How likely is it that intelligent aliens on extra-solar planets will have recognizably human forms? Even if the planet's environment closely resembles Earth's, do the inhabitants have to look like Terran creatures? In Heinlein's HAVE SPACESUIT, WILL TRAVEL, the evil aliens stand upright and have heads on top but could never be mistaken for human. Yet they breathe the same kind of atmosphere we do and covet our planet. The narrator remarks that the fact they don't look like us doesn't prevent them from fitting into the same environment we enjoy; after all, spiders look a lot less human and live in our houses.
Almost-human aliens predominate on television to save money on costumes. With a few interesting exceptions such as the Horta (essentially a sentient rock), most of the ETs on STAR TREK are either near-human bipeds (rubber-forehead aliens) or energy beings (which avoid the problem of costuming altogether). In prose fiction, human or humanoid extraterrestrials are easier for readers to empathize with, an especially important factor in romance. As Jacqueline mentions in this week's post, in the quest for an HEA readers want to see people like themselves, people they can identify with. Authors can invoke convergent evolution to justify the frequency of human-like beings on other worlds. Even on Earth, unrelated animals that evolve in similar environments can look almost identical. Xenobiologists theorize that the most efficient body shape arranges major sense organs together near the brain, hence the likelihood that any advanced organism will have something recognizable as a head. Intelligent creatures will typically need appendages free for manipulation of their surroundings, so we'd expect them to stand upright and have "hands" of some kind. Those constraints, however, leave plenty of room for variation. Even among land animals on Earth, we find both cleverness and manipulative appendages in many nonhuman creatures, including apes, monkeys, bears, raccoons, elephants, and some birds.
In fantasy and SF romance, how human does the alien love object have to be? Mermaids immediately come to mind, and Megan Lindholm wrote a novel of a sexual liaison between the heroine and a satyr. How far toward nonhumanoid can a romance range without squicking some readers? One of Mercedes Lackey's novels includes loving intimacy between a human woman and a bird man (no details given, though). Assuming the partners aren't worried about interspecies fertility or the absence thereof, love might find a way regardless of superficial unlikeness. As the Vulcans would say, "We rejoice in our differences."
Margaret L. CarterCarter's Crypt