According to available data, the building of ditched enclosures in Portugal ended in the last centuries of the 3rd millennium BC. Some show signs of occasional occupations during Bronze Age. But there is no evidence of ditches being built after 2000 BC until the Late Bronze Age, at least in the area of the great concentration of Late Neolithic and Chalcolithic enclosures: the Alentejo´s hinterland.
Radiocarbon dates for portuguese prehistoric ditched enclosures
The big question is why? Why such important architectures disappear abruptly? Especially after some of them reach sizes and complexities never reached before.
My answer, published in several papers, is that the reason for the disappearing of ditched enclosures has to do with the disappearance of the reasons for their construction. And that reason was an ideological, cosmological, one. They appeared to respond to a Neolithic world view and related social practices. When that cosmological perception was ending, they reach their biggest sizes and complexity, just like in the end of Middle Ages, feudal societies produced their most emblematic and exuberant architectures: the cathedrals. And then they abruptly disappeared. A significant change occurred by the end of the 3rd millennium beginning of the 2nd. Building ditched enclosures made no more sense. Not because communities stoped having defense problems or draining problems (functionalities that for some are the reasons for these architectures). But because the ideological frame that justified the development of these architectures was changed. The disappearance of ditched enclosures (and of megalithic traditions) in South Portugal marks the end of the Neolithic cosmologies. And a new world view would developed through the Bronze Age, naturally with some detectable continuities, but clearly revealing a new social organization and new perceptions of the world and of human ontologies. Ditched enclosures like the Neolithic and Chalcolithic ones had no place in this new world.