[SAI_Peregrinus]

Doors are such an important invention that multiple unrelated animals have evolved modified body parts to serve as doors to burrows¹. Being able to store food is critically important for surviving low-food periods like winter without migrating. "Indoors" lets you store food without insects or other animals getting to it & stealing it. Fire allows for hardening clay, which lets you make a special tiny "indoors" called a "pot" for storing food. Also bricks so "indoors" can be made anywhere. With a roof the rain stays out & you can stay dry & warm, and not freeze at night. A significant portion of why fire is so important is it enables creating various sorts of "indoors".

¹https://en.wikipedia.org/wiki/Phragmosis

[thaumasiotes]

> "Indoors" lets you store food without insects or other animals getting to it & stealing it.

This isn't true of human doors; insects are very small.

We've had the technology to keep things in wax-sealed clay jars for quite a while, but I'm not aware that this was done with grain, where preventing spoilage would have been most valuable. Granaries are open to the air. (And devote quite a lot of effort to slowing the spoilage of the grain.)

If you wanted food that wouldn't rot, instead of keeping it in an airtight environment, you dried it.

[bluGill]

Every different food idem needs to be stored differently. There sometimes more than one option that will work, but you cannot treat everything the same.

[IAmBroom]

Dried food requires indoor storage.