I was daydreaming and got the idea for a sci-fi novel in my head. Because all planets are separate, developing within their own atmosphere, each planet is going to evolve differently, and my idea was a planet which had 3 or 4 intelligent species which had all evolved to the technological level together, obvs there was just something in the atmosphere that led intelligence to co-operation instead of intra-species warfare at a very early stage so maybe they developed technology quicker than humans, maybe slower, maybe in some ways quicker and in some ways slower, but then they get out into space and start exploring the universe and are totally blindsided by the idea of other , warlike species. I would make them the good guys, of course, and they eventually prevail, maybe by outwitting the others, or seeking alliances with other star-faring, war-knowing creatures, but who weren’t actually trying to kill them, and then I realized that parts of the idea were similar to a book I read, probably when I was about 11 or 12.
I think it might have been Heinlein, it was right up his alley, but if so it’s not one of his most famous. Anyway, in it a bunch of kids were chosen by the aliens (who’d just made contact with Earth) to go to some camp on another planet, kind of a scout outing/survival experiment/audition for the human race to see if we could join the federation of planets, and the main thing I remember is that there was more than one intelligent species on the planet. Does anybody know what book I’m talking about? I’d kind of like to find it and read it again.