A parcel of dough around a filling turns up in cuisines with no historical contact, in forms that are recognisably related. Independent invention makes sense once the problems it solves are laid out.
It stretches a scarce ingredient across a meal
A small quantity of meat, cheese or vegetable distributed through many parcels of cheap dough feeds far more people than the same quantity served alone.
The dough is filling and made from a staple grain, so the expensive component becomes seasoning rather than substance.
Every food culture faced this constraint for most of its history, which is enough on its own to explain repeated invention.
The wrapper solves storage and transport
Enclosing a filling protects it from drying and from handling, so the food can be carried to a field, a market or a journey without a container.
The parcel is also portioned by construction, which makes distribution and pricing straightforward without any weighing or cutting.
Many forms freeze or dry well, so a batch made in quantity keeps, which suits households that cooked in large sessions rather than daily.
It uses odds and ends without appearing to
Fillings are chopped or minced, so trimmings, tougher cuts and small quantities of several vegetables can be combined into something uniform.
Seasoning is applied to the filling directly rather than to a whole piece, which allows strongly flavoured additions to correct anything unremarkable.
The result presents as a deliberate dish rather than as leftovers, which is a large part of why the format persisted in prosperity as well as in scarcity.
Cooking is efficient in fuel and equipment
A thin wrapper and a finely divided filling cook through quickly, so boiling or steaming a batch takes a fraction of the fuel a large roast would need.
Steaming in particular cooks a stacked quantity over one pot of water, which was significant where fuel was gathered rather than bought.
Boiling, steaming, frying and baking all work on the same parcel, so the method could follow whatever equipment a household actually had.
The form absorbs local ingredients without changing
The wrapper can be made from wheat, rice, other grains or starches, and the filling can be anything, so the concept survives being moved anywhere.
That flexibility means a cuisine can adopt the form and express itself entirely through the filling and the accompanying sauce.
What looks like a shared dish across many countries is therefore better understood as a shared solution that each cuisine filled with its own contents.