Re: Humanoids, the TOS excuse was summed up in one word: budget. The few nonhumanoid aliens they had (Horta, Melkotians, Excalbians, etc) looked like what they were, cheap rubber and paper-mache sculptures. It had to wait until TNG to come up with a decent in-story retcon... Oops, I mean reason for it. Ancient humanoids with weird and nonsensical motivations (turning other races into living memorials instead of, say, saving themselves). So in that universe, at least, panspermia was a fact.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
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