People have lived along the Portuguese coast at least since Marine Isotope Stage (MIS) 5, over 100,000 years ago. While there are many known sites and archaeological evidence of human settlement on land, there are only a handful of known submerged or nearsubmerged locations, and these are all in the present-day intertidal zone. Throughout the period, diet was based on both terrestrial and marine mammals as well as fish and shellfish. This dietary regime was already in existence when

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... populated the region. It appears that marine foods started to be used more frequently when the first anatomically modern humans arrived, some 33,000 years ago. Among the Mesolithic people who lived along the estuaries of the major rivers, marine food frequently composed c. 50% of the diet. With the introduction of agriculture, coastal resources became less important, although some submerged sites of Neolithic date testify to habitation directly at the seashore. Despite the current absence of known underwater prehistoric sites, apart from those in the intertidal zone, recent studies of offshore topography have identified a number of areas with good potential for archaeological prospection, including cliff lines with underwater caves and drowned river valleys.