Towns developed at the same time as the great lowland temples, and are identifiable from about 2000 BC. Sinclair Hood (1971, p. 50) mentions the theory that the temples (though he treats them as palaces) at Knossos and Phaistos were founded by foreign dynasts who invaded Crete at the beginning of the Middle Minoan period; according to this view, urbanization occurred in Crete as a result of the arrival of alreadyurbanized conquerors. There is evidence of the arrival of migrants at various stages in Crete’s prehistory, but it seems too facile to attribute each change in the island’s culture to the arrival of a new group of immigrants.