An article I saw prompted a train of thought that's been simmering for a while to bubble over and hiss on the burner of my attention span.
The article's short, but in summary some scientists did a little experiment. They raised male zebra finches in an sex-segregated population and found that upon coming of age, the majority of these finches selected mates from within the group and settled down into monoagmous pair bonds (many bird species are renowned for their monogamous habits, taken to a degree that would put most ostensibly-monogamous humans to shame).
These finches were presumably normal in every other respect; there's no reason to think they in particular would have pursued a same-sex romance (not an overblown word there; -- the birds are adorably affectionate and devoted to one another) had they been raised in a mixed population. Instead, for over half of them the drive to mate was satisfied by an affectional bond with another male.
And here's the kicker -- when they then introduced these couples into a mixed-sex population, only three out of eight elected to abandon their mates and seek out an opposite-sex partner. And now I'm just visualizing some poor, brokenhearted little male finches who lost their boyfriends to that darn breeder urge...
Anyway, that's a much larger percentage of the population willing to get into, and stay in same-sex relationships than we'd expect from statistical estimates of homo/bisexuality in the human population. In fact it almost seems too high, by that mark -- *assuming* that you treat sexual orientation as primarily a fixed-choice or even statistical phenomenon. I admit to not having done any population surveys of zebra finches, but I'm fairly sure they don't typically opt for homosexual relationships at a rate of over fifty percent. It seems very much like the social context was what determined, for many of these feathery little guys, what defined an acceptable or appealing choice of mates. Given only a pool of other males to operate over, whatever evolutionary algorithm you care to speculate is responsible for mate choice managed to score a resounding hit more often than not!
What's more, while clearly some did stray when given the opportunity to establish heterosexual relationships, a majority of those who got involved with their peers in the first place elected to stay with them.
It almost seems like forming affectional bonds is the goal; the criteria for doing so are malleable or fluid, or at any rate *flexible* enough to cope with situations that do not look like a normal sex-based population distribution. Whether the choice to stay is down to that remarkable avian monogamy or not, I can't say -- but it seems significant that the birds preferentially sought *relationships* rather than reproductive sex, and preferred to maintain existing relationships rather than give them up to gain access to it.
It's a common cliche among certain people, and something of a flammable subject within queer spaces, that "everyone is bi." The first thing I will say is that I don't think that simplistic, if memorable framing is accurate or helpful. It would be difficult to make the case scientifically, at any rate, if we went solely by observed behavior -- most people do in fact pursue heterosexual unions with decent odds of fertility. But I think it's significant that while people may desire children, that desire is found in people of any orientation -- not universally, certainly, but it's present. Clearly in an evolutionary sense reproduction is sort of the goal as far as DNA is concerned...but we aren't beholden solely to it's drives, and this is something I think a lot of evolutionary psychology advocates miss; namely, that when you're dealing with an organism as complex as a human being, the physiological and neurological implementations of that basic drive to reproduce are going to be remarkably complicated. How do you motivate mate-seeking in a creature so smart it can communicate in terms of wholly-abstract symbols, and yet so inherently arational that its cognition uses its own crudity to hack shortcuts through conceptual space?
I think it's safe to say that whatever chemical, physiological and psychological tools you care to include in the set that, taken collectively, defines how a human being evaluates mating strategies, it's very complex in operation, yet laughably simple to model compared to the systems that compose it, and at any rate it does not specify "inclusive genetic fitness" as its core goal content. I'm going to go out on a limb and say it seems like humans perform a similar routine to the finches in the study -- we look for suitable partners on the basis of whether we feel socially attracted and physically aroused by them. The two factors balance differently for different individuals, and the list of things that can decide either of them can be quite long for any given individual. What we don't do is inherently, emotionally seek to maximize our inclusive genetic fitness -- that's DNA's "goal"; the robot can still rebel, and will because its own priorities are substantially different and optimized for a different domain of problem solving.
Okay, so I'm saying we're attracted to others who turn us on and provide what we're looking for, more often than not. That's nearly tautological. Here's where I'm going with this:
PZ Meyers, in his talk "A Skeptical Look At Aliens", goes over a series of tropes and common misconceptions, or really just heavily-biased conceptions, about the depiction of alien life. You can find that here: http://scienceblogs.com/pharyngula/2011/07/a_skeptical_look_at_aliens.php
What I'm interested in is this part: http://scienceblogs.com/pharyngula/2011/07/the_teeny-tiny_bit_of_my_tam_t.php
In it, Meyers discusses the frequency of interspecies romance in science fiction. He then points out the (not terribly erotic, for most people) display of a female chimp in estrus as an example of sexual cues that utterly fail to translate across the species barrier, yet are the very epitome of sexy in one of our nearest biological relatives. He concludes that the odds of real aliens striking anyone as sexy, of a *typical* person being aroused or turned on by an intelligent being from another world, are as good as none.
To which I can only say: are you sure about that? Have you really taken a good look at how humans form sexual relationships? And are the tiny minority you acknowledge with your "Rule 34" comment really as anomalous as you think?
Granted, I find it similarly difficult to believe that, in a hypothetical SF society of humans as we know them, voluntary xenophilia in the face of more conventional options would be considered mainstream. Not unless you want to posit some reeeeeaaally divergent cultural development there. But let's take a look at some of the things real human beings do with their sex drive so often that each of them has a dedicated subculture:
-Other humans with limited mobility or amputated limbs
-Statues and mannequins
-Fictional beings such as giants, human-animal hybrids, and mythical creatures
-Other humans known to have committed major crimes
-People with physical deformities
I could go on.
True, most of these examples are pretty rare in terms of practice -- and it's rather difficult to literally act out an attraction to beings that don't technically exist. But take a look at them, and consider the many taboos, legal boundaries or just the difficulty of finding someone who shares that interest willingly (I'm not even going to hold to "safe, sane and consensual" standards here -- that is a methodological ideal for kink, not something coded into the way we formulate the sensation of sexual attraction in our brains). Consider the many normative messages driving them all underground.
For some reason, I have stricken many people in my life as remarkably safe to self-disclose to. I will name no names and specify no details, but a *whole* lot of people I've met over the years, from strangers or acquaintances to close friends and loved ones, in at least some cases people I was simply sitting next to on the city bus, have seen fit to share with me the "dirty little secrets" of their sexual attractions. Most of these people didn't seem like the type who were comfortable with such emotions, or even with fulfilling fantasies in private -- indeed, many of them were uncomfortable even having such feelings. I sometimes wonder why I in particular was deemed so safe to share this with -- suffice to say, I've got blackmail material on an unbelievable number of people, not that I'd ever use it. >>
I guess what I'm saying is, I think that the human mechanism for selecting partners or even just getting off is much, much more complex, malleable and counterintuitive than even many dedicated kinksters and sex-positive types are ready to acknowledge. Let alone mainstream society, and certainly moreso than would be obvious to anyone who thinks of sexuality primarily in terms of maximizing inclusive genetic fitness.
My point is not "everyone is bi", or "everyone is kinky", or "everyone has dirty little secrets. My point is that when I see societies like the one in Robert J. Sawyer's Neanderthal Parallax trilogy (sex-segregated the majority of the time, everyone takes a same-sex spouse and an opposite-sex spouse -- Sawyer is a cis hetero guy and so doesn't develop the complexities or edge cases...) or the case of settings like Teelaverse (where at least some people engage in recreational, social or emotional sex with members of other species because that's the pool they have to draw from and it's not tabooed by their cultural training), or one where some significant proportion of humanity (ie, much moreso than here and now) is habitually non-mongamous in an open and socially-normal way, I don't find it terribly difficult to believe. And the reasons behind that make me strongly suspect that our own social context has much more to do with the way people in the real world approach sex and sexuality, than any hard-written rules firmly embedded in our genomes or brains or bodies or whatever.
This is at a level quite different from real people's modern identities -- I think it's just possible that for a significant portion of humanity, the primary constraints on how weird sexuality can get, and thus what behavioral schema might be plausible within speculative fiction, are rooted in where and when you live, and what cultural programming you absorbed in the process of doing so.
(If there is a part 2, it'll be clarifying the difference between just making this assertion, and condoning squicky depictions in SF/F of really divergent cultural models of sex. I am conducting the equivalent of a napkin sketch of the difference between identity and society and basic drives, not attempting a defense of stuff like Gor or the many examples in SF of authors getting a wee bit creepy or overbearing injecting their own fetish fuel into their work. Though I suppose one could readily accuse me of doing that latter with Teelaverse...)