David Gerrold has denied any knowledge of Robert Heinlein's THE ROLLING STONES when he wrote "The Trouble With Tribbles," which makes the similarities an incredible coincidence.
Incredible? I wouldn't say that. It's actually commonplace for different people to come up with the same idea independently. Like I said before, it's the number one reason why pitches to TV shows get rejected.
Anyway, the ST legal department noted the similarity and gave Heinlein a heads-up. His response, according to Gerrold's making-of book "The Trouble With Tribbles"
, was, "Let me add that I felt that the analogy to my flat cats was mild enough to be of no importance -- and we both owe something to Ellis Parker Butler . . . and possibly to Noah." Butler had written a story called "Pigs is Pigs"
about a similar overpopulation problem with guinea pigs. Heinlein believed it may have been an inspiration for "The Rolling Stones," but if he'd read it, it had been so long before that he couldn't remember.
Which just illustrates why it isn't at all incredible if two writers independently come up with the same idea. Every story is built on prior influences, and any two people in the same society and within a generation or so of each other will be influenced, consciously or otherwise, by a lot of the same things, whether it's famous movies or books or news events or just pervasive memes.