Comment by ants_everywhere

You can model parallel computation by an arbitrary finite product of Turing machines. And then, yes, you can simulate that product on a single Turing machine. I think that's the sort of thing you have in mind?

But I'm not aware of what "inherently serial" means. The right idea likely involves talking about complexity classes. E.g. how efficiently does a single Turing machine simulate a product of Turing machines? An inherently serial computation would then be something like a problem where the simulation is significantly slower than running the machines in parallel.