the beauty of India is it is crowded enough that self selection happens, but large enough that there is much variation, which self-selects and takes over a center or two, but bounded enough that no one can leave, so the various variegated self-selected groups have to develop tolerance and protocol to interact, hence both profiting. the mountains and sea ensure homogenity (indian) and the vast space ensures variety (castes languages crops diets, weather, culture, seafaring traders, on-camel traders ...etc)

that is why india is a rich melting pot , and the diet usually follows