Ideas Never Wait Their Turn

So, despite having an overfull plate of Things To Do, my brain has been on overdrive of late.  In the past couple weeks, rather than go full out with Shield of the People (note well: I still went, like, half-to-three-quarters out), I went and wrote a novelette that's tangential to all the Maradaine stories.*  And then I had one of those 2am ideas where you must jot down some notes on a project that you really do not have time to write.  And despite not having the time, my brain was all, "Well, we need to at least lay down some particulars" before I can let it rest in the mental crockpot and simmer while I work on other things. 
But this is how my brain goes in moments like this:

Me: OK, new idea, let's just write some notes--
Brain: Perfect. First step, understand what's happening in every part of the world as they transition from neolithic to early bronze.
Me: That's absurd!
Brain: You're right. It's neolithic to chalcolithic.
Me: I don't need any of that! That's, like, 8000 years before this story would be set!
Brain: Well, sure, then: half-ass it. Just decide cultures based on your whim without any sense of historical build up!
Me: That doesn't--
Brain: I mean, if you want to just cheat, sure.
Me: How is that cheating?
Brain: You have no idea what cultural or technological influence those two continents to the southeast might have.
Me: I don't even know what's there, yet.
Brain: Exactly my point. Cheating. So where were we? Ah, yes, neolithic era!
Me: Wait, but I just wanted a---
Brain: You're right, that's still taking the easy way. First a common origin point of humanity-- just humans on this world?-- and then their diaspora to fill the world and the effects that has on megafauna and other natural life.
More
Me: No, that's... I just had an idea for a story with deiselpunk motorcycles!
Brain: Oh, is that what you want?
Me: Yes!
Brain: Then we're going to have to go back even further and figure out the Mesozoic equivalents to justify oil deposits.
Me: I hate you so much.

But this is how my brain always works.  I've accepted that.  The point is: I had to exorcise some ideas this weekend.  But it's all good.  And now, for real: full steam ahead on Shield of the People.  And editing that novelette.  And maybe something else.
Maybe.

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*- It's set on the island where Kaiana was born.