# Environmental Changes and Cultural Transitions in SW Iberia during the Early-Mid Holocene
## 4 Discussion
### Human Groups in Dynamic Littoral Habitats
Some Mesolithic sites exhibit layers of Neolithic occupations (Castelejo, Barranco das Quebradas, Rocha das Gaivotas, Vale Boi, Palmones), although with hiatuses of several hundred years. The existence of several seasonal camps (Alcalar 7, Ribeira de Alcantarilla, Vale Santo I, Padrao, El Retamar) suggests the maintenance of previous subsistence strategies until this period. However, Neolithic times also involve new settlement patterns with sites located near rivers, shell deposits thinner than those in the Mesolithic, and caves. Only two sites suggest clear sedentary occupation (Castelo Belinho, Campo de Hockey) and the presence of seasonal camps reveals that the mobility was still key in the provisioning of different resources. Although the aim of this paper is not to discuss the origins of the Neolithic in the study area, the coexistence of previous (Mesolithic) and new (Neolithic) settlement patterns would be coherent with the idea of an integration of the two populations, rather than with the disappearance of the hunter-gatherer way of life [120]. It is noteworthy to mention that except the pre-existing sites and some exceptions such as Praia do Forte Novo, El Retamar, and Campo de Hockey, all the Neolithic sites are located a few kilometres inland. Some changes in dietary habits regarding aquatic resources may be linked to this new settlement pattern, with the increased consumption of cockles and clams [121] typical from transitional brackish environments (rias), in contrast to the rocky-like shellfish preferred during the Mesolithic. Some ideas of what may lie behind this change in settlement patterns are:  
* Different populations would have a different perception of the same habitat, so they develop preferences for settling in distinct areas. * The maximum flooding of some river valleys would have forced human groups to settle in areas less close to the coastline. It should be also considered that archaeological sites located in the mouth of these rivers could have been buried or destroyed after this flooding episode and only those located in inland areas are preserved. * The weakening of the coastal upwelling during the Holocene Thermal Maximum may have caused a displacement toward areas with more stable resource availability, like what occurred in the Tejo and Sado estuaries _ca._ 8.2-8 ka BP. Due to the bias in the preservation of Mesolithic sites in the study area, it is not possible to delineate to what extent this would have affected Mesolithic populations and to compare it to the Neolithic groups. * The aridity crisis reflected in the vegetation _ca._ 7.5 ka BP and recorded in other sequences _ca._ 7.5-7 ka BP may have led human groups to settle in areas more suitable for livestock and/or agriculture activities with available freshwater sources. One might speculate whether the aridity phase experienced during this period might have influenced the adoption of new subsistence strategies. Regarding the resource exploitation and subsistence strategies, the introduction of a farming economic system resulted in a major dietary shift towards terrestrial food during this transitional period [123]. In relation to the agricultural practices, the first evidences were dated _ca._ 7.5-7 ka BP in Eastern Andalusia and Central-South Portugal, while there is not any direct evidence of their origins in the Occidental Andalusia and the Algarve area [124]. Livestock and grazing activities have direct testimony in zooarchaeological material. With respect to palynology, anthropogenic indicators are most likely to be identified in continental and especially archaeological deposits than in marine cores. However, the first manifestations of agricultural activities are only documented _ca._ 6 ka BP in areas with previous and important Mesolithic occupations [124]. In relation to the preservation of human settlements, the lack of data in the central coast of the Gulf of Cadiz for both Mesolithic and Neolithic periods must be considered.