Science fiction has a problem: everyone looks the same. I know there are a few series that have aliens that look unimaginably different from human beings. But those are the exception, not the rule. Most major sci-fi series – Star Wars, Babylon 5, Mass Effect, Star Trek, Farscape, Stargate – have alien species that are hominid.
Consider the above image. Of the twenty visible species, only five are visibly not hominid. That’s right, I count the prawn, xenomorph, predator, Cthulhu and A.L.F. as being hominid. I grant that it’s a bit of a stretch. A more conservative evaluation would be that only two of the twenty are truly hominid. The others, which we’ll call pseudo-hominids, still share the following with humans: bipedal locomotion; bilateral symmetry; a morphology of head, trunk, two arms, and two legs; upright posture; and forward-facing, stereoscopic eyes. I grant they don’t look precisely human, but the similarities are too striking to be swept into the nearest black hole.
Even the most strident supporter of parallel evolution would laugh in the face of anyone who claimed that the most intelligent species on nearly every planet in the universe just happened to evolve the exact same physiology. In series like Star Trek and Mass Effect, where interspecies relationships are possible, this cross-species compatibility is made even more preposterous. We all suspend our scientific disbelief to enjoy the story and the characters. No one believes for a second that the first species we meet in the cosmos is going to look just like us save for some pointy ears and a bowl haircut.
But what if many species in the universe do look like humans? How in Carl Sagan’s cosmos could we explain parallel evolution of that magnitude? Star Trek: The Next Generation, manages to give a scientifically plausible answer to the question of hominid and biologically compatible alien species in an episode entitled “The Chase.” Which lead me to develop the Hominid Panspermia Theory of Science Fiction Aliens.