assumption to make. It could be just as likely that they'd resemble us as not. And why would they be vastly different emotionally? Although some would like us to believe that our emotions separate us from animals, more recent research shows that animals can and do feel many emotions as we do. Why would that be a quirk unique to this planet?
Why would they be limited to fairly basic things connected to survival? You could argue that that is also true of us!
No, it really isn't a huge assumption at all. It's simply the outcome of a different environment, something which is more likely to be the case than not. The chances of having a) an earth-like environment; b) the various events that produced life here coming together in exactly the same way there; c) the various events that led to the dominant life-forms developing the same emotional associations, thought-patterns, and reaction-response patterns as we have ... not to mention the different biochemical and genetic patterns, all of which play a part in psychology ... the probability of all these and other factors coming together to produce something like human emotions, as complex as they are, is basically nil. Animals have analogous, but not identical, feelings. They are close enough for us to see similarities, but they are NOT the same. They do not have the complex overlay of the higher brain functions that modifies them the way our emotions do, for one thing. I've long been a proponent of the fact that animals do have emotions, feel pain, etc., and should be treated with respect accordingly... but they really are not the
same emotions. And where they are closest to us tend to be areas which are very basic, coming out of either survival or pleasure/pain responses. Yet they evolved here on this planet, exposed to many of the same influences and pressures as we were. A lifeform evolving under circumstances even slightly different will have a vastly different set of experiences and pressures than us; the emotions would differ accordingly. Who and what we -- and the other lifeforms that share our planet -- are, is the result of very specific and local causes, including the makeup of our planet itself, its distance from the sun, the type of sun we have, the amount of atmosphere, etc., etc., etc. All of which influence the development of brain-and-gland functions such as thought and emotion. (And, on a physical level, this is one of the major flaws with fantasy set on different worlds: horses, cows, etc. The likelihood of humanoids, or of any of the creatures we know from our little planet, evolving elsewhere to exactly such forms, is so vanishingly small as to be ludicrous. But various writers have set them there, nonetheless.)
This is one of the problems with presenting realistic alien life-forms: getting inside the head of something that
is alien. We (quite naturally) anthropomorphize, as human reasoning and human emotions, human motivations, are what we understand most easily, and in fact all we can really understand (on any more than a very vague abstract level) emotionally. When it comes to emotional responses, any reading we give to other creatures is filtered through our own emotional coloring; our own bias, if you will. Presenting a truly alien creature, as was long since proven, would be impossible; we are simply not capable of imagining something we haven't encountered in some form. All our imagining is a distortion of some experience we've had; our minds simply aren't capable of anything more than that; which is why nearly all fictional aliens are so easily understood. They really are only humans with a few tweaks emotionally, no matter how alien their appearance -- and even there it is something that relates to things we know. Try imagining a genuinely alien appearance... something that has nothing whatsoever to do with anything you've ever encountered. It can't be done. We combine, we transpose, we alter... but at base, it's something we
know. The genuinely
other is beyond our abilities to imagine. But life, if it exists out there, is as likely as not going to be of such an alien sort... so much so that we very well might not realize it was life at all -- yet that would not in the least mean that it isn't; just that we're too limited to see it.
Now, that's why I made the statements I did about the problems with having non-human characters. If you want to know the advantages and drawbacks, then this is one of the drawbacks. It's one that's popular, as the majority of readers do anthropomorphize; it's more comfortable. As for Lenny's statements... they really reinforce my statements: we tend to "humanize" non-human charaters. His choice of Cthulhu is a particularly infelicitous one, as Lovecraft's (
not his imitators') creations are seldom human in motivation. There is so little common ground that we don't understand their motivations, their emotions (if they even have such, which is debatable), their psychology, any of it. Since we see them through the filters of other characters' emotions, the narrators often assign motives to them, but even there this is done quite shakily, and -- like the mythologizing of his alien beings -- done to show how we can't reach beyond our own experiences to truly grasp the alien. This is why Lovecraft's creations are never characters -- they are phenomena that the human characters encounter, but they remain removed from us emotionally and psychologically at all times.
This is not, however (as I indicated) to say you can't do fantasy with non-humans. You can people the stories with any form of life you like, whether it be animal, vegetable, or mineral; you can make some accommodations for the difference in form so that their responses aren't quite what most people would have to any given situation; but at base the reactions will still be human. That's a long-accepted convention of both sf and f. Exotic such lifeforms may be... alien they really are not. And, if you want your work to be successful, that's almost certainly better so. As I said above:
So I'd base it on whether or not you're wanting the prototypical fantasy creatures, or something of your own. Either way, you can have them react in understandable human terms, but it tends to be more successful with those we've learned through the millennia to accept in that way; a new creation would need much more of the difference to make it believable -- and that opens up other story possibilities, as the reader gets to understand the psychology of this species enough to feel comfortable in their skin.
It really depends on what you want to achieve -- the more traditional type of fantasy, or something a bit different. Either way, the motivations and emotions will be humanocentric; but I think it's wiser, if you're going to avoid using elves, dwarfs, trolls, giants, gods, etc., to attempt to have something a bit different emotionally where you can, to set them off from the stereotype. It also opens up, as I say, more storytelling possibilities, as your readers become aware of these new creatures, and learn to live inside their skin -- one of the attractions of sf and fantasy (think of the way White did with the lad's training in
The Sword in the Stone, where he became different creatures; or the Moties in
The Mote in God's Eye, etc.). This also makes them more memorable (if done well) because they
are exotic, they don't blur into the thousands of other creatures peopling fantasy, but stand out on their own. So base it on what your story needs, and go from there. But as for your argument about life elsewhere likely resembling us... no.
Possibility? Yes.
Probability? Zero.
