In Zoomorphism in Science Fiction–In or Out? Heather Massey wonders whether designing fictional aliens to resemble Earth animals is stretching plausibility. Well, it depends on the story, writer, and reader:
Execution can make the difference between a pulpy, campy story and one much more sophisticated in tone. In other words, believability. When zoomorphism is in the house, it takes a high level of authorial skill for me to suspend my disbelief. Done well, the characters feel organic to the worldbuilding and/or they’re compelling enough that their boar-like appearance isn’t a deterrent. But even in the hands of a competent author, I find myself distracted by characters whose hooves, horns, and tails resemble the cast of Old McDonald’s farm.
For me, it’s more of a question of intention rather than believability. If the author is going towards the space opera/science fantasy route, I do not care as much. In those types of stories, it’s not about the science but about the adventure. If the story is trying to get a message across to today’s readers, I can view these futurist visions of chimeras as metaphors and representations rather than real aliens, per se.
But if the author is going to use any science to explain the aliens, they had better have a damn good reason why those aliens look like us and/or Fido. Because who’s to say that any aliens out there have DNA like us (or even your garden variety Escherichia coli) let alone the same chemistry?
I would like aliens that are truly alien. Aliens that have completely different motivations and behaviors than what we are familiar with. I would like them to go even further than bug-eyed monsters, because insectoid aliens are still too Earth-like to me. Any biologist worth their salt has at least taken a gene regulation class and have discovered that the fly* is much closer to us than popular perception would have you believe.
So, aliens. They had better be alien. And if you’re trying to put some humanity into them, well, wouldn’t it just be easier to make them human?
*See the hox genes, for starters.