One interesting way to look at what is maintained and what is lost as indigenous methods of food preparation (and indigenous foods) adapt to changing circumstances is to look at what happens with urbanisation. As time becomes shorter and cooking fuel has a cash-cost rather than a time-collection-cost, some foods are abandoned, and many are maintained but their preparation method changes (often with the help of the market): so maize is ground into maizemeal instead of boiled whole (East Africa); brown beans are cooked in bulk commercially and sold hot in the street instead of prepared at home (Nile Valley); wheat grains are pre-broken or semi-cooked as with bulgur or couscous in North Africa and the Middle East. Whole new dishes are invented with the fermentation of soaked lentils (which speeds up cooking time) in the Indian sub-continent.
I have seen cassava leaves prepared in a far less time consuming way in the Comoro Islands than is described for Rwanda, in part by shredding the leaves before cooking.
The ultimate way of cooking in a fuel-short context is chinese cooking, where dishes are prepared by spending most of the time on cutting portions up into very small pieces which will cook rapidly. It is then possible to stir-fry or boil the vegetables and meat (if any) in as little time as it takes to cook the rice.
All these methods are indigenous methods too, as additional constraints kick in.
I am glad the moderator includes indigenous methods of food storage among his concerns. They are very important and not always well understood. The drying of foods such as green leaves, vegetables and fruits is very important in some areas and so is pickling in Asia and Europe.
Links and resources:
Indigenous Peoples’ food systems: the many dimensions of culture, diversity and environment for nutrition and health
Comparative Assessment of Indigenous Methods of Sweet Potato Preservation among Smallholder FArmers: Case of Grass, Ash and Soil based Apporoaches in Zimbabwe
FSN Forum discussion: Looking back to effective rural practices ... Did we miss something?